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Opening / Closing Ceremony

Mon-24 Jun | 5:30 – 6:50 | Music Tent, Alpensia Resort
Welcome & Opening, General Assembly & Inaugural Concert

Fri-28 Jun | 5:30 – 6:00 | Level 2, Forest Hall, Alpensia Convention Center
Closing, Awards & AOGS2025

Key Lectures

Mon-24 Jun | 11:00 - 12:30 | Auditorium, Alpensia Convention Center
AS Distinguished Lecture

Speaker(s): Masahiro (Masa) WATANABE, Professor, Atmosphere and Ocean Research Institute (AORI) Deputy Director, UTokyo Center for Climate Solutions (UTCCS) The University of Tokyo

Value of Climate Models in Attributing and Projecting Large-Scale Climate Changes
Mon-24 Jun | 11:00 - 12:30 | Auditorium, Alpensia Convention Center
AS Kamide Lecture

Speaker(s): Min-Seop AHN, Assistant Research Scientist Global Modeling and Assimilation Office (GMAO), NASA Goddard Space Flight Center (GSFC) Earth System Science Interdisciplinary Center (ESSIC), University of Maryland

Madden-Julian Oscillation: Physical Mechanism and Model Simulation
Mon-24 Jun | 11:00 - 12:30 | Pyeongchang Hall III, Alpensia Convention Center
BG Distinguished Lecture

Speaker(s): Forrest HOFFMAN, Oak Ridge National Laboratory

Systematic Assessment of Terrestrial and Marine Biogeochemistry in Earth System Models
Mon-24 Jun | 11:00 - 12:30 | Pyeongchang Hall III, Alpensia Convention Center
BG Distinguished Lecture

Speaker(s): Satish C.B. MYNENI, Princeton University

Rises in Sea Levels and Changes in the Coastal Biogeochemical Processes
Mon-24 Jun | 4:00 - 5:30 | Music Tent, Alpensia Resort
Axford Lecture

Speaker(s): Axel TIMMERMANN, Director and Professor IBS Center for Climate Physics (ICCP), Pusan National University

Past Climate Impacts on Human Evolution

Speaker(s): William McKINNON, Professor Department of Earth, Environmental, and Planetary Sciences, and McDonnell Center for the Space Sciences Washington University in St. Louis

Exploration of Kuiper Belt in the 21st Century, What Have We Learned and What is to Come?
Tue-25 Jun | 11:00 - 12:30 | Pyeongchang Hall II, Alpensia Convention Center
HS Distinguished Lecture

Speaker(s): Eiichi NAKAKITA, Director and Professor, Disaster Prevention Research Institute Deputy Executive Director, Kyoto University

Early Detection of Baby-Rain-Cell Aloft in a Severe Storm and Risk Projection for Urban Flash Flood -Advanced Utilization of Weather Radar-
Tue-25 Jun | 11:00 - 12:30 | Pyeongchang Hall II, Alpensia Convention Center
HS Kamide Lecture

Speaker(s): Yoko YAMAGAMI, Japan Agency for Marine-Earth Science and Technology

Arctic Sea-Ice Reduction and Gulf Stream Warming under Global Warming: Implication for the Further Development of GCMs
Tue-25 Jun | 11:00 - 12:30 | Pyeongchang Hall III, Alpensia Convention Center
IG Distinguished Lecture

Speaker(s): Shunichi KOSHIMURA, Deputy Director, Professor, International Research Institute of Disaster Science, Tohoku University Co-founder & CTO, RTi-cast, Inc.

Catastrophic Tsunami Disaster – Its Impact, Disaster Response, and Mitigation
Tue-25 Jun | 11:00 - 12:30 | Pyeongchang Hall III, Alpensia Convention Center
IG Kamide Lecture

Speaker(s): Daran ZHENG, Nanjing Institute of Geology and Palaeontology (NIGPAS) Chinese Academy of Sciences

The Spatiotemporal Evolution of The Early Cretaceous Jehol Biota in East Asia
Wed-26 Jun | 11:00 - 12:30 | Pyeongchang Hall III, Alpensia Convention Center
PS Distinguished Lecture

Speaker(s): Philippe LOGNONNÉ, Professor in Geophysics, University Paris Cité Planetary Seismologist, Institut de physique du globe de Paris

Planetary Seismology on Mars, The Moon and Beyond
Wed-26 Jun | 11:00 - 12:30 | Pyeongchang Hall III, Alpensia Convention Center
PS Kamide Lecture

Speaker(s): Honglei LIN, Associate Research Professor Institute of Geology and Geophysics, Chinese Academy of Sciences

From Apollo to Chang’e-5, What Have We Learned About the Water on The Moon?
Wed-26 Jun | 11:00 - 12:30 | Pyeongchang Hall III, Alpensia Convention Center
ST Distinguished Lecture

Speaker(s): Jongchul CHAE, Professor in Astronomy Program Department of Physics and Astronomy Seoul National University

Toward Understanding the Habitability of an Exoplanet Orbiting a Magnetically-active Star from Our Current Understanding of the Sun-Earth Connection in the Heliosphere
Wed-26 Jun | 11:00 - 12:30 | Pyeongchang Hall III, Alpensia Convention Center
ST Kamide Lecture

Speaker(s): Shan WANG, Assistant Professor Peking University

An Introduction of Magnetic Reconnection: Particle Dynamics and Waves
Thu-27 Jun | 11:00 - 12:30 | Pyeongchang Hall II, Alpensia Convention Center
OS Distinguished Lecture

Speaker(s): Jing ZHANG, Advisor to the President Faculty of Science University of Toyama

Understanding the Water and Nutrient Transport Between Land and Ocean: Toward the Healthy, Productive, and Sustainable Asian Marginal Seas
Thu-27 Jun | 11:00 - 12:30 | Pyeongchang Hall II, Alpensia Convention Center
OS Kamide Lecture

Speaker(s): Changming DONG, Dean, School of Marine Sciences, Nanjing University of Information Science and Technology

AI Applications in Oceanography
Thu-27 Jun | 11:00 - 12:30 | Pyeongchang Hall III, Alpensia Convention Center
SE Distinguished Lecture

Speaker(s): J. Bruce H. SHYU, Professor Department of Geosciences National Taiwan University

Upper-Plate Structures Along Major Convergent Plate Boundaries: Structural Characteristics and Earthquake and Tsunami Hazards
Thu-27 Jun | 11:00 - 12:30 | Pyeongchang Hall III, Alpensia Convention Center
SE Kamide Lecture

Speaker(s): Shengji WEI, Principal Investigator, Earth Observatory of Singapore (EOS) Associate Professor & Associate Chair, Asian School of the Environment (ASE) Nanyang Technological University

Recent Earthquake Rupture Imaging and New Insights to Fundamental Earthquake Physics
Fri-28 Jun | 4:00 - 5:30 | Level 2, Forest Hall, Alpensia Convention
Axford Medal Lecture

Speaker(s): Jian LIN, Director and Professor Advanced Institute for Ocean Research, Southern University of Science and Technology (SUSTech)

Critical Roles of International Geoscience Cooperation in Addressing Pressing Global Issues
Fri-28 Jun | 4:00 - 5:30 | Level 2, Forest Hall, Alpensia Convention
Wing-Ip Medal Lecture

Speaker(s): Chih-Pei CHANG, Distinguished Chair Professor, National Taiwan University Distinguished Professor Emeritus, Naval Postgraduate School

Maritime Continent Monsoon: Topographic Effects and Mesoscale – Large Scale Interactions

Panels, Special Sessions & Workshops

Wed-26 Jun | 2:00 – 3:30 | Luge Hall, Alpensia Convention Center
Transforming Hydrology by Integrating Remote Sensing, Modeling, and Data Sciences
Convener: Eunsang Cho, Texas State University
Hyunglok Kim, Gwangju Institute of Science and Technology
Speakers: Ana P. Barros, University of Illinois at Urbana-Champaign
John Bolten, Hydrological Sciences Laboratory, NASA Goddard Space Flight Center
Venkataraman Lakshmi, University of Virginia
Zong-Liang Yang, Department of Earth and Planetary Sciences, University of Texas
Session Description: Remote sensing and modeling have transformed hydrologic science and applications. Spaceborne missions are dedicated to interlinked global hydrologic processes. Furthermore, computational techniques are accelerating analyses of these data and integrating them into the modeling. However, there are existing gaps and challenges the hydrologic community faces such as data uncertainties, limited model physics, and inequitable data availability across the world. How will the hydrologic community use these resources to better understand the world's water resources and to overcome related challenges facing society, particularly in Asia and Oceania. In this invited talk session, we will discuss the benefits, challenges, and opportunities of remote sensing for advancing hydrologic research, integrating multidisciplinary and multisensor data, and employing data assimilation and AI/machine learning.
Thu-27 Jun | 11:00 – 12:30 | Luge Hall, Alpensia Convention Center
Co-creating the Future of CMIP (Coupled Model Intercomparison Project)
Convener: Beth Dingley, European Space Agency
Speakers: Tomiki Miyakawa, The University of Tokyo
Douglas Rao, North Carolina State University
Session Description: The World Climate Research Programme’s (WCRP) Coupled Model Intercomparison Project (CMIP) has coordinated international climate model experimentation, to develop a better understanding of past, present, and future climate change. Over four decades, CMIP has grown in scope and complexity, targeting climate science addressing the WCRP objectives and serving IPCC Assessments. CMIP6, the latest phase, yielded more than 25 PB of data, with contributions from 131 models, from 48 institutions, representing 26 countries.
Work has commenced on future CMIP7 planning. The project aims to meet the growing community needs, enabling climate science and providing actionable climate information to aid policymakers. To facilitate next steps, the two panels that oversee the project, the CMIP and Working Group on Coupled Modelling (WGCM) Infrastructure (WIP) Panels have established seven Task Teams to guide CMIP7 scope and design and facilitate coordinated infrastructure development. These aim to increase CMIP’s scientific and social relevance, widen participation, improve data accessibility, and reduce the carbon footprint.
We invite our growing community to attend. We will describe ongoing planning, highlight engagement, and feedback opportunities, and invite attendee feedback and participation. The town hall will be presented by members of the CMIP Panel, Fresh Eyes on CMIP group, and CMIP7 Task Teams.
Thu-27 Jun | 2:00 – 3:30 | Luge Hall, Alpensia Convention Center
Workshop: Making the Most of CMIP Data: Analysis, Access, and Tools
Convener: Beth Dingley, European Space Agency
Speakers: Douglas Rao, North Carolina State University
Froila Palmeiro, Centro Euro-Mediterraneo sui Cambiamenti Climatici
Evgenia Galytska, Bremen University
Alistair Duffey, University College London
Nebiyu Tekesa, Arba Minch University
Gen Tolhurst, The Bureau of Meteorology
Beth Dingley, European Space Agency
Associated Sections: AS, HS, IG, OS (Not Limited To)
Description: The Coupled Model Intercomparison Project (CMIP) is an international climate modelling project, designed to better understand past, present, and future changes in the climate. More than 50 modelling centres around the world participated in CMIP6, which has already generated in excess of 14 PB of unique data. From its inception, there has been a focused effort to make the model intercomparison data available to scientists beyond the climate modelling community. With more data access platforms and analysis tools being created every year to support the use of CMIP data, it can be difficult to know where to begin. Primarily led by members of the new Early Career Scientists group, Fresh Eyes on CMIP, this workshop will provide an overview of ways to access CMIP data and present some useful analysis tools and methods to help with using it. The key topics across the session will cover:
  1. CMIP experimental structure and MIPs.
  2. Scientific limitations of CMIP data.
  3. Different methods for accessing CMIP data, and their advantages and limitations.
  4. Analysis and evaluation tools.
In this workshop, participants will learn about CMIP data and how to access and analyze it efficiently. The session will be interactive with a lot of time to ask questions in between presentations, videos, and live demonstrations. The session is open to anyone who wants to use CMIP data from any sector.
Thu-27 Jun | 4:00 – 6:30 | Luge Hall, Alpensia Convention Center
Workshop: Exploring High-Resolution Downscaled Climate Projections
Convener: Weile WANG, NASA Ames Research Center
Instructors: Weile WANG, NASA Ames Research Center
Hugo Kyo LEE, NASA Jet Propulsion Laboratory
Koji DAIRAKU, University of Tsukuba
Dong-Hyun CHA, Ulsan National Institute of Science and Technology
Tsengdar LEE, NASA Headquarters
Associated Sections: AS, HS, IG, OS (Not Limited To)
Description: The goals of this workshop are:
  1. To disseminate statistically downscaled CMIP6 GCM predictions and open-source software for analyzing the downscaled dataset to the AOGS community
  2. To provide training to potential users to gain a deeper understanding of the datasets and other related resources for providing informed decision support
  3. To foster communication and collaboration between NASA and the AOGS community on conducting climate-change research and decision-making workflows.
This instructional training session will begin with presentations by the convenors on their downscaled datasets and the significance of downscaled climate projections in developing and implementing climate actions. Following that, a brief presentation will outline the motivation and objectives of NASA's investments to support the United States National Climate Assessment. After the lecture, we will guide participants in accessing the Jupyter Lab server, which will be set up for all participants to use the RCMES software with their own laptops. No prerequisite software will be required. We will furnish detailed examples and step-by-step instructions to assist workshop participants in effectively analyzing and visualizing the downscaled climate projections tailored to their specific area of interest. Researchers, graduate students, and practitioners who are interested in using downscaled climate projections for climate change assessment, adaption, and mitigation research and applications are all welcome.
Fri-28 Jun | 11:00 – 12:30 | Pyeongchang Hall III, Alpensia Convention Center
Interdisciplinary Panel: From Lab to Society: Showcasing South Korea's Climate-Tech Entrepreneurial Scientists

In the era of the escalating climate crisis, the significance of climate technology to mitigate and adapt to these changes is on the rise. There is a growing need for the research and development of various technologies particularly those grounded in the expertise of Geoscience, and the widespread adoption of climate tech based on these innovations. In this session, we will firstly introduce the overall concept and current status of climate technology, followed by a leading climate tech company to share their insights into the commercialization process of the technologies and discuss the future of the climate tech industry. Lastly, we intend to explore avenues for collaboration by discussing the vision and activities of the Chung Mong-Gu Foundation, which fosters and supports the climate tech industry.

Fri-28 Jun | 11:00 – 12:30 | Pyeongchang Hall II, Alpensia Convention Center
Workshop: A Mini Tutorial for Ensemble Data Assimilation and the Data Assimilation Research Testbed with Applications for the Model for Prediction across Scales
Convener: Lili Lei, Nanjing University
Instructors: Jeffrey Anderson, U.S. Geological Survey
Soyoung Ha, National Center for Atmospheric Research
Associated Sections: AS, HS, OS (Not Limited To)
Description: This workshop is designed to be a short course that provides a practical introduction to ensemble filters from theories to tools along with realistic applications. There will be two main lectures, one is for “Introduction to Ensemble Data Assimilation” and the other is for “Introduction to the Data Assimilation Research Testbed (DART) and its Applications for the Model for Prediction Across Scales (MPAS)”. Basic ensemble filter algorithms will be covered along with an overview of extensions required for successful application in large earth system models. Various flavors of ensemble filters can be tested through the Data Assimilation Research Testbed (DART), a community software facility for ensemble filter data assimilation. DART can produce high-quality weather predictions but can also be used to build a comprehensive forecast system for any prediction model and observations. DART has been applied to NWP at scales ranging from sub-kilometer to global, but also to space weather, oceans, sea ice, terrestrial systems, hydrologic models, and many other earth system applications. This workshop is open for all participants to AOGS who have interests. Attendees will leave with a solid foundation that will allow them to explore using DART for existing models and observations, especially the Model for Prediction Across Scales (MPAS) for global and regional applications. They will also have a basic understanding of what would be required to develop DART assimilation capabilities for new models or observations.
Fri-28 Jun | 2:00 – 3:30 | Pyeongchang Hall III, Alpensia Convention Center
Interdisciplinary Panel: Climate Change and Infrastructure Reassessment

Disasters occur or are mitigated based on the relative magnitude between the ‘hazard’ factor to drive them and the ‘societal capacity’ factors to withstand them. Non-stationarity in climate, which began to be detected in the late 20th century, have now become widespread to the point that they are noticeable by the general public. In other words, climate change is increasingly recognized as a major driver of extraordinary disasters worldwide, and it has become the focus of numerous studies in almost every country. However, there is relatively less public interest in the societal capacity required to cope with disasters. Vulnerability, especially concerning ‘aging’ social infrastructure, is undoubtedly crucial especially in developed nations with a long history of urban development. In summary, we are confronting to a combined difficulty with two major challenges, the ‘changing climate’ and the ‘aging infrastructure’. Taking South Korea as an example, the first multipurpose dam, Soyanggang Dam, celebrated its 50th anniversary in 2023, and from now on, a multitude of social infrastructure will age beyond 50 years in the coming years. This session is designed to re-evaluate the issue of aging social infrastructures in the context of climate change and to discuss forward-looking scientific and technological alternatives and policy directions to address it.

Public Lectures

Wed-26 Jun | 12:30 – 2:00 | Daegwallyeong II, Alpensia Convention Center
The Meaning of Life and Our Place in The Universe

Speaker(s): Prof Sang-Mook LEE , Marine Geoscientist
Seoul National University

Scientific developments are considered the primary source of the economic prosperity of a country. This faith in science appears stronger among economists and policymakers than those involved in day-to-day activities. However, science policy is often confused with a policy for science. The former is dictated by national interest and ideology, including long-term plans for the country. Because it is so crucial, whether to let scientists formulate the science policy of a nation is a long-standing issue in many countries. Policymakers and politicians generally provide the overall picture with some help from scientists. A common approach adopted by developing countries is the so-called ‘mid-level entry strategy.’ The idea is to dispense basic science to developed countries and focus on those areas that may bring immense profits. And when the time comes, and technology matures, bet heavily on those specific areas and jump ahead of the flock to reap the benefit. However, many consider DARPA (Defense Advanced Research Projects Agency) the most successful research and development (R&D) institution in the US. It is said that the accomplishment of the agency was possible because they started with basic science and moved up to applied and practical research. Doing so dominated the entire value chain, and the know-how was then disseminated to the public. Such observation leads one to conclude that, contrary to the myth of mid-level entry strategy, the real big reward for R&D of a country comes from starting at the fundamental level. On the other hand, because scientific and technological development is not straightforward, some examples may point to the contrary. detected polar stratospheric jets associated with polar fronts. Other heating mechanisms proposed in the literature, such as Joule heating, polar haze heated by sunlight, etc., seem only the secondary mechanisms that follow atmospheric ionization caused by the energetic particle bombardment.

Thu-27 Jun | 12:30 – 2:00 | Emerald, Tower Condo, YongPyong Resort
Jupiter's North Polar Mid-IR Hotspot: The 44-Year Mystery May Now Be Solved

Speaker(s): Prof Sang Joon KIM , Planetary Scientist
Kyung Hee University

Jupiter's mid-infrared north polar hot spot, ~20 K warmer than the surrounding polar stratosphere, has been observed for over four decades. Its unusual appearance and longevity have not been fully understood, although several mechanisms have been proposed to explain its existence. We utilized the Gemini Near-Infrared Spectrograph at Gemini/North telescope to spectrally map Jupiter in the 3-micron emission lines of CH4 (methane) and C2H6 (ethane) across Jupiter's northernmost latitudes where its mysterious north polar hotspot is located. These lines are emitted high above the stratosphere and are excellent monitors of auroral energy being deposited downward into the stratosphere. By comparing the emission from CH4 with that from C2H6, we demonstrate that the transient heating and bright line emissions from these molecular species are caused by increased precipitation of high-speed auroral particles, which are produced in Jupiter's turbulent magnetosphere and ionosphere near its poles. The heating extends down into the stratosphere where the hotspot is located. At that depth, heating up and cooling off is much more gradual than at higher altitudes. Additionally, the free flow of warm gas in the hot spot to the surrounding polar regions is resisted by recently detected polar stratospheric jets associated with polar fronts. Other heating mechanisms proposed in the literature, such as Joule heating, polar haze heated by sunlight, etc., seem only the secondary mechanisms that follow atmospheric ionization caused by the energetic particle bombardment.

Scientist Led Field Trips

Atmospheric Sciences

Mon-24 Jun | 8:30 - 10:30 | Auditorium, Alpensia Convention Center
AS04 - The Asian Monsoon and Climate Change

Session Chair(s): Jai-Ho OH, Nano C&W, Ramesh KRIPALANI, Indian Institute of Tropical Meteorology

AS04-A028 | Invited
Global Monsoon Response to Anthropogenic Forcing and Internal Feedback Processes

Bin WANG#+
University of Hawaii

This talk discusses a modern perspective of the monsoon concept and its climate variabilities and projected future changes, focusing on land monsoon rainfall (LMR) that provides water resources for about 70% of the world’s population. The talk will begin with discussing the emerging concept of Global Monsoon and its critical role in driving annual variation of Hadley circulation, Intertropical convergence zone, deserts, and subtropical high. I will then discuss the observed global LMR variabilities on the intraseasonal to multidecadal time scales and their primary drivers, including attribution of the recent trends and exploration of the decadal predictability of Northern Hemisphere LMR. Continued global warming and urbanization have caused a significant rise in the intensity and frequency of extreme rainfall events in all monsoon regions over the past century. The critical physical processes responsible for the projected changes in climate sensitivity of monsoon rainfall to global warming will be deliberated. We emphasize that the thermodynamic effects of the greenhouse gas forcing may be weaker than those described in the literature, and their spatially uniform increases cannot explain markedly different regional LMR changes. The anthropogenic forcing-induced circulation changes (dynamic effects) are primarily responsible for the regional differences. The models’ biases in projected regional SST and land–sea thermal contrast likely contribute to the models’ uncertainties in the projected monsoon rainfall changes.

AS04-A025 | Invited
Preceding Winter Okhotsk Sea Ice as a Precursor to the Following Winter Extreme Precipitation in South China

Jianping LI1#+, Kai JI2, Zhongshi ZHANG2, Ruiqiang DING3, Yurun TIAN4,5, Yongqi GAO4, Jiayu ZHENG4
1Ocean University of China, 2China University of Geosciences, 3Beijing Normal University, 4Chinese Academy of Sciences, 5Hebei Normal University

The winter extreme precipitation over South China (SC) experiences a large year-to-year variability, causing uncertainty in its prediction. Here, we find that the boreal winter sea ice concentration (SIC) in the Okhotsk Sea can serve as a precursor to the following winter's extreme precipitation frequency (EPF) over SC, which has important implications for its prediction. Further analysis reveals that the Okhotsk Sea SIC anomalies help to reinforce North Pacific Oscillation-like atmospheric variability over the North Pacific, which induces the development of El Niño-Southern Oscillation (ENSO)-like SST anomalies in the equatorial eastern Pacific. The ENSO may act as a “power amplifier” to boost the impact of the Okhotsk Sea winter SIC anomalies on the following winter EPF over SC via a positive atmosphere–ocean feedback process. Our findings suggest that the Okhotsk Sea SIC may act as a potential precursor for the winter EPF over SC leading by about 1 year, and further improve our understanding of extratropical-tropical interactions and aid predictability of winter extreme precipitation over SC.

AS04-A023 | Invited
Moist Baroclinic Instability of the East Asian Summer Monsoon

Tim LI1#+, Guang YANG2
1University of Hawaiʻi at Mānoa, 2North Carolina State University

A unique feature of the East Asian summer monsoon is dominated eastward-propagating synoptic-scale disturbances along a subtropical Meiyu front. The synoptic disturbances are strongly coupled with moisture and precipitation, and cannot be explained by traditional dry baroclinic instability theory. In this study, a new theoretical framework is developed, and it extends a traditional 2-level baroclinic model by considering a moisture tendency equation and feedbacks among perturbation moisture, precipitation and circulation. An eigenvalue analysis shows that the most unstable mode has a preferred zonal wavelength of 3400 km, an eastward phase speed of 10 m/s and a westward tilted vertical structure, all of which are in good agreement with observations. Both horizontal and vertical advection processes contribute to low-level moistening. Sensitivity tests show that the instability and the scale selection arise primarily from the moistening and condensational heating processes, while the modest background vertical shear provides an additional energy source for the perturbation growth. The new moist baroclinic instability theory explains well the observed characteristics of the development of synoptic-scale disturbances along the subtropical Meiyu front.

AS04-A005 | Invited
Dynamical Processes of ENSO’s Impact on Southeast Asian Summer Monsoon and Their Future Changes

Song YANG1#+, Shuheng LIN1, Buwen DONG2
1Sun Yat-sen University, 2University of Reading

The dynamical response of Southeast Asian summer monsoon (SEASM) to ENSO shows a large spread among CMIP6 models, and only some models can capture the observed features of ENSO’s impact on the monsoon. The problem of the bad-performance models is that the ENSO-related warm SST anomalies extend too far westward in the western equatorial Pacific (WEP) and are overly persistent, caused by a weak negative shortwave radiation feedback due to a low sensitivity of precipitation to local SST changes related to the cold bias in climatological SST. On the other hand, from the mature winter to the decaying summer of El Niño, the El Niño-related anomalous eastward current does not reverse to westward current because of the weak El Niño discharge process, attributed to the weak westerly wind anomalies associated with El Niño. The prolonged anomalous eastward current thus also contributes to the slow decay of WEP SST anomalies via inducing excessively persistent warm zonal advection in the WEP. For a warmer climate, CMIP6 models projects an enhanced response of the SEASM to ENSO, attributed to weakened warm SST anomalies in WEP during El Niño decaying summer. The El Niño related WEP SST anomalies decay rapidly and eventually dissipate from El Niño mature winter to the following summer, intensifying the anomalous anticyclonic circulation over the western North Pacific by enhancing the zonal gradient of SST anomalies between the tropical Indian Ocean and the WEP. The fast decay of WEP SST anomalies is mainly determined by increased latent heat flux from oceans to the atmosphere due to strengthened surface wind, caused by the eastward shifts of ENSO-induced anomalous Walker circulation and associated precipitation anomalies that are resulted from the El Niño-like change in background SST in the equatorial Pacific under global warming.

Asian-Australian Summer Monsoons Linkage to ENSO Strengthened by Global Warming

Chenxi XU1#+, S. Y. Simon WANG2, Krishna BORHARA2, Brendan M. BUCKLEY3, Ning TAN1, Yaru ZHAO1, Wenling AN1, Masaki SANO4, Takeshi NAKATSUKA4, Zhengtang GUO1
1Chinese Academy of Sciences, 2Utah State University, 3Columbia University, 4Nagoya University

The El Niño-Southern Oscillation (ENSO) used to affect the Asian summer monsoon (ASM) and Australian summer monsoon (AusSM) precipitation in different ways but global warming may have changed it. This study built robust annual ASM (AusSM) precipitation reconstructions during 1588–2013 (1588–1999) to examine the ENSO-monsoon relationship and how it has changed. During the period of 1588–1850 when natural climate variability was dominant, the ENSO-monsoon and inter-monsoon relationship was weak and non-stationary. Since 1850, however, both the inter-monsoon and ENSO-monsoon relationships saw an enhancement and this trend has been persistent to the present day, suggesting the influence of anthropogenic climate warming. Further analysis of climate model projections found that global warming can strengthen the ENSO-monsoon association that, subsequently, acts to synchronize the ASM and AusSM variations.

Robust Changes in Global Subtropical Circulation Under Greenhouse Warming

Shijie ZHOU#+, Ping HUANG
Chinese Academy of Sciences

The lower tropospheric subtropical circulation (SC) is characterized by monsoons and subtropical highs, playing an important role in global teleconnections and climate variability. The SC changes in a warmer climate are influenced by complex and region-specific mechanisms, resulting in uneven projections worldwide. Here, we present a method to quantify the overall intensity change in global SC, revealing a robust weakening across CMIP6 models. The weakening is primarily caused by global-mean surface warming, and partly counteracted by the direct CO2 effect. The direct CO2 effect is apparent in the transient response but is eventually dominated by the surface warming effect in a slow response. The distinct response timescales to global-mean warming and direct CO2 radiative forcing can well explain the time-varying SC changes in other CO2 emission scenarios. The declined SC implies a contracted monsoon range and drying at its boundary with arid regions under CO2-induced global warming.

AS04-A006 | Invited
Constraining the Global Mean Surface Temperature During 1850-1880 with New Statistical Physical Model

Qingxiang LI#+
Sun Yat-sen University

As IPCC ARs stated, global warming is estimated based on the global average temperature of pre-industrialization (represented by the average throughout 1850 to 1900 with relatively sparse observations). Given the impossibility of massive increasing observation data in the early stages, accurately constraining this baseline has become an unresolved issue. Based on a data-driven research paradigm, we developed a new statistical physical model to quantify the contribution of external forcings to global warming as a “deterministic trend” of the surface temperature series (instead of as non-stationary processes that yield a stochastic trend) and by which constrained the reconstruction of the early time series (1850-1880). The results suggest that the latest AR6 still slightly underestimates the rate of global warming since pre-industrialization, as the existing dataset slightly overestimates surface temperature anomalies over this baseline period. Our study provides a new perspective on the attribution and historical reconstruction of global warming since industrialization. These insights should also help humanity develop future climate change adaptation and mitigation strategies.

PDO and AMO Modulation of the ENSO–Asian Summer Monsoon Teleconnection During the Last Millennium

Na WANG1#+, Sylvia DEE1, Jun HU2, Nathan STEIGER3, Kaustubh THIRUMALAI4
1Rice University, 2Xiamen University, 3Hebrew University of Jerusalem, 4The University of Arizona

Observations show that the teleconnection between the El Niño-Southern Oscillation (ENSO) and the Asian summer monsoon (ASM) is non-stationary. However, the underlying mechanisms are poorly understood due to the inadequate availability of reliable, long-term observations. This study uses two state-of-the-art data assimilation-based reconstructions of last millennium climate to examine changes in the ENSO–ASM teleconnection; we investigate how modes of (multi-)decadal climate variability (namely, the Pacific Decadal Oscillation, PDO, and the Atlantic Multidecadal Oscillation, AMO) modulate the ENSO–ASM relationship. Our analyses reveal that the PDO exerts a more pronounced impact on the ASM variability than the AMO. By comparing different linear regression models, we find that including the PDO in addition to ENSO cycles can improve the prediction of the ASM, especially for the Indian summer monsoon. In particular, the dry (wet) anomalies caused by El Niño (La Niña) in India will be enhanced during the positive (negative) PDO phases due to a compounding effect. However, composite differences in the ENSO–ASM relationship between positive and negative phases of the PDO and AMO are not statistically significant. A significant influence of the PDO/AMO on the ENSO–ASM relationship occurred only over a limited period within the last millennium. By leveraging the long-term paleoclimate reconstructions, our findings underscore the non-stationary nature of the PDO and AMO in modulating the ENSO–ASM relationship.

Active and Inactive Lightning Frequency Cases During the Quasi-stationary Band-shaped Precipitation Systems in 2023

Hisayuki KUBOTA1#+, Yukihiro TAKAHASHI1, Mitsuteru SATO1, Yoshihisa YAMANOUCHI2, Akiyoshi FUKAYA2
1Hokkaido University, 2IHI Corporation

Recently heavy rainfall events are increasing in Japan. Especially during the Baiu-Meiyu rainfall season, heavy rainfall associated with quasi-stationary band-shaped precipitation systems frequently occurred. It was found that lightning frequencies were active during the heavy rainfall observed in July 2017. On the other hand, lightning frequencies were inactive during the heavy rainfall observed in the following year in July 2018. It was analyzed that convective systems were different between the two cases and that leads the difference of lightning activities. In this study 25 lightning and weather observation systems were deployed over the Southeast Asia, western north Pacific islands and Japan to monitor the lightning activities over these regions. During July 10, 2023, heavy rainfall was observed over northern Kyushu Island in Japan and rainfall amount reached 266 mm within 12 hours. Lightning was very active during the heavy rainfall. Another heavy rainfall was observed over Shikoku Island in Japan during August 9 to 10, 2023 and rainfall amount reached 638 mm within 24 hours. On the other hand, lightning activities were very weak during this case. We analyzed the difference of environmental conditions between the two cases. During the heavy rainfall in northern Kyushu case, west-southwesterly low-level wind provided moisture into the convective clouds. The origin of the moisture can be traced back to China continent. Rich amount of aerosol may lead to create more graupel in the clouds for favorable conditions for lightnings. However, heavy rainfall in Shikoku Island case, south-southeasterly low-level wind was dominant which was blown from the open ocean over the Pacific Ocean. Poor amount of aerosol moisture may suppress creating graupel in the clouds for lightning. It is similar to our previous study that we observed less lightning activity in the tropical cyclone generated far from southeast Asian islands.

Atmospheric Rivers Over East Asia During Early Boreal Summer: Role of Indo-western Pacific Ocean Capacitor

Zesheng CHEN1+, Yan DU1#, Renguang WU2, Zhiping WEN3
1Chinese Academy of Sciences, 2Zhejiang University, 3Fudan University

Atmospheric Rivers (ARs), corridors of intensive water vapor transport, have received much attention recently due to their potential large economic and societal impacts. However, a comprehensive understanding of the interannual variability of ARs over East Asia is still lacking. This study examines the frequency of AR occurrence over East Asia based on the EAR5 reanalysis. It is shown that the frequency of AR occurrence over East Asia displays obvious seasonality, with its peak in early boreal summer. ARs contribute to up to 50% of total precipitation and largely modulate the interannual variability of precipitation in East Asia during early boreal summer. The interannual variability of ARs over East Asia during early boreal summer is largely controlled by the Indo-western Pacific Ocean Capacitor (IPOC) effect, which is mainly triggered by El Niño-Southern Oscillation and sometimes by Indian Ocean dipole. During early boreal summer, a higher frequency of AR occurrence over East Asia is associated with anomalous anticyclonic circulation (AAC) over the Indo-western Pacific region. The AAC, the atmospheric signal of the IPOC mode, indicates an enhanced East Asian summer monsoon and a northwestward shift of the western North Pacific subtropical high, favoring the AR occurrence over East Asia. This study illustrates that a strong positive Indian Ocean dipole event could impact AR activity over East Asia in the following summer by triggering the IPOC effect. The IPOC-related signals 2-4 months ahead could be useful to predict the AR occurrence over East Asia during early boreal summer.

Tue-25 Jun | 8:30 - 10:30 | Luge Hall, Alpensia Convention Center
AS58 - Atmospheric Reactive Organic Carbon (ROC) and Reactive Nitrogen (RNr) and Environmental Impacts

Session Chair(s): Defeng ZHAO, Fudan University, Weigang WANG, Institute of Chemistry Chinese Academy of Science, Zhe WANG, The Hong Kong University of Science and Technology, Cheng WU, Gothenburg University

Important Roles of Oxygenated Volatile Organic Compounds in Photochemical Pollution in Hong Kong

Zhe WANG#+
The Hong Kong University of Science and Technology

Oxygenated volatile organic compounds (OVOCs) are crucial reactive pollutants with profound implications for air quality and human health. They play critical roles in tropospheric photochemistry and oxidation capacity, significantly influencing radical cycling and O3 formation. Despite their increasing recognition, the lack of precise quantification hampers a full understanding. We present an integrated study of OVOCs employing both real-time online measurement and the cartridge-based analytical method in the coastal atmosphere of Hong Kong. Using PTR-ToF-MS, we measured 83 VOC species, where OVOCs constituted the majority (77.4%) of concentrations, contributing significantly (>50%) to photochemical OH reactivity and ozone formation potential (OFP). The newly developed analytical method based on UHPLC-MS/MS identified and quantified 47 carbonyl compounds, which play a substantial role in peroxyl radical and ozone formation. Furthermore, previously unmeasured long-chain carbonyls (C≥5) and di-carbonyls, absent in conventional methods, displayed noteworthy abundance and photochemical reactivity, enhancing the O3 formation rate by up to 30%. This comprehensive study underscores the importance of OVOCs, especially carbonyl compounds, in photochemical pollution, providing insights for effective photochemical pollution control. The developed methodologies enrich our understanding of OVOC chemical composition and reactivity, augmenting our grasp of their significance in atmospheric chemistry and air quality.

Characteristics and Origins of C1–C5 Alkyl Nitrates Observed at a Coastal Site in Hong Kong

Hao SUN#+, Dasa GU
The Hong Kong University of Science and Technology

Alkyl nitrates (RONO2) constitute a vital subclass of total reactive nitrogen (NOy) within the Earth's atmosphere. These compounds play a pivotal role in atmospheric chemistry, exerting a substantial influence on air quality. The concentration of alkyl nitrates exhibits considerable variability across diverse regions of human habitation. Characterizing the variations in alkyl nitrate concentrations poses a significant challenge, essential for evaluating the intensity of photochemical reactions and discerning contributions from various sources. Hereby, we present the alkyl nitrate measurement results via canister sample collection and GC-MSD/ECD analysis at a coastal site in Hong Kong during 2021. An analysis of the source apportionment of eight C1-C5 alkyl nitrate species, employing anthropogenic and marine tracers, indicates that the predominant contributors to alkyl nitrates in Hong Kong are associated with secondary formation. Moreover, heightened contributions from biomass combustion were observed during the autumn and winter seasons. Notably, marine emissions exert a significant influence on methyl nitrate levels, particularly in the summer. Our study underscores the noteworthy impact of inland biomass burning on photochemical pollutants in Hong Kong. Consequently, recognizing the regional interdependence, cross-regional cooperation in governance within the Greater Bay Area is imperative for a more comprehensive management strategy addressing secondary photochemical pollution.

Molecular Chemical Composition and Sources of Organic Aerosol in Shanghai Based on Online Analysis

Shuhui XUE+, Defeng ZHAO#, Hao LUO, Zhuosi WANG, Hongru SHEN, Ying ZHANG, Lin WANG, Shanshan WANG, Jianmin CHEN, Chengyu NIE, Zhen SONG
Fudan University

Organic aerosols (OA) account for a large portion of atmospheric aerosols, which have played a significant role in climate change and human health. The typical sources of POA (Primary OA) like biomass burning, cooking and transportation had been obtained by different measurement techniques. The specific sources of SOA (Secondary OA) are still unclear due to limited highly sensitive and quickly responsive measurement techniques, which have been proven challenging. Source apportionment is key to understand the formation and air pollution control for policy makers. However, the detailed sources of OA in megacities are currently unclear due to lack of information of chemical composition of OA at molecular level. Particularly, specific precursors and formation processes of SOA in megacities remain largely unclear. The newly developed high-resolution online measurement technology like extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF-MS) can provide specific information of OA at molecular level. In this study, we measured chemical composition of OA at molecular level using EESI-TOF-MS at Shanghai in February to March, 2022 and investigated the sources of OA. More than 1000 organic species were detected. Twelve sources (factors) are determined on mass spectra by bin-PMF (Positive Matrix Factorization), of which seven factors are identified as POA and five factors as SOA. POA sources are identified its source based characteristic tracers and time series. SOA sources are identified by linking to their precursors and processes based detailed mass spectra, their time series, and concomitant measurement of physiochemical parameters and gas-phase species. We found that both POA and SOA contribute significantly to OA in winter at urban Shanghai. Online molecular composition in this study reveals under-appreciated sources and processes of OA in megacities. These information enables better understanding of OA sources and more effective air pollution control strategy.

AS58-A022 | Invited
Direct Determination, Characteristics, and Origins of Fine Particulate Amines at a Coastal Mountain Site in Northern China

Xinfeng WANG#+, Mingxuan LIU, Zhiyi LIU, Yueru JIANG, Min LI, Yujiao ZHU, Likun XUE, Wenxing WANG
Shandong University

Amines are important nitrogenous compounds in the atmosphere, they affect new particle formation, aerosol properties, climate change and human health. Due to the relatively high volatility, strong polarity, and low ambient concentrations, they are subjected to great difficulty in the accurate determination. In this study, a derivatization- free determination method based on HPLC-MS was developed to determine the amines in fine particle samples collected at coastal Mt. Lao in the spring of 2021. The samples were pre-treated with a non-derivatization method and separated with a hydrophilic interaction column. 16 amines were identified and quantified with the limits of detection from 0.59 to 75.46 ng mL−1 and the recovery rates ranging from 59% to 92%. The average concentration of amines at the sampling site was around 60 ng m−3. Dimethylamine was the most abundant specie with mean fraction of 27% among the quantified amines, followed by diethylamine and ethanolamine. Meanwhile, amines exhibited higher concentrations during the daytime than nighttime at the mountain site. Most amines primarily came from terrestrial activities, while TMA was mainly from marine sources. Seven source factors were identified by PMF model, including agricultural emissions, industrial production, biomass burning, coal combustion, marine emissions, traffic emissions and crustal dusts. Notably, high contributions from agricultural source and biomass burning were observed at this coastal mountain site.

Identification of Simple and Complex Nitro-aromatic Compounds Derived from Lignin Pyrolysis in PM2.5 in Urban Guangzhou Using UPLC-Orbitrap MS

Yuhuang CHENG#+, Jian Zhen YU
The Hong Kong University of Science and Technology

Lignin is a polyphenolic polymer commonly found in the supportive tissue of plants. When biomass burns, lignin can release various phenolic compounds into the atmosphere. These lignin-derived phenols can be easily nitrated due to the strong electron-donating effect of the hydroxyl group and methoxy group on their benzene ring. The resulting nitrated products are nitro-aromatic compounds (NACs), which are important components of brown carbon. While simple NACs have been identified, including 4-nitrophenol (4NP), 4-nitrocatechol (4NC), 2-methyl-4-nitrophenol (2M4NP), 3-methyl-4-nitrophenol (3M4NP), and 5-nitrosalicylic acid (5NSA), lignin-derived NACs with more and larger substituent groups on the benzene ring have received little attention. In this study, we applied a high-resolution UPLC-Orbitrap mass spectrometer (MS) system to analyze NACs in 58 ambient PM2.5 samples collected at an urban site in Guangzhou in 2013. The outstanding resolution of Orbitrap MS enabled us to identify NACs with 30 different molecular weights and more than 300 individual NACs, taking isomers into consideration. Among the simple NACs with authentic standards or quantification surrogates, the four most abundant ones were 5NSA, 4NC, 3NSA, and 4NP, with average concentrations ranging from 4.4 to 14.2 ng m-3. In addition, we classified a group of complex lignin-derived NACs, which included hydroxypropyl-dinitrophenol, dimethoxy-nitrophenol, hydroxyethyl-dinitrophenol, hydroxyethyl-nitrophenol, ethyl-nitrocatechol, and nitrovanillic acid. These compounds contain multiple substituent groups (e.g. methoxy group, hydroxypropyl group, and hydroxyethyl group) originating from lignin. We observed a strong correlation (R2 ranges from 0.50 to 0.98) between most of these complex NACs and the simple NACs throughout the entire sampling year, indicating the simple NACs likely originated from the burning of lignin. Furthermore, we detected other untargeted NACs, such as trinitrophenol and nitrobenzenetriol, in our samples.

Global Model Underestimation of Ozone Production Tied to Unknown Sources of Reactive Nitrogen and Reactive Carbon in the Tibetan Plateau

Jianshu WANG1+, Chunxiang YE1#, Haoqi WANG2, Shaojie SONG2
1Peking University, 2Nankai University

Tropospheric ozone (O3) plays a crucial role in air quality, climate change, and human health. The large span of tropospheric O3 photochemistry across various global chemical transport models hinders our ability to evaluate tropospheric O3 distribution and its environmental impacts. An in-depth understanding of O3 photochemistry relies on observational constraints on the O3 chemical budget, especially in pristine environments or free troposphere. Here we present a detailed O3 chemical budget observation at a remote site over the Tibetan Plateau. Surprisingly high production rate of peroxy radicals was observed, which was mainly attributed to oxidation reactions of oxygenated volatile organic compounds (OVOCs). Radical chain propagation rates were promoted by elevated nitrogen oxides (NOx) and further facilitated O3 production. Neither OVOCs nor NOx could be explained by their local chemical production, suggesting missing sources of them. A global chemical transport model, GEOS-Chem, underestimated both OVOCs and NOx and hence underestimated the O3 production rate by 60%. The global model also underestimated photolysis frequencies and water vapor and therefore underestimated the O3 destruction rate by 20%. Our findings indicate a need for additional observations on the fate of reactive carbon and reactive nitrogen, to improve the model's ability to predict tropospheric O3.

Photocatalytic Oxidation of Nitrogen Dioxide on Titanium Dioxide : Evidence to a Novel Heterogeneous Source for Dinitrogen Pentoxide

Yuan LIU1+, Biwu CHU2#
1University of Chinese Academy of Sciences, 2Chinese Academy of Sciences

N2O5 serves as a pivotal intermediate in the atmospheric nitrogen cycle. Utilizing a flow tube reactor, we have unveiled a previously undocumented source of N2O5 during the photocatalytic oxidation of NO2 on the TiO2 surface. The release rate of N2O5 from TiO2 was found to be contingent on initial NO2 concentration, relative humidity, O2/N2 ratio, and irradiation intensity. Both experimental evidence and quantum chemical calculations concur that NO2 can react with surface hydroxyl groups and electron holes generated on TiO2, subsequently combining with another NO2 molecule to form N2O5. This N2O5 physiosorbs on TiO2, exhibiting a low adsorption energy of -0.13 eV. Box model simulations suggest that this newfound source of N2O5 emitted from TiO2 could elevate daytime N2O5 concentrations by up to 20% in urban areas where abundant TiO2-containing materials and high NOx concentrations are co-present. Our research not only presents a novel chemical mechanism for N2O5 formation but also holds significant implications for air quality in urban settings.

Nitrogen Shares in Future Global Air Pollution and the Scope of Feasible Interventions

Yixin GUO1#+, Lin ZHANG2, Wilfried WINIWARTER3, Jinfeng CHANG4
1The Hong Kong University of Science and Technology, 2Peking University, 3International Institute for Applied Systems Analysis, 4Zhejiang University

Reactive nitrogen emissions from energy and food production (Nr; nitrogen oxides, NOx, and ammonia, NH3) contribute substantially to global PM2.5 and O3 air pollution, damaging human, ecosystem and vegetation health. To illustrate the role of Nr controls in near-term air quality management, we quantify how the shares of Nr in global PM2.5 pollution evolve from the present to the year 2050. We use the GEOS-Chem atmospheric chemistry transport model and future emission scenarios under various climate-socioeconomic pathways. We find that the phase-out of anthropogenic NH3 emissions remains necessary for achieving the WHO target for PM2.5 and that this is more effective than phasing out NOx. For more moderate Nr control levels of 25% and 50%, NHcontrols become less effective than NOx controls in many locations. This is because climate mitigation policies enable clean energy transitions thus reductions of NOx and SO2 emissions, the chemical regime shifts towards a NH3-saturated regime. The later NH3 is addressed, the more ambitious reduction level is required for effectiveness to emerge. To illustrate the technological and policy feasibility of Nr controls, we assess achievable Nr (NH3 and NOx) emission mitigation potentials and evaluate consequent reductions in global air pollution, and human and ecosystem health impacts. We construct an integrated modeling framework that combines future N intervention scenarios, integrated assessment models and the GEOS-Chem model. We find that, through improving crop nitrogen use efficiency and exploiting abatement technologies for industrial, transport and power sectors, global NH3 and NOx emissions can be reduced by 40% and 52%, respectively, of 2015 levels by 2050, generating a wide array of consequent benefits for air, yields, ecosystems and human health. Without nitrogen interventions, environmental/health objectives examined will deteriorate by 2050 compared to 2015. Nr interventions remain a key strategy for improving global environmental health that should not be overlooked.

Tue-25 Jun | 8:30 - 10:30 | Pyeongchang Hall I, Alpensia Convention Center
AS31 - Urban Greenhouse Gases Monitoring: Observation, Modeling, and Application

Session Chair(s): Jooil KIM, Scripps Institution of Oceanography, UC San Diego

Evaluating the Carbon Absorption Capacity of Urban Forests by GPP Quantification based on Multi-scale Observations

Jangho LEE#+, Sujong JEONG
Seoul National University

Vegetation in urban areas, referred to as ‘urban forests’, is recognized as a localized carbon sink for removing a considerable amount of atmospheric CO2 and the areas of them are changing as urbanization accelerates. Thus, quantifying the carbon uptake of vegetation in urban areas is necessary for improving GHG inventories in cities. Given that the carbon sequestration of urban forests is calculated based on coarse spatiotemporal resolution statistics, the carbon absorption capacity of urban forests is often inadequately quantified and easily overlooked. However, there are limited studies estimating GPP in urban forests due to substantial variation in environmental factors directly related to photosynthesis in cities and the difficulties of obtaining data that can isolate the influence of vegetation. Therefore, we deployed hyperspectral devices (FloX, JB Hyperspectral Devices) to observe Solar-induced chlorophyll fluorescence (SIF) and Eddy covariance system instruments to measure CO2 fluxes together in two urban forests (Changgyeongung and Namsan Park) in Seoul to explore the carbon uptake capacity of urban forests. We primarily analyzed seasonal trends in Net Ecosystem Exchange (NEE) using CO2 flux data to examine whether or not urban forests are carbon sinks. By comparing canopy-level SIF with satellites SIF on the same date, along with the CO2 flux, we found ground-observed SIF can represent the dynamic plant physiological responses. Subsequently, we attempted to quantify GPP at these multi-scale observation sites by partitioning NEE and Soil Canopy Observation of Photosynthesis and Energy fluxes (SCOPE) model simulation. This study holds significance in utilizing diverse scale observational data to help us understand the physiological function and responses of urban forests and improve GHG inventories within cities. Additionally, it introduces the first multi-scale observation site that simultaneously measures CO2 flux and SIF in the same urban forests, emphasizing the need for high spatiotemporal resolution data through the ground-based observation network.

Practical Application of AICAN (Asian Initiative for Clean Air Networks) Against Episodes of Wildfires, Fireworks, and High PM

Chan Ryul PARK#+, Hong-Duck SOU, Daun RYU, Jinsuk JEONG
National Institute of Forest Science

Tree and forests can have a potential to abate the fine dust through the adsorption and deposition under the tree canopy against episodes of wildfire, fireworks and high PM in a city. During high PM episodes in Winter and Spring, most peoples do hesitate to take a field activity of walking, trekking, and climbing in hilly and mountainous landscapes dominated by 63.5% of forests in Korea. Thus, National Institute of Forest Science (NIFoS) has been established Asian Initial for Clean Air Networks (AiCAN) across the Korean Peninsula (44 locations, 132 points) to measure TSP, PM10, PM2.5, PM1.0 and meteorological factors (wind velocity, relative humidity, and temperature) with the equipment of GRIMM EDM 365 from 2019 to 2022. All observation data was monitored in ten minutes interval and the maintenance process of equipment was followed by the legislation of Korean Government. We analyzed the annual amount of PM reduction by forests comparing with the observation point between forests and urban by the analysis of AiCAN dataset. The PM reduction in the forest was the highest in spring and winter when high PM concentrations were observed, and the annual PM10 and PM2.5 were reduced by 32.9kg/ha and 22.7kg/ha in 2021, 26.4kg/ha and 19.3kg/ha in 2022, 29.2kg/ha and 18.9kg/ha in 2023. In consideration of theoretical value was estimated as 46kg/ha, the observation values were distributed at the range of theoretical values. This abatement could be attributed to the effects on absorption, adsorption, blocking, and deposition of fine dusts under tree canopy of forests. NIFoS will utilize this platform to understand the interaction between forests and aerosol not only for predictable and controlled Events of high PM episodes, yellow dusts, heat waves, and typhoon, also un-predictable and un-controlled events of wildfires and fireworks.

Enhancing Methane Inventory Accuracy in Urban Waste Sector: A Case Study in Seoul

Donghee KIM#+, Sujong JEONG, Dong Yeong CHANG
Seoul National University

Methane (CH4) is important greenhouse gas with a high Global Warming Potential (GWP) that significantly contributing to climate change. In urban, methane emissions are mainly come from the energy and waste sectors. This study aims to enhancing our understanding of methane emissions from the waste sector, especially solid waste disposal, as a major contributor to total urban methane emissions. Landfills, a key source in the waste sector, substantially contribute to methane emissions through the decomposition of organic waste. The emissions are influenced by weather conditions, but existing methane inventories inadequately consider this variability. In this study, we introduce an improved methane inventory methodology that includes meteorological conditions, offering a more comprehensive representation of methane emissions. In the context of Seoul, we present spatiotemporally high-resolution methane inventories derived from the waste sector. The results show a significant increase in methane emissions during the spring and summer seasons, emphasizing the seasonal variability associated with waste decomposition processes. This detailed understanding is crucial for effective urban methane management. The implementation of our methodology holds significance in improving the accuracy of methane emission estimates from the waste sector. By integrating weather conditions into the methane inventory, this study contributes to a more improved understanding of methane emissions in urban area. This enhanced methodology can support the development of more effective waste management policies and strategies to mitigate methane emissions, addressing climate change in urban environments.

Quantifying and Attributing Methane Emissions from Coal Mine Aggregation Areas Using High-frequency Ground-based Observations

Fan LU+, Kai QIN, Jason COHEN#
China University of Mining and Technology

This work introduces the results of an intensive 15-day surface observation campaign of methane (CH4) and adapts a new analytical method to compute and attribute CH4 emissions. The selected area has a high atmospheric concentration of CH4 (campaign-wide minimum/mean/standard deviation/max observations: 2.0, 2.9, 1.3, and 16 ppm) due to a rapid increase in the mining, production, and use of coal over the past decade. Observations made in concentric circles at 1km, 3km, and 5km around a high production high gas coal mine were used with the mass conserving model free emissions estimation approach adapted to CH4, yielding emissions of 0.73, 0.28, and 0.15 ppm/min respectively. Attribution used a 2-box mass conserving model to identify the known mine’s emissions from 0.042-5.3 ppm/min, and a previously unidentified mine’s emission from 0.22-7.9 ppm/min. These results demonstrate the importance of quantifying the spatial distribution of methane in terms of control of regional-scale CH4 emissions.

Significant Methane Emissions from Urban Manholes

Jaewon JOO+, Sujong JEONG#, Jaewon SHIN, Dong Yeong CHANG
Seoul National University

Sewer networks are one of the major sources of greenhouse gas (GHG) emissions in urban areas. However, they are currently missing in South Korea's national GHG inventory. Here, we measured atmospheric methane emissions from urban sewer networks in old residential and commercial areas of Seoul (Gwanak district) using a GHG monitoring platform consisting of the electric vehicle and GHG monitoring instruments such as methane (CH4), and ethane (C2H6). The results of this research showed significant CH4 emissions of about 573 [395-831] CH4 t y-1 from sewers through the manholes and rain gutters. The CH4 emissions in the study area are primarily due to microbial activity within the sewer networks, as suggested by the majority of C2:C1 ratios being below 0.005. This is because more than 90% of the sewer network in Seoul is a gravity drain type of combined sewer network, resulting in the generation of CH4 emissions from the microbial activity. Thus, manholes and rain gutters, which are directly connected to the combined sewer networks are major sources of atmospheric methane emissions in Seoul. The results of this study suggest that proper treatment of sewer networks especially manholes and rain gutters are required to mitigate the one of the significant methane emissions in urban areas of South Korea. This work was supported by Korea Environmental Industry & Technology Institute (KEITI) through "Project for developing an observation-based GHG emissions geospatial information map", funded by Korea Ministry of Environment (MOE)(RS-2023-00232066).

Eddy Covariance Measurements of Methane Flux in Urban Beijing

Yibo HUANGFU1#+, Bin YUAN1, Xianjun HE1, Ziyang LIU1, Thomas KARL2, Martin GRAUS2, Marcus STRIEDNIG2, Xiaodong CHEN3, Hongjuan LI3, Min SHAO1
1Jinan University, 2University of Innsbruck, 3Ausao Ecological Instrument Co., Ltd.

Methane was recognized as one of the most important greenhouse gases after carbon dioxide. Accurate estimation of methane emission is the key to establishing a reasonable and effective reduction target and strategy for achieving the goal of limiting global warming to 1.5 ℃ within reach. Using the eddy covariance technique, methane flux was measured at a meteorological tower in Beijing, China in the summertime to increase the understanding of methane emission in urban regions. The footprint climatology (90% contour lines) demonstrates that the measured flux can represent the summer emission characteristics of ~70 km2 of surrounding areas categorized as the typical urban landscape in the megacity of Beijing. The quality assurance and quality control results show more than 50% of the flux data can be labeled with high quality. Compared with the methane flux measured in other cities, the methane flux measured in Beijing, 152.6 ± 107.9 nmol/m2/s, was relatively large. There was no significant diurnal pattern and no clear correlation between methane flux and temperature/solar radiation can be found, which suggests that the biogenic source might not be the dominant source of methane within the footprint area. Constant background emission due to natural gas leakage was likely the main contributor. 

Carbontracker-CH4: NOAA’s Atmospheric Assimilation System for Estimating Methane Emissions Consistent with Measurements of Methane and Its Isotopes

Youmi OH1#, Lori BRUHWILER1, Xin LAN1, Sourish BASU2, Sylvia MICHEL3, John B. MILLER1+, Arlyn ANDREWS1
1NOAA Global Monitoring Laboratory, 2NASA Goddard Space Flight Center, 3University of Colorado Boulder

Atmospheric methane (CH4) is currently more than 160% above pre-industrial levels, and the 2020-2022 growth was the fastest since systematic measurements started in the 1980s. This rapid increase is a challenge for reaching the climate mitigation goals of the Global Methane Pledge from COP26, which requires steep cuts in CH4 emissions by 2030. Slowing or reversing the accelerating growth in atmospheric CH4 will require an improved understanding of the anthropogenic and natural CH4 budget, which is currently underconstrained. We have improved our understanding of the global CH4 budget via precise measurements of 13C:12C (δ13C-CH4), a tracer capable of separating fossil and microbial emissions. When atmospheric CH4 increased rapidly after 2006, δ13C-CH4 decreased after increasing for the last 200 years, indicating that the CH4 rise has been dominated by microbial sources such as wetlands and agriculture, not fossil fuels. To provide quantitative estimates of global CH4 emissions that are consistent with observed patterns of atmospheric CH4 and δ13C-CH4, we updated CarbonTracker-CH4 by jointly assimilating atmospheric measurements of CH4 and δ13C-CH4, optimizing source-specific fluxes at a grid-scale, and extending our estimation from 1997 to 2021.Our inversion shows that the global CH4 emission has increased more than 100 Tg yr-1 since 2000 and reached ~650 Tg yr-1 in 2021, and the large long-term increase was from Asia and North America regions. We find that the dual-tracer inversion of CH4 and δ13C-CH4 attributes the growth in atmospheric CH4 in 2020-2021 to a large increase in microbial sources and a slight decrease in fossil sources. The large increase in emissions was mostly from the tropical and Eurasian regions. In contrast, the inversion that uses CH4 data only does not match atmospheric δ13C-CH4 and simulates an increase in fossil sources in 2020-2021. All our results are publicly available at

Characteristics and Origins of CH4, CO2 and CO Observed at a Coastal Site in Hong Kong

Wai Ming CHAN1+, Dasa GU1#, Ka Fung LEUNG1, Yuchen MAI1, Sin Ka MAK1, Hao SUN1, Xin LI1, Xiangyunong CAO1, Tsz Ching TSE1, Zhenxing LIANG1, Zijie XU1, Donald BLAKE2
1The Hong Kong University of Science and Technology, 2University of California, Irvine

The industrial revolution escalated greenhouse gas (GHG) emissions, driving climate change to a critical juncture that necessitates immediate action. Monitoring essential GHGs like CO2 and CH4 is imperative for comprehending their impact on the climate system. East Asia, with high energy consumption and robust industrial activity, is a significant GHG emitter, emphasizing the need for meticulous monitoring. While CO is not a direct GHG, it reacts with atmospheric OH radicals, affecting the lifetime of CH4 and influencing radiative forcing and the global climate. CO is an important trace gas of combustion processes and industrial activities, providing insights into the sources of CH4 and CO2. Thus, monitoring CH4, CO, and CO2 enhances our understanding of climate change and, to a lesser extent, improves air quality, yielding dual benefits. To investigate the characteristics of CH4, CO2, and CO, we established a sampling and instrumental analysis system at the Hong Kong University of Science and Technology. Observation results revealed pronounced seasonality, with higher concentrations in the cold season and lower concentrations in the warm season for all three gases. Non-parametric wind regression and the HYSPLIT back trajectory model indicated that continental air masses carried more concentrated gases, while oceanic air masses contributed to local air dilution. Fluctuations around the background level showed a strong correlation between CH4 and CO, while CO2 exhibited a lower correlation with the other two. This suggested distinct sources in Hong Kong compared to typical Chinese cities, where CO2 and CO exhibited a higher correlation usually. Further analysis utilizing the Potential Source Contribution Function (PSCF) identified Central and East China, as well as northern Guangdong, as major source regions for CH4 and CO, with Central China being the dominant source region for CO2. These findings provide valuable insights for developing effective carbon neutrality policies in Hong Kong and China.

Comprehensive Monitoring of Urban Greenhouse Gases and Air Quality Using Observations from Ground to Space: The Seoul-Tokyo EM27/SUN Campaign

Hayoung PARK1#+, Sujong JEONG1, Jin-Soo PARK2, Matthias FREY3, Hiroshi TANIMOTO3, Isamu MORINO3, Hirofumi OHYAMA3, Astrid MUELLER3
1Seoul National University, 2National Institute of Environmental Research, 3National Institute for Environmental Studies

Seoul and Tokyo, as major global contributors to greenhouse gas emissions and air pollutants, are focal points for emission reduction initiatives with significant implications for global climate change mitigation. In the winter of February 2022 and 2023, Seoul National University Climate Lab and the National Institute for Environmental Studies (NIES) conducted an extensive observational campaign in both cities using portable ground-based FTIR spectrometers, EM27/SUN, offering a comprehensive analysis of column-averaged dry air mole fractions of CO2, CH4, and CO (XCO2, XCH4, XCO). In addition, we incorporated integrated observations of CO2, CH4, and CO concentrations using ground-aircraft-satellite measurements intensively carried out in Seoul to monitor greenhouse gases and air quality in a megacity. We analyze the spatial distributions and variations of greenhouse gases and air pollutants within the urban area of Seoul, as well as assess the emission characteristics using a combination of the Column-Stochastic Time-Inverted Lagrangian Transport model (X-STILT) and ratio analysis. This study presents results from the two-year campaign, offering a comparative analysis of greenhouse gas concentrations in Seoul, South Korea and Tokyo, Japan. Overall, this research aims to monitor the current atmospheric conditions in the two major cities, as well as to analyze the three-dimensional structure of greenhouse gases and air pollutants in Seoul.

Tue-25 Jun | 8:30 - 10:30 | Daegwallyeong II, Alpensia Convention Center
AS11 - Extreme Events: Observations and Modeling

Session Chair(s): Venugopal VURUPUTUR, Indian Institute of Science, Bangalore, Sridhara NAYAK, Japan Meteorological Corporation

Exploring the Asian Australian Monsoon Rainfall Extremes via Moisture Transport Patterns with Insights from Explainable Machine Learning

Jia Xin GUO+, Wei-Ting CHEN#
National Taiwan University

The Asian Australian Monsoon (AAM) region, characterized by abundant precipitation and hydrological extremes, necessitates in-depth explorations of crucial synoptic environmental factors influencing extreme rainfall events. Building on previous research highlighting moisture content and low-level dynamic flow, we developed a data-driven framework using Variational Autoencoder (VAE), an unsupervised and explainable machine learning model, to dissect prominent moisture transport patterns and explore their linkage to extreme precipitation emergences. The vertically-integrated water vapor transport (IVT) from ECMWF Reanalysis v5 (ERA5) is adopted as the primary indicator of moisture environment. Through VAE, daily fields of IVT spanning from 2001 to 2019 are encoded into two-dimensional vectors on a continuous latent space and classified into different regimes. Each latent dimension captures the seasonal progression and synoptic to sub-seasonal variability, respectively, of the large-scale moisture transport pattern. The heat maps of extreme rainfall occurrence derived from Integrated Multi-satellitE Retrievals of Global Precipitation Measurement (IMERG) 0.5-hourly data reveal distinctive patterns across various moisture transport regimes. This hints a potential correspondence between distinct extreme rainfall distributions and specific moisture transport configurations in the AAM region. Detailed investigations into each moisture transport regime, employing composite analyses of synoptic fields and tropical variability indices, elucidate the modulation of moisture transport and the possible mechanisms in influencing extreme rainfall emergence. The current VAE model serves as a foundational step in interpreting the primary factors driving variations in moisture transport patterns and offers the opportunity for estimating future changes in extreme convective systems' hotspots using the “storyline approach”, given the higher confidence in synoptic flow modeling in General Circulation Models. Results and discussions based on CMIP6 models will also be presented to provide valuable insights to the broader scientific discourse on extreme rainfall events in the AAM region.

Glo3DHydroClimEventSet(v1.0): A Global‐scale Event Set of Hydroclimatic Extremes Detected with the 3D DBSCAN‐based Workflow (1951–2022)

Zhenchen LIU#+, Wen ZHOU
Fudan University

The emergency of global‐scale hydroclimatic extremes (i.e., meteorological droughts, extreme precipitations, heat waves and cold surges) and associated compound events has recently drawn much attention. A global‐scale unified and comprehensive event set with accurate information on spatiotemporal evolutions is necessary for better mechanism understanding and reliable predictions in sequential studies. Accordingly, this manuscript describes the first‐generation global event‐based database of hydroclimatic extremes produced with the newly proposed 3D (longitude–latitude–time) DBSCAN‐based workflow of event detection. The short name of this database is Glo3DHydroClimEventSet(v1.0) , which is obtained from the FigsharePlus webpage ( ). The 1951–2022 ERA5‐based multiscale and multi‐threshold daily running datasets of precipitation and near‐surface air temperature are calculated and employed as the input data. A comprehensive event set of hydroclimate extremes is the output of the 3D DBSCAN‐based workflow. From perspectives of spatiotemporal evolutions, this event‐based database is also measured and attached with metric information. For case‐based validation, some recently reported hydroclimatic extremes (e.g., the 2020 summertime flood‐inducing Yangtze River extreme precipitation event) are employed and accurately detected in the Glo3DHydroClimEventSet(v1.0) database. Meanwhile, global‐scale spatiotemporal distributions are preliminarily analysed. For example, global‐scale event counts of extreme heatwaves displayed an increasing tendency since 2005, with a rapid increase after 2010. To sum up, this Glo3DHydroClimEventSet(v1.0) database may facilitate new scientific achievements concerning event‐based hydroclimatic extremes, especially in communities of atmosphere, hydrology, natural hazards and associated socioeconomics. The DOI-based paper linkage is

Typical Synoptic Patterns Responsible for Summer Regional Hourly Extreme Precipitation Events Over the Middle and Lower Yangtze River Basin, China

Jingwen ZENG#+, Anning HUANG, Danqing HUANG
Nanjing University

Based on the hourly rainfall gauge data and ERA5 reanalysis for the period 1980–2020, typical synoptic patterns responsible for summer regional hourly extreme precipitation events (RHEPE) over the middle and lower Yangtze River basin have been objectively identified using a circulation clustering method. It is found that the Meiyu front with different locations and intensities imbedded in the East Asian summer monsoon, and landfalling typhoons are the leading contributors. As the dominant synoptic pattern, the Meiyu front pattern is associated with ∼92% of the total RHEPE occurrence and can be categorized into a southerly strong-Meiyu type and a northerly weak-Meiyu type. The RHEPE occurrence shows a predominant morning peak associated with the southerly strong-Meiyu type and a secondary late afternoon peak related to the northerly weak-Meiyu type, in which the Meiyu front is pushed northward by the strengthened western North Pacific subtropical high accompanied by accelerated low-level southwesterly flow

Interannual Variability and Drivers of Extreme Precipitation Over the Yangtze River Basin

Yucong LIN#+
Ca' Foscari University of Venice

Utilizing ERA5 reanalysis data, we carried out a series of analyses to investigate the spatiotemporal characteristics of extreme precipitation over the Yangtze River Basin (YRB) and the major drivers influencing the interannual variability of summer extreme precipitation during 1950-2021. The results indicate that anomalous anticyclones/cyclones over the western North Pacific (WNP) and El Niño/La Niña like sea surface temperature (SST) patterns in the preceding winter are associated with increased/decreased summer extreme precipitation over the YRB. Furthermore, the El Niño and Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD), and the anomalous Indian Ocean Basin Warming (IOBW), which occur in boreal autumn/winter, are shown to have delayed effects on the YRB's extreme precipitation in the subsequent summer. Both ENSO and IOD have the capability to generate anomalous anticyclones/cyclones over the Western North Pacific (WNPAC/WNPC), which in turn can enhance or diminish water vapor transport, leading to an increase or decrease in summer extreme precipitation over the YRB. However, the impact of negative ENSO-IOD forcings is generally weaker than that of positive forcings. The persistence of the abnormal tropospheric WNPAC/WNPC is primarily driven by local thermodynamic forcing and feedback from the IOBW. It is noteworthy that only strong ENSO events can trigger the anomalous IOBW, resulting in more pronounced responses in summer extremes. Notably, the negative ENSO-IOD phases yield non-linear outcomes, thus offering less robustness for the predictability of summer extremes over the YRB. This study provides valuable insights into the interannual variability of summer extreme precipitation in the YRB, highlighting the key predictors and physical mechanisms responsible for these variations. Keywords: Yangtze River Basin; extreme precipitation; ENSO; IOD; Indian Ocean Basin Warming; WNPAC.

The Spatiotemporal Distribution and Evolution of Short-term Intense Precipitation in China

Shoujuan SHU#+
Zhejiang University

Based on meteorological observation from stations over the past thirteen years, China was divided into seven regions: Central China, East China, Southwest China, Southeast China, North China, Northeast China, and Western China. A study was conducted on the spatial and temporal distribution characteristics and their evolution of short-duration intense precipitation in China. The results found that the occurrence of short-duration intense precipitation in China is seasonal, mainly occurring in spring and summer, and primarily concentrated from May to September. Among them, the southern regions have the highest frequency in summer, followed by East China and Central China, then the eastern coastal areas of North China and the southern coastal areas of Northeast China, with the Western region having a very low frequency. In terms of daily occurrence of short-duration intense precipitation, it occurs mostly in the early morning in the Southwest and Central China; while in the downstream Southeast and East China, it mainly occurs in the afternoon, with the highest frequency in coastal areas. In the plains of Northeast China, it also occurs mainly in the afternoon, but with a frequency far less than that of the Southeast and Southwest regions. In the plains of North China, there is no significant difference in the daily time period of occurrence, with occurrences in the early morning, afternoon, and evening. In terms of average intensity of short-duration intense precipitation, the Southeast and North China regions are more intense than other regions. The early morning short-duration intense precipitation in the Southwest and Central China has an eastward transmission characteristic, showing that after the convective cell is generated, it moves eastward, and intensifies in the afternoon upon reaching East and South China. Over the thirteen years, the occurrence of short-duration intense precipitation has shown different evolutionary characteristics in different regions.

Impact of Aeolus Wind Data Assimilation on a Heavy Rain Forecast

Japan Meteorological Agency

As the first satellite mission to give wind profile information on a global scale, Aeolus was launched in 2018, and its horizontal line of sight wind data has been available from the European Space Agency (ESA) Earth Online Portal since May 2020. The significant positive impact of this data on numerical weather prediction has been reported in many researches (Rennie et al., 2021; George et al., 2021). We presented about the assimilation impact on JMA’s global data assimilation and forecasting system and the impact on typhoon forecasting in AOGS 2021 and 2022 (Okabe and Okamoto 2024, accepted). We have started investigating the assimilation impact on heavy rain forecasts using both global and regional data assimilation systems. The configuration of the control experiments (CNTLs) in these assimilation experiments mirrored the operational global system as of December 2019 and the operational regional system as of April 2020 of the Japan Meteorological Agency. The test experiments (TESTs) were the same as CNTLs except the use of Aeolus data. The target event is the heavy rainfall incident that struck Kumamoto and Kagoshima prefectures on the southern Japanese island of Kyushu, on July 4th, during the heavy rain events of July 2020 in the middle of the Baiu season (the East Asian rainy season). As a result of flooding and landslides, more than seventy people were confirmed dead, and approximately 15,000 buildings were destroyed, damaged or flooded. In the TEST of the global experiments, the positional error in heavy rain forecasts has been slightly improved. The investigation into the assimilation impact in the regional experiments is ongoing. The detailed results will be shown in the presentation.

Evaluation of WRF Land Surface Model Accuracy in Sub-seasonal to Seasonal Rainfall Prediction Skill Across Thailand

Kritanai TORSRI1#+, Chakrit CHOTAMONSAK2, Duangnapha LAPYAI2, Kevalin INLAUNG2, Punnathorn THANADOLMETHPHORN2, Rati SAWANGWATTANAPHAIBUN 1, Pattarapoom PEANGTA1, Apiwat FAIKRUA1, Jakrapop AKARANEE1
1Ministry of Higher Education, Science, Research and Innovation, 2Chiang Mai University

This study assesses the WRF model's accuracy in predicting sub-seasonal to seasonal rainfall in Thailand, specifically focusing on the performance using Noah and Noah-MP land surface models. The research aims to contribute insights into the WRF model's efficacy for sub-seasonal to seasonal rainfall prediction, improving understanding and reliability for the region. The analysis utilizes weekly summer rainfall data with a fine 5 km resolution nested domain driven by CFS Reanalysis data. The study centers on a selected 2021 summer monsoon event marked by a strong Madden-Julian Oscillation. Evaluation of model predictions for six sub-regions reveals increased rainfall in Weeks 2 and 9, generally aligning with observations. Discrepancies exist, particularly in the model's overestimation in the east and south but accurate predictions in the southwest. Probability Distribution Function plots highlight divergent rainfall patterns. Noah-MP outperforms Noah, suggesting its suitability for refining the model to enhance rainfall predictions in Thailand.

Can a 12 KM Global Model Simulate the Observed Cloud Microphysical and Extreme Rainfall Relationship of Indian Summer Monsoon?

Tanmoy GOSWAMI#+, Parthasarathi MUKHOPADHYAY, R. Phani Murali KRISHNA
Indian Institute of Tropical Meteorology

The increase in the frequency of extreme precipitation in different parts of the world is well documented and a cause for concern in terms of global climate change. Although clouds are the only source of precipitation, there is a lack of knowledge about the type of clouds involved in extreme precipitation events. Observations by MODIS and IMD show that over the central Indian region (19oN-26oN, 75oE-85oE), about 60% of the extreme precipitation comes from deep convective clouds (DCC), which have a cloud top pressure (CTP) of less than 440 hPa and an optical cloud thickness (COT) of over 23. It was also observed that cloud water liquid (CWL) and COT show the highest correlation with extreme precipitation and also show the highest contrast between extreme and non-extreme precipitation events. Simulations (hindcast) of a global 12KM model are also analysed for extreme precipitation events. It is found that the model underestimates the threshold for extreme precipitation (99th percentile climatology) with increase of lead time. Simulations of the associated cloud optical parameters also deteriorate with increasing lead time. The model tends to overestimate the convection and cloud water liquid during an extreme precipitation event. The model also fails to capture the observed relationship between the frequency of extreme precipitation and the frequency of deep convective clouds and shows no correlation between them at all lead times.

Tue-25 Jun | 8:30 - 10:30 | Auditorium, Alpensia Convention Center
AS04 - The Asian Monsoon and Climate Change

Session Chair(s): Jai-Ho OH, Nano C&W, Lakshmi Kumar T. V., Jawaharlal Nehru University

AS04-A063 | Invited
Causes of 2022 Pakistan Flooding and Its Linkage with China and Europe Heatwaves

Huang-Hsiung HSU1#+, Chi-Cherng HONG2, An-Yi HUANG 3, Wan-Ling TSENG1
1Academia Sinica, 2University of Taipei, 3Oregon State University

In boreal summer of 2022, Pakistan experienced extremely high rainfall, resulting in severe flooding and displacing over 30 million people. At the same time, heatwaves persisted over central China and Europe. The coexistence of these extreme events suggests a possible linkage. Our analysis indicated that the record rainfall was mainly induced by compounding factors. These included (1) La Niña-induced strong anomalous easterlies over the northern Indian subcontinent, (2) intense southerlies from the Arabian Sea with an upward trend in recent decades, (3) an interaction between extratropical and tropical systems, specifically the northerly flow downstream of the Europe blocking and the southerly monsoon flow from the Arabian Sea. Wave activity flux and regression analyses unveiled a distinct stationary Rossby wave-like pattern connecting the flooding in Pakistan and heatwaves in Europe and China. This pattern, an emerging teleconnection pattern in recent decade, exhibited substantial differences from the reported teleconnection patterns. We also noted the positive feedback of the excessive Pakistan rainfall could further enhance the largescale background flow and the heavy rainfall itself. The 2022 Pakistan flood event was an intensified manifestation of the 2010 Pakistan flood event, which was also caused by compounding factors, but occurred in a more pronounced upward trend in the both tropics and extratropics.

Moisture Dynamic Processes Driving the Westward Propagation of Quasi-biweekly Oscillation in Asian Tropical Summer Monsoon Rainfall

Weizhen CHEN1+, Song YANG1, Wei WEI1#, Yuhao CAI1, Zeming WU2
1Sun Yat-sen University, 2Zhejiang University

The quasi-biweekly oscillation (QBWO) is an important component of tropical monsoon variations. The QBWO rainfall demonstrates a westward propagation chain from the western North Pacific to the Arabian Sea. Specifically, a delay of about 2 days is observed in the rainfall increase over the Bay of Bengal following an increase over the South China Sea. The mechanisms for the development of QBWO rainfall in the Asian tropical monsoon region is revealed by a moisture budget analysis. Positive specific humidity anomalies are primarily induced by the leading horizontal moisture advection at the lower level. The interaction between QBWO anticyclones circulation anomalies and mean moisture gradient facilitates the increase of moisture in the Asian tropical monsoon region, thereby instigating the westward extension of QBWO. Furthermore, the mean zonal cross-equatorial flow also contributes to the moisture transportation dynamics. The westward propagation chain revealed may benefit the subseasonal rainfall prediction in the Asian tropical monsoon region.

Middle East Warming in Spring Enhances Summer Rainfall Over Pakistan

Lei ZHOU1#+, Baosheng LI2, Jianhuang QIN3, Tianjun ZHOU4, Dake CHEN2, Shugui HOU1, Raghu MURTUGUDDE5
1Shanghai Jiao Tong University, 2Ministry of Natural Resources, 3Hohai University, 4Chinese Academy of Sciences, 5University of Maryland

The South Asian summer monsoon is one of the most spectacular monsoon systems in the world. It affects the production and lives of billions of people. Climate change is reshaping the spatial distribution of summer monsoon rainfall. This study has found that rainfall over Pakistan and northwestern India during the summer monsoon has increased by 46% from 1979 to 2022 and is increasing at a rate of 0.4-0.6 mm/day per decade. The enhancement of summer rainfall on the edge of the South Asian monsoon is mainly caused by the rapid warming in spring over the Middle East. The Middle East is one of the most significant regions in terms of global warming, which is found to be 0.5 K per decade during spring. The spring Middle East warming can trigger a decrease in sea level pressure in the region and result in the enhancement of the cross-equatorial winds, which in turn leads to the emergence of low-level jet (LLJ) winds in spring. This process persists until the onset of the summer monsoon, when the LLJ is further strengthens and shifts northward. Since LLJ transport boatloads of moisture into the subcontinent, the northward shift of the LLJ results in the excess supply of moisture to Pakistan and northwestern India. This new research implies that arid and semi-arid countries and regions such as Pakistan and northwestern India, which are on the edge of the monsoon, are now exposed to frequent heavy rainfall events. This will lead to more disasters like the 2022 Pakistan Floods with unacceptably high loss of life and property.

The Synergistic Effect of the Preceding Winter Mid-latitude North Atlantic and Summer Tropical Eastern Indian Ocean SST on Extreme Heat Events in Northern China

Hao WANG1+, Jianping LI1#, Fei ZHENG2
1Ocean University of China, 2Sun Yat-sen University

Summer extreme heat events happen frequently in northern China (NC) during recent decades, which have serious impacts on the society and ecosystem. The present study reveals that there is a synergistic effect of the preceding winter positive mid-latitude North Atlantic SST anomaly (pMNA SSTA) and summer negative tropical eastern Indian Ocean SST anomaly (nTEI SSTA) on strengthening the summer extreme heat events in NC. The extreme heat events are stronger and more frequent when the two factors cooccur, and the probability of a strengthened extreme heat events is higher, which indicates a synergistic effect of the two factors. The preceding winter pMNA SSTA and summer nTEI SSTA exert their synergistic effect through a series of atmospheric and snow cover bridges. The preceding winter pMNA SSTA could lead to an anomalous anticyclone over central Asia via the eastward propagating Rossby wave, which decreases snowfall and the subsequent snow cover there. The negative snow cover anomaly may persist into spring and induce a local anomalous anticyclone in summer via the snow-hydrological effect, which is accompanied by an atmospheric teleconnection featured with an anomalous cyclone over West Siberia and an anomalous anticyclone over NC. The summer nTEI SSTA can also induce the anomalous anticyclone there via the Rossby wave propagation. Thus, the two factors exhibit evident synergistic effect on the atmospheric circulation anomaly over NC. The anomalous anticyclone corresponds to the increased atmosphere thickness, which favors the increase of air temperature in NC and the strengthening of extreme heat events. Therefore, the preceding winter pMNA SSTA and summer nTEI SSTA have significant synergistic effect on strengthening the summer extreme heat events in NC.

The Quadrupole Precipitation Pattern Over Eastern China and its Associated Atmospheric Circulations and Ocean Conditions

Yuting LIU+, Danqing HUANG#
Nanjing University

The purpose of this study is to understand the regime shifts of the East Asian summer monsoon precipitation in different warming periods. We revealed a new precipitation pattern over eastern China as a “+ - + -” precipitation pattern from south to north. The circumglobal teleconnection, the negative phase of the interdecadal Pacific oscillation, the warming over the high-latitude North Atlantic, and the warming over Northern Hemisphere can be used to explain the quadrupole precipitation pattern. These findings could highlight the role of jet streams linking the quadrupole pattern to the teleconnections, dominant decadal ocean variabilities and the warming over Northern Hemisphere. 

Intensification of the East Asian Summer Monsoon Lifecycle: Dynamics of Consecutive Compound Wet and Hot Extremes

Suyeon MOON1+, Hyungjun KIM2,1#
1The University of Tokyo, 2Korea Advanced Institute of Science and Technology

Serving as the lifeblood, summer monsoon precipitation fuels agriculture, industry, and daily life in East Asia (EA). Yet, its dark side emerges when severe events batter densely populated regions, causing havoc and disaster. In recent years, South Korea, China, and Japan have all faced the wrath of extreme precipitation events. We zoom into the role of stationary front-induced precipitation, a key character that shapes more than 40% of EA’s summer rainfall narrative. Sifting through observations from 1958 to 2015, we have found a 19.8% surge in the intensity of frontal rainfall. With the Large Ensemble simulations, we have untangled the role of anthropogenic greenhouse gas forcing impact, revealing it as the primary cause behind the amplified EA summer frontal rainfall. Behind this intensification, two culprits emerge: the amplified western North Pacific subtropical high (WNPSH) and increased water vapor convergence. In addition to the enhanced frontal rainfall, the hot extremes have become more severe in the subsequent season. The westward and northward expansion of WNPSH evokes the hot extremes over EA. Our findings suggest that human-induced global warming is radically reshaping the EA summer wet and hot extremes, by sharing a key regional climate mechanism. This transformation is likely to continue, potentially redefining the future of summer extremes in EA.

Monsoon Onset Mechanism and Its Reproducibility in Global Climate Models

Yoshiyuki KAJIKAWA1#+, Tsuyoshi YAMAURA2
1Kobe University, 2RIKEN Advanced Institute for Computational Science

Monsoon onset signifies the commencement of the rainy season and the reversal of wind circulation over the Asian monsoon area. The factors of the monsoon onset include the thermal condition and arrival of disturbances (e.g. tropical cyclones, Intraseasonal variability). While the prediction of the monsoon onset timing remains a challenging issue, the Cloud system resolving global climate model (CRGCM), which has the advantage of reproducing the tropical disturbance, shows the potential to extend the predictability of the onset timing. Here, we analyze the historical experiment of the Global climate model (MIROC) and CRGCM (NICAM) with prescribed observed SST, especially focusing on the monsoon onset. The results show less reproducibility interannual variability. Of interest is the significant negative interannual correlation between seasonal mean Indian summer monsoon (ISM) strength and the ISM onset timing (summer monsoon tends to be stronger following the early onset) in the GCM and CRGCM while the observational data does not show such significant interannual relation. The ISM system in the model might be mainly driven by the thermal condition in longer persistency. We will discuss the effects of less intraseasonal activity in the model and advance the comprehensive understanding of the combinational effects of different time scale variations such as thermal conditions and disturbances.

Weather Types and Rainfall Variability During Northeast Monsoon Over Malaysia Associated with ENSO

New XIA YAN#+, Liew JUNENG, Fredolin TANGANG
Universiti Kebangsaan Malaysia

Extreme precipitation often dominant around Malaysia during the Northeast Monsoon. However how the extreme precipitation is associated to different monsoonal synoptic circulation is not fully understood. Based on the weather types classification method, this study examines the dominant large-scale patterns related extreme precipitation in Malaysia during Northeast Monsoon season. Daily weather types (WTs) during Northeast Monsoon season (November to February) over Malaysia region (3°S-10°N, 100°–120°E) has been analyzed using 850hPa winds from the Fifth Generation of the European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis Data (ERA5) from 1981-2020 by using k-means clustering. Ten WTs were obtained to analyzed in terms of circulation patterns, frequency of occurrence, typical progression and precipitation characteristics and relation to El-Nino Southern Oscillation (ENSO). The resulting WTs represent and include the main synoptic circulation patterns related to the Cold Surge and Borneo Vortex. Cold surge patterns are predominant in January and February while weakening cold surges show significantly reduced frequency during November and December. Three out of ten clusters show Borneo Vortex occurring in different locations over the South China Sea. Most of the WTs remain on the same type during transition and persistence not exceeding 6 days. Clusters that exhibit Borneo Vortex occurrence typically produce heavy rainfall near east coast of Peninsular Malaysia while weakening cold surge shows significant heavy rainfall near south of Borneo. Lastly, the extend to which the El-Nino-Southern Oscillation modulates the probability of occurrence of each of the ten WTs is then discussed.

Mechanisms Behind Variabilities of Monsoon Onset and Advancement Over India

Indian Institute of Science, Bangalore

Rainfall over Indian subcontinent in June is associated with the onset of summer monsoon and its subsequent advancement. Observations, however, show that the pace of north-westward advancement of monsoon is uncorrelated with the timing of onset over southeast peninsular India. This study focuses on the physical mechanisms behind the inter-annual variations of monsoon onset and advancement. Analyses show that Madden Julian Oscillation (MJO) not only plays a crucial role in onset but also dictates its subsequent advancement. Northward propagation of precipitable water due to the phase transition of MJO (from phase-2 to phase-5) is identified as an important factor for the fast advancement of monsoon. On the other hand, slow advancement is seen when the MJO is locked in phase-2 that results in strong negative precipitable water anomalies over Central and North-West India. It is also observed that, in the years with fast advancement, the onset over Kerala and Central India happens due to strong positive anomalies of precipitable water convergence due to MJO along with high mean background precipitable water. In the years with slow advancement, it is the 10-20-days Intra-seasonal Oscillations and synoptic activities which results in onset over Kerala and Central India respectively. High mean background precipitable water intensifies the aforesaid activities by increasing instability. Therefore, both dynamics and thermodynamics plays important role in monsoon onset and advancement.

Exploring a New Aspect of Multi-phase Rotated Empirical Orthogonal Function for Capturing Spatiotemporal Variations in Temperature

Kamana MISHRA#+, Sarita AZAD
Indian Institute of Technology Mandi

The Northwest Himalayan (NWH) region has experienced substantial impacts from climate change, necessitating a thorough examination of its dynamic spatiotemporal patterns through suitable statistical methods. To capture systematic trends and elucidate localized characteristics, we employed Rotated Empirical Orthogonal Functions (REOFs) on mean temperature data spanning from 1981 to 2021. Utilizing REOF analysis, we subdivided the NWH region into snow and non-snow cover areas, enhancing the precision of data representation. Particularly in the western parts of Uttarakhand (U.K.) and Himachal Pradesh (H.P.), the second REOF mode of mean temperature exhibited noteworthy fluctuations, explaining 38.7% of the overall variance. However, the associated principal component (PC) failed to accurately depict the data patterns in these regions. In response, we introduced Multi-phase REOF analysis for the first time, aiming to identify PCs that faithfully represent the original data and offer insights into specific temporal variations. Additionally, we explored potential factors contributing to these variances in the specified NWH locations. The deduced physical properties and identified temperature zones from this analysis can enhance climate change modeling in the area.

Tue-25 Jun | 8:30 - 10:30 | Meadow Hall, Alpensia Convention Center
AS66 - Aerosols, Clouds, Radiation, Precipitation, and Their Interactions

Session Chair(s): Xiquan DONG, The University of Arizona, Chuanfeng ZHAO, Peking University

Ice-over-water Multilayer Cloud Properties and Identification in an Artificial Neural Network Approach

Sunny SUN-MACK1,2#+, Patrick MINNIS2, William L. SMITH JR.2, Yan CHEN1, Gang HONG1,2
1Analytical Mechanics Associates, Inc, 2NASA Langley Research Center

Clouds are a crucial component of the atmospheric energy system, particularly the radiative balance within, above, and below the troposphere. The vertical distribution of cloud mass and phase determines layer heating rates, the loss of radiation to space, and the amount of radiative heating at the surface. Thus, it is important to know how clouds are distributed both vertically and horizontally at all times of day. Satellite remote sensing is the only approach available to monitor clouds day and night around the globe. In this paper several artificial neural network (ANN) algorithms, employing several Aqua MODIS infrared channels, profiles of relative humidity and temperature from GMAO numerical weather analyses, and the retrieved total cloud visible optical depth, are trained to detect multilayer ice-over-water cloud systems and to retrieve some of their properties as identified by a year of 2008 Aqua MODIS data matched with CloudSat and CALIPSO (CC) cloud profiles. The CC lidar and radar profiles provide the vertical structure that serves as output truth for the multilayer algorithm. The neural networks were trained using one year (2008) of cloud top height data from the CC dataset, with correlation around 0.94 (0.95) and MAE as low as 0.82 (0.81) km for nonpolar regions during the day (night). Applying the trained ANN to independent year 2009 MODIS data resulted in a combined ML and single layer hit rate of 86.4% (85.1%) for nonpolar regions during the day (night). Since the ANN is trained using near-nadir MODIS pixels, infrared radiance corrections were developed as a function of view zenith angle from MODIS and applied to off-nadir pixels when processing MODIS swath data. The multilayer amount derived with the ANN is relatively invariant with increasing view zenith angle compared to the multilayer amount without the corrections.

Characteristics of Mesoscale Convective Systems Associated Warm Sector Rainfalls for the Hong Kong Region

Shiwei YU1+, Hui SU1#, P.W. CHAN2
1The Hong Kong University of Science and Technology, 2Hong Kong Observatory

Mesoscale convective systems (MCSs) are known to induce heavy rainfall and pose significant weather hazards in tropical and extratropical regions. As a subset of MCSs, warm sector rainfalls (WSRs) refer to heavy rainfalls within a weakly forced synoptic environment under the impact of monsoonal airflows. They are often formed in the southern coast of the East Asian monsoon region (e.g. southern China) during the pre-summer season (April-June). Despite extensive studies on the mechanisms of MCS rainfall and the considerable improvement in predictive skills, accurately forecasting MCS-associated WSRs remains challenging. Hong Kong, as a subtropical coastal city in southern China, frequently experiences MCS-associated WSR events. In order to gain a better understanding these events, we analyzed 214 MCSs and 9 WSRs that occurred in the Hong Kong region between April and June from 2005 to 2023. Firstly, we examined the water vapor conditions around Hong Kong using the global navigation satellite system (GNSS) technique. Our findings revealed that during WSRs, the water vapor hovered at a higher level of 62 mm for approximately 36 hours, in contrast to the gradually increasing pattern observed in the other MCSs. Additionally, we investigated three factors - moisture, lift, and instability – related to MCSs using the European Centre for Medium-Range Weather Forecasts reanalysis dataset (ERA5). Our analysis indicated that low moisture deficit lasted for 36/48 hours before the initial/maximum precipitation of WSRs. Furthermore, a stronger convergence in the low atmosphere was observed 36/48 hours before the initial/maximum precipitation of WSRs, compared to the 0/12-hour signal found in other MCSs. In terms of instability, we observed a rapid reduction preceding the maximum precipitation of the MCSs, while the decline shows a smoothing pattern with a small magnitude for the initial time reference. Interestingly, the instability did not display significant fluctuations during WRSs.

Amplified Interhemispheric Rainfall Contrast in Boreal Summer Due to Reduction in Anthropogenic Emissions Under COVID-19 Green Economic-recovery Scenarios

Xiaochao YU1, Hua ZHANG1#+, Bing XIE1, Piers M. FORSTER2
1China Meteorological Administration, 2University of Leeds

Our study looks at the precipitation responses to two possible future emission-mitigation pathways, pushed by the continuing Coronavirus Disease 2019 pandemic (Covid-19) and achieving carbon neutrality in the mid-21st century. We find that simultaneous-reduction in well-mixed greenhouse gases (WMGHGs) and aerosol emissions results in enhanced interhemispheric precipitation contrast in 2040s by amplifying interhemispheric thermal contrast and strengthening meridional overturning circulation at tropics. Reduced aerosol emissions induce generally-increased precipitation in the Northern Hemisphere (NH) and an amplified intertropical rainfall contrast, while reduced WMGHG emissions dominates decrease in precipitation in the areas away from aerosol emission sources. Further, the above precipitation contrast will be enhanced under stronger emission-mitigation pathways, mainly attributed to larger precipitation increases in the NH caused by reduced aerosols. More aggressive WMGHG mitigation policies are required to offset the NH warming driven by aerosols, to avoid the risk of regional drying or wetting driven by the asymmetry in interhemispheric energy budgets.

Urban Effect on Air Pollution and Precipitation

Zhining TAO1#+, Mian CHIN2
1Morgan State University, 2NASA Goddard Space Flight Center

More than 50% of the global population live in urban areas that contribute to 0.5% of the world’s total land. The resulting concentrated economic and social activities make urban a unique micro-environment that affects air quality and precipitation. Usually, it is more polluted in urban space than its surrounding areas with elevated aerosol levels. The microphysical and radiative effects of aerosols (AMR) would impact cloud and precipitation developments. The direction and magnitude of such urban effect on local precipitation and storms remains an open scientific question. In this study, a fully coupled regional chemistry transport model – the NASA Unified Weather Research & Forecasting (NU-WRF) model – has been applied to the Houston metropolitan area to untangle the complex interactions among urban landscape, aerosols, and precipitation. The simulation results have been evaluated against the measurements of local meteorology and air quality. A series of sensitivity experiments have been conducted to quantify the effect of urban land vs. anthropogenic aerosols on local precipitation onset and intensity. The results show that the urban effects greatly enhanced convection right before rainfall starts via AMR interactions. With the same storm system, aerosols can either suppress or intensify precipitation depending on the underlying land use.

Effect of Vertical CCNC Explosion on Hail and the Uncertainty Evaluation Compared with Initial Meteorological Condition

Xiaofei LI#+
Northwest University

The uncertainty of the cloud condensation nuclei concentration (CCNC) effect on hail precipitation due to perturbed initial meteorological conditions (IC) has been evaluated using an ensemble data from an idealized hailstorm by the high-resolution Weather Research and Forecasting (WRF) simulation. Varied CCNC from clean to polluted condition in six concentrations with uneven intervals resulted in a curve pattern that increasing firstly and then decreasing with single peak for hail precipitation rate. Vertical sensitive simulations showed that CCN at 750-800 hpa plays a dominant role in the change of hail rate, while the total precipitation is dominated by 700-800 hpa height CCNC. However, we found some tiny perturbed ICs from ECMWF, including thermodynamic (TQ, potential temperature and mixed water vapor ratio) and kinematic condition (UV, U wind speed and V wind speed), can even change the curve style with multiple peaks, indicating a potential large uncertainty for CCNC effect on hail in an uncertain IC. Although the meteorological perturbations produce large uncertainties in both hail and total precipitation, varying CCNC by an order of magnitude causes even larger uncertainties than the meteorological perturbations. Changing CCNC modifies the predictability of hail precipitation, with higher predictability in moderately polluted environments compared with very clean and polluted environments. Perturbing the initial meteorological conditions does not qualitatively change how aerosols affect hail and total precipitation.

Determination of Cirrus Occurrence and Distribution Characteristics Over the Tibetan Plateau Based on the Swop Campaign

Dan LI1+, Jiali LUO2#, Zhen YANG2
1Chinese Academy of Sciences, 2Lanzhou University

Balloon sounding with the Compact Optical Backscatter Aerosol Detector (COBALD) and Frost Point hygrometers (FPs) provides in situ data for a better understanding of the vertical distribution of cirrus clouds. In this study, eight summer balloon-borne measurements in Kunming (2012, 2014, 2015, and 2017) and Lhasa (2013, 2016, 2018, and 2020) over the Tibetan Plateau were used to show the distribution characteristics of cirrus clouds. Differences of cirrus occurrence were compared by different indices: the backscatter ratio (BSR) at a 455 nm/940 nm wavelength (BSR455 > 1.2/BSR940 > 2), the color index (CI > 7), and the relative humidity with respect to ice (RHice > 70%). Analysis of the profiles indicated that BSR455 > 1.2 was the optimal criterion to identify the cirrus layer and depict the distribution of the CI and RHice within cirrus clouds. The results showed that the median CI (RHice) within the cirrus clouds at both sites was mostly in the 18–20 (90%–110%) range at pressures below 120 hPa. Furthermore, the balloon-borne measurements combined with Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) measurements indicated a high frequency of cirrus occurrence near the tropopause in Kunming and Lhasa. The top height of cirrus occurrence at both sites was above the cold point tropopause and the lapse rate tropopause. Both Kunming and Lhasa had the highest frequency of thin cirrus clouds in the 0–0.4 km vertical cirrus thickness range.

Analysis of Global Light Rain System from GPM/DPR Observation and Its Seasonal Variations

Seoeun CHOI1#+, Sang-Moo LEE1, Jihoon RYU2, Euijong KANG1, B.J. SOHN1
1Seoul National University, 2Korea Institute of Atmospheric Prediction Systems

Atmospheric cloud system and the associated precipitation is responsible for variations in how moisture is released and how heat is distributed in Earth's atmosphere. The global distributions of clouds significantly impact on local weather patterns as well as overall climate system. While light rain may not boast high intensity compared to heavy rain, it accounts for significant fraction of rain occurrence and light rain system has recognized as one of the most important atmospheric phenomena to understand global hydrological cycle. The launch of Global Precipitation Measurement (GPM) Dual-frequency Precipitation Radar (DPR) has enabled a nearly-global (65oS–65oN) detection of the horizontal and vertical structures of clouds, enabling to understand global precipitation distributions. This research aims to analyze drop size distribution (DSD) characteristics and cloud echo-top height (CETH) defined as the top height of DPR echo from the ground altitude to avoid land elevation interference of light rain using GPM/DPR measurement from 2019 to 2021. In this study, a Gaussian mixture model (GMM) clustering was employed to categorize the light rain system globally. The parameters utilized for the classification in this study are mass-weighted mean diameter (Dm), and normalized intercept parameter (log10Nw) at the clutter-free bottom level, and CETH from GPM/DPR-retrieved products. By using both of microphysical and macrophysical properties of clouds, global light rain was clustered as the following three types: (1) oceanic shallow, (2) oceanic moderate, and (3) continental types. Additionally, to classify prevailing types across different seasons, GMM clustering was conducted seasonally, following the same method. On a global scale, distinct rainfall characteristics are notably disparate between summer and winter, with uniquely classification into two types: oceanic and continental in winter. Henceforth, the DSD parameters will be examined and predominant regions will also be discussed for a comprehensive understanding of the variations in rainfall patterns across seasons.

A Modeling Study of Aerosol Effect on a Summer Nocturnal Convective Precipitation Event in Beijing

Yue ZHOU1#+, Chuanfeng ZHAO2, Yue SUN1
1Beijing Normal University, 2Peking University

Using the Weather Research and Forecasting Model with Chemistry (WRF-Chem) model, this study investigates the potential contributions of aerosol direct effect (ADE) and aerosol indirect effect (AIE) on a nocturnal convective precipitation event occurred on 9-10 September 2019 in Beijing. It shows that the ADE and AIE both contribute to the spatial distribution of rainfall in urban areas. The ADE plays a more important role to the changes of heavy precipitation. The ADE causes a slight decrease in precipitation before 13:00 (UTC, hereafter) on 9 September (precipitation I), while increases precipitation during 13:00-21:00 (Precipitation II). The AIE has a weak effect on precipitation before 18:00 on 9 September, while decreases precipitation after 18:00. Further simulation analyses show that the ADE suppresses convection and precipitation by inducing greater surface shortwave radiative cooling and stability during Precipitation I, which reduces the convective energy (CAPE) losses and then increases the later CAPE. The ADE-induced CAPE increase makes the updraft stronger, increasing the cloud fraction and transporting more cloud water into the upper troposphere. This, in turn, causes greater latent heat release from freezing and then stronger convection, resulting in higher rain rate during Precipitation II. During 12:00-18:00, the AIE causes a decrease in CAPE, which weakens the updraft. The AIE decreases the snow mixing ratio above 700 hPa except at 15:00-16:00 on 9 September, which can decrease the release of latent heat from freezing, contributing to the decrease in precipitation after 18:00. Due to the greater stability before 10:00 and longer time required for the updraft to overcome this stability, the ADE necessitates 2-3 hours to adjust the simulated rainfall time series in the study area.

Tue-25 Jun | 8:30 - 10:30 | Lake Hall, Alpensia Convention Center
AS79 - Asian Summer Monsoon, Its Dynamics and Impact on Atmospheric Composition

Session Chair(s): Kenneth JUCKS, NASA Headquarters, Ja-Ho KOO, Yonsei University

AS79-A002 | Invited
The Silk Road Teleconnection Along the Summer Subtropical Asian Jet: Dynamics and Changes Under Global Warming

The University of Tokyo

The Silk Road teleconnection is a waveguide teleconnection along the summer subtropical Asian jet along the northern periphery of the Asian summer monsoon anticyclone, also known as the Tibetan/South Asian high. The teleconnection induces undulation of the monsoon anticyclone. It often causes extreme weather events in East Asia such as heat waves and heavy rains. Our analysis of the energetics of the interannual Silk Road teleconnections shows that the baroclinic energy conversion associated with meridional heat transport in the mid- to lower troposphere is key to its maintenance. In a large ensemble AGCM simulation dataset d4PDF and CMIP6 simulations, we find the teleconnection significantly weakens under global warming. This is because baroclinic energy conversion becomes less efficient under reduced linkage with the mid- to lower tropospheric circulation anomalies due to the uplift of the jet axis and enhanced tropospheric stratification. Besides, the southward shift of the Asian jet associated with global warming prevents wave packet injection from the North Atlantic subpolar jet.

Intraseasonal Variability of the Asian Summer Monsoon Anticyclone

Joowan KIM#+, Hyeong-Gyu KIM, Dahuin CHONG
Kongju National University

The variability and related dynamical mechanisms of the Asian Summer Monsoon Anticyclone (ASMA) were examined on intraseasonal time scale. The intraseasonal behavior of the ASMA is largely related to the convective activity over Indian and East Asian regions reflecting its developing mechanisms. In addition, generation and propagation of Rossby waves over the Eurasian continent also significantly affect the behavior of the ASMA. Particularly, the Rossby wave patten frequently observed over the Eurasian jet (a.k.a. Silk Road Pattern, SRP) significantly influences the intraseasonal variability of the ASMA. The SRP's eastward propagation along the Eurasian jet and dynamical coupling with lower troposphere plays a crucial role in the dynamic variability within the monsoon anticyclone, leading to notable variations in surface weather and chemical transport in the upper troposphere and lower stratosphere across East Asia.

AS79-A009 | Invited
Characterizing Intraseasonal and Interannual Variability in the Composition of the Asian Summer Monsoon Anticyclone Using Aura Microwave Limb Sounder Measurements

Michelle SANTEE1#+, Gloria MANNEY2, Luis MILLAN1, Nathaniel. J LIVESEY1
1California Institute of Technology, 2NorthWest Research Associates

The Aura Microwave Limb Sounder (MLS), launched in July 2004, makes simultaneous co-located measurements of trace gases and cloud ice water content (a proxy for deep convection) in the upper troposphere / lower stratosphere (UTLS) on a daily basis. With its dense spatial and temporal sampling, extensive measurement suite, and insensitivity to aerosol and all but the thickest clouds, Aura MLS is well suited to characterizing UTLS composition in the region of the Asian summer monsoon (ASM) and quantifying the considerable spatial and seasonal variations therein. In addition, the 19-year MLS data record is invaluable for assessing interannual variability in the impact of the ASM on the UTLS. In this talk we will examine MLS measurements of cloud ice and both tropospheric (CO, CH3Cl, CH3CN, HCN) and stratospheric (O3, HNO3, HCl) tracers, along with meteorological reanalyses, to place the 2017 and 2022 ASM seasons observed in detail by the StratoClim and ACCLIP field campaigns, respectively, into the spatial and temporal context of other monsoons in the last two decades. We will also briefly look at the 2024 ASM season that will just be getting underway.

AS79-A007 | Invited
The 2022 Asian Summer Monsoon Chemical and Climate Impacts Project (ACCLIP)

Paul A. NEWMAN1#+, Laura L. PAN2, Elliot ATLAS3, Bill RANDEL2, Troy THORNBERRY4, Brian TOON5
1NASA Goddard Space Flight Center, 2National Center for Atmospheric Research, 3University of Miami, 4NOAA Chemical Sciences Laboratory, 5University of Colorado at Boulder

The Asian summer monsoon Chemical and Climate Impact Project (ACCLIP) used the NASA WB-57f research aircraft, the NSF/NCAR Gulfstream V (GV) research aircraft, the Korean NARA King Air, and a broad set of balloon launches to investigate atmospheric processes that influence ozone depletion and climate in the Korea/Japan region. The NASA WB-57 and NSF GV were flown from Osan Air Base, Republic of Korea during the July-August 2022 period. The circulation of the summertime northern hemisphere upper troposphere – lower stratosphere (UTLS) is dominated by the Asian summer monsoon anticyclone (ASMA or oftentimes called the Tibetan anticyclone). This anticyclonic summer flow develops in response to the southern Asia monsoon and is broadly centered on Tibet. ACCLIP was designed to examine how the ASMA circulation and transport influences the UTLS chemical and aerosol behavior, including links to surface emissions. This presentation will provide background on the ASMA and discuss its wider importance. We will highlight observed dynamical and transport aspects during the summer of 2022, including comparisons to climatological behavior. The ACCLIP mission focused on sampling the ASMA’s eastern flank and outflow into the Pacific Ocean, including mapping the vertical and horizontal structure of UTLS circulation and composition.

A Transport Overview for ACCLIP (2022) Airborne Observations: From Deep Convection to the Lower Stratosphere

Warren SMITH1#+, Laura L. PAN1, Rei UEYAMA2, Shawn HONOMICHL1, Teresa CAMPOS1, Silvia VICIANI3, Francesco D'AMATO3, Giovanni BIANCHINI3, Marco BARUCCI3
1National Center for Atmospheric Research, 2NASA Ames Research Center, 3National Research Council - National Institute for Optics

The Asian summer monsoon (ASM) has long been known as a weather system, but only recently has its role in atmospheric composition come to be explored in detail. During boreal summer, an anticyclone forms in the upper troposphere and lower stratosphere (UTLS) over Asia which is associated with a pronounced enhancement of chemical and aerosol species lofted from the boundary layer (BL) by ASM deep convection. Transport from the ASM UTLS anticyclone to the global atmosphere was the target of a recent airborne field campaign: The Asian Summer Monsoon Chemical and Climate Impact Project (ACCLIP, 2022). In this work, we overview the transport characteristics contributing to ACCLIP airborne sampling with the aid of Lagrangian trajectory modeling. Specifically, we use backward trajectories to connect airborne sampling to deep convection over Asia, and forward trajectories to connect airborne sampling to the stratosphere. Airborne measurements of the tropospheric tracer carbon monoxide (CO) from ACCLIP are used to link model results with the observed UTLS environment. This analysis provides valuable context for the ACCLIP observations, as well as new insight into the role of ASM transport in impacting global atmospheric composition. We show that ACCLIP sampling had convective contributions from both the East and South Asian summer monsoons, with East Asian convection contributing preferentially higher pollutant concentrations. We also show the majority of sampled air masses in the upper troposphere reached the tropopause within the subsequent week.

The Unique Tropopause Structure Over the Asian Summer Monsoon and Its Role in UTLS Transport

Laura L. PAN1#+, Shawn HONOMICHL1, Warren SMITH1, Troy THORNBERRY2, Glenn DISKIN3, Rei UEYAMA4, Paul BUI4, Jonathan DEAN-DAY4, Silvia VICIANI5, Francesco D'AMATO5
1National Center for Atmospheric Research, 2NOAA Chemical Sciences Laboratory, 3NASA Langley Research Center, 4NASA Ames Research Center, 5National Research Council - National Institute for Optics

The Asian summer monsoon (ASM) anticyclone is known as the region with the highest tropopause during the season, ranging from 380-400 K potential temperature on average, in contrast to the tropical tropopause at ~375 K. The ASM anticyclone, therefore, appears to be a large continental-scale convection-driven tropospheric "bubble" over the subtropical background stratosphere. The east-west oscillation of the anticyclone at the top of the convection creates a unique mixing zone of stratospheric and tropospheric air near the eastern edge of the anticyclone, where the ACCLIP campaign conducted research flights. Using the WB-57 measurements of temperature, ozone, water vapor, carbon monoxide, together with the large-scale tropopause analysis, we characterize the mixing zone and its implication on the transport of convectively lofted Asian boundary layer air into the UTLS of greater northern hemisphere.

UT/LS Ozone Variability and Its Impact on Satellite-based Total Ozone Retrievals in East Asia

Chiyoung KIM+, Sangseo PARK#
Ulsan National Institute of Science and Technology

In the East Asian region, particularly during the winter and spring seasons, the occurrence of secondary ozone peaks in the Upper Troposphere/Lower Stratosphere (UT/LS) at approximately 14 km altitude coincides with active stratosphere-to-troposphere exchange (STE). The significance of these phenomena lies in their contribution to the spatiotemporal variability of total ozone levels, a critical parameter for understanding atmospheric composition and dynamics. The variability in UT/LS ozone emerges as a crucial factor influencing the overall spatiotemporal variation in total ozone. This emphasizes the need to address and account for the complexities arising from vertical ozone distribution when interpreting satellite-retrieved total ozone data. The study focuses on a comprehensive analysis utilizing data from two distinct satellites: the Infrared Atmospheric Sounding Interferometer (IASI), which relies on infrared (IR) channels, and the TROPOspheric Monitoring Instrument (TROPOMI), employing ultraviolet (UV) channels. For the 5-year dataset, we examine the contribution of uncertainties resulting from changes in ozone vertical distribution, with a specific emphasis on UT/LS ozone variability, to the retrieval accuracy of total ozone levels. By comparing the datasets obtained from these two satellite instruments, each utilizing different spectral regions, we aim to enhance our understanding of the challenges associated with satellite-based total ozone retrievals.

Improving Chemical Boundary Conditions of a Regional Chemistry-transport Model for UTLS Ozone Simulation

Taehee KIM1#+, Kyung-Hwan KWAK1, Heon-Seok DO1, Ja-Ho KOO2, Sangseo PARK3, Jae-Heung PARK4
1Kangwon National University, 2Yonsei University, 3Ulsan National Institute of Science and Technology, 4Seoul National University

The upper troposphere-lower stratosphere (UTLS) ozone distribution is primarily determined by the complex interactions between the troposphere and stratosphere. To fully understand the dynamic and physiochemical processes in the atmospheric layers, comprehensive data representing UTLS ozone variations are essential. To fill this knowledge gap, researchers from the National Center for Atmospheric Research and the National Aeronautics and Space Administration in the United States have collaborated with researchers in Korea and conducted the ACCLIP (Asian Summer Month Chemical and Climate Impact Project) campaign. This study performs numerical simulations for the ACCLIP campaign periods using the Weather Research and Forecasting (WRF) model coupled with the Community Multiscale Air Quality (CMAQ) model. The faithful chemical boundary conditions are vitally important in order to O3 simulations in the UTLS. In our simulation, we employ the Whole Atmosphere Community Climate Model, characterized by 6-hour time steps. This model is selected from a range of global models due to its ability to capture the complex dynamics of the atmosphere across diverse altitudes and regions. Ozonesonde observations were made 38 and 11 times in the Anmyeondo and Osan, respectively, in August 2022. The study aims to assess the feasibility of simulating ozone concentrations in the middle and upper troposphere (3-10 km altitude) using the WRF-CMAQ modeling system by incorporating proper chemical boundary conditions. To simulate ozone distribution in the UTLS, the model top of WRF was extended from 50 hPa to 10 hPa. The number of vertical grids increased. The simulation results were evaluated and showed the reliability of ozone simulations concerning tropospheric altitude. In addition to validation, the principal dynamics and chemical processes influencing UTLS ozone variability were investigated. This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (RS-2023-00219830).

Tue-25 Jun | 8:30 - 10:30 | Alps Rm, Alpensia Convention Center
AS10 - Marine Aerosols: Formation and Climate Impacts

Session Chair(s): Lin DU, Shandong University

AS10-A002 | Invited
Chemical and Optical Characterization and Sources of Atmospheric Organic Aerosols in Coastal Areas

Caiqing YAN1#+, Haibiao CHEN2, Qingpeng MENG1, Yanjun YANG1, Ruiyu LI1, Xiang DING3
1Shandong University, 2Environment Research Institute, 3Chinese Academy of Sciences

Located in the junction of land and ocean, coastal areas can be affected by land-based and marine emissions. And atmospheric organic aerosols in coastal cities may have significant regional characteristics. In this study, atmospheric fine particulate matter (PM2.5) were collected across different seasons at a coastal rural site in Qingdao, China using a high-volume particle sampler, to investigate the chemical and optical characterization of PM2.5-bound organic fractions (especially water-soluble organic carbon, WSOC) in the coastal suburbs of under the influences of different weather scenarios and air masses. Major PM2.5 species, molecular composition of water-soluble organic fractions, and primary and secondary organic tracers were analyzed using different types of chromatographs and mass spectrometers. Furthermore, absorption and 3D fluorescence spectra were obtained by advanced spectral analysis instruments. The results showed that, compared to marine air masses influenced samples, WSOC affected by continental air masses exhibited higher light absorption coefficients and generally had a higher degree of aromaticity and unsaturation, as well as contained more molecular formulas of WSOC, especially enriched with sulfur-containing compounds. In contrast, relatively more abundant halogen-containing compounds and higher ship emissions source contributions were identified in the marine air masses influenced samples. Furthermore, the isoprene-sourced SOA contribution from marine emissions was also identified in this study. More detailed discussions will be presented in this talk.

Formation and Transformation of Sea Spray Aerosols: Insights from Laboratory Studies

Lin DU#+
Shandong University

Sea spray aerosol (SSA) represents a major source of aerosol particle populations and significantly impacts the Earth’s radiation budget, cloud formation, and microphysics. It is thus crucial to investigate SSA formation and its atmospheric transformation. Here sea spray aerosol generators were first built and used to study the effects of different organic matters on the production efficiency, size, and morphology of SSA. The molecular weight and concentration of the polymer would affect the production efficiency of SSA. Combining with the measurement of surface tension, we found no clear relationship between surface tension and the yield of SSA, due to the properties of the substances themselves. In addition, the key chemical processes such as the interaction between surface-active molecules, water-soluble organic compounds, and biological macromolecular enzymes at the gas-liquid interface were studied through combination of a Langmuir model and infrared reflection–absorption spectroscopy (IRRAS). We found that the adsorption of glucose and trehalose on the fatty acid monolayer led to the expansion of the mean molecular area. Saccharide–lipid interactions increased with increasing complexity of the saccharide in the order of glucose < trehalose. In a seawater solution, the effects of dissolved saccharides on the ordering and organization of fatty acid chains were muted. The enhancement of the carbonyl band to the low wavenumber region implied that soluble saccharides can form new hydrogen bonds with fatty acid molecules by displacing large amounts of water near the polar headgroups of fatty acids. Our studies provide sufficient insights into formation and transformation of SSA, which would be helpful for improving the accuracy of aerosol emission model parameters.

The Critical Role of Dimethylamine in the Rapid Particles Formation of Marine Areas

Xiuhui ZHANG#+, Haotian ZU
Beijing Institute of Technology

Recent experiment (He et al, 2021, Science) revealed a vital nucleation process of iodic acid (HIO3) and iodous acid (HIO2) under the marine boundary layer conditions. However, HIO3-HIO2 nucleation cannot effectively derive the observed rapid new particle formation (NPF) in broad marine regions. Dimethylamine (DMA) is a promising basic precursor to enhance nucleation considering its strong ability to stabilize acidic clusters and the wide distribution in marine atmosphere, while its role in HIO3-HIO2 nucleation remains unrevealed. Hence, a method combining quantum chemical calculations and Atmospheric Cluster Dynamics Code (ACDC) simulations was utilized to study the HIO3-HIO2-DMA nucleation process. We found that DMA can compete with HIO2 to accept the proton from HIO3 as a basic precursor in the most stable configurations of HIO3-HIO2-DMA clusters. DMA can significantly enhance the cluster formation rates of HIO3-HIO2 kinetically for more than 103-fold in regions with abundant amine and scarce iodine based on combined factors of high nucleation ability and high concentration of DMA. Furthermore, the iodine oxoacids nucleation enhanced by DMA may explain the sources of rapid NPF events under different conditions corresponding to multiple ocean regions, which can provide important inspirations to understand the frequent and intensive NPF events in broad marine regions.

Formation Mechanism of Sea Spray Aerosols

Xiaofei WANG#+
Fudan University

Bubble bursting on water surfaces is believed to be a main mechanism to produce submicron drops, including sea spray aerosols, which play a critical role in forming cloud and transferring various biological and chemical substances from water to the air. Over the past century, drops production mechanisms from bubble bursting have been extensively studied. They usually involve the centrifugal fragmentation of liquid ligaments from the bubble cap during film rupture, the flapping of the cap film, and the disintegration of Worthington jets after cavity collapse. Here, we show that a major fraction of previously identified as “bubble bursting” submicron drops are in fact generated via a new underwater mechanism, which are not from bursting process at the water surface. This finding may reshapes our understanding of sea spray aerosol production.

Factors Controlling Inorganic Sulfate and Organosulfate Formation from the Reaction of Sulfur Dioxide with Organic Peroxides

Narcisse TSONA TCHINDA#+, Lin DU, Xiaofan LV
Shandong University

As important reservoirs for alkoxy radicals and organic peroxy radicals (ROx), organic peroxides are well-known determinant tracers in ROx chemistry. To evaluate the contribution of these peroxides in chemical processes and aerosol formation, we used quantum chemical modeling to examine the pH effect on the degradation of two selected organic peroxides (methyl hydroperoxide (MHP) and benzoyl peroxide (BZP)) by reaction with dissolved SO2 (S(IV)). Results showed that due to the presence of the hydroperoxyl group in its structure, MHP preferably forms inorganic sulfate and methyl sulfate in the pH range 1.81 – 6.97, while forming methyl sulfate, exclusively, at pH > 6.97, unlike BZP that exclusively forms benzoyl sulfate in the pH range investigated. The kinetics of these reactions, explored over the ranges pH 1 – 10 and 240 – 340K, indicate that the effective rate constants of the transformation of both organic peroxides exhibit positive pH and temperature dependencies in the pH and temperature ranges investigated. Over this pH range, BZP is more effectively degraded than MHP, with estimated atmospheric lifetimes in the ranges 5.02×10-19 s – 8.25×10-3 s for BZP and 1.34×10-5 s – 5.05×1010 s for MHP, at 298.15 K. The high reactivity of BZP relative to MHP can be attributed to the activation effect of the benzyl ring on the peroxyl function. Besides the pH effect, this study highlights the role of different substituents on the -O-O- function in altering the kinetics of organic peroxides degradation, and would serve as a ground to evaluate the pH effect in more kinetic analysis of different sources of particulate sulfate. This study further indicates that the aqueous-phase degradation of organic peroxides can adequately drive the change in the chemical composition of dissolved organic matters, both in terms of organic and inorganic sulfate mass fractions.

Anthropogenic-biogenic Interactions During Biogenic Volatile Organic Compounds Oxidation in the Presence of SO2

Li XU#+
Uniersity of Science and Technology of China

Mixing of anthropogenic pollutants and biogenic volatile organic compounds impacts the formation of secondary organic aerosols (SOA) to an elusive extent. SO2 is one prevalent anthropogenic pollutant whose role on biogenic SOA formation remains unclear, especially under atmospheric complex pollution conditions. The present study explores factors including relative humidity (RH), NOx and NH3 that may influence the role of SO2 on biogenic SOA formation. Results showed that with a constant SO2 concentration, the increase in RH transformed SO2 sinks from stabilized Criegee intermediates to peroxides in aerosol particles. The associated changes in particle acidity and liquid water content may collectively first lead to decreased and then increased SOA yield with increasing RH. The reaction between peroxides and SO2 under high RH is responsible for the formation of organosulfates, especially highly oxidized organosulfates. When NO2 and SO2 coexisted, aerosol yields were higher than with either pollutant alone. Such a synergistic effect of SO2 and NO2 on aerosol formation is mainly because that the nucleation of sulfuric acid could further promote the gas-particle partition of products from NO3· oxidation and particle-phase reactions, In the coexistence of SO2 and NH3, NH3 weakened the enhancement effect of SO2 on SOA yields. The neutralization of aerosol acidity by NH3 may be the main reason for the antagonistic effect between NH3 and SO2. Our research highlight that it is necessary to comprehensively consider RH and the concentration levels of NOx and NH3 when evaluating effects of SO2-involved anthropogenic-biogenic interactions on SOA formation from the oxidation of biogenic volatile organic compounds.

Interfacial Oxidation Processing of Riverine and Marine Surface Microlayers: An Impact on VOCs and SOA in the Atmosphere

Chinese Academy of Sciences

Ozone (O3) and sulfur dioxide(SO2) oxidation chemistry on the organic film and water surface microlayer (SML) generates volatile organic compounds (VOCs) to the atmosphere. To shed light on the proposed significance of this chemistry, we investigated the formation of VOCs through heterogeneous chemistry of O3 (100 ppb) and SO2(30 ppb)with authentic SML collected from 10 sites in the South China Sea using a reactor coupled to proton transfer reaction−time of flight−mass spectrometry (PTR−TOF−MS) and a high-resolution quadrupole Orbitrap mass spectrometer(SESI-Orbitrap-MS), subsequently identified by off-line techniques. On the basis of the semiquantitative data of the identified compounds, we estimated the production rates of the key saturated and unsaturated ketones and aldehydes, which correspond to the experimental conditions applied in this study. These results provide a significant update to our understanding of abiotic formation of VOCs in the marine atmosphere, which should be considered in future model studies to properly evaluate the VOC contribution of ozone heterogeneous chemistry with the SML.

Role of Sea Spray Aerosol at the Air-sea Interface in Transporting Aromatic Acids to the Atmosphere

Yaru SONG+, Lin DU#
Shandong University

Aromatic acids are ubiquitous in seawater and can be transported to the atmosphere via sea spray aerosol (SSA). Despite their importance in affecting the global radiative balance, the contribution of marine aromatic acids and their transport mechanisms through SSA remain unclear. Herein, the distribution of particle size and number concentration of SSA produced in seawater containing nine different aromatic acids (i.e., benzoic acids, benzenedicarboxylic acids, hydroxybenzoic acids, vanillic acid, and syringic acid) was studied using a custom-made SSA simulation chamber; moreover, enrichment of aromatic acids in SSA and their emission flux to the atmosphere were analyzed. Transmission electron microscopy (TEM) images clearly revealed that aromatic acids can be transferred to the nascent SSA. Interestingly, the morphology associated with benzene dicarboxylic acids-coated particles showed that aromatic acids can promote the growth of other surfaces of sea salt, thus making the sea salt core spherical. Aromatic acids showed a significant enrichment behavior at the air-sea interface, which clearly indicated that SSA represent a source of aromatic acids in the atmosphere. Vanillic acid had the largest global emission flux through SSA (962 tons yr-1), even though its concentration in seawater was lower. The calculated results indicated that the global annual flux of aromatic acids was not only affected by the concentration in seawater, but also by their enrichment factor (EF). These data are critical for further quantifying the contribution of organic acids to the atmosphere via SSA, which may provide an estimate of the potential influence of the atmospheric feedbacks to the ocean carbon cycle.

Governance of Marine Emissions and Terrestrial Air Masses: Influence on the Composition and Properties of Carbonaceous Aerosols Over the Eastern China Marginal Seas

Kuanyun HU+, Lin DU#
Shandong University

Marine aerosols contribute significantly to atmospheric aerosols, playing substantial roles in influencing the regional and global environment and climate. Marine aerosols over the Eastern China Marginal Seas (ECMS: Bohai Sea-BS, Yellow Sea-YS and East China Sea-ECS) are co-controlled by productive seawater and populated land, but the composition and variation of marine aerosols remain poorly understood. In this study, marine aerosol samples were collected in spring of 2023 covering the entire ECMS to explore the spatial variation and the optical properties of carbonaceous species. Due to significant terrestrial transport, the concentration of TSP and carbonaceous species shows a spatial variation of high in the north and low in the south at latitude. Utilizing satellite data and backward trajectory analysis, the elevated solubility of organic carbon (OC) in southern YS may possibly be influenced by long-range transport and atmospheric aging of terrestrial biomass combustion and marine bioactive gases. Terrestrial transport increases aerosol light absorption, while marine sources and solar radiation weaken it. Humic-like substances are the predominant fluorescent chromophores, and marine sources can regulate the abundance of protein-like substances. The elevated simple forcing efficiency (SFE) and relative radiative forcing (RRF) in the near ultraviolet and visible light range indicate considerably warming effect attributed to terrestrial pollutants. The current results suggest that emphasis should be placed on the effect of terrestrial source transport in BS, while in the relatively open YS and ECS, more attention should be paid to the contribution of marine sources to marginal sea aerosols.

Experimental Evidences for Droplets Formation Through Film Flapping During Bubble Bursting

Xiaofei WANG#, Xinghua JIANG+
Fudan University

Tiny water drops produced from bubble bursting play a critical role in forming cloud, scattering sunlight, and transporting pathogens from water to the air. Bubbles burst by nucleating a hole at their cap foot and may produce jets, or film drops. The latter originate from the fragmentation of liquid ligaments formed by the centripetal destabilization of opening hole rim. They constitute a major fraction of the aerosols produced from bubbles with cap radius of curvature (R) > ~ 0.4 × capillary length(a). However, our present understanding of the corresponding mechanisms does not explain the production of most submicron film drops, which represent the main number fraction of sea spray aerosols. In this study, we report observations showing that bursting bubbles with R < ~0.4a are actually mainly responsible for submicron film drops production, through a mechanism involving the flapping shear instability of the cap with the outer environment. With this newly proposed pathway, the complex relations between bubble size and number of drops produced per bubble can be better explained, providing a fundamental framework for understanding production flux of aerosols and the transfer of substances mediated by bubble bursting through the air-water interface and the sensitivity of the process to the nature of the environment.

Tue-25 Jun | 8:30 - 10:30 | Meeting Room, InterContinental
AS33 - Earth System Predictability, Prediction and Projection

Session Chair(s): Noel KEENLYSIDE, University of Bergen

AS33-A002 | Invited
Conundrums of Earth System Predictability

Chidong ZHANG#+
NOAA Pacific Marine Environmental Laboratory

This presentation discusses several conundrums in the current studies of Earth system predictability. This presentation focuses on the potential predictability including its source and limit, instead of the actual predictability (prediction skills). Boundary conditions as the source of climate predictability at the early stage of climate prediction using atmosphere-only models disappear in fully coupled Earth system models (except at the top of the atmosphere). Slowly evolving phenomena, such as the MJO, ENSO, and AMOC, have been cited as the sources of predictability from intraseasonal to decadal timescales. But most of these slowly evolving phenomena are now the targets of prediction and their sources of predictability remain ambiguous. Restrictively speaking, initial conditions are the only sources of predictability for a fully coupled Earth system. If sources of weather predictability come from signals of perturbations in initial conditions, sources of climate predictability come from signals of the mean state in initial conditions, then sources of S2S predictability would be a combination of signals of both perturbations and the mean state in initial conditions. Finally, it is argued that a predictable phenomenon must have a constant feature, which can take various non-static and spatially/temporally varying forms. 

Developing a Global Coupled Configuration at the Met Office for Implementation at All Timescales and Ready for Future HPC Infrastructures

Charline MARZIN#+
Met Office

The Met Office along with its partners has recently released a Global Coupled configuration GC5 which will be the baseline for upcoming upgrades to the NWP, seasonal and climate modelling systems. As well as improving most aspects of atmosphere and ocean parametrisation, the development of this configuration made use of an extensive and innovative seamless testing framework to test and improve the model using data assimilation, ensemble, coupled and climate change tests. The configuration provides significant improvements to the southern Ocean, tropical rainfall and several key modes of variability and performance metrics. Additional work to understand the impact of latest development on climate sensitivity and the use of perturbed parameter ensembles will be presented. This configuration is also forming the baseline for the next generation modelling system that will enable better scalability on future infrastructures and preliminary results will be presented.

Supermodelling to Improve Climate Prediction

Noel KEENLYSIDE1#+, Francine SCHEVENHOVEN1, Ping-Gin CHIU1, Tarkeshwar SINGH2, Francois COUNILLON2, Mao-Lin SHEN1, Gregory DUANE1,3
1University of Bergen, 2Nansen Environmental and Remote Sensing Center, 3University of Colorado

Climate models are plagued by long-standing biases that degrade predictions. While increasing resolution of global climate models to km scales promises to reduce biases, there is little evidence so far of improvements with currently available computing power. Supermodelling is an alternative approach that has demonstrated reductions in long-standing biases, such as the double ITCZ and tropical SST biases, at a fraction of the computational cost of km scale models. A supermodel is a combination of models that interact during their simulations to mitigate errors before they develop into large-scale biases. Here I will present recent results from a supermodel based on three Earth System Models (NorESM, CESM, MPIESM) trained using observed SST. The models were combined using ocean data assimilation with monthly frequency. The simulation of tropical climate is markedly improved in the supermodel compared to that of the respective standalone models. Seasonal predictions performed with this model are underway and first results will be shown. In addition, I will summarize work on combining atmospheric models that promises to lead to even greater improvements in simulating global climate.

A Multi-year Climate Prediction System Based on CESM2

Yong-Yub KIM1#+, June-Yi LEE2, Axel TIMMERMANN2, Yoshimitsu CHIKAMOTO3, Sun-Seon LEE2, Eun Young KWON1, Wonsun PARK2, Nahid A. HASAN3, Ingo BETHKE4, Filippa FRANSNER4, Alexia KARWAT2, Abhinav R. SUBRAHMANIAN1
1IBS Center for Climate Physics, 2Pusan National University, 3Utah State University, 4Bjerknes Centre for Climate Research

Here we present a new seasonal-to-multiyear earth system prediction system which is based on the Community Earth System Model version 2 (CESM2) in 1° horizontal resolution. A 20- member ensemble of temperature and salinity anomaly assimilation runs serves as the initial condition for 5-year forecasts. Initialized on January 1st of every year, the CESM2 predictions the exhibit only weak climate drift and coupling shocks, allowing us to identify sources of multiyear predictability. To differentiate the effects of external forcing and natural climate variability on longer-term predictability, we analyze anomalies calculated relative to the 50-member ensemble mean of the CESM2 large ensemble. In this presentation we will quantify extent to which marine biogeochemical variables are constrained by physical conditions. This analysis provides crucial insights into error growth of phytoplankton and the resulting limitations for multiyear predictability.

Potential Predictability of Forage, Pelagics and Demersals Biomass

Hyung-Gyu LIM1#+, Colleen PETRIK2
1Korea Institute of Ocean Science and Technology, 2University of California San Diego

With the emergence of predictive skills of climate variability, we currently stand at the horizon of being able to forecast marine ecosystems. However, the assessment of the capacity to predict high trophic levels of marine ecosystems has been rarely investigated. Here, we investigate predictability of fish biomass integrated by spatially explicit mechanistic model of fish with three functional types. We also evaluate the bottom-up biophysical drivers of fish that are predicted by decadal prediction outcomes from an Earth system model, initialized through forced ocean-sea ice simulations. We found that temperature drivers have longer predictability ~8 years while biological drivers have predictabilities within 1-2 years. The fish biomasses have skillful predictability within 2 years globally, extended more years regionally. These findings build upon prior research in evaluating the predictability of bottom-up drivers on fish, potentially illuminating a path towards operating forecast systems of living marine resources.

Exceptional Multi-year Prediction Skill of the Kuroshio Extension in the CESM High-resolution Decadal Prediction System

Who KIM1#+, Stephen YEAGER1, Gokhan DANABASOGLU1, Ping CHANG2
1National Center for Atmospheric Research, 2Texas A&M University

The Kuroshio Extension (KE) has far-reaching influences on climate as well as on local marine ecosystems. Thus, skillful multi-year to decadal prediction of the KE state and understanding sources of skill are valuable. Retrospective forecasts using the high-resolution Community Earth System Model (CESM) show exceptional skill in predicting KE variability up to lead year 4, substantially higher than the skill found in a similarly configured low-resolution CESM. The higher skill is attained because the high-resolution system can more realistically simulate the westward Rossby wave propagation of initialized ocean anomalies in the central North Pacific and their expression within the sharp KE front, and does not suffer from spurious variability near Japan present in the low- resolution CESM that interferes with the incoming wave propagation. These results argue for the use of high-resolution models for future studies that aim to predict changes in western boundary current systems and associated biological fields.

Estimating Seasonal to Multi-year Predictability of Statistics of Climate Extremes Using the CESM2-based Climate Prediction System

Alexia KARWAT1#+, June-Yi LEE1, Christian FRANZKE1, Yong-Yub KIM2
1Pusan National University, 2IBS Center for Climate Physics

Climate extremes, such as heat waves, heavy precipitation, intense storms, droughts, and wildfires, have become more frequent and severe in recent years as a consequence of human-induced climate change. Estimating the predictability and improving prediction of the frequency, duration, and intensity of these extremes on seasonal to multi-year timescales are crucial for proactive planning and adaptation. However, climate prediction at regional scales remains challenging due to the complexity of the climate system and limitations in model accuracy. Here we use a large ensemble of simulations, assimilations, and reforecasts using Community Earth System Model version 2 (CESM2) to assess the predictability of statistics of climate extremes with lead times of up to 5 years. We show that the frequency and duration of heat waves during local summer in specific regions are predictable up to several months to years. Sources of long-term predictability include not only external forcings but also modes of climate variability across time scales such as El Niño and Southern Oscillation, Pacific Decadal Variability, and Atlantic Multidecadal Variability. This study implies opportunities to deepen our scientific understanding of sources for long-term prediction of statistics of climate extremes and the potential for the associated disaster management.

Future North Atlantic Warming Hole Modulates Interhemispheric Temperature Change

In-Hong PARK#+, Sang-Wook YEH
Hanyang University

Accurately projecting the impact of the North Atlantic subpolar cooling region despite global warming, known as 'warming hole', on global climate is critical but uncertain due to its complex mechanisms. Here, we use the latest multi-model simulations (CMIP6) to investigate the impact of changes in the warming hole on future climate change. We find that changes in the warming hole play an important role in creating an asymmetry in temperature and precipitation patterns between the hemispheres: the weaker the warming hole (corresponding to strong warming in the North Atlantic subpolar region), the greater non-radiative fluxes (sensible and latent heat flux) transported to the atmosphere, leading to greater warming in the Northern Hemisphere than the Southern Hemisphere. This difference in warming leads to an energy imbalance between the hemispheres, resulting in a northward shift of the Inter-Tropical Convergence Zone (ITCZ). These changes have a significant impact on the distribution of precipitation, contributing to the precipitation imbalance between the two hemispheres. Our findings highlight that a better understanding of the warming hole is important for accurate projections of future global climate, especially hemispheric temperature and precipitation patterns.

Changing Footprint of the Pacific Decadal Oscillation on Global Land Surface Air Temperature

Zhenzhong ZENG1#+, Alan ZIEGLER2, Deliang CHEN3, Philippe CIAIS4, Laurent LI5, Shijing LIANG1, Dashan WANG1, Rongrong XU1, Lili LIANG1
1Southern University of Science and Technology, 2National University of Singapore, 3University of Gothenburg, 4Institut Pierre Simon Laplace, 5Laboratoire de Météorologie Dynamique

Decadal-scale periods of global warming slowdown and acceleration are associated with varying phases of the Pacific Decadal Oscillation (PDO). However, the footprint of the PDO on land temperature has not been determined and how this footprint has changed over time remains unknown. Here we use an observational dataset of global land temperature since 1901 to search the footprint of the PDO and its influence on the variability of climate warming rates. We find that a warming acceleration associated with the transition of PDO from negative to positive phase has remained high and has been expanding in area since the early 20th century. Meanwhile, the warming slowdown associated with the reverse transition appears to be shrinking worldwide. This configuration implies that in the coming decade with a likely occurrence of an ascending transition of the PDO, a period of faster anthropogenic global warming could be anticipated.

Tue-25 Jun | 11:00 - 12:30 | Luge Hall, Alpensia Convention Center
AS52 - The Physical Processes Over Complex Topography: the Interactions Among Meteorology, Boundary Layer Turbulence, Clouds, Tracer Transport, and Chemistry

Session Chair(s): Wei-Ting CHEN, National Taiwan University, Shih-Hao SU, Chinese Culture University

Cold Fog Amongst Complex Terrain (CFACT)

Zhaoxia PU#+
University of Utah

Fog frequently forms in high-elevation complex terrain as over water bodies but is less understood and difficult to predict. Cold fog forms via various thermodynamic, dynamic, and microphysical processes when the air temperature is less than 0°C. It occurs frequently during the cold season in the western United States yet is challenging to detect using standard observations and very difficult to predict. The Cold Fog Amongst Complex Terrain (CFACT) project goals are to 1) investigate the lifecycle of cold-fog events over complex terrain with the latest observation technology, 2) improve microphysical parameterizations and visibility algorithms used in numerical weather prediction (NWP) models, and 3) develop data assimilation and analysis methods for current and next-generation (e.g., sub-kilometer scale) NWP models. The CFACT field campaign took place in Heber Valley, Utah, during January and February 2022, with support from NSF’s Lower Atmospheric Observing Facilities (managed by NCAR’s Earth Observing Laboratory), the University of Utah, and Ontario Technical University. A network of ground-based and aerial in situ instruments and remote sensing platforms were used to obtain comprehensive measurements of thermodynamic profiles, cloud microphysics, aerosol properties, and environmental dynamics. Nine intensive observation periods (IOPs) explored various mountainous weather and cold-fog conditions. Field observations, NWP forecasts, and large-eddy simulations provided unprecedented data sources to help understand the mechanisms associated with cold-fog weather and to identify and mitigate numerical model deficiencies in simulating winter weather over mountainous terrain. This presentation summarizes the CFACT field campaign, its observations, and recent progress in science data analysis, fog process studies, numerical simulations, and model validation. [References: Pu, Z., E. Pardyjak, S. Hoch, I. Gultepe, A. G. Hallar, A. Perelet, R. Beal, G. Carrillo-Cardenas, X. Li, M. Garcia, S. Oncley, W. Brown, J. Anderson, J. Witte, A. Vakhtin, 2023: Cold Fog Amongst Complex Terrain. Bulletin of the American Meteorological Society. 104, E2030-E2052.].

Effects of In-land Breeze Induced by Neighboring Land Type Patches on Vertical Energy Transport in Large Eddy Simulations of VVM

Wei-Ting CHEN#+, Tzu-Han HSU, Chien-Ming WU, Po-Yen CHEN
National Taiwan University

Boundary layer turbulence, crucial for vertical energy and moisture transport, can be influenced by coherent horizontal flows driven by diurnal heating difference in land surfaces. This study employs Large Eddy Simulations of the vector vorticity equation cloud-resolving model (VVM) coupled with the Noah Land Surface Model to explore these processes. Three land type configurations are examined: a combination of half grassland and half urban land (HALF), entire grassland (GRASS), and entire urban land (URBAN). All experiments adopt a 12.8 12.8 km2 horizontal domain with 100 m grid spacing and 20 m vertical resolution. The initial condition reflects a stable, windless environment with convective available potential energy close to zero, sourced from a 06 LST radiosonde observation over the western plain of Taiwan during springtime. As the simulated solar insolation varies from 06 to 14LST, the developed circulation features a near-surface horizontal flow from grassland to urban reaching 2 m/s at noon and a weaker but thicker upper-layer return flow from urban to grassland. The urban patch exhibits an overall updraft with the maximum of 0.3 m/s. Both urban and the grass regions in HALF exhibit weaker vertical turbulent kinetic energy compared to URBAN and GRASS. The boundary layer over the grassland patch in HALF is more stable, with a significant transition zone at the boundary layer top. In HALF, the latent heat flux is predominantly contributed by the grassland patch, exceeding that in GRASS by 9% at noon. The column water vapor (CWV) over the grassland patch in HALF remains constant over time, while the CWV over the urban patch increases. As the induced circulation crossing different land types in HALF potentially plays a dominant role in energy transport, future investigations will focus on its influence on local stability, entrainment at boundary layer top and local surface fluxes.

Numerical Simulation of Water Vapor Changes in Yilan Under Cold High-pressure Conditions

Pei-Di JENG+, Jou-Ping HOU#
National Defense University

To understand the difference in the amount of water vapor transported to Yilan under the influence of the northeast monsoon, this study used the WRF model (Weather Research and Forecasting Model, WRF) to simulate water vapor transported by different types of cold high pressure with the highest spatial resolution of 500 m. Calculate the total amount of water vapor and water vapor flux in the Lanyang Plain, and analyze the potential precipitation trend in this area. The research results found that on November 26, 2021, and October 25, 2022, the cold high pressure was at a higher latitude (40 N), and the low-level water vapor content in the Yilan was higher; on December 6, 2023, and December 7, 2023, the cold high pressure was at a lower latitude (30 N), and the low-level moisture is lower. Such a result may be related to the strength of the cold air mass, the path and time of the cold air mass passing through the ocean, and the physical mechanism of cold air mass transformation in the ocean boundary layer.

Examining the Long-term Variations in the Winter Rainfall Features in Yilan, Taiwan and the Future Projections Under Climate Change Scenarios

Chin-Hsiang WU, Shih-Hao SU#+
Chinese Culture University

The northeast Taiwan region, particularly Yilan, exhibits distinct spatial rainfall patterns during wintertime northeasterly conditions. These patterns are intricately connected to the interaction between large-scale background flow and complex topography. Kabasawa (1950) initially described the characteristic winter rainfall in Yilan, noting a decrease in precipitation from the coast towards the southwestern mountainous region. Su et al. (2022) further developed a conceptual model during the YESR2020 campaign, elucidating the interplay between local circulation and rainfall patterns influenced by northeasterly winds and complex terrain. This model contrasts with Kabasawa's (1950) findings, revealing a decline in rainfall distribution from the southwestern mountains towards the plains. Spatial rainfall characteristics are intricately linked to variations in large-scale background wind features and moisture flux distribution. Over the past 40 years, an analysis of Yi-Lan's rainfall unveiled terrain-locked precipitation patterns, emphasizing the ERA5 reanalysis data to assess long-term changes in wind features and moisture distributions. Notably, rainfall hotspots were identified on the windward side of prevailing northeasterlies in the mountainous region, decreasing towards the plains. Average rainfall exhibited an upward trend, particularly pronounced in the southern mountain region. High-resolution cloud model experiments illustrated that alterations in large-scale background wind features influence local circulation patterns over terrain, impacting convective initiation locations. This characteristic pattern was consistently observed through cluster analysis of historical rainfall data. The southern mountains experienced higher moisture flux and more easterly wind directions during precipitation hotspots. In essence, understanding the relationship between background winds and rainfall aids in projecting future changes in precipitation characteristics in Yilan under climate change scenarios.

UAV-assisted Exploration in Topographic-induced Wind and Rainfall During YESR in Yilan, Taiwan

Hou Lun LAO1#+, Sheng-Hsiang WANG1, Shih-Hao SU2, Hung-Chi KUO3
1National Central University, 2Chinese Culture University, 3National Taiwan University

During the winter Northeast Monsoon season, northern Taiwan experiences recurrent episodes of heavy rainfall. Especially in the southern Yilan, due to the unique interaction between its distinctive topography and the Northeast Monsoon, resulting in prolonged and intense rainfall. Notably, this region broke Taiwan's annual rainfall record in 2022. However, the intricacies of the interaction between the Northeast Monsoon and local topography lack clarity, primarily due to a dearth of vertical observational data. To bridge this knowledge gap, the Yilan Experiment of Severe Rainfall was executed in both 2021 and 2022 (YESR2021, YESR2022), providing comprehensive three-dimensional datasets. Utilizing two decades of meteorological station and reanalysis data, this study classifies wind directions in the Yilan region under varying environmental wind conditions. Results indicate a prevailing westward surface wind component during periods dominated by the Northeast Monsoon, with a maximum of 76.5% occurring at ambient wind directions between 50-70 degrees. This aligns with the periods of maximum rainfall duration and intensity. Moreover, the maximum frequency of intense rainfall in the plains and coastal mountain areas occurs under different angles of the environmental wind, indicating distinct mechanisms for heavy rainfall in these regions. Additionally, this study is going to incorporate high-temporal and spatial resolution unmanned aerial vehicle (UAV) vertical observations from YESR2021 and YESR2022. The aim is to calculate moist Froude number and moist static energy, providing insights into the convection location and intensity. By integrating stability analysis with ground station results, a comprehensive exploration of the favorable conditions for rainfall in the Yilan will be conducted. 

Performance Assessment of PBL Structures Based on Observation and Model Study

Fang-Yi CHENG#+, Hong ZHAO
National Central University

Due to the advances in the atmospheric boundary layer observation technique, many high spatial- and temporal-resolution instruments are deployed to investigate turbulence structures. This study conducts observation and model simulation to investigate the planetary boundary layer structures. The radial wind profiler, Doppler wind lidar, microwave radiometer profiler, and radiosonde were used to study the PBL mean and turbulent fields. We performed high-resolution WRF simulations with various types of PBL schemes to assess the impact of the PBL parameterizations on the meteorological fields. When model resolution approaches the scales of the most energy-containing turbulence, the gray-zone problem occurs. This study characterized the turbulence kinetic energy based on the observation and model simulation and assessed the model performance against the observation data. Details will be discussed during the conference.

Dispersion Simulations for an Oil Burn Experiment in Alaska

Fong NGAN1,2#+, Mark COHEN1, Hyun-Cheol KIM3, Brian GULLETT4, Johanna AURELL4, Josip ADAMS5, Victoria SCHOLL5, Chris OWEN4, Karen STONE6
1National Oceanic and Atmospheric Administration, 2University of of Maryland, 3NOAA Air Resources Laboratory, 4U.S. Environmental Protection Agency, 5U.S. Geological Survey, 6U.S. Department of Interior

An oil burn experiment was conducted at the University of Alaska Fairbanks’ Poker Flat Research Range on a subset of a 1 ha artificial pond during August 2-3, 2022. The downwind PM 2.5 concentrations were measured with unmanned aircraft systems (UAS) flown by the U.S. Geological Survey carrying the U.S. Environmental Protection Agency’s (EPA) “Kolibri” sampler. The near-field wind velocity, temperature, and relative humidity were collected using radiosonde. In this study, we used the Weather Research and Forecasting (WRF) model to provide meteorological fields in a sub-kilometer spatial resolution for running NOAA’s dispersion model, HYSPLIT, to simulate the transport and dispersion of one of the oil burn experiments. One of the sources of uncertainty in dispersion modeling is the accuracy of the meteorological input used to drive the model. Potential errors in the simulated wind fields may cause the modeled plume to move in the wrong direction, while the uncertainty of stability and turbulent parameters may result in an inaccurate mixing in the dispersion simulation. We assimilated the radiosonde data in WRF simulations through observational nudging to improve the meteorological fields that later were used to drive HYSPLIT dispersion modeling. There were seven burns in this experiment. Burn 3 was conducted on August 3, 2022, starting at 1711 UTC. The observational nudging with the wind profiles collected by the radiosonde successfully reduced the bias in wind speed and direction prediction. The nudged simulation still underpredicted the wind speed, but its variation along with altitude was much improved by the observational nudging using the radiosonde data. We compared the transport pattern from HYSPLIT results driven by two sets of WRF meteorological data (non-nudged and nudged). When using the WRF wind fields corrected by the wind measurements, the modeled plume moved in a direction more consistent with the UAS measurement.

Tue-25 Jun | 11:00 - 12:30 | Pyeongchang Hall I, Alpensia Convention Center
AS31 - Urban Greenhouse Gases Monitoring: Observation, Modeling, and Application

Session Chair(s): Chaerin PARK, Seoul National University

AS31-A002 | Invited
Watching the Earth Breathe: Observations of Carbon Dioxide and Solar-induced Fluorescence with OCO-2 and OCO-3

Thomas KUROSU#+, Abhishek CHATTERJEE, Vivienne PAYNE
California Institute of Technology

The Orbiting Carbon Observatory-2 and the Orbiting Carbon Observatory-3 are NASA's first two missions designed specifically for the space-based measurement of carbon dioxide. OCO-2 was launched in 2014 and, as part of NASA’s “A Train”, has been making continuous global measurements of dry-air column CO2 (XCO2) and solar-induced fluorescence (SIF) from a sun-synchronous, low-earth orbit with a fixed 1336h equator crossing time. In 2019 OCO-3, the spare instrument copy of OCO-2, was installed on the International Space Station (ISS). Like OCO-2, OCO-3 also measures XCO2 and SIF but does so at all times between dawn and dusk, without a fixed repeat cycle and limited to ±52º latitude due to the inclined orbit of the ISS. Both instruments perform observations in nadir, ocean glint, and target geometry, with an extra mode added to OCO-3 that is dedicated to map urban areas. This presentation will give an overview of the two missions, highlight some of the challenges of CO2 monitoring from space, and provide a summary of the contributions OCO-2&3 observations have made to advance our understanding of carbon cycle science on global and local scales.

AS31-A017 | Invited
Urban Fossil Fuel-CO2 Emissions, and the Role of the Biosphere, Based on Measurements of Atmospheric Radiocarbon

John B. MILLER1#+, Scott J. LEHMAN2, Charles MILLER3, Brian MCDONALD4
1NOAA Global Monitoring Laboratory, 2University of Colorado, Boulder, 3California Institute of Technology, 4NOAA Chemical Sciences Laboratory

Despite inventory-based, or “bottom-up”, estimates of fossil fuel-CO2 (CO2ff) emissions likely being accurate to within 10% at annual, national scales for most developed countries, uncertainties can be much larger at urban scales. Top-down approaches can also provide additional information such as the seasonality of emissions and can be closer to real time than most bottom-up approaches. We will present CO2ff emissions estimates based on atmospheric radiocarbon (14C) and CO2 measurements for the U.S., with a focus on Los Angeles. Whether from ground-based in situ sensors, or via ground-based or satellite remote sensing, measurements of CO2 concentrations alone are not sufficient to determine fossil emissions. This is because terrestrial ecosystem CO2 exchange can influence, and even dominate, spatio-temporal gradients of CO2, confounding the interpretation of CO2. The rarest isotope of C, 14C, is completely absent from fossil fuels allowing us to use precise measurements of atmospheric CO2 and its 14C:C ratio to separate the fossil and biospheric contributions to observed gradients. We will present estimates of CO2ff emissions for Los Angeles for 2015, August 2021 and summer 2023 based on regular monitoring and intensive measurement campaigns. These top-down results will be compared to bottom-up emissions estimates from Vulcan and the GRAAPES emissions data products. We will also present a summary of results from other urban areas in the United States and elsewhere highlighting the significance of the urban biosphere. Finally, we will demonstrate the application of measurements of nitrogen oxides and carbon monoxide to improve the spatial and temporal disaggregation of total CO2 into its fossil and biospheric fractions.

AS31-A014 | Invited
CarbonWatch-Urban: Granular CO2 Emissions Information for Every Town and City in New Zealand

Jocelyn TURNBULL1#+, Sara MIKALOFF FLETCHER2, Gordon BRAILSFORD2, Sally GRAY2, Rowena MOSS2, Stijn NAUS2, Lucy HUTYRA3, Kevin GURNEY4
1GNS Science, 2National Institute of Water and Atmospheric Research, 3Boston University, 4Northern Arizona University

Urban areas are responsible for the vast majority of fossil fuel CO2 emissions, thus mitigation actions are often taken at the city level. Detailed information about urban emissions and offsetting potential is needed to guide mitigation actions and to evaluate the efficacy of these actions. CarbonWatch-Urban is a multi-tiered approach to provide fine-scale CO2 emissions and sink information for all of New Zealand’s urban areas. First, we have established a high resolution (street segments and buildings, hourly) bottom-up inventory of Auckland's fossil fuel CO2 emissions from a variety of data sources and optimised the UrbanVPRM land surface model to estimate the biogenic CO2 budget of the Auckland region. We use in situ and flask observations of CO2, 14CO2, CO, COS and black carbon to separate and quantify the various components of Auckland’s CO2 flux, and an atmospheric inversion framework to rigorously validate and improve the bottom-up flux estimates. Yet the majority of New Zealand’s urban CO2 emissions are from smaller towns and cities, and simply extending the Auckland observation framework across the country is not feasible due to topography, urban form and cost constraints. Therefore use Auckland experience to expand the bottom-up flux modelling framework nationally, applying the improvements identified in Auckland. We use a less rigorous but realistic campaign-style flask observations system from a range of towns and cities spanning New Zealand’s climate, topography and urban from to validate and improve the flux models and provide the best estimates of New Zealand’s urban emissions, with granular information in space and time. 

Characterizing Tokyo’s Methane Sources from Vehicle-based Measurements

Taku UMEZAWA1#, Yukio TERAO1+, Masahito UEYAMA2
1National Institute for Environmental Studies, 2Osaka Metropolitan University

Cities are the major source of greenhouse gases and thus target for emission reduction. Recent reports on atmospheric measurements of methane and its fluxes in urban areas suggest that substantial emissions occur in many cities, and emission inventories are highly uncertain for urban sources such as energy and waste sectors. Tokyo is Japan’s and world’s largest megacity and urgently needs investigation of accurate greenhouse gas emissions to support mitigation actions. We developed a vehicle-based mobile measurement system with a mid-infrared absorption spectrometer for methane and ethane (MIRA ULTRA, Aeris Technologies). Ethane helps us identify leakage of natural gas since its representative methane/ethane composition is known. In September–October 2023, we conducted 3-week mobile measurements in Tokyo and surrounding areas with total driving distance of about 2400 km. About 1000 points with high methane elevations were identified, and ethane/methane enhancement ratio calculated for individual points were used to group them into biogenic, fossil fuel and combustion sources. The ethane-methane classification indicated that major contributions to Tokyo’s methane emissions come from biogenic and fossil fuel sources, while combustion sources are relatively minor. Strong biogenic methane peaks were found around landfill sites and wastewater treatment plants, and fossil fuel peaks were found frequently in residential and industry areas. Presentation will include discussion on emission magnitudes.

On the Large Variation in Atmospheric CO2 Concentration at Shangdianzi GAW Station During Two Dust Storm Events in March 2021

Xiaolan LI1#+, Weijun QUAN2, Xiao-Ming HU3
1China Meteorological Administration, 2Environmental meteorology Forecast Center of Beijing-Tianjin-Hebei, 3The University of Oklahoma

Dust storms have large impacts on air quality and meteorological elements; however, their relationships with atmospheric greenhouse gases (e.g., CO2) and radiation components remain uncertain. In this study, the co-variation of dust and CO2 concentrations and its possible influencing mechanism are examined using observations at the Shangdianzi (SDZ) regional Global Atmosphere Watch (GAW) station along with simulations of the Vegetation Photosynthesis and Respiration Model coupled with the Weather Research and Forecasting model (WRF-VPRM), during two dust storm events on March 15 and 28, 2021. During these events, hourly CO2 concentrations decreased by 40–50 ppm at SDZ while dust concentrations increased to 1240.6 and 712.4 µg m−3. The elevated dust increased diffusive shortwave irradiance by 50–60% and decreased direct shortwave irradiance by ~60% along with clouds. The dust events were attributed to the passages of two cold front systems over northern China. At SDZ, during the frontal passages, wind speed increased by 3–6 m s−1 and relative humidity decreased by 50–60%. The CO2 variations associated with the frontal systems were captured by the WRF-VPRM despite the overestimated surface CO2 level at SDZ. Biogenic CO2 flux plays an indistinctive role on the large CO2 variation at SDZ as it is weak during the non-growing season. The cold fronts pushed polluted air southeastward over the North China Plain and replaced it with low-CO2 air from Northwest China, leading to the declines in CO2. These findings demonstrate that meso-scale synoptic conditions significantly affect the regional transport and dispersion of CO2, which can influence the prediction of terrestrial carbon balance on a regional scale.

Atmospheric CO2 Concentrations and Contributions from Biogenic and Anthropogenic Sources in the Pearl River Delta Region of China

Boru MAI#+
China Meteorological Administration

The dynamics of atmospheric CO2 concentrations in urban agglomerations have been a topic of interest in research on global climate change, yet there remain significant uncertainties within the estimates of CO2 contributions from biogenic and anthropogenic sources. In this study, the Weather Research and Forecasting model coupled with the Vegetation Photosynthetic Respiration Model (WRF-VPRM) was implemented with local VPRM parameters to simulate the atmospheric CO2 concentration in the Pearl River Delta (PRD) region of China during 2019–2021. The results show that (1) WRF-VPRM accurately simulates the distribution of the atmospheric CO2 concentration in the PRD region from 27-km grids to 4-km grids, with the hourly average bias of 4-km grids being −1.27 ppm. The accuracy of CO2 simulations is significantly impacted by solar radiation, while ocean winds increase the CO2 simulation bias in coastal areas. The increase in motor carbon emissions during evening rush hours also affects the CO2 simulation accuracy in urban areas. (2) In spring, summer, autumn, and winter, the average CO2 concentrations in the PRD region were 431.56±3.01 ppm, 427.55±3.51 ppm, 426.20±3.89 ppm, and 434.27±3.82 ppm, respectively. Anthropogenic emissions were the main factor, accounting for 20.59% of the total CO2 concentration in the region; by contrast, the contribution from vegetation emissions was only 1.57%. (3) High CO2 concentration centers (CO2 exceed 436 ppm) occur throughout the year at the border of Yunfu and Zhaoqing, northeast Qingyuan, and southern Huizhou. CO2 concentrations were below 426 ppm in the region around the Pearl River Estuary in summer and fall.

Tue-25 Jun | 11:00 - 12:30 | Daegwallyeong II, Alpensia Convention Center
AS11 - Extreme Events: Observations and Modeling

Session Chair(s): Sridhara NAYAK, Japan Meteorological Corporation, Kritanai TORSRI, Ministry of Higher Education, Science, Research and Innovation, Zhenchen LIU, Fudan University

AS11-A042 | Invited
Interhemispherical Footprint on Indian Monsoon Floods

Venugopal VURUPUTUR1#+, Rajat JOSHI2, Pritam Jyoti BORAH1
1Indian Institute of Science, Bangalore, 2Princeton University

The seasonal extremes of Indian Summer Monsoon Rainfall (ISMR) - floods and droughts – are often thought to be triggered by external forcing such as the El Niño Southern Oscillation. Specifically, La Niña (El Niño) conditions are believed to modulate monsoon circulation leading to seasonally anomalous excess (deficit) rain over India. However, historical records suggest that nearly 40-50 % of these seasonal extremes (floods or droughts) over India have occurred when the equatorial Pacific sea surface temperatures were near neutral. Here, we focus specifically on monsoon floods and highlight the differences in rainfall evolution during (i) flood and normal rainfall years, and (ii) floods associated with La Niña and No La Niña conditions. Our analysis suggests that floods appear to be mainly because of increased rainfall either at the beginning and/or end of the season. In particular, we show that during Non La Niña floods, there is a near-doubling of rainfall during late-August/early-September. More importantly, we show using reanalysis that this abrupt increase in rainfall accumulation can be related to an interplay between atmospheric conditions in the northern and southern midlatitudes. Specifically, our analysis suggests that a wave train curving in from northern mid-latitudes towards equator, coupled with a blocking high centred around (60N, 15E) and an anomalously strong low level jet, in late August may have led to the observed heavy rain over India. Equally importantly, a large pressure gradient between India and Madagascar over a 20-day period in late-August appears to be a critical driver for strengthening of the low-level jet.

Arctic Sea-ice Decline Causes Extreme Tropical Precipitation Events Under Greenhouse Warming

Sandeep NARAYANSETTI#+, Swapna P, Krishnan RAGHAVAN
Indian Institute of Tropical Meteorology

Arctic sea-ice decline has been accelerating under greenhouse warming. We investigate the tropical precipitation extreme events response to declining Arctic sea-ice using observations and climate model simulations. Idealized warming experiments in which Arctic becomes ice free under greenhouse warming show robust response on the tropical precipitation extreme events. We find enhancement of mean tropical precipitation and increasing propensity of extreme precipitation events over South Asian region. The enhanced Arctic sea-ice melt increases the mid-latitude waviness transcending energy further southwards into the tropics. This in addition to northward shift of intertropical convergence zone enhances tropical precipitation. The enhanced energy in the tropics along with the anomalous mid-latitude intrusions provide a conducive environment for moisture convergence and intense summer monsoon precipitation events over South Asia. Our findings suggest that the intense precipitation events over the South Asian Summer monsoon region are projected to increase as the Arctic continues to warm more quickly than the rest of the planet under greenhouse warming.

Simulation of Heavy Rainfall Event on August 28, 2023 in West Sumatra Using 3DVar and 4DVar Weather Radar Data Assimilation

Jaka PASKI1#+, Donaldi PERMANA2, Junshi ITO1
1Tohoku University, 2Indonesian Agency for Meteorology, Climatology and Geophysics

On August 28 2023, heavy rainfall of 102 mm/day occurred over West Sumatra in Indonesia and caused flooding and landslides in the vicinity. To improve the NWP simulation of this rainfall event, weather radar data assimilation is one way to improve the initial atmospheric data conditions. This research aims to investigate the effect of Doppler weather radar data assimilation on the Weather Research Forecasting (WRF) numerical model and compare between three-dimensional and four-dimensional variations data assimilation methods (3DVar and 4DVar). Three simulations were conducted using the WRF model, i.e. without data assimilation, with 3DVar and 4DVar data assimilation. The simulation was then compared with surface rainfall observation data and Quantitative Precipitation Estimation (QPE) from Doppler weather radar data. The results indicate improvements in the numerical model using assimilated data.

Climatology of Convectively Coupled Equatorial Waves Using 20 Years of High-resolution IITM GFS Model Hindcast Simulations

Himabindu HANUMANTHU+, Parthasarathi MUKHOPADHYAY#
Indian Institute of Tropical Meteorology

Fundamental modes of tropical variability consist of convectively coupled equatorial waves (CCEWs). The understanding and simulations of CCEWs remained a significant issue in weather and climate modelling. Using 20 years of IITM GFS T1534 (~12.5 km resolution) hindcast data from 2000 to 2019, the climatology of CCEWs and the Madden-Julian Oscillation (MJO) in particular are analyzed for the first time in the present study. We evaluated the high resolution 12km GFS model prediction of tropical variability with respect to observations like IMERG rainfall and NOAA OLR data. The results shows that the features are well simulated up to day 3 forecast. However, there are certain biases noted in the simulation of tropical waves which need further improvement. The main characteristics of the climatological equatorial rainfall through it’s space–time spectra are accurately portrayed, and the model's performance is assessed by analyzing the rainfall's diurnal phase. These long-term results can serve as benchmarks to enhance the model physics for predicting such wave patterns and further improvement.

Development of UAV-mounted Image Disdrometer for Observing Raindrop Particle Size Distribution at High Altitude

Tokyo University of Science

In recent years, accurate monitoring of precipitation has become increasingly important in Japan, as heavy rainfall disasters have been becoming more frequent due to global warming. As a current rainfall monitoring system, tipping bucket rain gauges are widely used throughout Japan, but the spatial resolution are too large to capture rainfall pattern precisely. Therefore, there is a rising demand for weather radar that can observe precipitation intensity at a finer spatial resolution. Presently, Multi-Parameter Radar (MP Radar) is used as a radar-based rainfall observation system. This radar can estimate real-time raindrop particle size distribution and utilize them for rainfall intensity calculations. However, the accuracy of the estimated raindrop particle size distribution has not been sufficiently validated. In this study, we aim to validate the accuracy of the raindrop particle size distribution estimated by the MP Radar. To achieve this, we modified the Image Disdrometer developed by Onomura et al. (2019) to create an instrument capable of measuring raindrop size distributions at high altitudes. Specifically, we miniaturized the conventional Image Disdrometer to less than 1/4 of its original size and mounted it on a drone. Before conducting actual observations by flying the drone over a target region of MP Rader, we hovered it at a few meters above the ground to verify the accuracy of the raindrop particle size distribution observed by a conventional laser disdrometer and the UAV-mounted observation instrument. The results of this observation will be presented at AOGS2024.

Tue-25 Jun | 11:00 - 12:30 | Auditorium, Alpensia Convention Center
AS04 - The Asian Monsoon and Climate Change

Session Chair(s): Jianping LI, Ocean University of China, Huang-Hsiung HSU, Academia Sinica, Anja KATZENBERGER, Potsdam Institute of Climate Impact Research

AS04-A027 | Invited
Changing Characteristics of Extreme Precipitation and Temperature Across Northeast India and Bangladesh

Rajib MAITY#+, Subharthi SARKAR, Ashesh Rudra PAUL
Indian Institute of Technology Kharagpur

Northeast part of India including West Bengal (henceforth referred as NEI) and Bangladesh is facing the impacts of changing climate. A recent study revealed some interesting and crucial findings using a multi-model multi-scenario analysis on the complexity of future precipitation and temperature dynamics across NEI, including Bangladesh (Paul and Maity, 2023). Under the SSP585 scenario, the Simple Daily Intensity Index (SDII) is projected to increase by 2.4 mm/day over the last three decades of the present century (2071-2100) compared to the base value of 14.4 mm/day over 1981-2014. The analysis also reports significant changes with respect to Consecutive Dry Days (CDD), Consecutive Wet Days (CWD), Number of Summer Days Index (SU) and Warm Spell Days Index (WSDI). The maximum and minimum temperatures are expected to increase by 4.0˚C and 5.5˚C, respectively, with a higher rate of rise in minimum temperature, leading to a decrease in the Diurnal Temperature Range (DTR) by up to 1.5˚C. Other studies involving the entire Indian mainland established the most of the NEI as ‘Climate change Hotspots’ (Sarkar and Maity, 2024), with particularly pronounced exposure in multi-attributed precipitation and temperature characteristics over future than rest of the country. Further analysis including two crucial socioeconomic factors, namely, population density and Human Development Index (HDI) reveals most part of NEI to be ‘vulnerable’ to changing climate as well (Sarkar and Maity, 2024). We expect these findings to be helpful in climate-informed planning and management of multiple sectors such as, water resources, agriculture, infrastructure etc. across NEI and Bangladesh.

Exploring Temperature Sensitivity and Changes in Snow Persistency in High-mountain Asia

Manuel Tobias BLAU1,2#+, Pratik KAD2, Jenny V. TURTON3, Kyung-Ja HA2
1IBS Center for Climate Physics, 2Pusan National University, 3Arctic Frontiers AS

Snow-covered regions span over large portions of the Northern Hemisphere and polar regions. Also, alpine regions in high mountain ranges are often covered by snow. The snow cover of High-Mountain Asia (HMA) from the Hindu Kush Himalayan is undergoing an unprecedented and mostly irreversible state due to global warming. These changes pose a significant threat to two billion people and are exacerbating the risk of species extinction. Recent results indicate an overall decline in snow cover over the HMA. Our preliminary findings highlight the declining trend of snow persistence. Using current reanalysis data, satellite observations, and state-of-the-are climate simulations for the climate model intercomparison project phase 6 (CMIP6), we derived a significant decline in mountain snow persistence and its sensitivity to temperature changes. In our analysis, we identified global warming as the predominant factor contributing to the loss of snow, as opposed to regional warming. We investigated the stochastic link between the variability of the South Asian monsoon circulation and the snow cover in the HMA region. The results indicate a strong sensitivity of snow persistency and depth to regional and global warming and to the changes in accumulation rates determined by the differing strength of the monsoon systems. Further, we highlight the dependence of the results on the spatial resolution of the dataset.

Impact of Tibetan Plateau Spring Snow on the Summer Heat Wave Frequency Over the Indochina Peninsula

Xiaojing JIA#+
Zhejiang University

In this work, we investigated the impact of the interannual variation in Tibetan Plateau snow cover (TPSC) on the summer heat wave frequency (HWF) over the Indochina Peninsula (ICP) (HWF_ICP) for 1981-2020. This study shows that the spring TPSC variation over the central TP is positively correlated with the summer HWF_ICP and can explain up to 30% of the summer HWF_ICP variance. Analysis of the apparent heat source shows that more-than-normal spring snow cover over the central TP has a cooling effect on the above atmosphere, which induces negative geopotential height anomalies in the upper troposphere. The anomalous spring TPSC and its cooling effect can persist until summer. In summer, the TPSC-associated low anomalies propagate eastward to the East Asia-Japan Sea area. The anomalous westerly winds along the south flank of these low anomalies strengthen the climatological westerly jet. Changes in the westerlies are accompanied by anomalous ascending and descending air motion north and south of 30°N over the coast of East Asia and the western Pacific. The anomalous descending air motion south of 30°N causes an enhanced subtropical high, less cloud cover, and more downward solar radiation, which are favorable conditions for a greater occurrence of heat waves over the ICP. The results of current study may provide useful information for improving the seasonal forecast skill of the summer HWF_ICP variation.

The Influence of Snow Cover Over the Tibetan Plateau on Surrounding and Remote Regions' Climate

Zhibiao WANG1#+, Renguang WU2
1Chinese Academy of Sciences, 2Zhejiang University

The influence of winter-spring eastern Tibetan Plateau snow anomalies on the East Asian summer monsoon has been the focus of previous studies. The present study documents the impacts of boreal summer western and southern Tibetan Plateau snow cover anomalies on summer rainfall over East Asia and the relationship between the eastern Tibetan Plateau snow cover and the North American air temperature in spring. Analysis shows that more snow cover in the western and southern Tibetan Plateau induces anomalous cooling in the overlying atmospheric column. The induced atmospheric circulation changes are different corresponding to more snow cover in the western and southern Tibetan Plateau. The atmospheric circulation changes accompanying the western Plateau snow cover anomalies are more obvious over the midlatitude Asia, whereas those corresponding to the southern Plateau snow cover anomalies are more prominent over the tropics. As such, the western and southern Tibetan Plateau snow cover anomalies influence the East Asian summer circulation and precipitation through different pathways. Moreover, a stable relationship is identified between the eastern Tibetan Plateau snow cover and the North American SAT in spring before the mid-2000s. Positive snow-cover anomalies over the eastern Tibetan Plateau induce cooling in the local atmospheric column. The atmospheric cooling stimulates a large-scale atmospheric wave pattern at the upper level that extends northeastward from the eastern Tibetan Plateau via northeast Asia and the North Pacific to North America. An anomalous high forms over North America, accompanied by anomalous descent. In the northwestern part, the horizontal advection by anomalous southerly winds along the west flank of anomalous anticyclone induces SAT increase. In the central part, the enhanced surface sensible heat flux following anomalous descent-induced downward shortwave radiation increase leads to SAT increase.

The East-asian Spring to Summer Monsoon Weather Calendar Constructed by Self-organizing Maps of Atmospheric Low-level Winds and Applied to Taiwan Meiyu and Tropical Cyclone Analysis

Sheng-Fong HUANG#+, Mong-Ming LU
National Taiwan University

East Asian monsoon (EAM) exists substantial changes during April-July. As part of the EAM, the first distinct rainy period in Taiwan known as Meiyu occurs from pentad 27 (May 11-15) to pentad 36 (June 25-29). It makes up about one third of the annual total rainfall. The Meiyu is sensitive to a narrow rainband oriented in southwest-northeast direction from northeast Vietnam through Taiwan to Okinawa. In this study we aim to document the relationship between Taiwan Meiyu and the progression of the daily weather types and tropical cyclones (TC) in the EAM region (0°-37.5°N, 90°E-140°E). The progression is characterized by a monsoon weather calendar built on the wind patterns of 44 years (1979-2022) of April-July daily 850-hPa winds using the self-organizing map (SOM) method. The daily wind patterns are classified into 9 units of a 3×3 SOM. The occurrence frequency of each unit on the pentad basis suggests that the period of April-July can be separated to late spring (pentad 19-24), transition (pentad 25-33), and early summer (pentad 34-42) monsoon evolution stages. The monsoon weather calendar reveals the relationship between Taiwan Meiyu, TC and EAM. After separating the years to the groups with and without TCs, we found that over the SCS and the southern Philippine Sea the westerly flow is stronger and rainfall amount is larger during the years with TCs, whereas stronger northeasterly wind and less rainfall are observed over Taiwan. The results suggest that the monsoon weather calendar can be useful for identifying the unusual years of which the progression of the daily weather types is distinctly different from others and the extreme/rare events are more likely to occur.

Spatial Heterogeneity of Summer Rainfall Trends Over the Tibetan Plateau Contributed by Different Rainfall Intensities

Meirong WANG1#+, Jun WANG2, Xiuping YAO3
1Nanjing University of Information Science & Technology, 2Nanjing University, 3China Meteorological Administration Training Centre

Recent years have witnessed contrasting trends in summer total rainfall (STR) over the Tibetan Plateau (TP), with an increase in the northern and a decrease in the southern TP. This study identifies four significant centers of rainfall trends: eastern TP (“region A”), Qiangtang Plateau (“B”), Qaidam Basin (“C”), and the northern foothills of the Himalayas (“D”). Heavy rainfall dominates STR trends in regions A and D, accounting for 55.6% and 52.0%, respectively. In region B, moderate and light rainfall contribute almost equally, accounting for 37.3% and 44.8% of the STR trend, respectively. Region C is primarily influenced by light rainfall, explaining 71.2% of the STR trend. Notably, the contributions of different rainfall intensities to STR in each region vary annually, with region A experiencing more heavy rainfall, region B having moderate dominance but less light rainfall, and region C and D showing reduced and increased light rainfall contributions, respectively. Mechanistically, the strengthening of the upper-level westerly jet and the South Asian High, coupled with changes in moisture transport and convective available potential energy, collectively cause variations in rainfall intensity, characterizing the spatial heterogeneity in STR in the TP.

Monsoon Break Over the South China Sea During Summer: Statistical Features and Associated Atmospheric Anomalies

Minghao BI+, Ke XU#, Riyu LU
Chinese Academy of Sciences

This study identifies break events of the South China Sea (SCS) summer monsoon (SCSSM) based on 42 years of data from 1979 to 2020, and investigates their statistical characteristics and associated atmospheric anomalies. A total of 214 break events are identified by examining the convection evolution during each monsoon season. It is found that most events occur between June and September and show a roughly even distribution. Short-lived events (3–7 days) are more frequent, accounting for about two thirds of total events, with the residual one third for long-lived events (8–24 days). The SCSSM break is featured by drastic variations in various atmospheric variables. Particularly, the convection and precipitation change from anomalous enhancement in adjoining periods to a substantial suppression during the break, with the differences being more than 60 W m−2 for outgoing longwave radiation (OLR) and 10 mm d−1 for precipitation. This convection/precipitation suppression is accompanied by an anomalous anticyclone in the lower troposphere, corresponding to a remarkable westward retreat of the monsoon trough from the Philippine Sea to the Indochina Peninsula, which reduces the transportation of water vapor into the SCS. Besides, the pseudo-equivalent potential temperature declines sharply, mainly attributable to the local specific humidity reduction caused by downward dry advection. Furthermore, it is found that the suppressed convection and anomalous anticyclone responsible for the monsoon break form near the equatorial western Pacific and then propagate northwestward to the SCS.

Characteristics of the Precipitating System Caused Nocturnal Rainfall Over the Southern Meghalaya Plateau, Northeast India

Fumie MURATA1#+, Toru TERAO2, Hiambok J. SYIEMLIEH3, Laitpharlang CAJEE3, Shyam Sundar KUNDU4
1Kochi University, 2Kagawa University, 3North-Eastern Hill University, 4North Eastern Space Applications Centre

Diurnal variation of precipitation is distinct over the tropical region. In the Indian monsoon region, nocturnal rainfall is dominant over the upslope area of the Himalayas and Megalayas, where climatologically heavy rainfalls occur. There are several studies which investigated the mechanism of the nocturnal rainfall from observations and numerical modeling. However, investigations using in-situ weather radars have not been conducted. This study conducts a case study of a nocturnal rainfall on 20-22 July 2019, using the ISRO Cherrapunji Doppler radar, which was continuously operated in every 15 min. The radar reflectivity was corrected by the GPM DPR and in-situ disdrometer. The analysis period was in an active spell, and southwesterly wind was dominant. The convective activity became active in the south of the plateau in the nighttime and a small rainband with less than several tens kilometers was formed, approached toward the plateau.

Tue-25 Jun | 11:00 - 12:30 | Meadow Hall, Alpensia Convention Center
AS66 - Aerosols, Clouds, Radiation, Precipitation, and Their Interactions

Session Chair(s): Xiquan DONG, The University of Arizona, Chuanfeng ZHAO, Peking University

AS66-A022 | Invited
Libera and Continuity of the Earth Radiation Budget Climate Data Record

1University of Colorado Boulder, 2Jet Propulsion Laboratory

The Libera Mission, named for the daughter of Ceres in Roman mythology, will provide continuity of the Clouds and the Earth’s Radiant Energy System (CERES) Earth radiation budget (ERB) observations from space. Libera’s attributes enable a seamless extension of the ERB climate data record. Libera will acquire integrated radiance over the CERES FM6-heritage broad spectral bands in the shortwave (0.3 to 5 μm), longwave (5 to 50 μm) and total (0.3 to beyond 100 μm) and adds a split-shortwave band (0.7 to 5 μm) to provide deeper insight into shortwave energy deposition. The Libera science objectives associated with continuity and extension of the ERB data record are to identify and quantify processes responsible for ERB variability on various times scales. Key to our understanding of outgoing shortwave radiation is the radiative effects of clouds aerosols. Libera’s stewardship of the ERB record begins in the latter part of this decade, at an important juncture in the monitoring of climate change trends. The Libera split-shortwave channel will provide additional information to help quantify shortwave cloud and aerosol effects. This talk will examine our latest understanding of radiative perturbations due to clouds and aerosols and the expected contributions and advances from the Libera mission.

Global Clear-sky Downwelling Shortwave Flux Using CCCma and MODTRAN6 Radiative Transfer Models

Baike XI1#+, Xiquan DONG1, Xiang ZHONG1, Jordann BRENDECKE1, Jiangnan LI2, Howard BARKER2
1The University of Arizona, 2Environment and Climate Change Canada

Challenges persist in providing accurate estimates of Earth’s surface shortwave (SW) radiation budget at the global scale. This is partly because Radiation Transfer Models (RTMs) are needed to determine surface fluxes. In this study, clear-sky total, direct, and diffuse SW fluxes at the surface were calculated by two RTMs: the computationally taxing high-spectral resolution MODTRAN6.0.2.5 (M6.0); and a computationally efficient low-spectral resolution correlated k-distribution (CKD) (Li and Barker 2005). Both RTMs used the same inputs, which includes profiles of state variables, aerosol properties, and surface albedos. The computed SW fluxes from these RTMs were compared to the NASA CERES SYN1deg product that was computed by NASA Langley’s modified broadband Fu-Liou RTM, which is widely used to study Earth’s radiation budget. Initial comparisons between three surface SW fluxes are encouraging: global annual means are 246.5 for M6.0, 245.4 for CKD, and 242.3 Wm-2 for SYN1. While regional differences can be large, most are less than CERES’s estimated uncertainty for monthly-mean surface SW irradiance of ~6 W m-2. Sensitivities of clear-sky SW/μ0 fluxes, where μ0 is cosine of solar zenith angle, to precipitable water vapor (i.e., clear-sky water vapor radiative kernel) are about -0.7 W m-2/(kg m-2) over oceans from both M6.0 and CERES SYN1 products (Zhong et al. 2024). To quantitatively estimate their SW flux uncertainties, surface observations from seven sites in different climatic regions (polar regions, oceans, lands, desert) were used (see Brendecke et al. 2024). Computed SW fluxes from M6.0 and CKD are summarized in Table 1 (without aerosol), and three RTMs calculations with aerosols against the surface observations are listed in Table 2. Mean difference between two RTMs in Table 1 is 0.6 Wm-2, whereas their differences in Table 2 are 1.9 and 3.8 Wm-2 compared to surface observations.

Aerosol-cloud-radiation Interactions in Determining Multi-decadal Trends of Solar Radiation Reaching the Surface

Mian CHIN1#+, Huisheng BIAN2, Martin WILD3, Donifan BARAHONA1, Hongbin YU1, Yun QIAN4, Anton DARMENOV1, Paul STACKHOUSE, JR.5, Norman LOEB5, Rachel PINKER6, Yuanchong ZHANG7
1NASA Goddard Space Flight Center, 2University of Maryland, Baltimore County, 3ETH Zurich, 4Pacific Northwest National Laboratory, 5NASA Langley Research Center, 6University of Maryland, College Park, 7Columbia University

Incoming solar radiation drives the Earth’s climate system. Long-term surface observations of solar radiation reaching the surface have shown decreasing or increasing trends in different regions of the world in the past several decades, indicating the change of atmospheric components that reflect and/or absorb the solar radiation. This study investigates the roles of aerosols and clouds play in determining the multi-decadal surface radiation trends through a series of model simulations with the NASA GEOS model and analysis of ground-based observations and satellite-derived data products. We will 1) assess the effects of climate variability on trends of cloud cover and aerosol amount, 2) estimate the effects of aerosols on cloud variations and trends through aerosol-cloud-radiation interactions, and 3) identify the roles of aerosol, cloud, and climate change in multi-decadal trends of solar radiation reaching the surface in different regions of the world.

Impacts of Atmospheric Environment on Arctic Surface Radiation Balance by Changing Cloud Properties

Chuanfeng ZHAO1#+, Yan XIA2, Haotian ZHANG2
1Peking University, 2Beijing Normal University

Atmospheric environmental variables including the aerosols, the stratospheric ozone and large scale atmospheric circulations, can modify the surface radiation balance and then affect Arctic climate by changing cloud properties. Using observation data, we found that aerosols from mid-latitude via long-range transport can change the cloud properties by decreasing cloud droplet effective radius and increasing cloud liquid water path, particularly in winter. Correspondingly, aerosols from mid-latitude enhance cloud thermal emissivity, contributing to Arctic warming by 8-10 W/m2 in winter. Using reanalysis meteorology data, we further found that depletion of stratospheric ozone has a significant contribution to the Siberian warming occurred in Spring 2020. A good correlation is found between the surface warming in Siberian region and stratospheric ozone depletion. Further analysis shows that the depletion of ozone depletion increases the upper troposphere air instability, resulting in a significant increase of upper level clouds, further causing surface warming. Also using reanalysis data, we found the significance of North Atlantic Oscillation (NAO) on the surface radiation balance over Greenland ice sheet (GrIS) by modulating the spatial distribution of clouds. It shows that the spatial and temporal variations in clouds in different phases over the GrIS are closely related to the NAO, and the response of clouds to changes in the atmospheric circulation field during the NAO varies in different regions of the GrIS. Shortly, this study provides the potential warming contribution in the Arctic by modulating cloud properties from three environmental factors, aerosols, depletion of stratospheric ozone, and NAO.

Distinctive Aerosol-cloud-precipitation Interactions in Marine Boundary Layer Clouds from the ACE-ENA and SOCRATES Aircraft Field Campaigns

Xiquan DONG#+, Baike XI, Xiaojian ZHENG
The University of Arizona

The aerosol-cloud-precipitating interaction within the cloud-topped Marine Boundary Layer (MBL), are being examined using aircraft in-situ measurements from Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA) and Southern Ocean Clouds Radiation Aerosol Transport Experimental Study (SOCRATES) field campaigns. SOCRATES clouds have a larger number of smaller cloud droplets compared to ACE-ENA summertime and wintertime clouds. The ACE-ENA clouds, especially in wintertime, exhibit pronounced drizzle formation and growth, attributed to the strong in-cloud turbulence that enhances the collision-coalescence process. Furthermore, the Aerosol-Cloud Interaction (ACI) indices from the two aircraft field campaigns suggest distinct sensitivities. The aerosols during ACE-ENA winter are more likely to be activated into cloud droplets due to more larger aerosols and strong vertical turbulence. The enriched aerosol loading during SOCRATES generally leads to smaller cloud droplets competing for available water vapor and exhibiting a stronger ACI. The ACI calculated near the cloud base was noticeably larger than the layer-mean and near-cloud-top, owing to the closer connection between the cloud layer and sub-cloud aerosols. Notably, the sensitivities of cloud base precipitating rates to cloud-droplet number concentrations are more pronounced during the ACE-ENA than during the SOCRATES campaigns. The in-cloud drizzle evolutions significantly alter sub-cloud cloud condensation nuclei (CCN) budgets through the coalescence-scavenging effect, and in turn, impact the ACI assessments. The results of this study can enhance the understanding and aid in future model simulation and assessment of the aerosol-cloud interaction. From this talk, we want to tentatively answer the following three questions: What are the characteristics of MBL aerosol and clouds properties, and their similarities and differences over these regions? What are the cloud microphysical responses to the sub- and above-cloud aerosols/CCN (ACIs) To what extent the drizzle drops influence the sub-cloud aerosols/CCN (ACPIs)?.

Variation of Cloud Properties with Dust and Anthropogenic Aerosols in Northwestern Pacific

Keying LI1+, Tianyi FAN1#, Chuanfeng ZHAO2, Xin YANG1
1Beijing Normal University, 2Peking University

Dust and anthropogenic aerosols from East Asia are transported to the Northwestern Pacific (NWP) by westerlies and active extratropical cyclones, modifying clouds of different types and affecting the energy budget of Earth. These aerosols have diverse effects on cloud properties and radiation forcing due to their distinct optical and hygroscopicity properties. In this study, we investigate the variation in the cloud properties of different cloud types with dust and anthropogenic aerosols under specific weather patterns. We classify the clouds into regimes based on the "K-means" clustering algorithm utilizing the Himawari-8 satellite cloud products. Weather patterns are classified by the principal component analysis in T-mode (T-PCA) to identify the meteorological factors that favor the formation of the prevailing cloud regime under the weather systems. Events dominated by the two types of aerosols are identified based on the largest dust and anthropogenic AOD anomalies, respectively. Our analysis suggests that the sensitivities of cloud properties to AOD depend on aerosol types. Considering the influence of meteorology on the cloud processes, the relative contribution of aerosols and meteorological factors are assessed using multiple linear regression. This study helps to improve our understanding of the variation of clouds with different types of aerosols in NWP.

Tue-25 Jun | 11:00 - 12:30 | Lake Hall, Alpensia Convention Center
AS79 - Asian Summer Monsoon, Its Dynamics and Impact on Atmospheric Composition

Session Chair(s): Joowan KIM, Kongju National University

Sub-seasonal Variability of Asian Summer Monsoon Transport of Aerosols and CO to the UTLS in the Context of Recent Aircraft Observations in the Asia

Mian CHIN1#+, Huisheng BIAN2, Gao CHEN3, Peter COLARCO4, Paul A. NEWMAN1
1NASA Goddard Space Flight Center, 2University of Maryland, Baltimore County, 3NASA Langley Research Center, 4National Aeronautics and Space Administration

We present our study on the sub-seasonal variability of UTLS aerosols and CO that is a result of the variability induced by the sub-seasonal variability of the Asian summer monsoon (ASM) dynamics. We use the NASA global model GEOS simulations that incorporates emissions from anthropogenic, biomass burning, volcanic, and other natural sources to simulate CO, aerosols and related gases with model experiments separating source types (anthropogenic, biomass burning, volcanic) and source regions (East Asia, South Asia). Using the model results that are evaluated with observations from recent aircraft measurements (StratoClim, summer 2017 and ACCLIP, summer 2022) in the UTLS over the Asian summer monsoon regions, we will discuss (1) the sub-seasonal variability of transport pathways of surface-generated pollutants to reach UTLS, and (2) sub-seasonal variability of aerosol composition that is determined by the variability of source type and source regions, and (3) similarities and differences of ASM dynamics between two summers of 2017 (StratoClim) and 2022 (ACCLIP) in the context of ASM interannual variability.

Aerosol Size Distribution in the Troposphere Over the Tibetan Plateau

Dan LI#+, Janchun BIAN, Zhixuan BAI
Chinese Academy of Sciences

The Tibetan plateau around by the Taklimakan and Gobi deserts in the West and North, through have limited human activities. The aerosol vertical distribution play a key role in radiative balance. In-situ measurements are needed to investigate the size distribution of the particles in the troposphere. Aerosol size (0.13-3μm) distributions and concentration were measured by balloon-borne sensors (POPS) launched Kunming (25.01°N, 102.65°E) since 2015. However, balloons payload with POPS were launched systematically every tow month from June 2020 to November 2023 in Lhasa (29.66°N, 91.14°E) or Golmud (36.48°N, 94.93°E) or Lijiang (100.22°E, 26.85°N) over the Tibetan Plateau. In total, 36 profiles will give a vertical distribution of particles from surface to the lower stratosphere (25 km) around the Tibetan Plateau. Concentration decreased for all particle sizes above the boundary layer where smallest particles increased in the Asian tropopause aerosol layer (ATAL) around the tropopause. Furthermore, volcano and dust storm have significant impact on aerosol size distribution around the tropopause.

Possible Effects of Siberian Wildfire on Variation in Vertical Distribution of Hydrocarbons Over East-Asian UTLS During Asian Summer Monsoon

Donghee LEE1+, Ja-Ho KOO1#, Laura L. PAN2, Patrick SHEESE3, Kaley WALKER3
1Yonsei University, 2National Center for Atmospheric Research, 3University of Toronto

As many reported, the strength of Asian Summer Monsoon Anticyclone (ASMA) has increased recently. ASMA is one of the pivotal pathways of surface chemical species into upper troposphere and lower stratosphere (UTLS) over Northern Hemisphere. Also, the previous research on the linkage between intensity of ASMA and Siberian wildfire activity has been presented. Therefore, we examined the long-term variation of hydrocarbons in East Asian UTLS related to Siberian wildfire during Asian summer monsoon period. For this purpose, we used Atmospheric Chemistry Experiments (ACE)-FTS v4.1/4.2 to investigate vertical profiles of hydrocarbons (HCN, CO, C2H2, C2H6 etc.) in East Asia, and Moderate Resolution Imaging Spectroradiometer (MODIS) MOD14/MYD14 and MCD64A1 to analyze wildfire activity (Fire Count (FC) and Burned Area (BA)) in Siberia. As a result, we found the enhancement of hydrocarbons in summer (June to August) over UTLS (8-13km altitude). In addition, Siberian wildfire occurred mainly in the summer season. These enhancements of hydrocarbons in north China show the highest correlations with FC and BA in Siberia (R = ~ 0.5 to 0.6), meaning that Siberian wildfire might affect variability of hydrocarbons composition in UTLS. Additionally, we found that activity of Siberian wildfire has increased in conjunction with expanded ASMA area recently, investigated from Modern-Era Retrospective analysis for Research and Application version 2 (MERRA-2). As the ASMA expanded, we confirmed higher geopotential height, warmer temperature, arid weather in Siberia near surface. Furthermore, interesting point is that hydrocarbon concentration in UTLS has increased when ASMA intensified. However, we need to carefully evaluate increased hydrocarbon concentration related to expanded ASMA since the pattern of enhanced hydrocarbon concentration by latitude is different. This work was supported by Korea Environment Industry & Technology Institute (KEITI) through "Climate Change R&D Project for New Climate Regime", funded by Korea Ministry of Environment (MOE) (2022003560006).

Vertical Ozone Profile Pattern in August, South Korea Based on the Ozonesonde Measurement

Ja-Ho KOO1#+, Joowan KIM2, Hyungyu KANG2, Sangjun KIM1, Seonggyun NA1, Sangseo PARK3, Jin-Soo PARK4
1Yonsei University, 2Kongju National University, 3Ulsan National Institute of Science and Technology, 4National Institute of Environmental Research

In this study, we show preliminary results about the comparison of summertime (August) ozonesonde measurements from 2021 to 2023. Ozonesonde measurements were performed in both western (Anmyeon, Seosan, and Osan) and eastern (Pohang) region of Korean peninsula. First, we found that the annual variation of tropopause height. Ozone tropopause heights are higher in 2022 compared to those in 2021 and 2023. Interestingly, surface ozone at Anmyeon is lower and tropospheric convection is more intensified in 2022, implying that the tropospheric stability affects the extent of stratospheric intrusion to the troposphere, which seems associated with the enhancement of surface ozone. If we compare the ozone vertical profile between western and eastern region (i.e.,, Anmyeon vs. Pohang), free-tropospheric ozone level is higher but near-surface ozone level is lower in the east of Korean peninsula, indicating that the effect of stratospheric ozone intrusion is not much significant to the enhancement of near-surface ozone. For understanding this discrepancy, we need to consider the different pattern of air pollutant emission between the west and east of Korean peninsula; A number of power plants and industrial complex are located near the Anmyeon and Seosan). Based on these results so far, we can conclude that the intrusion of stratospheric ozone-rich air mass should be considered for assessing the high level of near-surface ozone in the region where the large emission and chemical processes of precursors happen. Additional further analyses are still necessary for better understanding.

Analysis of Ozone Intrusion Events and Comparison with Chemical Reanalyses Using Daily Ozonesonde Measurements

Hyungyu KANG1#+, Subin OH2, Sanghyun AN1, Joowan KIM1, Ja-Ho KOO3, Sangseo PARK4
1Kongju National University, 2National Institute of Meteorological Research, 3Yonsei University, 4Ulsan National Institute of Science and Technology

In order to understand the impact of the summer monsoon on ozone distribution over East Asia, 24 daily ozonesonde measurements were conducted at the Anmyeon site (36.54°E, 126.25°N), South Korea in August 2021. Electrochemical Concentration Cell (ECC) type ozonesonde was used for the ozone profiling from August 5 to 31, and it revealed an average Total Column Ozone (TCO) of 300 DU, consistent with regional climatology. Notably, TCO increased by approximately 17%, reaching 351 DU from August 17 to 19. This ozone concentration increase in the upper troposphere and lower stratosphere (UTLS) was linked to a Stratosphere-Troposphere Exchange (STE) event over the Korean Peninsula. The elevated ozone concentrations in the UTLS were examined through mid-tropospheric ozone observations, indicating a connection to the eastward expansion of the Asia summer monsoon anticyclone and subsequent anticyclonic wave breaking. Horizontal transportation also played a role in mid-tropospheric ozone concentration increases. Analysis of potential vorticity from reanalysis data revealed a coherent vertical structure with the intruded high ozone signature. Ozone data from chemistry reanalyses (MERRA-2 and CAMS) were compared to the ozonesonde measurements to assure their data quality. While TCO and stratospheric ozone are similar among the three datasets, the lower troposphere and surface values show significant spreads, revealing their uncertainty.

Source Identification of High NOx Events Observed During ACCLIP

Shawn HONOMICHL1#+, Laura L. PAN1, David EDWARDS1, Sara MARTINEZ-ALONSO1, Warren SMITH1, Allessandro FRANCHIN1, Eleanor WAXMAN2, Andrew ROLLINS2
1National Center for Atmospheric Research, 2National Oceanic and Atmospheric Administration

Lightning is one of the leading sources of upper tropospheric (UT) active nitrogen (NOx) which is an important catalyst for the production of ozone and destruction of methane in the UT. Tropospheric ozone is an important greenhouse gas and radiative forcing calculations are particularly sensitive to changes in ozone concentrations in the cold UT. Lightning NOx has a significant impact on the tropospheric ozone budget and global climate, and understanding its sources is of interest. Currently, a large range exists in estimated global emission rates of lightning NOx (2-8 Tg/yr) from models and more needs to be done to reduce this uncertainty. The Asian Summer Monsoon (ASM) has been identified as a strong source region for UT NOx. During the ACCLIP field campaign, there were numerous instances where pockets of high NO2/NO concentrations were observed in the UT by instruments on the NCAR GV and NASA WB-57 research aircraft. Since deep convection in the ASM also pumps up NOx from boundary layer sources, separating the contributions from pollution and lightning are challenging. To tackle this issue, we explore an analysis of multiple datasets, taking advantage of the high spatial and temporal resolution GEMS satellite NO2 data. With the assistance of a Lagrangian trajectory model, we examine the relationship of high NOx data from airborne in situ measurements with the GEMS high NO2 hot spots and lightning data from the Earth Networks Global Lightning network. This exploratory study aims to identify and distinguish lightning and pollution sources for high NOx measurements and provide insight for general source identification.

Monsoon Dynamics In Southern Luzon, Philippines: Raindrop Size Distribution and Soil Erosion Insights

Jefferson RAPISURA1#+, Decibel FAUSTINO-ESLAVA1, Wei-Yu CHANG2, Gabriel Angelo MAMARIL1, Bianca Maria Laureanna PEDREZUELA1, Maria Regina REGALADO1, Earvin Jon GUEVARRA1, Jenielyn PADRONES1, Loucel CUI1, Juan Miguel GUOTANA1, Rosemarie Laila AREGLADO1, Carla DIMALANTA3, Ben Jong-Dao JOU4
1University of the Philippines Los Baños, 2National Central University, 3University of the Philippines Diliman, 4National Taiwan University

This study investigates raindrop size distribution (RSD) characteristics during the Northeast Monsoon (NEM) and Southwest Monsoon (SWM) seasons in Southern Luzon, Philippines, from 2018-2023, using an OTT Parsivel disdrometer installed at the University of the Philippines Los Baños - National Agromet Station (UPLB-NAS) in Los Baños, Laguna (14.1647°N, 121.2501°E). The research reveals that smaller raindrops dominate in the NEM, while larger drops prevail in the SWM. Both monsoons exhibit predominantly stratiform rainfall, with convective rains in both SWM and NEM, displaying continental-like characteristics. Intensity-based analysis indicates a concentration of smaller drops during NEM and a higher occurrence of small drops in SWM during torrential events (> 30mm/hr). Larger drops (>3mm) are notably present in SWM across all intensity categories. Simultaneously, the study explores soil erosion processes during NEM and SWM, considering the region's susceptibility to heavy rainfall and erosion. Using the same disdrometer, the research established a relationship between rainfall intensity (R) and kinetic energy (KE). Kinetic energy expenditure (KEexp) and kinetic energy content (KEcon) expressions are introduced, exploring their relationships with R through linear, power, exponential, and logarithmic models. This integrated approach advances understanding of both precipitation dynamics and soil erosion during NEM and SWM in Southern Luzon. The implications extend to the development of accurate erosion prediction models and sustainable land management practices, enhancing the resilience of the region during these critical monsoon periods.

Tue-25 Jun | 11:00 - 12:30 | Alps Rm, Alpensia Convention Center
AS19 - Biological Aerosols in the Anthropocene

Session Chair(s): Fangxia SHEN, Beihang University, Jungho HWANG, Yonsei University

AS19-A003 | Invited
Inhalable Particle-bound Marine Biotoxins in a Coastal Atmosphere: Concentration Levels, Influencing Factors and Health Risks

Yan WU#+
Shandong University

Marine biotoxins can be aerosolized into the atmospheric environment and cause negative health effects through respiratory exposure and other pathways. Characterizing marine biotoxins (MBs) composition in coastal aerosol particles has become essential to tracking sources of atmospheric contaminants and assessing human inhalable exposure risks to air particles. Here, coastal aerosol particles were collected over an almost 3-year period for the analysis of eight representative MBs, including brevetoxin (BTX), okadaic acid (OA), pectenotoxin-2 (PTX-2), domoic acid (DA), tetrodotoxin (TTX), saxitoxin (STX), ciguatoxin (CTX) and ω-Conotoxin. Our data showed that the levels of inhalable airborne marine biotoxins (AMBs) varied greatly among the subcategories and over time. Both in daytime and nighttime, a predominance of coarse-mode AMB particles was found for all the target AMBs. Based on the experimental data, we speculate that an ambient AMB might have multiple sources/production pathways, which include air-sea aerosol production and direct generation and release from toxigenic microalgae/bacteria suspended in surface seawater or air, and different sources may make different contribution. Regardless of the subcategory, the highest deposition efficiency of an individual AMB was found in the head airway region, followed by the alveolar and tracheobronchial regions. This study provides new information about inhalable MBs in the coastal atmosphere.

AS19-A008 | Invited
Influence of Aerosol Acidity on Biological Components

Guangjie ZHENG#+
Tsinghua University

Aerosol Acidity largely regulates the atmospheric multiphase chemistry. In addition, recent studies have suggested the potential role of acidity on the biological components of particulate matter. Here, we investigated into this issue by simultaneous measurements of the chemical and biological components in Beijing, a megacity in China. Based on these measurements, the aerosol acidity can be estimated, and its potential influence on the biological components are investigated.

AS19-A002 | Invited
The Exometabolome of Culturable Microorganisms from an Urban Atmosphere

Wei HU#+, Rui JIN, Pingqing FU
Tianjin University

Atmospheric microorganisms are important components of bioaerosols and potentially impact terrestrial ecosystems and climate. The survival and metabolic activities of atmospheric microbes in suitable settlements may affect cloud chemistry and characteristics and functions of microbiomes in surface ecosystems. Therefore, the metabolic processes and characterization of metabolites occurring in atmospheric viable microorganisms settled suitable habitats remain highly explorable. This study used ultra-high resolution Fourier transform ion cyclotron resonance mass spectrometry (ESI-) to characterize the exo-metabolites of typical bacterial and fungal strains isolated from atmospheric particles at the molecular level, and the molecules were annotated using the KEGG database to investigate their metabolic processes. Microbial culture results showed that Proteobacteria, Firmicutes, and Actinobacteria dominated the culturable bacteria, while fungi were dominated by Ascomycota, with Aspergillus and Penicillium being the predominant genera. The molecular compositions of exo-metabolites from bacteria and fungi were characterized by distinct differences, with bacteria having a higher molecular diversity than fungi. Bacterial exo-metabolites were mainly composed of CHON and CHONS compounds, which accounted for over 90% of all detected compounds. While, fungal exo-metabolites were dominated by CHO and CHON compounds. Pantoea vagans produced more unsaturated hydrocarbons compounds containing amino or amide groups. The exo-metabolites (CHO compounds) of Talaromyces sp. were mainly CRAM-like compounds. The metabolite formulas were annotated and enriched using the KEGG database, revealing significant differences in central metabolic pathways between the different bacteria and fungi. Lipid metabolism was predominant in Pantoea vagans and Bacillus subtilis, while carbohydrate metabolism was the main pathway in Pseudomonas baetica and Bacillus toyonensis. The methane metabolism and lysine biosynthesis were the primary pathways in Aspergillus, and Talaromyces sp. specialized in aflatoxin biosynthesis. This study further illustrates that atmospheric microorganisms could have intense metabolic activities and provides a basis for evaluating their impacts on cloud chemistry and surface ecosystems after deposition.

Dynamic Changes of Bacterial Aerosols in Haze and Sandstorm Events: Implications for Atmospheric Processes and Public Health

Fangxia SHEN#+, Jiahui MA, Yinghan TENG
Beihang University

The adverse health effects of air pollutants are closely related to their components. Bioaerosols, as an integral part of particles, play a crucial role. However, the dynamics of bioaerosols during pollution processes are not well understood. In this study, we investigated the dynamics of bacterial aerosols over a one-week period. During the sampling period, haze and sandstorm events occurred sequentially, with a transition period in between. We applied 16S rDNA and 16S rRNA sequencing techniques to explore the total bacterial community and the active bacteria, respectively. A distinct profile of bacterial aerosols was observed during the haze and the sandstorm event. The highest bacterial diversity was observed in the sandstorm samples, while the lowest was observed in the haze samples. Furthermore, the bacterial aerosols during the haze showed the greatest difference from those during the transition period when compared to the sandstorm samples. The total bacterial profile, as revealed by 16S rRNA sequencing results, was found to be distinct from the active bacterial communities in the sandstorm samples. Similarly, the underlying ecological drivers shaping the bacterial community structures showed different patterns. We found that the selective forces played a role in shaping the active bacterial communities in the sandstorm samples, as well as the total bacteria in the haze samples. A common feature during the haze and sandstorm episodes was the long residence time of bacteria in the air, indicating that the prolonged residence can lead to changes in the structure of airborne bacterial communities. Furthermore, the results indicate that several pathogens or opportunistic pathogens were more prevalent in the active bacterial communities of the sandstorm samples and the total bacteria in the haze samples, suggesting an increased health risk for humans, animals and even plants.

Airborne Microbes in Five Important Regions of Chinese Traditional Distilled Liquor (Baijiu) Brewing: Regional and Seasonal Variations

Xue QIAO#+
Sichuan University

Baijiu is one of the six primary distilled spirits in the world. It is produced through the solid-state fermentation of grains in the open environment, so high-quality Baijiu brewing largely depends on terrior. Environmental microbes are one of the most important factors affecting the quality, quantity, and flavors of Baijiu. As atmosphere is a pool and transport pathway for microbes from the ambient environment to Baijiu brewing ecosystems, we explored the functional microbes of Baijiu brewing in five important regions. The regions fell into two topographical types, namely, plain and river-valley. In total, 41 functional microbes were identified rich (relative abundance >0.1%) in at least one of the regions, such as the fungi of Aspergillus, Candida, Cladosporium, Debaryomyces, Penicillium, Pichia, Rhizopus, Saccharomyces, and Wickerhamomyces) and the bacteria of Acetobacter, Bacillus, Clostridium, Enterobacter, Lactobacillus, Methanosarcina, Methanobacterium, Methanobrevibacter, and Pseudomonas. However, some functional bacteria (e.g., Clostridia, Gluconacetobacter, and Weissella) and fungi (e.g., Dekkera, Eurotium, Issatchenkia, Mucor, and Phoma) were not rich or were not detected in the atmosphere. Airborne microbiomes and the Phylogenetic Diversity (PD) index were significantly different between the main brewing season (winter) and the summer break in each region, except for the fungi in one region. In winter, airborne microbiomes were significantly different among almost all the regions. The relative abundance of bacterial fermentation function in each region increased from summer to winter. The relative abundances of fungal yeast function were higher in winter for the plain regions but were higher in summer for the river-valley regions. In sum, our results suggested that: (1) atmosphere was one but not the sole important source of functional microbes for Baijiu brewing and (2) microbiomes in different regions might be quite different but they could share some major functions related to Baijiu brewing.

Metagenomic and Machine Learning Meta-analyses Characterize the Airborne Resistome Features and Their Hosts in China Mega-cites

Dong WU#+
East China Normal University

Urban ambient air contains a cocktail of antibiotic resistance genes (ARGs) emitted from various anthropogenic sites. However, what largely unknown is whether the airborne ARGs exhibit site-specificity or their pathogenic hosts persistently exist in the air. Here, by retrieving 1.2Tb metagenomic sequences (n = 136), we examined the airborne ARGs from hospitals, municipal wastewater treatment plants (WWTPs) and landfills, public transit centers, and urban sites located in seven China’s megacities. As validated by the multiple machine learning-based classification and optimization, ARGs’ site-specificity was found to be the most apparent in the hospital air, with featured resistances to clinical-used rifamycin and (glyco)peptides, whereas the more environmentally prevalent ARGs (e.g. resistance to sulfonamide and tetracycline) were identified being more specific to the non-clinical ambient air settings. Nearly all metagenome-assembled genomes (MAGs) that possessed the site-featured resistances were identified as pathogenic taxa, which occupied the upper-representative niches in all the neutrally distributed airborne microbial community (P < 0.01, m = 0.22 – 0.50, R2 = 0.41 – 0.86). These niche-favored putative-resistant pathogens highlighted the enduring antibiotic resistance hazards in the studied urban air. These findings are critical, albeit the least appreciated till our study, to gauge the airborne dimension of resistomes’ feature and fate in urban atmospheric environments.

Release of Inhalable Particles and Viable Microbes to the Air During Packaging Peeling: Emission Profiles and Mechanisms

Yan WU#+
Shandong University

Packaging is necessary for preserving and delivering products and has significant impacts on human health and the environment. Particle matter (PM) may be released from packages and transferred to the air during a typical peeling process, but little is known about this package-to-air migration route of particles. Here, we investigated the emission profiles of total and biological particles, and the horizontal and vertical dispersion abilities and community structure of viable microbes released from packaging to the air by peeling. The results revealed that a lot of inhalable particles and viable microbes were released from package to the air in different migration directions, and this migration can be regulated by several factors including package material, effective peeling area, peeling speed and angles, as well as the characteristics of the migrant itself. Dispersal of package-borne viable microbes provides direct evidence that viable microbes, including pathogens, can survive the aerosolization caused by peeling and be transferred to air over different distances while remaining alive. Based on the experimental data and visual proof in movies, we speculate that nonbiological particles are package fibers fractured and released to air by the external peeling force exerted on the package and that microbe dispersal is attributed to surface-borne microbe suspension by vibration caused by the peeling force. This investigation provides new information that aerosolized particles can deliver package-borne substances and viable microbes from packaging to the ambient environment, motivating further studies to characterize the health effects of such aerosolized particles and the geographic migration of microbes via packaging.

Microbial Ecology of Indoor Environments: The Significance of Shoe Dust in Shaping Indoor Microbiota

Fangxia SHEN#+, Mengzhen WANG, Chenji LI, Haidan LI
Beihang University

The role of indoor microbial exposure in human health has received increasing attention, given that individuals spend a significant portion of their time indoors. However, the factors influencing the microbial dynamics within inhabited environments are not yet comprehensively understood. This study aimed to investigate the bacterial dynamics in both the air and floor dust within occupied environments. Residences, dormitory and office environments were chosen. And the sampling was performed over a month during which window openings were infrequent. We employed amplicon sequencing techniques to characterize the indoor bacterial and fungal communities. Our findings revealed a diverse microbial community present in both the indoor air and floor dust samples. Specifically, the bacterial communities in the air exhibited greater similarity compared to those in the floor dust, whereas the fungal communities showed less discrepancy. Analysis using the Sloan Neutral Model (SNM) indicated that stochastic processes significantly influenced the structure of both the airborne and floor-borne bacterial communities. Furthermore, we investigated the microorganisms associated with the dust on the soles of shoes and compared them to the indoor microbiome. Interestingly, we observed a high degree of similarity between the shoe-related microorganisms and those found in the floor dust. This suggests that shoe-associated microorganisms could potentially be used to “re-wild” the indoor microbiota.

Tue-25 Jun | 11:00 - 12:30 | Meeting Room, InterContinental
AS39 - Systematic and Collective Evaluation of Earth System Models

Session Chair(s): Jiwoo LEE, Lawrence Livermore National Laboratory, Yun-Young LEE, APEC Climate Center

AS39-A007 | Invited
Novel Approaches to Multi-resolution Evaluation of Climate Models: Hierarchical and Topological Data Analysis

Hugo LEE1#+, Alexander GOODMAN1, Jae Won CHOI2
1California Institute of Technology, 2The University of Texas at Dallas

Earth System Models (ESMs) exhibit varying spatial resolutions, distinct from satellite observations. We aim to determine the optimal spatial resolution for new simulations that enhance our understanding of regional climate change. Traditional upscaling, by averaging high-resolution data onto coarser grids, loses critical details. Our novel toolkit for climate model evaluation counters this by integrating Hierarchical and Topological Data Analysis (HDA and TDA) into the Jet Propulsion Laboratory's system, enabling multi-resolution analysis. The multi-resolution evaluation separately characterizes spatial features of key climate model variables at coarse and fine scales, examining their resolution-dependent performance. We leverage HDA based on the Hierarchical Equal Area isoLatitude Pixelization (HEALPix) to evaluate temperature and humidity from climate models against state-of-the-art level 3 (L3) products from AIRS and CrIS. Unlike standard latitude-longitude representations, HEALPix grids consist of hierarchical and equal-area cells that can be efficiently upscaled. We have pioneered a prototype HDA for Earth science datasets, enabling dynamic spatial resolution changes and analysis of spatial variability at multiple scales, showcasing the value of high-resolution data. Topology, the study of shapes, and the emerging field of TDA, lie at the intersection of algebraic topology, machine learning, and statistics. Topological data can reveal latent structures and play a crucial role in understanding spatiotemporal patterns in datasets. Currently, no quantitative metric measures spatial pattern differences in Earth science datasets across spatial resolutions. We developed topological descriptors that summarize the spatial structures of climate models and satellite observations into persistence diagrams (PDs). Our TDA-based measure allows for systematic evaluation of multi-resolution data without the need for regridding. TDA's greatest advantage is its ability to quantitatively compare shape properties, which are invariant under continuous transformations, thus offering a significant step forward in climate model evaluation.

NIMS/KMA Plans for Climate Change Projection Production and Utilization on CMIP7

ChuYong CHUNG1#+, Young-Hwa BYUN1, Hyun Min SUNG1, Jin-Uk KIM2, Sungbo SHIM1
1National Institute of Meteorological Sciences, 2Korea Meteorological Administration

The NIMS/KMA has been actively contributing to the CMIP program since CMIP3. NIMS participated in CMIP6 by utilizing the UKESM developed by the UK Met Office to generate future climate change scenarios for four distinct Shared Socio-economic Pathways. NIMS also employed the KMA Advanced Community Earth (K-ACE) model, a modified version of HadGEM2-AO developed through in-house research, to analyze global climate projections. Five different regional climate models were used for the regional climate simulations: HadGEM3-RA, RegCM4, CCLM, GRIMs, and WRF, organized under the CORDEX-EA program. Furthermore, for the South Korean area, NIMS produced 1km resolution climate change scenario data using the statistical downscaling technique, PRIDE. These projections played a pivotal role in contributing to the preparation of the Sixth Assessment Report by the IPCC and provided crucial foundational data for national climate change adaptation efforts. Currently, NIMS has initiated preparations for CMIP7 participation. In this program, K-ACE will be employed for producing global climate projections, having undergone improvements such as coupling with an ocean-biogeochemistry model, TOPAZ, and modifications to the cloud-aerosol process, among other enhancements. NIMS plans to use a reduced number of RCMs compared to the CMIP6 phase but intends to increase the ensemble members by combining physical processes. Currently under consideration as RCM candidates are WRF and WRF-ROMS. To comprehend the impact of climate change on local-scale heavy rain, a Convection Permitting Model can be employed. For the South Korean region, our objective is to produce more high-resolution, detailed climate scenarios through sensitivity experiments and reliability verification studies. This presentation aims to introduce KMA's Earth System Models, aligning with recent trends and developments outlined in CMIP7, and presenting the overall plans for the generation and utilization of global-regional-local climate projections in line with CMIP7.

A Close Connection Between the Double-ITCZ Biases in Atmospheric and Coupled Climate Models at Monthly Time Scale

Baijun TIAN1,2#+, Ji-Won KIM1, Michael ZHAO3
1California Institute of Technology, 2University of California, Los Angeles, 3Rutgers University

The double-intertropical convergence zone (ITCZ) bias (DIB) is one of the most prominent and long-standing tropical precipitation biases in coupled global climate models and its root causes are still unclear. Here, we examine the relative contribution of the DIB in atmospheric models and the tropical sea surface temperature (SST) bias in coupled models to the DIB in coupled models at monthly instead of annual time scale using 59 paired atmospheric and coupled models from Coupled Model Intercomparison Project Phases 5/6. We find the DIBs in atmospheric and coupled models are positively correlated at each month although with no correlation at annual mean. In contrast, the high correlation between the DIB and tropical SST bias in coupled models at annual mean becomes much weaker at each month. These changes are particularly large during boreal winter (December-April) and summer (July-September). Our results suggest that both the DIB in atmospheric models and the tropical SST bias in coupled models play an important role in producing the DIB in coupled models.

Evaluation of Seasonal-to-multiyear ENSO Prediction Skill in Multiple Decadal Prediction Systems

Jung CHOI#+, Seok-Woo SON
Seoul National University

Near-term climate predictions that incorporate seasonal-to-decadal time scales have recently received much attention from policymakers, stakeholders, and the climate science community in the context of climate risk management. The primary source of seasonal-to-multiyear prediction skill is the low-frequency variability of sea surface temperature, such as the El Niño–Southern Oscillation (ENSO). This study assesses the seasonal-to-multiyear prediction skill of ENSO using large ensembles of the Coupled Model Intercomparison Project phases 5 and 6 retrospective decadal predictions. By taking advantage of large ensemble sizes, the relative importance of the ensemble size versus the multi-model ensemble average in predicting multi-year ENSO index is evaluated. The results show that a multi-model ensemble reforecast successfully predicts ENSO over a year in advance. While its seasonal prediction skill in the following spring and summer is achieved by multi-model ensemble averaging of relatively smaller ensemble members, the multi-year prediction of winter ENSO needs a larger ensemble size. The methodology used in this study, which verifies the impact of the ensemble size and multi-model ensemble average, could be applied to any climate prediction studies and would improve our understanding of climate prediction. (Reference: Choi, J. and S.-W. Son, 2022, Seasonal-to-decadal prediction of El Niño–Southern Oscillation and Pacific Decadal Oscillation, npj Climate and Atmospheric Science 5:29;

Changes in Importance of Teleconnection Patterns Associated with Heat Wave in East Asia Under CMIP6 CDR-reversibility

Ji-Seon OH1+, Maeng-Ki KIM1#, Young-Hwa BYUN2, Hyun Min SUNG2
1Kongju National University, 2National Institute of Meteorological Sciences

In this study, we analyzed changes in teleconnection patterns associated with heat wave in East Asia using 1pctCO2 (ramp-up, 1%/yr increase) and 1pctCO2-cdr (ramp-down, 1%/yr decrease) simulations of the CMIP6 CDR-reversibility. To examine changes in teleconnection patterns associated with heat wave, Empirical Orthogonal Function (EOF) analysis was performed for the 250hPa geopotential height shifted by one year for every 30 years during the total period to show mode changes over time. The first mode represented a trend, showing consistent spatial patterns of increased and decreased geopotential height in response to change in CO2 concentration. The second mode exhibits a pattern similar to Circumglobal Teleconnection (CGT), gradually transitioning to a sub-mode during the ramp-up period with a weakening pattern. The pattern recovers during the ramp-down, but it remains in the sub-mode. The fourth mode is similar to the Arctic-Siberian Plain (ASP) pattern, which is responsible for the high-latitude East Asian heat wave pattern and is mainly in the sub-mode during the ramp-up but becomes the main mode after the transition to the ramp-down. These results suggest that the main mode of the teleconnection patterns that affect heat wave in East Asia may change as CO2 concentrations increase and decrease. [This work was funded by the Korea Meteorological Administration Research and Development Program under Grant (KMI2022-01311)].

Consistent Inter-model Spread of Extratropical Westerly Jet Meridional Positions in CMIP6 Models Between the Northern and Southern Hemispheres in Boreal Winter

Li TANG#+, Riyu LU
Chinese Academy of Sciences

This study investigates the inter-model spread of extratropical westerly jets between 52 Coupled Model Intercomparison Project phase 6 (CMIP6) models in boreal winter. The results show that there is a substantial spread in latitude of upper-tropospheric westerly jet between models, characterized by large inter-model standard deviations to the poleward and equatorward of jet axis, although the multi-model ensemble mean (MME) of the models performs well in simulating meridional position of westerly jets. Furthermore, we detect the consistency of inter-model jet position spread between the northern and southern hemispheres, based on the inter-model empirical orthogonal function (EOF) decomposition and correlation of regional-averaged zonal winds. Specifically, the models that simulate the westerly jets poleward/equatorward than MME position in one hemisphere tend to also simulate the jets poleward/equatorward in the other hemisphere. Accordingly, we define a global jet spread index to depict the concurrence of jet shift in the two hemispheres. The results of regression analyses based on this index indicate that the models positioning the jets poleward than MME tend to simulate a wider Hadley Cell, a poleward-shifted Ferrel Cell in the southern hemisphere, and a wider intertropical convergence zone (ITCZ). Finally, the inter-model spread of ITCZ width is mainly determined by the spread of convective precipitations between the models, implying that different convection parameterization schemes may play a crucial role in inducing the inter-model spread of extratropical westerly jets and the concurrence of meridional jet shift in the two hemispheres.

Intermodel Spread of the Southern Hemisphere Hadley Circulation Expansion in CMIP6

Ije HUR1#+, Changhyun YOO1, Sang-Wook YEH2, Young-Ha KIM3
1Ewha Womans University, 2Hanyang University, 3Seoul National University

The Hadley Circulation (HC) is a large-scale overturning circulation in the tropics that plays an important role in the Earth's energy and water cycles. Both observations and climate models show that the HC has been expanding poleward in recent decades, and this expansion is accelerating in future projections of the Coupled Model Intercomparison Project Phase 6 (CMIP6) models. However, the CMIP6 models differ widely in their projections of how much the HC will continue to expand, especially in the Southern Hemisphere (SH). In this study, we investigate the mechanisms by which the inter-model spread in SH HC expansion takes place. We use of the 22 CMIP6 model simulations with the historical and Shared Socio-economic Pathway (SSP) 5-8.5 scenarios. The HC is defined as the zonal mean mass streamfunction, and its edge is defined by the latitude where the sign of the streamfucntion at 500 hPa changes to positive in the subtropics. The intermodel spread in the HC trends is investigated by using the intermodel empirical orthogonal function (EOF) of the mass streamfunction trend patterns. We find that the first leading EOF (EOF1), which shows an anomaly at the HC edge, explains the 49.7% of the variance between the trend patterns and shows a significant correlation of 0.87 with the change of the HC extent. In the simulations with a relatively large HC expansion, the mean wind and temperature fields show an enhanced poleward jet shift and an increase in static stability in the subtropics. The difference in the mean fields results in intermodel spread and the eddy field. Analysis using the Eliassen-Kuo equation suggests that the meridional eddy heat flux dominantly explains the intermodel spread, while the eddy momentum flux contribution is about the half of the eddy heat flux.

Introduction to the PCMDI Metrics Package (PMP), a Tool for Collective Earth System Model Evaluation

Jiwoo LEE1#+, Ana ORDONEZ1, Paul ULLRICH1, Peter GLECKLER1, Yann PLANTON2, Min-Seop AHN3, Bo DONG1, Kristin CHANG1
1Lawrence Livermore National Laboratory, 2Monash University, 3NASA Goddard Space Flight Center

The PCMDI Metrics Package (PMP) is an open-source Python-based framework that enables objective "quick-look" comparisons and benchmarking of Earth System Models (ESMs). The PMP’s connection to the Observations for Model Intercomparisons Project (obs4MIPs) enables considerations of multiple available observation-based reference datasets. The PMP has been used for routine and systematic evaluation of thousands of simulations from Coupled Model Intercomparison Projects (CMIPs), with atmospheric focus. Its results have been produced in the context of all model simulations contributed to CMIP6 and earlier CMIP phases, and we are making progress in preparing more seamless application of the tool and the result database for the next generation of CMIP (i.e., CMIP7) with particular attention to higher resolution simulations and regional-focused evaluations. The PMP offers capabilities for modeling groups to easily evaluate simulations and track changes during the development cycle, in the context of the range of structural errors in the multi-model ensemble. The latest version of PMP, version 3, emphasizes statistics of large- to global-scale annual cycles, tropical and extratropical modes of variability including ENSO and MJO, regional monsoons, cloud feedback, extremes, and high frequency characteristics of simulated precipitation. We are working toward implementing more metrics with extending scope of the realm, such as stratosphere (e.g, QBO), atmospheric dynamics (e.g. blockings), and high-latitude area (e.g, sea-ice). The PMP is prototyping the evaluation of higher resolution simulations such as from the HighResMIPs and cloud-resolving E3SM experiments. This presentation will introduce the PMP and discuss its future plan.

Tue-25 Jun | 8:30 - 12:30 | Level 2, Meadow & Lake Hall, Alpensia Convention Center
AS - Atmospheric Sciences Poster Session

The Interactions of Multiple Local Circulations and Their Impacts on Air Quality

Yuxi LIU+, Ning ZHANG#
Nanjing University, China

Impacts of local circulations and their interactions on ozone in Suzhou on 5 June 2019 are investigated using surface observations and three-dimensional air quality simulations. It is found that cities on the southeastern shore of Lake Taihu, such as Suzhou, Jiaxing, and Huzhou, have higher ozone concentrations compared with other cities in the Yangtze River Delta, although their emission levels are relatively low. Local circulations and their interactions are found to be the primary causes of the episode. The coupling of lake-land breeze circulation (LLBC), sea breeze circulation (SBC), and urban heat island circulation (UHIC) in regions on the southeastern shore of Lake Taihu such as Suzhou and Jiaxing create wind convergence zones, influencing the spatiotemporal distribution of ozone in the boundary layer. During the daytime, the LLBC plays a dominant role in maintaining the wind convergence zone. It transports pollutants to the surrounding regions of Lake Taihu, resulting in reduced pollution concentrations over the lake and worsen air quality in surrounding areas. The UHIC decouples with SBC at noon, leading to a stronger SBC, thus contributing to a reduction in pollution in upwind regions but hinders downwind diffusion. The UHIC enhances the convergence zones of secondary circulations, making it easier for the accumulation of ozone pollutants in areas between Lake Taihu and lakeside cities.

Aviation Non-volatile Particulate Matter (nvPM) Emissions and Contrail Prediction Based on Real Flight Data

Yi Wei ZHAO+, Long Fei CHEN#, Mei Yin ZHU, Meng Yun GAO, Qian ZHANG, Sheng Hui ZHONG, Kang PAN
Beihang University, China

In response to global warming, countries are actively pursuing carbon peak growth and carbon neutrality. As the only anthropogenic emission source in the upper troposphere, the wake cloud and induced cirrus clouds caused by aviation pollutants affect the radiation balance and water vapor distribution of the earth, and the contribution rate to global warming exceeds the aviation carbon dioxide emissions. Aviation emissions also harm the environment in the airport area, which can easily lead to haze smoke and other weather. Long-term exposure to these harmful air pollutants will seriously threaten human health. However, we still face some challenges in understanding the situation of aviation emissions: (1) the total flight distance is underestimated; (2) constant fuel flow may deviate from the design value; (3) ambient air parameters are from meteorological satellite data, with low spatial resolution, which inevitably brings uncertainty. This study uses real flight data and the latest AI-based aviation emission index prediction model to predict the global aviation nvPM emission distribution and its wake cloud coverage. The results show that nvPM emissions during the full aviation flight phase are concentrated in the northern hemisphere, and the wake cloud is mainly distributed in North America, Western Europe, and East Asia.

Changes in Air Pollution and Health Risks in the United States

Guzailinuer YASEN#+, Qi LIU, Weidong GUO
Nanjing University, China

The health effects of air pollution have become more important and apparent in recent years. Exposure to air pollutants is associated with increased mortality hospitalization rates. However, it should be noted that the health effects of air pollution may vary in different regions. Here we focus on the health risks of air pollution in specific areas and the underlying attribution analysis. Considering that Day-to-day (DTD) temperature variability is an important characteristic of air temperature, which significantly affects human health, we examined the long-term trends of DTD over the past 26 years in the United States, and its association with changing air pollution. By using the observed data and The Coupled Model Intercomparison Project Phase 6 (CMIP6) multi-model simulations, We demonstrate that the positive trend of the DTD index in US can be attributed to the anthropogenic aerosols, while the negative trend of which can be attributed to the natural forcing and greenhouse gas forcing. The observed DTD enhancement over 1997-2022 is dominated by the effect of anthropogenic aerosols, while natural forcing and GHGs partially counteract the effect of anthropogenic aerosols. Based on climate modeling experiments, we demonstrate that the reduced aerosol emissions in US can contribute to the enhanced trend of DTD in USA, Which may indicate that the effect of improved air pollution on health risks in US is not entirely positive.

NOx and ClNO2 Fluxes in Urban Beijing

Xiaoxiao ZHANG1+, Bin YUAN1#, Yibo HUANGFU1, Xianjun HE1, Thomas KARL2, Martin GRAUS2, Marcus STRIEDNIG2
1Jinan University, China, 2University of Innsbruck, Austria

We employed a modified the Cavity Attenuated Phase Shift NO2 monitor and Chemical Ionization Mass Spectrometer, coupled with the eddy covariance method, to quantify NOx and ClNO2 fluxes in urban Beijing. We assessed the temporal and spatial emission characteristics of NOx, and evaluating the anthropogenic NOx emission inventory. Through ClNO2 flux measurements, we also analyzed the impact of deposition on ClNO2 concentration and yield. Our findings highlight NOx flux exhibiting spatial and temporal heterogeneity in urban Beijing. Comparison results indicate that the current emission inventory overstates NOx emission in the city of Beijing. For ClNO2, our study reveals a significant influence of deposition on its concentration and yield.

Characteristics and Source Contributions to Aerosol Aminiums Over China Coastal Area and Seas

Ying CHEN#+
Fudan University, China

Atmospheric amines are gaining more and more attention in the field of atmospheric chemistry owing to their important roles in new particle formation and growth. In this study, aerosol aminiums over a coastal city (Shanghai) and the Yellow and East China seas (YECS) were characterised. The concentrations of ammonium, dimethylaminium (DMAH) and trimethylaminium plus diethylaminium (TMDEAH) over Shanghai were all found to be higher in the winter of 2018 than in the summer of 2019, suggesting their non-negligible terrestrial contributions. DMAH and TMDEAH concentrations over the YECS in summer were closely correlated and linked to surface phytoplankton biomass, implying that marine biogenic sources might be a predominant contributor to aminiums at this time. Aminiums over Shanghai generally showed a bimodal distribution with a main peak in droplet mode and a secondary peak in condensation mode, suggesting the notable contribution of aqueous-phase or heterogeneous reaction to the formation of aminiums. In contrast, aminiums over the YECS often showed a unimodal distribution, which may be caused by the competition between amines and NH3 for reaction with acidic compounds. We estimated the contributions of marine biogenic sources, 73.6% to DMAH and 80.1% to TMDEAH over the YECS, using methanesulfonate/non-sea-salt SO42– as an indicator. Our results suggest that marine biogenic emission of amines from China’s marginal seas may have a potential impact on coastal cities, and this source should be considered in modelling new particle formation and air quality in coastal areas.

A Detailed Analysis of Ammonia Emission Estimates from Fertilizer Application in the Indian Agricultural Context

Thirunagari BABY KEERTHI1+, Sri Harsha KOTA1#, Rajesh KUMAR2
1Indian Institute of Technology Delhi, India, 2University Corporation for Atmospheric Research, United States

Atmospheric ammonia emissions are deleterious due to their role in multifaceted environmental pollution. It has been demonstrated that volatile ammonia (NH3), through interacting with sulphur dioxide and nitrogen oxide gaseous emissions, contributes to the formation of airborne fine particulate matter contributing to air quality degradation, reduced visibility, and regional haze. Further, NH3 released by nitrogen (N) fertilizer applications (FA) worldwide leads to substantial economic loss in the agriculture sector. India, after China, stands as the world's second-largest producer and consumer of synthetic N-fertilizer. Despite the significance of NH3 in the global nitrogen (N) cycle, notable inaccuracies and uncertainties persist in India regarding its atmospheric emissions. Current assessments of emissions from fertilizer applications rely on 'fixed' emission factors, introducing limitations and uncertainties in the estimation process. This study aimed to enhance the accuracy of NH3 emission estimations by correcting the fixed emission factor with different modification factors (MFs). These MFs are functions of crucial influencing variables, including fertilizer type, soil pH, application method (basal and top dressing), application rate, and temperature. In 2018-19, the overall NH3 emissions in India reached approximately 3.15 tera-grams (Tg). The considered fertilizer types encompass Urea (2959 Giga-grams (Gg)), DAP (Di-ammonium phosphate (112.6 Gg), AS (15.30 Gg), and NPK (65.96 Gg). Considering all fertilizer types, the agroclimatic regions of India characterized by the highest NH3 emissions are the ‘Trans Gangetic Plain Region (525.61 Gg)’ followed by the ‘Upper Gangetic Plain Region (466.83 Gg)’. The total NH3 emissions were found to peak during the monsoon season (Jul-Sep; 1217.35 Gg) followed by winter (Dec-Mar; 926.36 Gg). The current study addresses the exigency to minimize NH3 emissions from FA and helps in implementing various stringent mitigation strategies and regulatory actions for sustainable environmental management.

Inter-annual Variation of Nitrate in Beijing Across Seasons from 2015 to 2019: The Trends and Drivers

Wenxing FU+, Momei QIN#, Jianlin HU
Nanjing University of Information Science & Technology, China

Nitrate has become an increasingly important component of fine particulate matter (PM2.5) in some major cities in China. It didn’t decrease as rapidly as the precursor nitrogen oxides (NOx) did (or even increased), which has attracted wide interest. However, previous research mainly focused on elevated nitrate in cold seasons, leaving seasonal disparities in the trends of nitrate unclear. Here we investigated the interannual trends in nitrate at an urban site in Beijing for all seasons over 2015-2019 and explored the drivers by assembling in-situ measurements, machine learning, and chemical transport model (CTM) simulations. The results show that nitrate would increase in all seasons with the impacts of meteorology removed (i.e., de-weathered), at rates ranging from 1.1% per year in winter to 9.8% per year in summer. Such emission-induced increases in nitrate were inhibited by meteorology in the fall and winter, as a result of decreased humidity, while enhanced in the spring and summer. In addition, the de-weathered nitrate concentrations increased nonlinearly with NO2, with steeper slopes of nitrate to the precursor in 2018-2019 than in 2015-2017, reflecting a higher nitrogen oxidation ratio (NOR) in more recent years. The reduced NOx emissions in spring, fall, and winter increased nocturnal NO3 radicals, which could facilitate the heterogeneous formation of nitrate at night and promote NOR. In summer, NOR increased as well, but this might primarily be related to increased daytime OH radicals and enhanced NO2+OH nitrate production. This study highlighted the distinct impacts of emission changes and meteorology on nitrate in four seasons, and the necessity for season-specific nitrate control strategies.

Simulating the Sources of Nitrous Acid and the Impacts on Secondary Pollutants in the Fall: A Case Study in the Yangtze River Delta

Xun LI+, Momei QIN#, Jianlin HU, Jingyi LI, Xiaodong XIE
Nanjing University of Information Science & Technology, China

Nitrous acid (HONO) is a significant primary source of OH radicals in the troposphere. Thus it affects the oxidizing capacity of the atmosphere and the formation of ozone (O3) and fine particulate matter (PM2.5). However, the abundance of HONO is always not constrained in the chemical transport models (CTMs), indicating the sources have not been well recognized. In this study, we updated the parameterizations of HONO formation, particularly considering the impacts of light intensity and relative humidity on heterogeneous reactions of NO2 on ground and aerosol surfaces, and added new sources (photolysis of nitrate, the heterogenous formation of HONO on soot, etc.) in the air quality model CMAQv5.3.2. We conducted simulations and investigated major sources of HONO at a rural site in the Yangtze River Delta region in the fall of 2020. The improved HONO chemistry case led to a substantial increase in HONO and reduced the gap between the simulation and observation (NMB from -0.83% to -0.40%). A sensitivity test indicated that negative biases of modeled NO2 (most likely due to emissions) explained the remaining model-observation discrepancies. Overall, the main formation pathway of HONO at the site was the heterogeneous reaction on ground surfaces, accounting for approximately 90% of HONO formation at night and ~80% during the daytime. Meanwhile, we found a 2× increase in the daytime average OH concentration and a 1.8× increase of HO2 with improved HONO simulation, resulting in enhanced nitrate, sulfate, ammonium, and SOA by factors of 1.3, 0.3, 0.8, and 1.1, respectively. This study emphasized the role of HONO chemistry in the formation of secondary pollutants, and future work needs constraint of radicals in the CTMs as well.

The Impact of Domestic Volatile Chemical Products on Air Quality in Megacities in YRD, China

Yongliang SHE#+, Jianlin HU, Momei QIN
Nanjing University of Information Science & Technology, China

Volatile chemical products (VCPs) have been considered one of the major sources of reactive organic carbon (ROC, including volatile organic compounds (VOCs), and semi/intermediate volatile organic compounds (S/IVOCs)) in megacities. Among VCPs, emissions from domestic volatile chemical products (DVCPs, for instance, personal care products, cleaning products, and insecticides) and the associated impacts are not well understood, particularly in China. In this study, we compiled an emission inventory for DVCPs and explored the impacts of DVCP emissions on the atmospheric environment over the Yangtze River Delta (YRD) using an air quality model. The newly estimated emissions from DVCPs are four times higher than those in the traditional inventory and accounted for 10% of total residential emissions in the YRD. The simulation with updated DVCP emissions compared well with measurements in terms of DVCP tracers (e.g., siloxanes, isopropanol) in urban Shanghai. With improved gas-phase chemistry for oxygenated VOCs as well as parameterization for secondary organic aerosol (SOA) from compounds that had been overlooked earlier, DVCPs contributed to the daily maximum 1-hour O3 and SOA by up to ~3 ppb and ~1 μg/m3 in November of 2019. The impacts were higher in the urban center of Shanghai and under unfavorable meteorological conditions (e.g., stagnation). This study revealed that DVCP emissions are sources that cannot be overlooked in urban centers. Considering the dynamic nature of DVCP emissions, which evolve alongside changes in formulas and our lifestyle, they need more attention in the future.

Characteristics of Ozone Formation Using BOXMOX Model at the Incheon Skyscraper During the Ozone Alert Period in 2023

Ilkwon NAM1,2+, Jiyoung KIM1, Jeong-Min PARK1, Beomsuk KIM3, Gangwoong LEE2, Yongjoo CHOI2#
1National Institute of Environmental Research, Korea, South, 2Hankuk University of Foreign Studies, Korea, South, 3POSCO International, Korea, South

Since the residential type in urban areas have moved to the high-altitude along with increasing the number of the tall buildings, the public demand for information about atmospheric pollutants at those levels including ozone also have increased. As the first air quality monitoring station (AQM) at high altitude, the AQM at the top of POSCO Tower Songdo (37.39 °N, 126.64 °E, 305m a.s.l.) has been measured since December 2022. Because POSCO Tower Songdo is located in the upwind region of the Seoul Metropolitan Area (SMA) along with industrial complexes and large point source nearby, it is suitable location for identifying the effects from both local emission and long-range transport of ozone and precursors. During ozone alert periods (from May to June 2023), gaseous pollutants (O3, NOx, SO2, CO) and non-methane VOCs (NMVOCs) were measured using Air Quality Monitoring System (AQMS, T series, Teledyne API.) and Selected Ion Flow Tube Mass Spectrometer (SIFT-MS, Voice 200, Syft Tech.), respectively. Also, the nitrogen oxides (HONO and HNO3) were obtained by Monitor for AeRosols and Gases in ambient Air (MARGA, 2060, Metrohm) We analyzed ozone formation characteristics at high altitude in SMA using the BOX Modeling eXtensions (BOXMOX) model by conducting the sensitivity test. We believed that these results could be scientific evidence for formulating ozone management policies.

Updating the EDGAR Emission Inventory with the Developed In-house Emission Inventory Prepared from the Ground-based Surveys and Analysing Its Impact Using WRF-Chem

Arpit KATIYAR1#, Sri KOTA1, Krunesh GARG2+
1Indian Institute of Technology Delhi, India, 2Punjab Pollution Control Board, India

This study emphasizes on the initial crucial step towards mitigating the particulate matter (PM2.5) by scientifically quantifying and pinpointing its sources. The need for the accurate emission inventories is of paramount importance, and among the diverse methods available, ground-based activity data stands out for its high precision. However, preparing such emission inventories poses challenges as it is very resource and time intensive. This study focusses on the preparation of a detailed emission inventory for PM2.5, with a resolution of 300m × 300m, using ground-based activity data for eight non-attainment cities in Punjab, India (Jalandhar, Amritsar, Patiala, Mandi Gobindgarh, Khanna, Naya Nangal, Dera Bassi, and Dera Baba Nanak). Furthermore, using this in-house emission inventory, Emissions Database for Global Atmospheric Research (EDGAR) which is a widely acclaimed database, is updated and WRF-Chem simulations are performed, the results of which are also a part of this study. The findings of this study reveal Jalandhar is the highest contributor to PM2.5 emissions, estimated 4296 tons/year, respectively, while Dera Baba Nanak emerges as the least contributor with total PM2.5 emissions of 92 tons/year. The primary sources identified across all cities are predominantly vehicular, road dust, industrial, and domestic emissions, making them the top four contributors. Another important insight from this study is the identification of the hotspots within each city from the gridded total emission maps. The results of this study hold critical importance for policymakers, providing a basis for informed decisions and targeted actions to reduce emissions and protect public health. Ultimately, the study emphasizes the importance of thorough emission quantification and source identification in developing effective strategies for reducing particulate matter.

Reconciling Missing OH Reactivity in the 3-D Chemical Transport Model

Hyeonmin KIM1+, Rokjin J. PARK1#, Saewung KIM2, Do-Hyeon PARK1, Sang-Woo KIM1, Hyeong-Ahn KWON3, Jinkyul CHOI4
1Seoul National University, Korea, South, 2University of California, United States, 3University of Suwon, Korea, South, 4University of Colorado at Boulder, United States

The OH reactivity (OHR), the reciprocal of the OH lifetime, indicates the total amount of reactive trace gases loading in the atmosphere. We examine the characteristics of OHR and the environment in South Korea during the Korea-United States Air Quality (KORUS-AQ) campaign by using the comprehensive NASA DC-8 airborne measurements. The data present that anthropogenic emissions control OHR in South Korea with significant contributions of CO, OVOCs, NOX, and hydrocarbons showing the increase of observed total OHR (tOHR) near and downwind regions of the primary emission sources. However, we found that a 3-D chemical transport model (CTM), GEOS-Chem, underestimates the concentrations of CO and OVOCs compared with observations, thus causing significant OHR underestimation. To reconcile the discrepancy between observed and simulated OHR (missing OHR), we examine the model's processes, such as emission inventories and chemistry schemes. We first adopt the observationally constrained VOC emission inventory based on the preceding studies using airborne and satellite observations. The adopted emission inventories lead to the increase of simulated OVOCs (~16%), aromatics (~23%), and O3 (~4%). Second, we update tropospheric chlorine chemistry to the model, resulting in the increases of simulated NOX (~12%), O3 (~2%), OH (~5%), and HO2 (~2%). Furthermore, we quantify the impact of CO underestimation in the model on the NOX-O3-HOX cycle and simulated OHR. As a result, we reconcile some parts of the missing OHR from ~52% to ~40%, but OVOCs and O3 underestimation in the model still need to be figured out.

Impact of Aerosol Liquid Water Content on the Heterogeneous Formation of Particulate Nitrate During High-PM2.5 Events

Yongmi PARK+, Subin HAN, Youn-Suk SON, Wonsik CHOI#
Pukyong National University, Korea, South

Secondary inorganic aerosols, including sulfates, nitrates, and ammonium, are known as the primary constituents of fine particulate matter (PM2.5). Recently, the proportion of sulfates has diminished while that of nitrates has increased with the reduction in sulfur emissions due to stricter regulations. To investigate the impacts of nitrates on PM2.5 concentration growth for pollution periods, we conducted field intensives at the Yongdang Campus of Pukyong National University, located in the coastal area of Busan, from January 2021 to June 2022. The measurement site is adjacent to a port and a small industrial complex. Measured components included water-soluble inorganic ions (PILS-IC, Metrohm Eco IC 883, Metrohm) and precursor gases (NO, NO2, NH3, O3; TEI instruments). The aqueous liquid water content (ALWC) and pH were calculated using the ISORROPIA II thermodynamic equilibrium model. First, we found that nitrates played a significant role in the accumulation of high PM2.5 concentrations, regardless of the season. This study attempted to elucidate the nitrate formation mechanism that contributed to the growth of PM2.5 concentrations under highly polluted conditions. We further analyzed temporal variations and correlations among the concentrations of inorganic particles, excess ammonium, humidity, ALWC, and Ox (NO2+O3) to support the nitrate formation processes we propose here. The tentatively proposed nitrate formation process that increases PM2.5 concentrations in this coastal site is as follows. Initially, the ALWC increased through the sea breeze system due to increasing specific humidity in the daytime, in turn, increasing relative humidity at night. Then, N2O5 reacted with the surface of aerosol H2O to form HNO3 (aq) at night, leading to the formation of nitrates. Thus, the heterogeneous formation increased the concentration of nitrates at night, which subsequently led to an increase in the PM2.5 levels.

Ozone Pollution in Urban Coastal Environments: Surface Ozone Concentration Gradient and Advection Rate During Sea Breeze Periods

Subin HAN+, Yongmi PARK, Wonsik CHOI#
Pukyong National University, Korea, South

In urban coastal environments, mesoscale atmospheric circulation can potentially influence air quality by affecting the chemical processes of air pollutants. In this study, we measured air pollutant concentrations (NO2, NO, and O3) in Incheon and Ulsan, developed urban coastal areas in South Korea. Based on highly spatially resolved observations, we investigated the spatiotemporal variations of pollutants affected by local emission environments. Additionally, we examined the effects of sea breeze on surface ozone concentrations and the associated chemical processes. To verify emission environments in Incheon and Ulsan, we referred to land cover maps. Incheon is primarily traffic-oriented due to its proximity to cargo terminals, ports, and an airport, while Ulsan features extensive industrial areas along the coastline. We installed air quality sensors in representative areas for each microenvironment and conducted measurements for two weeks. We found that the variation of the air pollutant concentrations varied depending on the emission environments. Notably, an inverse correlation was observed in the NOx and O3 changes during the diurnal pattern on weekdays, and this variation was more distinct in traffic and industrial areas. These variations of NOx and O3 concentration were also evident during sea breeze periods. Measured O3 near the coast was relatively high during sea breeze periods. However, in the industrial areas with high NOx emissions, O3 concentrations showed a decreasing gradient. This suggests that NOx emissions from inland areas contributed to the reduction in O3 concentrations. Based on the O3 concentration gradient, we evaluated the impact of sea breeze on O3 concentrations through quantifying O3 advection rates, and examined approaches to the chemical budget of O3 concentrations.

Estimation of Major Emission Sources of Carbonaceous Aerosols in Industrial Area Nearby Seoul Metropolitan Area in Korea

Seora WOO1#+, Yongjoo CHOI1, Jong Sung PARK2, Pilho KIM2
1Hankuk University of Foreign Studies, Korea, South, 2National Institute of Environmental Research, Korea, South

Although carbonaceous aerosols are higher health risk to humans than PM2.5, there are still uncertainty in Physicochemical properties, transportation, and spatiotemporal distribution. This study used one year semi-continuous PM2.5 chemical composition from the Gyeonggi Air Quality Research Center in Ansan, Korea (37.31°N, 126.80°E) to identify the major sources of carbonaceous aerosols in PM2.5. Because Ansan is a representative industrial and urban mixture area nearby Seoul Metropolitan Area, it is suitable to monitoring the various type of PM2.5 characteristics. Carbonaceous aerosols were analyzed using sunset OCEC analyzer based on NOISH (National Institute for Occupational Safety and Health) thermal optical transmittance (TOT) analysis protocol. Then, we classified the concentrations of organic carbon (OC; from OC1 to OC4) and elemental carbon (EC; from EC1 to EC6) detected depending on the analysis temperatures (310 °C to 870 °C). Additionally, the hourly-based 12 heavy metal components (Si, Ti, V, Mn, Fe, Ni, Cu, Zn, As, Se, Br, Pb) in PM2.5 was also measured using XRF (X-Ray Fluorescence spectrometer) and the major emission sources of carbonaceous aerosols will be identified using statistical approaches (such as principal component analysis (PCA) and/or a receptor model). Therefore, we believe that this research will be helpful to formulating effective regulation policies for the carbonaceous aerosols by estimating the contribution of emission sources, quantitatively.

Source Apportionment of PM2.5 in an Industrial Area Nearby Seoul in Korea During 2020 Using Positive Matrix Factorization (PMF) Model

Pilho KIM1+, Jong Sung PARK1#, Su-Hyun SHIN1, Changhyeok KIM1, Jeong-Min PARK1, Yongjoo CHOI2
1National Institute of Environmental Research, Korea, South, 2Hankuk University of Foreign Studies, Korea, South

To improve air quality, it is important to establish effective reduction and regulation policies for major pollutants by estimating their contributions and impacts on human health. For these purposes, comprehensive semi-continuous PM2.5 measurements from the Gyeonggi Air Quality Research Center in Ansan, Gyeonggi-do (37.3202 ºN, 126.8283 ºE, 13 m above sea level), which is located in industrial and urban mixture areas, has been conducted since 2020 to identify characteristics of complicated industrial areas. We selected hourly-based chemical species of PM2.5 from January 1 to December 31 in 2020, including inorganic ions from an ambient ion monitor (9000D AIM), trace elements from an online x-ray fluorescence spectrometer (XRF Xact 625i), and carbonaceous aerosol (organic and elemental carbon) from thermal optical transmittance analyzer (Semi-continuous OCEC Analyzer) based on a modified NOISH (National Institute for Occupational Safety and Health) Method. To estimate the contributions of sources, the Positive Matrix Factorization (PMF) receptor model was applied to PM2.5 chemical speciation data which passed the strict QA/QC criteria. The highest source contribution was ammonium nitrate as 39.6% and followed by ammonium sulfate (21.3%), Gasoline (10.9%), Diesel (9.8%), Roadway emission (7.7%), Industry (3.8%), Coal Combustion (2.6%), Oil Combustion (1.8%), Soil (1.4%), and Nonferrous metal (1.0%). Additionally, conditional probability function (CPF) analysis was performed to understand the influence of local emissions. Most emission sources were located in the west direction where an industrial area and a highway are located. However, the diesel emission source was highly contributed from the east direction, where Ansan Bus Terminal and major commercial facilities are located. We believe the evidence of local contributions will be useful in formulating policies that improve the air quality in industrial/urban mixed areas in Gyeonggi Province, Korea.

Simultaneous Measurements of Nocturnal NO3 Radical and N2O5 in the Wintertime in Seoul During the ASIA-AQ Campaign

Chisung YUN1+, Yongjoo CHOI1, Jeonghwan KIM1, Jiseon LEE1, Taekyung YI2, Changdong YUN2, Hyunmin LEE2, Meehye LEE2, Gangwoong LEE1#
1Hankuk University of Foreign Studies, Korea, South, 2Korea University, Korea, South

NO3 radical was found to play a critical role as a dominant oxidant in the nocturnal atmospheric chemistry, especially in the absence of the OH radical. It mainly oxidizes volatile organic compounds (VOCs) and NOx in an urban air mass during the night. Furthermore, N2O5, produced by the reaction with NO3 radical and NO2 in thermal equilibrium, contributes to the formation of nighttime secondary organic aerosol and the subsequent increase in daytime ozone production through a series of heterogeneous reaction. The chemistry of these reactive nitrogen oxides is significantly influenced not only by its source and sink mechanisms but also by complex weather conditions, including local and region circulations. Therefore, it is necessary to continuously monitor the chemical processes of NO3 radical and N2O5 for all seasons. We performed to measure NO3 radical in the summertime using a home-made Long-Path Differential Optical Absorption Spectroscopy (LP-DOAS) in Seoul. Currently, we also successfully developed Incoherent Broadband Cavity-Enhanced Absorption Spectroscopy (IBB-CEAS) to observe N2O5. This study aims to simultaneously measure and characterize the NO3 radical and N2O5 in the wintertime at Korea University in Seoul during the Asia-AQ campaign. Subsequent analysis will be conducted to assess the wintertime temporal variations and chemical mechanisms based on the production and loss of NO3 radical and N2O5 in Seoul with the simultaneous measurements of key trace gases, particulate pollutants and meteorological parameters. The detailed data analysis will be presented during the conference.

The Shear-relative Variation of Inflow Angle and Its Relationship to Tropical Cyclone Intensification

Jie MING1#+, Jun ZHANG2, Rogers ROBERT3
1Nanjing University, China, 2University of Miami, United States, 3NOAA's Atlantic Oceanographic and Meteorological Laboratory, United States

Characterizing inflow structure is important to better represent tropical cyclone impacts in numerical models. While much research has considered the impact of storm translation on the distribution of inflow angle, comparatively less research has examined its distribution relative to the environmental wind shear. This study analyzes data from 3655 dropsondes in 44 storms to investigate the radial and shear-relative distribution of surface inflow angle. Emphasis is placed on its relationship with intensity change. The results show that the radial variation in the inflow angle is small and not significantly dependent on the shear magnitude or intensity change rate. In contrast, the azimuthal distribution of the inflow angle shows a significant asymmetry, with the amplitude of the asymmetry increasing with shear magnitude. The maximum inflow angle is located in the downshear side. The degree of asymmetry is larger in the outer core than in the eyewall. Intensifying storms have a smaller degree of asymmetry than steady-state storms under moderate shear.

Statistical Seasonal Forecasting of Tropical Cyclone Landfalls on Taiwan Island

Ziqing CHEN+, Kelvin T. F. CHAN#
Sun Yat-sen University, China

Forecasting tropical cyclone (TC) activities has been a topic of great interest and research. Taiwan island is one of the key regions that is highly exposed to TCs in the western North Pacific. Here we utilize the mainstream reanalysis datasets in 1979–2013 and propose an effective statistical seasonal forecasting model, namely the Sun Yat-sen University (SYSU) Model, for predicting the number of TC landfalls on Taiwan island based on the environmental factors in the preseason. The comprehensive predictor sampling and multiple linear regression shows that the 850-hPa meridional wind over west of the Antarctic Peninsula in January, the 300-hPa specific humidity at the open ocean southwest of Australia in January, the 300-hPa relative vorticity at the west of the Sea of Okhotsk in March and the sea surface temperature in April at the South Indian Ocean are the most significant predictors. The correlation coefficient between the modeled results and observations reaches 0.87. The model is validated by the leave-one-out cross validation and recent 9-year observations (2014–2022). The prediction of the SYSU Model exhibits a 98% hit rate in 1979–2022 (43 out of 44), suggesting an operational potential in the seasonal forecasting of TCs landfall on Taiwan island.

Distinct Future Changes of ENSO-induced Tropical Cyclone Activities Between Atmosphere-only and Coupled Models in the CMIP6

Fang WANG1+, Zhao JIUWEI1#, Zhang LEYING2
1Nanjing University of Information Science & Technology, China, 2Nanjing Forestry University, China

This study utilizes the HighResMIP-CMIP6 data to investigate future changes in tropical cyclone (TC) activity, including TC genesis frequency (TCGF) and track density (TCTD), in response to El Niño-Southern Oscillation (ENSO). The TC activity changes from uncoupled (atmosphere-only) and coupled runs are very diverse, indicating large uncertainty for future projections. Full-coupled models projected an El Niño-like Sea surface temperature (SST) warming over the equatorial Pacific, while uncoupled (atmosphere-only) models reveal a La Niña-like warming pattern. This SST difference further induced diverse atmospheric circulation anomalies, eventually contributing to distinct TCGF and TCTD changes during ENSO phases for future projections. Further detailed analysis reveals that the El Niño-like or La Niña-like warming patterns are two extreme cases. It shows a strong variance of simulated SST across different models. The accurate projection and simulation of central Pacific SSTs and Eastern Pacific SSTs is the key to reducing the diverse behaviors of TC activity among these models. We detected three crucial regions, that is the central Pacific, the subtropical eastern North Pacific, and the equatorial eastern Pacific, that could modulate TC activity in response to ENSO in numerical models. These results help to further improve the accuracy of models to simulate future TC changes.

Assessment of an Experimental Version of fvGFS for TC Genesis Forecasting Ability in the Western North Pacific

Shu-Jeng LIN1#+, Huang-Hsiung HSU2
1Chinese Culture University, Taiwan, 2Academia Sinica, Taiwan

We evaluated the ability of the fvGFS with a 13-km resolution in simulating tropical cyclone genesis (TCG) by conducting hindcast experiments for 42 TCG events over 2018–19 in the western North Pacific (WNP). We observed an improved hit rate with a lead time of between 5 and 4 days; however, from 4- to 3-day lead time, no consistent improvement in the temporal and spatial errors of TCG was obtained. More “Fail” cases occurred when and where a low-level easterly background flow prevailed: from mid-August to September 2018 and after October 2019 and mainly in the eastern WNP. In “Hit” cases, 850-hPa streamfunction and divergence, 200-hPa divergence, and genesis potential index (GPI) provided favorable TCG conditions. However, the Hit–Fail case differences in other suggested factors (vertical wind shear, 700-hPa moisture, and SST) were nonsignificant. By contrast, the reanalysis used for validation showed only significant difference in 850-hPa streamfunction. We stratified the background flow of TCG into four types. The monsoon trough type (82%) provided the most favorable environmental conditions for successful hindcasts, followed by the subtropical high (45%), easterly (17%), and others (0%) types. These results indicated that fvGFS is more capable of enhancing monsoon trough circulation and provides a much better environment for TCG development but is less skillful in other types of background flow that provides weaker large-scale forcing. The results suggest that the most advanced high-resolution weather forecast models such as the fvGFS warrant further improvement to properly simulate the subtle circulation features (e.g., mesoscale convection system) that might provide seeds for TCG.

Evaluation of the Possibility of a Korean Typhoon Impact-based Forecast Using a Regional Multi-hazard Risk Index

Hana NA1,2#+, Woo-Sik JUNG2
1Chinese Academy of Sciences, China, 2Inje University, Korea, South

Typhoons affecting the Korean Peninsula are getting stronger and dying down (WMO, 2021; IPCC, 2021; Na and Jung, 2021). The National Oceanic and Atmospheric Administration (NOAA) and the National Weather Service (NWS) have established disaster prevention and changed the national management policy stance by providing information on risks in advance about the effects of extreme weather disasters, responding to them, and taking action in advance. A paradigm shift was attempted by declaring the Weather-Ready Nation (WRN), a national strategy to minimize damage, as a strategic plan for the next 10 years in 2011. Starting with the declaration of paradigm shift of WRN, various countries around the world (Britain, France, Japan, China, etc.) have conceptualized the words READY and PREPARE in relation to tropical cyclones such as typhoons and hurricanes, establishing disaster prevention. In addition, with the help of the World Meteorological Organization, several developing countries in East Asia (Philippines, Vietnam, Thailand, etc.), which are heavily affected by typhoons, are also actively introducing impact forecasts (Katie et al., 2016; Nguten et al., 2021; Nofal et al., 2021; Thuc et al., 2022; Do and Kuleshov, 2022).This study aims to evaluate the possibility of typhoon impact prediction in Korea by utilizing the risk index calculated by the Typhoon-Ready System, which was developed to establish the basis for typhoon impact prediction in Korea. The possibility and validity of the risk index were analyzed through the analysis of representative typhoon cases applying the complex weather disaster risk index based on impact prediction, and in particular, the possibility of typhoon impact prediction in Korea was evaluated through the risk level proposal for regional-specific risk indices, which are the core of impact prediction. This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No.RS-2023-00212688).

Evaluation of the Genesis Potential Indices in the CMIP6 Models with Bias Correction Methods and Projecting Future Tropical Cyclone Potential

Erandani Lakshani WIDANA ARACHCHIGE1,2#+, Wen ZHOU3, Ralf TOUMI2, Xuan WANG1, Oluwafemi Ebenezer ADEYERI1, Dushantha Sandaruwan Jayarathana WIJENDRA NAIDHELAGE 1,4
1City University of Hong Kong, Hong Kong SAR, 2Imperial College London, United Kingdom, 3Fudan University, China, 4University of Exeter, United Kingdom

Genesis Potential Indices (GPIs) indicate the potential of the Tropical cyclone (TC) occurrence in response to large-scale environmental conditions. Recent studies use simulated GPIs from the Coupled Model Intercomparison Project Phase 6 (CMIP6) to investigate the physical explanation of projected global TC changes. In this work, we first evaluate the ability of CMIP6 historical simulations (1979-2003) to capture long-term variations in GPIs (dynamic GPI and Emanuel GPI) compared to the GPIs from observational data sets. The presence of inherent biases in the models prevents both the GPI simulations and the individual terms of GPIs from adequately reproducing the observed variation. Thus, bias correction was conducted via direct approach using univariate (quantile delta mapping; QDM) and multivariate (N-dimensional probability density function transform; MBCn) methods and component-wise with QDM on CMIP6 simulated GPIs in historical and future projections (2075-2099) under high emission (SSP5-8.5) scenario. Overall model evaluation on all BC methods in historical GPI simulations under the direct bias correction exhibits a slightly better performance than the component-wise approach. Even though we observed no significant difference between the future changes from GPIs from bias-corrected CMIP6 and the raw models, we observed substantial model uncertainty reduction in the corrected models, emphasizing the improved reliability of the models for future projections. This study provides a comprehensive assessment of bias correction techniques used in CMIP6 models for GPI simulation, along with the projected potential for TC formation.

Straight-moving Tropical Cyclones Over the Western North Pacific Trigger the Wave Trains Over the North Pacific During Winter

Shuaiqiong MA#+, Bo PANG, Riyu LU
Chinese Academy of Sciences, China

This study investigates the large-scale circulation anomalies induced by straight-moving tropical cyclones (TCs) over the western North Pacific (WNP) during winter. Corresponding to the straight-moving TCs, a quasi-stationary wave train is excited as alternative geopotential height anomalies in the upper troposphere stretching from East Asia to the North Pacific. Specifically, the anomalous anticyclones are initially formed over East Asia to the north of TCs and then lead to the subsequent anomalies in the downstream areas. Further analysis reveals that the upper-level anticyclonic anomalies are excited by negative Rossby wave sources, which are mainly attributed to the poleward vorticity advection by anomalous divergence relevant to TCs. In addition, the diagnosis indicates that the generation of wave source is caused by the product of the TC-induced divergent flows and the prominent meridional vorticity gradient in association with East Asian upper-tropospheric westerly jet. The above processes differ from the recurving TCs in summer and autumn, which undergo extratropical transition when they move northward into the mid latitude. These findings imply that the tropical disturbances over the WNP, such as straight-moving TCs, can remotely affect weather over the extratropics, and thus have implications for improving the weather forecast over the extratropics through improving tropical disturbance forecast.

Examinations on Global Changes in the Total and Spatial Extent of Tropical Cyclone Precipitation Relating to Rapid Intensification

Yaxin LIU#+
Sun Yat-sen University, China

Moderate tropical cyclone precipitation (TCP) is of great significance to regional water resource supply, while extreme TCP could bring significant adverse impacts to ecosystems and society, especially when tropical cyclones intensify rapidly, leaving no time to take prevention actions. Whether rapid intensification (RI) of tropical cyclones (TCs) affect TCP in both land and ocean remains unknown. Here we classified TCs which have undergone increases in the maximum sustained wind speed (MSW) by at least 30 knots within 24-h into RI category. We analyzed TCP totals provided by daily precipitation from Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Climate Data Record (PERSIANN-CDR) and spatial extent from 1983 to 2019 in the four categories based on regions (land and ocean) and RI-experiencing characteristics (with- and without-RI). TCP totals and spatial extent was identified by the restricted moving neighborhood method and semi-variogram framework. The results show that TCP totals on the ocean are larger than those on the land, since RI-experiencing TCP are higher than TCP without RI experiencing, although RI processes tend to increase TCP totals in the extremely high percentiles more significantly on land than ocean. The four regions of the Northeast Pacific Ocean (EP), South Pacific Ocean (SP), Northwest Pacific Ocean (WP), and North Atlantic Ocean (NA) show increases in regional mean and extreme TCP totals. The highest increase in the extreme TCP totals (0.37 mm day−1 year−1) over the NA region occurs in the RI_ocean category, which is 2.6 times the average positive enhancement trend across all basins. The increasing rate of the extreme TCP totals over the WP region is higher in track points with RI-experiencing than without RI-experiencing. The category of RI_land over the regions of NA, EP and SP shows a significant increase in the regional mean TCP spatial extent.

Atmospheric and Oceanic Responses to Super Typhoon Mangkhut in the South China Sea: A Coupled CROCO-WRF Simulation

Mingyu LI#+, Chaoxia YUAN, Zhao JIUWEI
Nanjing University of Information Science & Technology, China

The South China Sea (SCS) is the largest marginal sea in the Northwest Pacific Ocean, and it encounters frequent typhoons. The atmosphere and ocean will create significant thermal and dynamic responses during the intense disturbance caused by typhoons. However, these responses have not been thoroughly investigated owing to the complicated marine environment. According to the satellite data, the SCS Basin was observed to have a strong SST response to Typhoon Mangkhut, resulting in widespread SST cooling. A coupled model was used to investigate the atmospheric and oceanic responses to Typhoon Mangkhut. Best-track data, satellite SST, and ARGO measurements show that the coupled WRF-CROCO simulation displays better track, intensity, SST, temperature, and salinity profiles than those of the WRF-only simulation. Results show that the typhoon induced rightward intensifications in wind speed, ocean current, and SST. The following are some remarkable atmosphere and ocean responses: (1) the SST below the inner-core region is cooled by 1°C, resulting in a 37%–44% decrease in wet enthalpy, and the central pressure is increased by ~9 hPa. Therefore, the changes in SST below the inner-core region of the SCS Basin have a significant impact on air-sea fluxes under high-wind conditions. (2) the ocean boundary layer analysis shows that near-inertial oscillations on the right side of the typhoon track and a strong inertial current up to ~2.28 m/s in the upper ocean were observed, which resonated with the local wind and flow field on the right side and induced strong SST cooling. (3) a decrease in SST decreased the moist static energy of the typhoon boundary layer, thereby weakening the typhoon’s intensity. The difference in equivalent potential temperature and sea surface pressure have a good correlation, indicating that the influence of moist static energy on typhoon intensity cannot be overlooked.

Features of Boundary Layer During Tropical Cyclone Landfall Observed at the Boseong Tall Tower

Jinhui JU1+, Doosun PARK1#, Young-Hee LEE1, Ki-Hoon KIM2, Hyeon-Ju GIM3, Taewon PARK4, Sora IN5
1Kyungpook National University, Korea, South, 2Korea Meteorological Administration, Korea, South, 3School of Earth and Environmental Sciences, Korea, South, 4Chonnam National University, Korea, South, 5National Institute Meteorological Sciences, Korea, South

This study examines the characteristics of PBL for landfalling TC cases using data from the Boseong Tall Tower. The Boseong Tall Tower, the second highest multi-level meteorological tower in Asia, provides vertical profiles of the lower planetary boundary layer (PBL), enabling investigation of the characteristics of the lower PBL over land. It is particularly useful when a tropical cyclone (TC) makes landfall, as observations with sonde over land can be difficult. Previous studies have suggested that the track, intensity and structure of a TC are influenced by turbulent processes in the Planetary Boundary Layer (PBL), and the parameterization of the TC boundary layer used in the ocean may not match well with land. Therefore, it is important to understand the characteristics of the PBL over land, especially when TCs make landfall, for better TC prediction and prevention. Based on our analysis, it appears that the log layer may not accurately represent the depth of the surface layer when assuming a near-neutral surface layer. This suggests that alternative assumptions may be necessary. In contrast to previous studies, our findings indicate that the fitted surface frictional speed (u*s) slightly increases with wind speed, while the fitted roughness length (z0) decreases with mean wind speed. These suggest that stronger surface wind speeds result in a wider range of wind speeds, which may be influenced by ocean surface features due to the proximity of the Boseong Tall Tower to the coastline. Additionally, we compare the vertical eddy diffusivity (Km) as measured by observation and the parameterization used in the numerical model. [Funding. This study was supported by the Korea Meteorological Administration Research and Development Program (KMI2022-01312)].

Enhancing Prediction of Precipitation and Winds During Typhoon Approaches

Minyeong KIM#+, Seonghee WON, Hyun-Soo LEE
Korea Meteorological Administration, Korea, South

A prediction system for wind and precipitation during typhoons affecting the Korean Peninsula was developed based on the characteristics of wind and precipitation areas along the track of past typhoons, and to improve the accuracy, sensitivity experiments were conducted based on the selection criteria for similar past typhoons. As a result of Typhoon KHANUN by selecting similar typhoon cases in the past, the wind prediction was good result, but precipitation prediction was relatively inaccurate. To improve the observation-based typhoon prediction system, we conducted a prediction experiment using an ensemble numerical model. Among the predicted ensemble members, we selected those whose typhoon centers were within 50 km of the official typhoon information and then averaged the precipitation/wind forecast fields. The wind prediction results showed over estimated, while precipitation prediction showed significant improvement in accuracy compared to observations.

Improvement in Typhoon BAVI Simulation Through Air-sea Coupling with Realistic Sea Water Salinity

Woojin CHO1#+, Dong-Hyun CHA1, Minho KWON2, Jiseok HONG2
1Ulsan National Institute of Science and Technology, Korea, South, 2Korea Institute of Ocean Science and Technology, Korea, South

The decrease in sea surface temperature (SST) with latitude is one of the factors that weakens the intensity of typhoons moving towards mid-latitude. Atmosphere-only models (i.e., WRF) with high horizontal resolution which use prescribed SST for low boundary conditions sometimes overestimate the intensity of decaying typhoons in mid-latitude. The air-sea interaction reduces this overestimate of typhoon intensity by producing realistic SST cooling below the typhoon. However, excessive SST cooling in coupled models often occurs and this can decrease the typhoon intensity. In this case, ocean vertical structure may be associated. We investigate the effect of air-sea interaction and the vertical structure of ocean below typhoon BAVI in 2020 by comparing 3-km high-resolution WRF and WRF-ROMS coupled model. For the WRF-ROMS experiment, 3D ocean data is necessary, and the HYCOM analysis data is usually used. However, the salinity of HYCOM in East China Sea has a large uncertainty because HYCOM does not fully reflect the Changjiang river freshwater. So we conducted WRF-ROMS simulation with Changjiang river discharge to create realistic salinity input for typhoon BAVI simulation. As a result, WRF with prescribed HYCOM SST overestimates the intensity of typhoon BAVI, but WRF-ROMS with HYCOM salinity underestimates the typhoon intensity. WRF-ROMS with realistic salinity shows the salinity in East China Sea is lower than normal due to high Changjiang river discharge, and the freshwater inflow makes ocean stratification in East China Sea. Ocean stratification makes a barrier layer and reduces the vertical mixing and SST cooling under typhoon BAVI, increasing typhoon intensity.

Understanding the Characteristics of Recurving Tropical Cyclones in the Western North Pacific

Md Afjal HOSSAIN+, Il-Ju MOON#, Md. Jalal UDDIN, Vineet Kumar SINGH
Jeju National University, Korea, South

Tropical cyclones (TCs) in the western North Pacific (WNP) follow two distinct tracks: some move in a west-northwest direction, while others recurve in a north-northeast direction. Recurving TCs possess a major disaster risk for the densely populated coastline of Korean Peninsula and Japan. While there have been studies on recurving TCs in the WNP, the statistical characteristics of the recurving TCs and whether their features are changing due to climate change have not been thoroughly investigated to date. Apart from that, there are discrepancies in extracting the recurving TCs in this basin. Therefore, this study proposes a new methodology comprising a set of criteria to realistically extract recurving TCs in this basin. TCs extracted based on proposed new criteria, we investigate statistical characteristics such as the seasonal distribution and trend, recurving location (latitude and longitude), the number of occurrences, lifetime maximum intensity (LMI) and recurving time nexus, translation speed, and the recurving angle of recurving TCs during the period 1981–2021 among others. Moreover, we further examine the reasons of varying frequencies of recurving TCs in different years. Results suggest that position and strength of WNP subtropical high (WNPSH) plays a pivotal role in recurving TCs varying frequencies in WNP. Finally, we investigate whether recurving TCs characteristics change over time. These findings will contribute to understanding the characteristics of recurving TCs in the WNP, especially in the face of climate change.

Westerlies Controlling of the Water Vapor Transport to the Tibet Plateau by the Tropical Cyclones in the Bay of Bengal

Xiaoli ZHOU#+
Fudan University, China

This study investigates the water vapor transport to the Tibetan Plateau (TP) induced by Bay of Bengal (BOB) tropical cyclones (TCs) in May during 1979-2019. The water vapor around the BOB TCs can be transported to the south of the TP by the southerlies at the upper troposphere east of the TC center. Whether the water vapor can cross the southern boundary of the Tibetan Plateau (SBTP) may rely on the different configurations of BOB TCs and long-wave trough and ridge. We found that the water vapor may (may not) cross SBTP if the TC’s wind field converges with the westerlies in front of the trough (ridge). The physical mechanism is explored according to the momentum equation. When the TC moves northward around the SBTP, its wind field could interact with the trough (Type-T TC) and ridge (Type-R TC) in the westerlies. In the area close to the trough line (ridge line), the meridional acceleration is positive (negative), hence meridional component of velocity increases (decreases). Therefore, it is more favorable for the water vapor transported northward if a Type-T TC enters the westerlies from the area close to the trough line than the ridge line. The simulation of the BOB TC cases configuration using WRF model confirms the importance of the relative position between the Type-T TC and the SBTP to the water vapor transport over the SBTP. For the Type-T TC, the meridional moisture budget over the SBTP is positively correlated with the TC intensity and negatively correlated with the distance between the TC center and the SBTP. However, for the Type-R TC, the meridional moisture budget is not related to the TC intensity and the distance. The configuration of TC and long-wave trough or ridge may be predictable through the intraseasonal oscillation activity in the eastern BOB and the southern Arabian Sea. May and October to December are the bimodal phases of BOB TC frequency, which decreases month by month from October to December and is relatively low in May. However, the contribution rate of MMBa is the highest in May. Seasonal variation in the meridional position of the westerlies is the key factor affecting the contribution rate. The relatively south position of the westerlies in November and December results in the lower contribution rate of MMBa.

Utilizing Satellite Remote Sensing and Meteorological Data to Evaluate Potential Wind Power Generation Sites Along the Coast and Offshore of Taiwan

Chih-Yen WANG#+, Po-Chun HSU
National Central University, Taiwan

This study evaluates potential sites for wind power generation in the Taiwan Strait and inland areas of Taiwan, employing data from multiple satellites, reanalysis, and meteorological stations. The calculation of wind energy is based on transforming these wind speed data to the elevation of wind turbines, considering blade surface area and other coefficients for potential electrical energy estimation. In offshore areas, water depth determines the suitability of fixed or floating wind turbines, with depths exceeding 60 meters being suitable for floating turbines, and shallower waters being appropriate for fixed ones. Inland Taiwan's wind patterns are influenced by topography and buildings. Due to the stability of the wind, coastal areas emerge as prime locations for wind turbine installation. The spatiotemporal characteristics of wind at each potential site are the primary considerations in this assessment. Wind speeds in the Taiwan Strait range from 4 m/s to 15m/s, typically higher in winter. According to the Meteorological Information Based Green Energy Operations Center in Taiwan, the effective wind speed range for turbines is 3 m/s to 25 m/s, which means that wind turbines can operate throughout the year in the Taiwan Strait. Additionally, climatic-scale variations in wind speed are also considered. From 2012 to 2023, an annual increase of approximately 0.15m/s was observed in February, April, May, October, and December in the Taiwan Strait. Comprehensive assessments indicate that the central offshore areas of the Taiwan Strait exhibit higher wind energy potential, with water depths conducive to fixed wind turbines.

Development of Long-term Climate Data Algorithm Based on GEMS Data

Ha Jeong JEON1+, Sangseo PARK1#, Jeong Ah YU2
1Ulsan National Institute of Science and Technology, Korea, South, 2National Institute of Environmental Research, Korea, South

The demand for long-term climate analysis is increasing with the flow of global climate change. Accordingly, the need for Level 3(L3) data from satellite observation has also increased in climate studies. In particular, the Geostationary Environmental Monitoring Spectrometer (GEMS) mounted on geostationary satellites is highly evaluated in East Asia, and it is time to develop a L3 algorithm tailored to the model grid to effectively utilize GEMS for climate analysis. Therefore, this study developed a long-term climate analysis data production algorithm based on GEMS data. Data for January 1, 2022, were estimated using GEMS AOD, NO2, and total O3 data. To consider the homogeneity of data, all data that produce L3 data was collected by using only Full Mode Scan. Data quality correction was performed by applying Cloud Fraction and Final Algorithm Flag. In addition, we used the area weighted average calculation method to achieve stable production. In this data production, the most used spatial resolution, 0.25° X 0.25°, was adopted, and using this data, the combination with other satellites for long-term data production will be conducted.

Cloud Top Characteristics of Vortices Generated on the Tibetan Plateau with Different Paths Revealed by FY-4

Bo LI#+, Yang GAO
China Meteorological Administration, China

The Tibetan Plateau Vortexes (TPV) can trigger mesoscale convective systems (MCSs) under appropriate conditions. These MCSs not only contribute most of the precipitation in the plateau area, but also move eastward along with TPV under appropriate conditions, triggering a series of mesoscale convective activities along the way. These precipitation events are often intense and long-lasting, often causing serious flooding disasters. However, due to the lack of observation data and complex terrain over plateau areas, the study of weather systems in plateau areas has always been a challenge. This work utilizes Fengyun-4 meteorological satellite and reanalysis data to study the cloud top structure characteristics of plateau vortices with different movement paths. A comparative analysis was conducted on the differences in cloud top height, cloud top temperature, cloud top brightness temperature, and brightness temperature difference of different satellite channels among three paths of plateau vortices: Colonel in situ, moving eastward but not descending to the plateau, and moving eastward beyond the plateau. The influence of these variables on the movement path of plateau vortices was also discussed.

Emission Estimation Using TROPOMI Satellite in East Asia

Jun-Yu LU#+, Fang-Yi CHENG
National Central University, Taiwan

The conventional emission estimation for air quality simulation was based on the bottom-up method, which relies on the accuracy of the emission inventory. During Taiwan's winter and spring seasons, the northeasterly monsoonal wind prevails, which transports the air pollutants from East Asia to Taiwan. However, the updates of emissions in East Asia is slow, making it challenging to promptly capture changes in emission sources. This leads to forecasting bias during transboundary pollution events. Recently, more real-time and high-resolution satellite data have been used to constrain the bottom-up estimated emissions. This study aims to use TROPOMI satellite data to update the bottom-up estimated emissions in East Asia. This correction intends to address the issue of underestimated transboundary air pollutants in Taiwan. Through a mass balance adjustment of emissions derived from satellite and model-retrieved NO2 column densities, the adjusted NOx emissions are higher than the bottom-up estimated emissions, which furthermore enhances the model performance of the transboundary pollution event.

Detection of Methane Gas Emissions in the Suncheon Area, North Korea Using Sentinel-2 Satellite Data

Minju KIM+, Jeongwoo PARK, Chang-Uk HYUN#
Dong-A University, Korea, South

As extreme weather events such as heatwaves and wildfires increasingly occur worldwide due to climate change, efforts are underway to reduce greenhouse gas emissions. Among various greenhouse gases, methane significantly impacts climate change, with a global warming potential approximately 82.5 times that of CO2 over a 20-year period. Reducing methane gas emissions, which have a relatively potent warming effect, is essential for mitigating climate change, and continuous monitoring is crucial for identifying and managing sources and amounts of emissions. Satellites can periodically observe the same areas, enabling continuous monitoring of methane emissions, and their global coverage allows for the detection of methane gas in extensive or inaccessible areas. The Sentinel-2 satellite, with its short revisit cycles and high-resolution imagery across various spectral bands, is useful for methane gas detection. Previous research has conducted methane detection studies on well-known methane emission sources using the shortwave infrared (SWIR) bands of various satellites. In this study, we utilized the Google Earth Engine (GEE), which allows for rapid analysis of satellite data in a web browser, to leverage the short revisit cycles and broad spectral band coverage of the Sentinel-2 satellite. We detected and monitored methane plumes from the 2.8 Jikdong Coal Mine located in Suncheon, South Pyongan Province, North Korea. The results of this study are expected to provide important data for the establishment of environmental policies and strategies for climate change mitigation. Furthermore, it demonstrates the practicality of remote sensing technology in methane emission monitoring and highlights the potential use of Sentinel-2 satellite data in climate change studies.

Fusion of Total Precipitable Water Using GK2A/AMI, NWP and Radiosonde Over East Asia

Seunghee LEE#+, Hyejin MOON, Jae-Young BYON, Myoung-Hee LEE
Korea Meteorological Administration, Korea, South

Total Precipitable Water(TPW), a column of water vapor content in the atmosphere, is an important meteorological factor and play a critical role in the occurrence of precipitation and atmospheric river. The current TPW algorithm operational at NMSC calculates TPW based on AMI Aerosol Profile(AAP) in for clear-sky areas, and uses values calculated from numerical weather prediction (NWP) for cloudy-sky regions. The validation results for this algorithm with radiosonde show an RMSE 6.9mm and a bias of 0.377mm. To fuse the distribution of TPW in all sky conditions, this study proposes a retrieval algorithm based on the light gradient boosting machine (LGBM) model using GK2A/AMI data, Radiosonde, ERA5, and three NWP models data. Through statistical verification, with a root mean square error (RMSE) of 6.697~7.056mm, a bias of -0.929~0.377, and a Pearson's R of 0.942~0.946. We utilize the previously generated NWP prediction field to retrieve TPW in real-time. Detailed introduction of new TPW will be presented in the conference. This research was supported by the “Technical development on high-impact weather detection and prediction using meteorological satellite data”(KMA2020-00121) of “Technical Development on Weather Forecast Support and Convergence Service using Meteorological Satellites” project funded by the National Meteorological Satellite Center, Korea Meteorological Administration.

Analysis on the Effects of Slant Path Simulation for the All-sky Data Assimilation Using a 1DVAR System

Dabin YEOM1+, Ji-Soo KIM2, Tae-Myung KIM1, Hyung-Wook CHUN3, Myoung Hwan AHN1#
1Ewha Womans University, Korea, South, 2Seoul National University, Korea, South, 3Korea Meteorological Administration, Korea, South

The theoretically calculated radiance (B) in the process of utilizing satellite data into numerical weather prediction models plays an important role in various processes. For example, the difference between observed data O and calculated B is used to understand the error characteristics of the observed data or to determine whether clouds are present in the observed data. Therefore, accurately calculating B is one of the most basic processes for the use of satellite data. To achieve this, various efforts are being made, such as improving the accuracy of radiative transfer models as well as accurately inputting surface characteristics. In this study, we focus on using temperature and humidity profiles along the slant path considering the direction in which satellite data is obtained, rather than the vertical path for the input of the radiative transfer model. Previous studies on clear-sky conditions have shown that applying a slant path result in a noticeable deviation when the viewing angle is far from nadir and in regions with high variability in atmospheric temperature and humidity. This study extends this to investigate the effect of the slant path radiative transfer model in the presence of clouds. When the horizontal range of clouds is not extensive, the presence of clouds varies depending on the chosen path. Furthermore, application of the slant path explicitly considers the parallax effect of clouds in the simulation process, allowing for a more accurate calculation of B values. Taking all these factors into account, we aim to analyze the impact of slant path simulations on vertical temperature and humidity retrieval by analyzing the results of 1DVAR models for all-sky cases.

Global Trends in Occurrence Frequency of Extremely Heavy Precipitation During 2001–2020 Derived from Various Satellite-based Precipitation Estimation Products

Hamin KOO+, Hyunho LEE#
Kongju National University, Korea, South

Heavy precipitation events are of great importance as large amounts of rainfall concentrated in a short duration can generate severe natural disasters, which then cause widespread damage to human societies. Many previous studies have shown an increasing trend in the atmospheric water vapor due to global warming, readily indicated by the Clausius-Clapeyron relation. However, most of studies on the occurrence frequency of heavy precipitation are generally conducted on regional or national scales.In this study, we use three satellite-based precipitation estimation products—Integrated Multi-satellitE Retrievals for GPM (IMERG), Global Satellite Mapping of Precipitation (GSMaP), and Global Precipitation Climatology Project (GPCP)—and one rain gauge-based precipitation product, NOAA Climate Precipitation Center (CPC), and examine the global trend in occurrence frequency of heavy precipitation from 2001 to 2020. Using the number of days when the daily precipitation amount exceeds the 95th percentile of precipitation amount (FP95) and utilizing the Mann-Kendall test, Sen’s slope estimator, linear regression, and innovative trend analysis, we find that the trends of FP95 from the various analysis methods are generally comparable but highly vary depending on the precipitation products. The trends of FP95 in the lands from IMERG and GPCP are generally similar with those from CPC. However, the trends in the oceans are noticeably inconsistent across all the products. The FP95 from GSMaP increases significantly both in the lands and in the oceans except for some regions, but those from GPCP are decreasing on most of the oceans. Because satellite-based precipitation estimation products derive the amount of precipitation indirectly from atmospheric elements such as water vapor, liquid water path, and cloud top temperature, trends in the atmospheric parameters provided by a polar orbiting satellite are also analyzed to explain the discrepancies in trends of FP95 across the precipitation products.

Use of Retrieved Thermodynamic Variables from the Satellite Observation for the Understanding and Predicting Convective Precipitation

Jinyeong KIM+, Jin LEE, Junha LEE, Suna CHO, Myoung Hwan AHN#
Ewha Womans University, Korea, South

Heavy rains occurring in a short time can cause significant damage, but it is difficult to accurately predict or observe its occurrence and dissipation. In this study, we investigated the possibility of understanding the development of convective precipitation clouds using thermodynamic variables (such as lifting convective level (LCL), level of free convection (LFC), stability index, etc.) with a 10-minute interval and 2 km spatial resolution produced by GK-2A. The accuracy of these variables produced by GK-2A is estimated by comparing with the collocated radiosonde data. In case of stability indices, the weighted linear regression coefficients for KI, LI, SSI, and TTI all showed values above 0.7, and the errors were randomly distributed without bias. The error for SSI and LI were larger at night than during the day, and the overall pattern of differences between satellite and radiosonde products was similar across stations. Furthermore, an analysis of 21 significant outlier cases that occurred during the comparison revealed that all outlier cases corresponded to one or more of the following: nighttime near-surface PBL, near-surface inversion layer, or instability in temperature and humidity profiles in the radiosonde data. LCL deviation ranged widely from -120 to 70, and RMSE varied between 30 and 130 based on initial ascent altitudes. Using 962.25 hPa as a reference, the deviation was -3.24, with an RMSE of 31.77, indicating the highest accuracy. Derived temperature and humidity profiles from GK-2A align closely with radiosonde data under suitable ascent altitudes. In selected convective cases, the LCL decreased by approximately 70.94 hPa (0.23 hPa/min) in the 6 hours before convective cloud formation, confirming a link between higher vertical convection altitudes and a heightened potential for strong convection. We also plan to present additional analysis on the relation of LFC and CAPE to the convective precipitation.

Study on U-Net-based Deep Learning Model for Detecting Convective Initiation Probability Using GK2A/AMI Satellite Data

JinYoung KIM#+, Eunha SOHN, Myoung-Hee LEE
Korea Meteorological Administration, Korea, South

Convective clouds, accompanied by heavy rainfall and thunderstorms, can lead to substantial damages. Hence, the detection of Convective Initiation (CI) plays a crucial role in weather monitoring and prediction. While radar observations mainly detect precipitation particles in the mature stage of convective clouds, satellite data can identify convection cells before the formation of precipitation particles. Satellite data also offers the advantage of covering a wide area with high temporal resolution. In this study, we aimed to predict convective initiation by adopting the U-Net-based LightningCast model, originally developed for lightning prediction by NOAA/CIMSS, as our foundational model. Since the GEO-KOMPSAT-2A (GK2A) satellite lacks a lightning detection sensor like Geostationary Lightning Mapper (GLM), we employed ground-based radar reflectivity as ground truth. After aligning radar echoes with the GK2A Korean Peninsula area, we selected radar reflectivity that exceeded 35dBZ at least once within 60 minutes as our target data. We utilized observation data from GK2A Advanced Meteorological Imager (AMI) during the summer as input and conducted a study to identify the optimal channel combination through sensitivity testing. This research was supported by the “Technical development on high-impact weather detection and prediction using meteorological satellite data”(KMA2020-00121) of “Technical Development on Weather Forecast Support and Convergence Service using Meteorological Satellites” project funded by the National Meteorological Satellite Center, Korea Meteorological Administration.

Prediction of Low-level Wind Fields Using ConvLSTM Model with GK2A and SCADA

Junghae HEUR#+, Yong-Sang CHOI
Ewha Womans University, Korea, South

Prediction of wind vectors in the low troposphere is beneficial in many application fields. Conventionally, Supervisory Control and Data Acquisition (SCADA) has been used for the low-level (1000 hPa) wind estimation. On the other hand, a recent study has developed the algorithm that can predict clear-sky high-level (500-750 hPa) wind vectors a few minutes to hours ahead using the Korean geostationary satellite (GK2A) water vapor channels only. Here we find the correlation between the two level wind fields from the GK2A and SCADA by using Convolutional Long Short-Term Memory (ConvLSTM) model. Then this model is applied to predict low-level wind fields for the entire Korean Peninsula. Our results show that our low-level wind fields have higher accuracy than those from the numerical weather prediction. Also shown is a potential that GK2A high-level wind can be used to predict low-level wind where the observations are unavailable. We expect that this study can serve to improve weather and wind power prediction.

Qualitative and Quantitative Evaluation of GK-2A Based Rapid-Scan Atmospheric Motion Vector

Soobong LEE1#+, Kwang-Deuk AHN2, Inchul SHIN1
1Korea Meteorological Administration, Korea, South, 2National Institute of Meteorological Research, Korea, South

The Rapid-Scan Atmospheric Motion Vector (RS-AMV) provides satellite-based three-dimensional wind information, and it can be useful information for initializing numerical weather prediction(NWP) model through data assimilation. In addition, It can be useful for a forecaster to be tracking the convection cell and analyzing wind information around the typhoon. Advanced Meteorological Imagery (AMI) on board the GEO-KOMSAT-2A(GK-2A) can capture the imagery of East Asia every two minutes. With this advantage, the RS-AMV can be generated with better spatio-temporal resolution than AMV. RS-AMV is derived as following steps: 1) target selection via optimal method using largest standard deviation in specific area, 2) height assignment based on cross-correlation with Cloud Top Pressure (CTP) product, 3) calculate displacement between the similar pixels in earlier or later image, 4) assign quality information on each vectors in RS-AMV via comparison with surrounding pixels. In this study, the quantitative and qualitative evaluations were performed using in-situ observation and analysis fields from NWP model. As the results of the quality assessment, we found that the major issues of RS-AMV are height assignment and wind speed. Additionally, the cause of the problem and which parts of the algorithm caused the problem were presented. This study was carried out with the support of the Korea Meteorological Administration R&D program[Meteorological satellite forecast support and convergence service technology development] (KMA2020-00121).

Research on Satellite Water Vapor Data Based Synoptic Meteorological Phenomena Analysis Methods

Ok Hee KIM#+
Korea Meteorological Administration, Korea, South

Water vapor imagery is a suitable satellite data to track upper atmospheric flow. It is useful for analyzing synoptic meteorological phenomena as tracking cyclonic flows, vorticities, dry areas and wet areas that appear in water vapor images, and identifying the location of troughs/ridges by utilizing the strengthening and weakening tendencies of dry areas and anticyclonic air flows. Synoptic meteorological phenomena can be analyzed extensively using water vapor image. Infrared and visible images are useful for analyzing clouds distributed in the upper, middle, and lower layers of the atmosphere. In water vapor images, upper-level waves and darkening-related troughs, which are precursor stages of low pressure system that cannot be seen in clouds that appear in visible and infrared images, can be identified through air flow analysis. In this study, we specifically showed some methods to analyze troughs through the tendency of dry areas to strengthen or weaken using water vapor imagery. Through this study, we found that the troughs are located right in front of the maximum brightness temperature area of the dry zone and the ridges are located in the area where the wet region begins to gradually dry in the water vapor image, and where the clouds begin to dissipate in the infrared and visible images.

Atmospheric Temperature and Humidity Profiles from FY4B-GIIRS Measurements: Physical Algorithm AAP vs. ANN-based Algorithm

Kyungsoo LEE1+, Sang-Moo LEE1#, Jaeeon KIM1, Junhyung HEO2, Byung-il LEE2, Hoyeon SHI3, B.J. SOHN1
1Seoul National University, Korea, South, 2Korea Meteorological Administration, Korea, South, 3Danish Meteorological Institute, Denmark

Hyperspectral infrared (IR) sounder measures radiances at CO2 and H2O bands with high spectral resolution, and these measurements can be used to retrieve atmospheric temperature/ humidity profiles which are important in short-term weather forecasts. GIIRS (Geostationary Interferometric Infrared Sounder) of FY-4B is the first hyperspectral IR sounder in the geostationary orbit, and measures wide area with high temporal resolution. GIIRS-measured radiances contain vertical information on atmospheric CO2 and H2O, allowing to estimate atmospheric temperature/humidity from space. Of course, development of relevant retrieval algorithm is necessary. Improving weather forecasting capabilities, the Korean National Meteorological Satellite Center developed a physical algorithm so-called AAP (Advanced Meteorological Imager (AMI) Atmospheric Profile) for the retrieval of atmospheric thermodynamical properties. The AAP algorithm is based on the 1D-Var scheme and was originally developed for GEO-KOMPSAT-2A AMI sensor. In this research, sensitivity tests were conducted to find the best set of GIIRS channels and observation/background error covariances. Then obtained results were used for adapting the original AAP algorithm for GIIRS sensor. It was found that the modified AAP algorithm performs well with 36 GIIRS channels. Results indicate that the rms error of the modified AAP algorithm compared with ERA5 atmospheric profile is reduced when the observation error is prescribed as larger value. In addition, artificial intelligence algorithm was also developed for temperature/humidity retrievals by training GIIRS-measured radiances with collocated ERA5 atmospheric temperature/humidity profiles. ANN, CNN, ResNet, and U-Net methods were used, and results were compared for that purpose. GIIRS-measured TBs were directly related to ERA5 profiles without any first guess profile. The test results show that the algorithm based on ResNet yields the highest performance compared to the other algorithms. However, it is noted that these neural network algorithms perform not better than the physical algorithm in terms of rms errors.

Regional Characteristics of Aerosol Optical Depth from GOCI-II Over East Asia

Joonhee KIM1+, Sang-Moo LEE1#, Hyeong-Ahn KWON2
1Seoul National University, Korea, South, 2University of Suwon, Korea, South

Geostationary Ocean Color Imager – II (GOCI-II) onboard GEO-KOMPSAT-2B has operated since 19 February 2020 and has monitored aerosol optical depth (AOD) over East Asia. Although GOCI-II has provided invaluable AOD datasets such as hourly measurements, biases of GOCI-II AOD are not sufficiently analyzed to exploit GOCI-II AOD data in a data assimilation system for air quality forecast. This study aims to analyze the characteristics of GOCI-II AOD data in terms of bias and root mean square (RMS) error from December 2021 to January 2023, by comparing GOCI-II data with aerosol optical properties derived from the AErosol RObotic NETwork (AERONET) data. To make comparable datasets between GOCI-II and AERONET, GOCI-II AODs were averaged within a square grid box centered on each AERONET site having size of xo. The sensitivity test was conducted by increasing the grid box size x from 0.1˚ to 1.0˚ with the increment of 0.1˚. The bias of GOCI-II AOD to AERONET AOD depends on the selected grid box size in most AERONET sites, showing smaller biases as grid box size decreases, possibly due to data representativeness. It is expected that there will be certain threshold at which bias will not decrease further. In addition, bias of GOCI-II AOD according to the aerosol type was examined. Here, aerosol types were classified into 6 categories: dust, non-absorbing coarse, mixture, high-absorbing fine, moderating-observing fine, and non-absorbing fine. AOD over the eastern China showed higher value compared to neighboring countries during the study period. The characteristics of GOCI-II AOD identified by this study will be utilized to improve a design of pre-processing process of satellite-derived AOD for data assimilation.

Comparison of AMV Calculated Using Optical Flow Method and GK2A Rapid-Scan-AMV

Ji-Hoon JEONG#+, Inchul SHIN
Korea Meteorological Administration, Korea, South

Atmospheric Motion Vector (AMV) is a satellite product that tracks atmospheric current by monitoring the movement of clouds and water vapor in three sequential satellite images. It is valuable for enhancing the precision of forecast and analysis fields in numerical model data assimilation. Additionally, it's crucial for understanding wind structures in typhoons. The National Meteorological Satellite Center (NMSC) from Korea Meteorological Administration (KMA) is currently producing Rapid-Scan (RS)-AMV, which has an improved spatiotemporal resolution than AMV, using the rapid-scan data from Geo-Kompsat-2A (GK2A). This output features a height assignment technique that utilizes Cloud Top Pressure (CTP) to obtain local wind information with less reliance on numerical weather prediction (NWP) models. In this study, we focused on increasing the vector count by computing vectors through optical flow. We analyzed atmospheric current using these vectors and validated the accuracy of the optical flow AMV by comparing them with RS-AMV. Optical flow is a technique that calculates the movement of pixels between two image frames as vectors. we used the Farnebäck algorithm, which calculates this movement for all pixel values in the image. Height assignment using GK2A Cloud Top Pressure (CTP) was applied to the optical flow AMV. The optical flow AMV calculated in this way was verified qualitatively and quantitatively through case analysis and observation data such as radiosonde and wind profiler.

Improvement of GK-2A Atmospheric Vertical Information with PCA

Junhyung HEO#+, Byung-il LEE, Myoung-Hee LEE
Korea Meteorological Administration, Korea, South

The GK-2A AAP (Geo-Kompsat-2A AMI Atmospheric Profile) and other 1D-Var atmospheric profile retrieval algorithms have common limitations related to ill-posed problems due to a lack of observed information, leading to unstable retrieved profiles or reliance on initial guess profiles. In our study, we addressed these challenges by employing Empirical Orthogonal Functions (EOFs) and Principal Components (PCs) for temperature and humidity profiles to mitigate the ill-posed equation problem through variable reduction. The number of components of vertical profile was reduced using main EOFs and PCs. Furthermore, we modified the GK-2A AAP based on Principal Component Analysis (PCA-AAP) to achieve optimized atmospheric vertical information. The temperature and humidity profiles were calculated using PCA-AAP, with the Unified Model (UM) and GK-2A radiance serving as inputs, mirroring the approach employed in GK-2A AAP. Validation of the PCA-AAP retrieved profiles was conducted using radiosonde data in August 2022. The accuracy of PCA-AAP was found to be nearly comparable to that of both the initial guess and GK-2A AAP. Notably, PCA-AAP successfully avoided retrieving inaccurate profiles observed in GK-2A AAP, attributed to the stabilizing effect of main EOFs. The results demonstrate that the PCA technique complements the GK-2A AAP algorithm, providing stable and continuous vertical profiles. Consequently, we plan to enhance the accuracy of EOFs by incorporating global radiosonde data and model analysis data. This improvement is anticipated to contribute significantly to supporting very short-range forecasting and nowcasting more effectively. This research was supported by the “Technical development for utilizing meteorological satellite data for numerical weather predication”(KMA2020-00122) of “Technical Development on Weather Forecast Support and Convergence Service using Meteorological Satellites” project funded by the National Meteorological Satellite Center, Korea Meteorological Administration.

Using Machine Learning to Convert Satellite Images Into Radar Reflectivity for Rainfall Intensity

Po Che HUANG1+, Chuan-Ming LIU1#, Lawrence Jing-Yueh LIU2
1National Taipei University of Technology, Taiwan, 2National Central University, Taiwan

Extreme weather often causes major disasters, such as the flash flood brought by intense rainfall. To assess rainfall position and intensity, we usually use satellite images and radar reflectivity as a reference. Radar reflectivity provides high-resolution information of rainfall structure, but the range that radar can detect is limited based on the location and range of each radar site. In remote areas or places such as the Pacific Ocean, the radar data cannot cover. In contrast, satellite images offer a broader range of coverage, providing information in a global scale. Therefore, we propose a machine learning framework to train models that combines radar reflectivity and satellite image data. Firstly, the visible light and infrared data are obtained from the Himawari-9 satellite in Taiwan area from July to December, 2023. Then, the radar reflectivity is provided by the Taiwan Central Weather Administration (CWA) in Taiwan area as labels. In this study, the U-net model captures the features of satellite images to predict rainfall intensity and generate radar reflectivity. The reason we choose U-net is because of its excellent performance in image segmentation. Hence, it is an optimal choice to identify the edges of cloud layers and predict rainfall intensity. This research not only aims to extend the detection range of radars, providing more comprehensive weather information, but also helps observe the formation and causes of typhoons and other severe rainfall events. This efficient framework can contribute to monitor various extreme weather conditions and provide real-time warnings, thereby reducing the losses caused by disasters.

AS23-A001 | Invited
Characteristics of Land Atmospheric Interaction as a Result of Plant Response in the East Asia and Its Impact on the Extreme Climate Events

Ji-Hye YEO1+, Daeha KIM2, Yeonghwa KO1, Kyung-Ja HA1#
1Pusan National University, Korea, South, 2Jeonbuk National University, Korea, South

In recent times, global temperatures have been rising due to global warming, with East Asia being one of the regions experiencing the highest rate of increase. Furthermore, under high CO2 emission scenarios, the increasing evaporative demand in the East Asia region is projected to rise more rapidly than land surface evaporation. This land-atmosphere moisture difference exhibits high vapor pressure deficits, which can lead to extreme temperatures and droughts. The estimation of potential evapotranspiration, a key indicator of evaporative demand, remains unclear in the available reanalysis or model data, as they do not account for plant responses to CO2. We only focused on stomatal changes in response to CO2 changes, and the results showed an increase in surface resistance with increased CO2, the effect of which was largely offset by vapor pressure deficits, which affects the increase in potential evapotranspiration. In particular, in the case of drought, when plant responses are not considered, potential evapotranspiration tends to overestimate drought in East Asia by approximately 17% compared to scenarios that take vegetation into account. We examined the characteristics of land-atmosphere interactions in East Asia based on land types using a land-atmosphere coupling matrix. Specifically focusing on the characteristics of land-atmosphere coupling and its changes with and without considering plant responses, we analyzed the resulting changes in extreme climate events such as heatwaves and droughts.

The Forecast Skill of the Summer Precipitation Over Tibetan Plateau Improved by the Adoption of a 3D Sub-grid Terrain Solar Radiative Effect Scheme in a Convection-permitting Model

Anning HUANG#+
Nanjing University, China

We have successfully incorporated a 3-dimensional sub-grid terrain solar radiative effect (3D STSRE) parameterization scheme into a convection-permitting Weather Research and Forecasting model (WRF_CPM) in this study. Impacts of 3D STSRE scheme on the ability of WRF_CPM in forecasting the precipitation in summer over the Tibetan Plateau (TP) and nearby regions with complex terrain have been systematically addressed by conducting experiments without and with the 3D STSRE scheme. Results show that the application of 3D STSRE scheme can obviously mitigate the overestimation of surface solar radiation (SSR) and rainfall over TP and nearby regions, especially over the areas with much more rugged terrain (i.e., southern TP) in the WRF_CPM without 3D STSRE scheme. Further mechanism analyses indicate that the decreased surface heating induced by the reduction of SSR reduces the intensity of the thermal-low pressure over the TP, which leads to the diminished strength of southwesterly winds and thereafter the weaker convergence of moisture flux over the southern TP. Moreover, the weakened surface thermal forcing makes the local atmosphere more stable, suppressing the vertical water vapor transport and local convection. These effects greatly alleviate the overestimation of precipitation over the southern TP produced by the WRF_CPM without the 3D STSRE scheme.

Changes in the Spatiotemporal Distribution of the Timing and Duration of the Soil Freeze–thaw Status from 1979 to 2018 Over the Tibetan Plateau

Xin LAI#+, Siyuan YAO
Chengdu University of Information Technology, China

Changes in the soil freeze–thaw status will inevitably affect the thermal conditions and properties of the Tibetan Plateau (TP), thereby affecting its upper atmosphere, and further afield in East Asia and even globally. In this study, using the soil temperature simulated by the Community Land Model Version 5.0, the timing and duration of the soil freeze–thaw status were divided into freeze start-date, freeze end-date, and freeze duration. Results showed: (1) The model effectively reproduces seasonal multi-layer soil temperature changes, showing strong correlation with observations. (2) There is a clear trend of delayed freezing, advanced thawing, and shortened freeze duration from northwest to southeast over the TP. From 1979 to 2018, the freeze start-date was delayed by 7.3 days (1.9 days/decade), the freeze end-date advanced by 6.4 days (1.7 days/decade), and the freeze duration shortened by 13.7 days (3.6 days/decade). The timing and duration of the soil freeze–thaw status vary across different regions of the TP. The freeze start-date in all areas of the TP has been delayed in the past 39 years. Except for the sub-cold zone and arid regions of the TP, the freeze end-date has occurred earlier and the freeze duration has shortened, with the most significant changes in the sub-cold zone and humid regions. (3) The timing and duration of the soil freeze–thaw status are significantly correlated with surface air temperature, elevation, and latitude. The strongest correlation is with surface air temperature, followed by altitude and latitude. The western TP shows a stronger correlation than the eastern TP. The rate of change in the soil freeze–thaw status increases with altitude to 3000 m above sea level, while this rate decreases with elevation above 3000 m. The greatest rate of change is observed at 29°N.

Biophysical Impact of Greening Vegetation on Near-surface Air Temperature Under Hot Extremes

Yipeng CAO+, Weidong GUO#, Jun GE
Nanjing University, China

Satellite data shows increasing leaf area of vegetation since 2000, which may exert biophysical effects on near-surface air temperature (SAT). However, such effects remain largely unknown because prior studies either focus on land surface temperature, which differs from SAT, or rely on simulations, which are limited by model uncertainties. As a widely used metric in climate and extremes research, SAT is more relevant to human health and terrestrial ecosystem functions. Therefore, it is necessary to explore impacts of greening on SAT and extremes based on observations. Here, we investigate the greening effects on SAT and subsequent extremes over 2001–2022 based on an enhanced global dataset for the land component of the fifth generation of European ReAnalysis (ERA5-land). We find that greening can cause cooling effects on the mean SAT and more pronounced cooling effects on SAT extremes in Europe, East Asia and Central North America, where evident greening was observed since 21st century. An attribution analysis suggests that the main driving factor for the additional cooling effect of greening in hot extremes is the enhanced evapotranspiration. Moreover, the biophysical effects of vegetation on high temperatures vary with climate conditions and vegetation types. Our study reveals a considerable climate benefit of greening on SAT, which may have implications for climate mitigation in different regions around world.

Research on Estimation/prediction of Surface Solar Irradiance Based on Machine Learning

Dongyu JIA#+
Lanzhou City University, China

This study used radiation observation data and remote sensing data to explore the different factors affecting radiation estimation and prediction based on machine learning algorithms. The results indicate that: (1) The estimation of radiation is influenced by weather condition levels and pollution levels, where the estimation of global solar radiation is linearly related to the weather condition level, while the diffuse solar radiation shows a non-linear relationship. In heavily polluted weather, the use of machine learning for solar radiation estimation performs poorly. (2) In all prediction scenarios, the feature selection (FS) of the Random Forest (RF) model is higher than that of the Support Vector Regression (SVR) model, and this performance advantage becomes more pronounced when the lead time exceeds 90 minutes. (3) Remote sensing data can assist in improving radiation prediction. Full-channel input of FY-4A remote sensing data can provide better prediction results, but considering time and computational cost, the optimal three-channel model is a better choice.

Can Climate Models Accurately Capture the Sub-seasonal Dynamics of Tibetan Plateau Snow Cover?

Xin MIAO#+, Weidong GUO
Nanjing University, China

The snow cover on the Tibetan Plateau (TP) undergoes sub-seasonal changes, which exert a substantial influence on weather and climate in the surrounding and downstream regions. However, current climate models struggle to accurately capture the rapid changes of TP snow cover. Our research indicates that, most global climate models in phase 6 of the Coupled Model Intercomparison Project (CMIP6) largely overestimate the snow amount over the TP, along with notable biases in the rapid fluctuations of TP snow cover. Similarly, these biases are also present in regional climate simulations. Through in-depth analysis, we identify snowfall and snowmelt as primary contributors to the observed rapid changes in TP snow cover. The simulated biases in rapid snow changes over the TP result from the excessive snowfall and albedo bias in both global and regional climate simulations. Our findings reveal the potential sources of simulated biases in rapid snow changes over the TP and offer a promising perspective for improving the accuracy of TP regional and global climate simulations.

Interdecadal Response of Eurasia Snow Cover to Northern Hemisphere Sea Surface Temperature

Xianru LI+, Zhigang WEI#
Beijing Normal University, China

Based on reanalysis data from ERA5_Land, MEERA2, HadISST, NCEP-NCAR reanalysisⅠ and other datasets, the response characteristics between interdecadal Eurasia snow cover in winter and spring and sea surface temperature in Northern Hemisphere (NHSST) in winter are investigated. Barnett and Preisendorfer canonical correlation analysis (BP-CCA) and regression analysis are used in this paper. Main conclusions are as follows: In the past 40 years, except for Equatorial East Pacific region, the NHSST has increased. And except for eastern Siberia, the snow cover basically decreased. The interdecadal influence of winter NHSST on Eurasia snow cover lasts until spring after removing the linear trend. In the first mode of BP-CCA, winter and spring snow cover increase in Europe and decrease in central Eurasia when the North Atlantic and Northwest Pacific Sea temperatures rise (AMO+, PDO-) in winter. At this time, the height field and surface temperature decrease, water vapor and precipitation increase, trough deepens in Europe, and then snow cover increases in winter and spring. In central Eurasia, the variations are revised. In the second mode of BP-CCA, there is a significant reverse change between snow cover over Eurasia and Northeast Pacific SST with a quasi-16a period, and the North Atlantic SST is a tripole type. When the SST increases in the Northeast Pacific Ocean and the mid-latitude Atlantic Ocean in winter, the trough and ridge in Eurasia all weaken, surface temperature increase, and then winter snow cover decrease. In spring, the water vapor flux and precipitation decreased significantly, and snow cover decreased.

Preference of Afternoon Precipitation Over Dry Soil in the North China Plain During Warm Seasons

Sixuan LI1+, Jianping GUO2, Zhanqing LI3,1#, Xuanze ZHANG4, Tianning SU3, Jing WEI3
1Beijing Normal University, China, 2Chinese Academy of Meteorological Sciences, China, 3University of Maryland, United States, 4Chinese Academy of Sciences, China

The influence of soil moisture on atmospheric precipitation has been extensively studied, but few of these studies have considered the role of land-atmosphere coupling in afternoon precipitation events at a sub-daily timescale. Here, using in-situ observations and reanalysis datasets, we investigated the effect of the soil moisture anomaly (SMA) on warm seasons’ afternoon precipitation in the North China Plain (NCP), which is identified as a strong land-atmosphere coupling region. Afternoon precipitation events (APE) were separated from all precipitation events in the NCP during the warm seasons of 2010 to 2019. It follows from a comparative analysis that APE is more likely to be initiated on drier soil, which has little dependence on the thresholds used for identifying APE. However, no affirmative relationship is found between precipitation amount in the first hour of APE (APE1hour) and the soil moisture. Further analyses indicate that larger amounts of APE1hour result from higher convective available potential energy (CAPE), higher moist static energy (MSE), or weaker vertical shear of horizontal wind. When considering the joint effects of SMA and atmospheric variables, APE tend to occur on drier (wetter) soil with lower (higher) lower-tropospheric stability, CAPE, or MSE. This study highlights the significant roles of land-atmosphere interactions on local atmospheric precipitation, especially the joint roles of soil moisture and atmospheric variables on precipitation.

Biophysical Factors Control the Interannual Variability of Evapotranspiration in an Alpine Meadow on the Eastern Tibetan Plateau

Shaoying WANG1#+, Yu ZHANG2, Xianhong MENG1, Lunyu SHANG1, Zhaoguo LI1
1Chinese Academy of Sciences, China, 2Chengdu University of Information Technology, China

Evapotranspiration (ET) is a key parameter regulating land–atmosphere interaction processes and the water cycle. The seasonal and interannual variability of ET and its environmental controls over an alpine meadow in a subfrigid humid zone of the Tibetan Plateau (TP) are reported on. Direct measurements were made using the eddy covariance method over a 10-year period with a significant increase in growing season length (GSL). The results showed that annual ET for the alpine meadow site was 492 ± 66 mm in comparison with 635 ± 88 mm of precipitation (P), with a ratio of ET/P ranging from 0.63 (2017) to 1.04 (2010). The path analysis and Priestley–Taylor coefficient (ET/ETeq) revealed that the daily ET experienced energy-limited and water-limited seasons within the year. During the water-limited non-growing season, the daily surface conductance (Gs) and ET/ETeq increased positively with soil water content (SWC). During the energy-limited growing season, the 16-day average ET, ET/ETeq, and Gs scaled positively with the normalized difference vegetation index (NDVI). ET/ETeq increased nonlinearly with an increase in Gs, but was insensitive to increases in Gs greater than the threshold Gs*. The mean Gs and Gs* were strongly regulated by the maximum NDVI. The maximum NDVI, Gs*, and annual mean Gs explained 46%, 80%, and 68%, respectively, of interannual variation in annual ET. Thus, we concluded that biophysical factors, rather than P and GSL, mainly controlled the interannual variability in annual ET. These findings are critical for understanding the response mechanism of ET to the changing biotic and abiotic conditions in the TP.

Simulation of Regional Soil Moisture at High Spatiotemporal Resolution Using WRF-Hydro

Chin-Chi YEH#+, Chia-Jeng CHEN
National Chung Hsing University, Taiwan

Soil moisture is one of the critical variables in the hydro-climate system; however, the gauge-based measurement poses a great challenge in its spatial coverage. To obtain more comprehensive soil moisture data over Taiwan, this study aims to leverage the Weather Research Forecasting model-Hydrological modeling system (WRF-Hydro). To ensure a more reliable regional simulation, the default soil texture, soil hydraulic parameters, and land use/cover data in WRF-Hydro are replaced with locally curated data to better reflect the actual surface characteristics of Taiwan. The Taiwan Hydraulic Digital Elevation Model (HyDEM) is used to configure catchment characteristics in the pre-processing of WRF-Hydro. Gauge- or radar-based precipitation is used as the meteorological forcing to drive WRF-Hydro. Simulated soil moisture will be compared and validated with gauge- and satellite-based data in Taiwan. We believe that the outcome of this work will provide more effective soil moisture information for ensuing hydro-climatic modeling and disaster monitoring.

Multi-scale Characterization in TP Summer Precipitation and Its Possible Mechanisms

Hao WANG#+
University of Chinese Academy of Sciences, China

The precipitation plays a crucial role in TP climate system, which links to the energy and water cycle over the TP. In recent decades, the warming and humidification over the TP is closely related to the multi-scale variations of the precipitation difference between the northern and southern TP. This study investigates the multi-scale variation on Difference of Precipitation between the Northern and Southern TP (DP) based on site observational data, remote sensing data and reanalysis data. The result shows that. On decadal scale, as the important forcing factors, the AMO (Atlantic Multi-scale Oscillation), PDO (Pacific Decadal Oscillation) are related to decadal variations of DPI significantly, representing as DPI lags PDO by around 10 years and exceeds AMO by around 10 years. So that the signal of SST(Sea Surface Temperature) anomalies can be used as a forecast factor for the decadal variation of the precipitation difference between the northern and southern TP.

Aerosol as a Potential Factor to Control the Increasing Torrential Rain Events in Urban Areas Over the Last Decades

Seoung Soo LEE#+
Earth System Science Interdisciplinary Center, United States

This study examines the role played by aerosol in torrential rain that occurred in the Seoul area, which is a conurbation area where urbanization has been rapid in the last few decades, using cloud-system-resolving model (CSRM) simulations. The model results show that the spatial variability in aerosol concentrations causes the inhomogeneity of the spatial distribution of evaporative cooling and the intensity of associated outflow around the surface. This inhomogeneity generates a strong convergence field in which torrential rain forms. With the increases in the variability in aerosol concentrations, the occurrence of torrential rain increases. This study finds that the effects of the increases in the variability play a much more important role in the increases in torrential rain than the much-studied effects of the increases in aerosol loading. Results in this study demonstrate that for a better understanding of extreme weather events such as torrential rain in urban areas, not only changing aerosol loading but also changing aerosol spatial distribution since industrialization should be considered in aerosol–precipitation interactions.

Impacts of an Aerosol Layer on a Mid-latitude Continental System of Warm Cumulus Clouds: How Do These Impacts Depend on the Vertical Location of the Aerosol Layer?

ChangHoon JUNG1#, Seoung Soo LEE2+, Junshik UM3
1Kyungin Women's University, Korea, South, 2Earth System Science Interdisciplinary Center, United States, 3Pusan National University, Korea, South

Effects of an aerosol layer on warm cumulus clouds in the Korean Peninsula when the layer is above or around the cloud tops in the free atmosphere are compared to those effects when the layer is around or below the cloud bases in the planetary boundary layer (PBL). For this, simulations are performed using the large-eddy simulation framework. When the aerosol layer is in the PBL, aerosols absorb solar radiation and radiatively heat up air enough to induce greater instability, stronger updrafts and more cloud mass than when the layer is in the free atmosphere. Interestingly, even though the aerosol layer in the PBL intercepts more solar radiation reaching the surface, resulting in reduced surface heat fluxes, instability, updraft intensity, and cloud mass, the overall effect still leads to more cloud mass. Hence, there is a variation of cloud mass with the location of the aerosol layer, which arises from an interplay between aerosol-induced changes in the surface fluxes and those in radiative heating of air. Even without impacts of aerosols on radiation, there is still more cloud mass when the aerosol layer is in the PBL, because aerosol-induced changes in droplet nucleation induces aerosol-induced invigoration of updrafts. However, the variation of cloud mass is much smaller when there is only aerosol impacts on droplet nucleation than when aerosol impacts on both of radiation and nucleation are present. Hence, aerosol impacts on nucleation and those on radiation work together to amplify the variation of cloud mass with the altitude of the aerosol layer. This study reveals that this variation of cloud mass also reduces as aerosol concentrations in the layer decrease. Furthermore, the transportation of aerosols by updrafts reduces aerosol concentrations in the PBL. 

Physical Properties of Clouds Embedded in the Cold-air Outbreaks Over the Yellow Sea Depending on Air Pollution

Subin JEON+, Hyunho LEE#
Kongju National University, Korea, South

In middle and high latitudes, marine stratocumulus clouds often form after cold fronts pass, with cold air flowing from the continents during winter. Because these stratocumulus clouds persist over a relatively broad region and a relatively long duration compared to clouds associated with typical low-pressure systems, they can produce significant cloud radiative forcing, which is negative owing to their low altitudes and large cloud water contents. As they move downwind, they usually experience transition to cumulus clouds with lower cloud fraction. While increasing sea surface temperature has been recognized as the main factor to control the transition, some recent studies have pointed out that precipitation, which can be modulated by aerosols, is also important to the transition. In this study, we present the physical properties of boundary-layer clouds embedded in the cold-air outbreaks over the Yellow Sea occurred from 2013 to 2023. We identify the entire cases seen on the MODIS observations during the period, a total of 119 cases. The cloud fraction peaks at the middle of the cloud trajectories and then decreases as the clouds move downwind. The cloud top temperature generally increases along the trajectories although the cloud top height is also increasing, while the cloud water path remains relatively unchanged as the clouds move downwind. Beyond analyzing the mean properties of the entire cold-air outbreak stratocumulus clouds, we select some cases and categorize them as either ‘clean’ or ‘polluted’ based on the average carbon monoxide concentration over the upwind region of the trajectories. We then illustrate the effects of pollution on the cloud evolution by comparing the properties of the two cloud groups. Additionally, we conduct a series of numerical simulations and examine in detail how aerosols influence the cloud evolution and the transition to cumulus clouds.

The Spatiotemporal Characteristics of Precipitation and Particulate Matter, and the Impacts of Wet Removal Based on Long-term Surface Measurements in Korea

Junshik UM1#+, Suji HAN1, Seoung Soo LEE2, ChangHoon JUNG3
1Pusan National University, Korea, South, 2Earth System Science Interdisciplinary Center, United States, 3Kyungin Women's University, Korea, South

Precipitation is an important process that contributes to the energy budget of the earth by modulating the water cycle and also assists in controlling the concentration of atmospheric pollutants by scavenging particulate matter (PM) (i.e., wet removal). Previous studies attempted to quantify the impact of wet removal mechanisms on PM concentrations, however, they performed the research based on short-term measurements, limited sites, or a few precipitation event cases. Thus, this study showed the spatiotemporal characteristics of precipitation and the concentration of PM (i.e., PM2.5 and PM10) in six regions (i.e., Seoul, Busan, Daejeon, Daegu, Gwangju, and Jeju) individually, and quantified the impact of the wet removal on the concentration of PM by precipitation events based on long-term measurements in six regions in Korea. Precipitation and PM10 surface measurements in six regions were used for 22 years (2001-2022), while PM2.5 surface measurements were only available for 8 years (2015-2022). All measurements were made with a one-hour resolution. The spatiotemporal variabilities (i.e., yearly, seasonal, and monthly averages) of precipitation and the concentration of PM were calculated in each region. The precipitation events were identified when the threshold time interval (i.e., 2 hours) was presented within the hourly precipitation data. Based on the duration, average intensity, and accumulated amount of precipitation events, the characteristics of precipitation events were analyzed. The variation in the concentration of PM during the precipitation events and the rate of wet removal were quantified as functions of the characteristics of precipitation events (i.e. duration, average intensity, and accumulated amount of precipitation events) for each of the six regions. The spatiotemporal characteristics of the regional wet removal effects that occurred by precipitation events were calculated, and the influence of the precipitation properties on the wet removal effects was evaluated.

Ensemble Coupling of the Atmospheric Model NICAM

Takashi ARAKAWA1#+, Hisashi YASHIRO2, Kengo NAKAJIMA1
1The University of Tokyo, Japan, 2National Institute for Environmental Studies, Japan

Meteorological phenomena are highly nonlinear, and small differences in initial values can significantly affect the results. Therefore, ensemble calculations are a commonly used computational technique in weather/climate simulations to reduce the inevitable uncertainty inherent in individual simulations and to quantitatively evaluate the degree of uncertainty. However, obtaining an average value with sufficient accuracy requires a large number of ensembles, which in turn requires significant computational resources. For example, in the case of the atmospheric model NICAM with a resolution of 3.5 km and 1024 ensembles, 131072 nodes were used, but with this number of nodes, it was not possible to calculate 1024 ensembles at once, and a method of repeating 4 cycles of 256-member ensemble calculations per cycle was employed. Therefore, in our study, we coupled a low-resolution ensemble with single high-resolution computation. This method can replace high-resolution large-scale ensembles with fewer computational resources. Furthermore, we can expect to obtain more accurate results by coupling low-resolution calculations, which excel in reproducing large-scale fields, with high-resolution calculations, which excel in reproducing detailed fields. A general-purpose coupler, h3-Open-UTIL/MP, was applied to this study. Two execution modes are possible on this coupler: many-to-one coupling, where multiple ensemble runs are coupled to a single model, and many-to-many coupling, where multiple coupled models are executed as an ensemble. In this study, the later mode was applied. We coupled low resolution NICAM ensemble and high resolution NICAM single model, on the Wisteria/BDEC-01 of the University of Tokyo. For the calculations, optimization of the single model and variable resource allocation were applied to minimize computational resources (node-time) as much as possible. In this presentation, the details of the ensemble coupling will be explained and the computational performance will be discussed.

Parallelized Remapping Algorithms for KM-scale Global Weather and Climate Simulations with Icosahedral Grid System

Chihiro KODAMA1#+, Hisashi YASHIRO2, Takashi ARAKAWA3, Daisuke TAKASUKA3, Shuhei MATSUGISHI3, Hirofumi TOMITA4
1Japan Agency for Marine-Earth Science and Technology, Japan, 2National Institute for Environmental Studies, Japan, 3The University of Tokyo, Japan, 4RIKEN Advanced Institute for Computational Science, Japan

Speeding up the post-processes in addition to the weather and climate simulation itself is important for speeding up the overall workflow. There are a wide variety of post-processes, but one typical post-process required for many models is remapping from model native grids to latitude-longitude grids. Here, we developed a series of parallelized remapping algorithms for NICAM, a global weather and climate model with an icosahedral grid system, and demonstrated their performance with global 14-0.87-km mesh model data on the supercomputer Fugaku. The original remapping tool in NICAM supports parallelization only in reading and interpolating data. In our proposed algorithms, the process of data writing is parallelized by separating output files or using the MPI-IO library, both of which enable us to remap 0.87-km mesh data with 670 million horizontal grid points and 94 vertical levels. The benchmark with 14-km mesh data shows that the developed algorithms significantly outperform the original algorithm in terms of elapsed time (by 7.4-8.7 times) and memory usage (by 2.8-5.0 times). Among the proposed algorithms, the separation of output files, along with reduced MPI communication size, leads to a better performance in the elapsed time and its scalability, and the use of the MPI-IO library leads to a better performance in memory usage. The remapping year per wall-clock day, assuming a six-hourly output interval, is up to 0.56 with 3.5-km mesh data, demonstrating the feasibility of handling global cloud-resolving climate simulation data in a practical time. This study demonstrates the importance of IO performance, including MPI-IO, in accelerating weather and climate research on future supercomputers.

Kilometer-scale Global Weather Forecasting Using the Korean Integrated Model: A Case Study of Extreme Heavy Rainfall in the Korean Peninsula

Ilseok NOH#+, Heeje CHO, Junghan KIM, Woo-Jin LEE
Korea Institute of Atmospheric Prediction Systems, Korea, South

The Korean Integrated Model (KIM) is a global weather forecast model independently developed by the Korea Institute of Atmospheric Prediction Systems (KIAPS). Comprising a spectral element-based dynamical core and a scale-aware physics package on cubed-sphere grids, KIM is currently deployed by the Korea Meteorological Administration (KMA) in a 12 km resolution, with data assimilation for weather forecasting. However, acknowledging the challenges in accurately simulating precipitation systems, particularly sudden and intense heavy rains around the Korean Peninsula, there is a growing need for a higher resolution model. In this study, we attempted to simulate KIM with a 3-4 km horizontal resolution, strategically avoiding cumulus parameterization specifically for cases of extreme heavy rainfall. The primary aim was to assess the possibility of positioning KIM as a Global Cloud-Resolving Model (GCRMs). As a result, KIM demonstrating a stable 10-day simulation of extreme rainfall case and more realistic compared to the 8 km simulation.

Retrieval of AOD Over Shallow and Turbid Coastal Waters from Himawari-8

Zibo YOU+, Yi WANG#
China University of Geosciences, China

Himawari-8, as a geostationary satellite, carries Advanced Himawari Imager which can perform full-disk observations every 10 minutes. Due to coastal water being turbid, shallow, and mixed with the land, the aerosol retrieval product cannot accurately retrieve the Aerosol Optical Depth (AOD) over shallow and turbid coastal waters. To fill the gap in this area, we developed a coastal water retrieval algorithm with a spatial resolution of 2 km. The land mask is first performed by normalized difference water index (NDWI), and then the cloud mask is performed by a spatial variation test based on 2.3 μm and some traditional reflectance and bright temperature threshold tests. After that, the water pixels are classified into open ocean pixels and coastal pixels by power-law fitting algorithm and Elevation and Topography at 1 arc minute (ETOPO1) bathymetry. After performing gas correction, the AOD and aerosol properties were retrieved using the Dark-Target algorithm for the open ocean pixels. For the coastal pixels, the AOD was retrieved using the 2.3 μm top of atmosphere reflectance and the aerosol properties of the nearest open ocean pixel. This algorithm can improve the accuracy and coverage of the coastal AOD.

Observation of the Background Levels of Atmospheric Aerosols and Greenhouse Gases Around Taiwan

Charles CHOU#+, Chih-Chung CHANG, Mao-Chang LIANG
Academia Sinica, Taiwan

Since the industrial revolution, human beings have produced a large amount of air pollutants. Air pollution results in changes in the atmospheric composition, which in turn alters the energy budget of the Earth system and, consequently, causes the present-day climate crisis. The main climate active substances in the air pollutants include the greenhouse gases and atmospheric aerosols. The greenhouse gases absorb IR radiation and cause warming of the atmosphere, whereas aerosols could cause warming or cooling effects, depending on the microphysical and optical properties. The eastern Asia is among the most polluted regions in the world. Along the course of energy transition and air pollution mitigation, monitoring data provide the crucial evidence to evaluate the status of environmental changes. This study has been conducting observation of atmospheric aerosols (PM10) and major greenhouse gases (CO2, CH4, N2O) at three remote sites (Penghu, Green Island, Cape Fuguei) around Taiwan. The preliminary results of observation for 2018 – 2019 showed that, in terms of annual mean level, the background mixing ratios of CO2, CH4, and N2O were 418 ppmv, 1.95ppmv, and 334.3 ppbv, respectively. Moreover, according to the observation data from the Penghu, Green Island and Cape Fuguei research stations, we estimated the background level of atmospheric aerosols (annual mean of PM10) was 30.6 ugm-3.

Application of GEMS AOD Data on Satellite- and Model-based Monitoring of Haze from Forest Fires in Southeast Asia

Efthymia PAVLIDOU1#+, Zhong Yi CHIA2, Chee-Kiat TEO2, Boon Ning CHEW2
1Meteorological Service Singapore, Singapore, 2Centre for Climate Research Singapore, Singapore

At the Meteorological Service of Singapore, Himawari geostationary data are used for transboundary haze monitoring and retrieval of Aerosol Layer Height with the application of different Random Forest architectures and Sentinel-5p/TROPOMI training data. The Numerical Atmospheric-dispersion Modelling Environment (NAME) is used for dispersal modelling and forecasting of forest fire emissions, and for further derivation of AOD. We evaluate performance of the system in recent haze incidents using the GEMS AOD product as reference. GEMS is the first satellite sensor dedicated to atmospheric monitoring in geostationary orbit, providing hourly AOD and Aerosol Layer Height information. The aim of this study is to explore the potential of GEMS to support operational, high frequency haze monitoring and validation of dispersion model outputs, specifically in the challenging environment of Southeast Asia.