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Predicting PM_(2.5) Concentration in the Yangtze River Delta Region Using Climate System Monitoring Indices and Machine Learning

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Journal of meteorological Research 2024年第2期38卷 249-261页

作者： Jinghui MA Shiquan WAN Shasha XU Chanjuan WANG Danni QIU Shanghai Typhoon Institute Shanghai Meteorological ServiceShanghai 200030 Key Laboratory of Polar Atmosphere-Ocean-Iice System for Weather and Climate Ministry of EducationDepartment of Atmospheric and Oceanic SciencesFudan UniversityShanghai 200438 Shanghai Key Laboratory of Meteorology and Health Shanghai Meteorological ServiceShanghai 200030 Yangzhou meteorological Office Yangzhou 225001 Department of Physics Yangzhou UniversityYangzhou 225003

Changing meteorological conditions during autumn and winter have considerable impact on air quality in the Yangtze River Delta(YRD)region.External climatic factors,such as sea surface temperature and sea ice,together with the atmospheric circulation,directly affect meteorological conditions in the YRD region,thereby modulating the variation in atmospheric PM_(2.5) concentration.This study used the evolutionary modeling machine learning technique to investigate the lag relationship between 144 climate system monitoring indices and autumn/winter PM_(2.5) concentration over 0-12 months in the YRD region.After calculating the contribution ratios and lagged correlation coefficients of all indices over the previous 12 months,the top 36 indices were selected for model training.Then,the nine indices that contributed most to the PM_(2.5) concentration in the YRD region,including the decadal oscillation index of the Atlantic Ocean and the consistent warm ocean temperature index of the entire tropical indian Ocean,were selected for physical mechanism analysis.An evolutionary model was developed to forecast the average PM_(2.5) concentration in major cities of the YRD in autumn and winter,with a correlation coefficient of 0.91.In model testing,the correlation coefficient between the predicted and observed PM_(2.5) concentrations was in the range of 0.73-0.83 and the root-mean-square error was in the range of 9.5-11.6μg m-3,indicating high predictive accuracy.The model performed exceptionally well in capturing abnormal changes in PM_(2.5) concentration in the YRD region up to 50 days in advance.

关键词： PM_(2.5)concentration machine learning evolutionary modeling seasonal prediction

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Study of Secondary Cosmic Rays and Astronomical X-Ray Sources using Small Stratospheric Balloons

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Research in Astronomy and Astrophysics 2024年第6期24卷 96-111页

作者： Rupnath Sikdar Sandip K.Chakrabarti Debashis Bhowmick indian Centre for Space Physics

The X-ray sources of the universe are extraterrestrial in nature which emit X-ray photons. The closest strong X-ray source is the Sun, which is followed by various compact sources such as neutron stars, black holes, the Crab pulsar, etc.In this paper, we analyze the data received from several low-cost lightweight meteorological balloon-borne missions launched by the indian Centre for Space Physics. Our main interest is to study the variation of the vertical intensity of secondary cosmic rays, the detection of strong X-ray sources, and their spectra in the energy band of10–80 keV during the complete flights. Due to the lack of an onboard pointing system, low exposure time, achieving a maximum altitude of only～42 km, and freely rotating the payload about its axis, we modeled the background radiation flux for the X-ray detector using physical assumptions. We also present the source detection method, observation of the pulsation of the Crab （33 Hz）, and spectra of some sources such as the quiet Sun and the Crab pulsar.

关键词： balloons instrumentation: detectors X-rays: stars

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Record-breaking summer-autumn drought in southern China in 2022:Roles of tropical sea surface temperature and Eurasian warming

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Science China Earth Sciences 2024年第2期67卷 420-431页

作者： Yuepeng HU Botao ZHOU Huijun WANG Dapeng ZHANG Collaborative Innovation Center on Forecast and Evaluation of meteorological Disasters/Key Laboratory of meteorological Disaster Ministry of Education/Joint International Research Laboratory of Climate and Environment ChangeNanjing University of Information Science and TechnologyNanjing210044China School of Atmospheric Sciences Nanjing University of Information Science and TechnologyNanjing210044China

From summer to autumn in 2022,a severe drought lasted in southern China,posing serious effects on economic growth and ecological systems.This study explored the atmospheric circulations accounting for this persistent drought event.It shows that the drought in southern China during the summer of 2022 was strongly linked to the divergence of water vapor flux and descending motions,which were respectively caused by the anomalous anticyclone over the western North Pacific and the northward movement of the East Asian subtropical jet(EASJ).Differently,the atmospheric background responsible for the sustained drought in autumn is manly featured by a cyclonic circulation anomaly over the region from the Bay of Bengal to the South China Sea,which led to decreased moisture and descending motions in southern China.Further investigation suggests that the rarely strong surface warming over northern Eurasia and the extreme La Nina-like pattern over the tropical Pacific jointly resulted in the anomalous anticyclone over the western North Pacific and the northward shift of the EASJ in the summer of 2022,while the cyclonic circulation anomaly prevailing over the region from the Bay of Bengal to the South China Sea in autumn was largely attributed to the extremely negative anomalies of the tropical indian Ocean sea surface temperature.

关键词： Summer-autumn drought Southern China Tropical sea surface temperature Eurasian warming

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Interdecadal Variations of ENSO Impacts over the Indo-Northwest Pacific Region and the Related Mechanisms

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Journal of meteorological Research 2024年第2期38卷 235-248页

作者： Hongxia LAN Jing MA Haiming XU Jingjia LUO Collaborative Innovation Center on Forecast and Evaluation of meteorological Disasters(CIC-FEMD)/Key Laboratory of meteorological Disaster Ministry of Education/Joint International Research Laboratory of Climate and Environment Change(KLME/ILCEC)Nanjing University of Information Science&TechnologyNanjing 210044 School of Atmospheric Sciences Nanjing University of Information Science&TechnologyNanjing 210044

Owing to limited observations,it remains unknown whether the impact of El Niño-Southern Oscillation(ENSO)on the indian Ocean-Northwest Pacific(IO-NWP)climate showed decadal changes in the early 20th century.Using multi-source reanalysis and hindcast datasets from the ECMWF and NOAA extending back to 1901,this study investigates interdecadal variations of the impact of ENSO on the IO-NWP climate from 1901 to 2009.It is found that the influence of ENSO on the IO-NWP climate shows“strong-weak-strong”interdecadal change during 1901-2009.This is characterized by much weaker indian Ocean sea surface temperature(SST)warming and a weaker NWP subtropical anticyclone(NWPSA)in the following summer of El Ni?o during 1946-1967,compared with those in the other two periods(1901-1945 and 1968-2009).Analyses of the datasets indicate that the interdecadal variation is mainly associated with the change in ENSO amplitude.In contrast to the period of 1946-1967,a greater SST variance occurred in the central-eastern equatorial Pacific during 1901-1945 and 1968-2009.A stronger El Ni?o tends to generate more significant anticyclonic anomalies over the southeast indian Ocean through teleconnection.The northwesterly anomalies to the south of the anticyclone weaken the southeast trade winds and warm the south indian Ocean SST via wind-evaporation-SST feedback,and the positive south indian Ocean SST anomalies trigger westward-propagating oceanic Rossby waves to induce stronger warming of the southwest indian Ocean,leading to a significant asymmetric wind pattern across the equator in spring.The profound northeastward winds on the north side weaken the southwest monsoon,leading to a“second warming”over the north indian Ocean in summer,which anchors the eastward-propagating warm Kelvin waves and results in a stronger NWPSA by inducing surface divergence and suppressing deep convection.

关键词： ENSO Indo-Northwest Pacific Northwest Pacific subtropical anticyclone decadal changes

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Assessing the Relationship between October-November-December Rainfall and indian Ocean Dipole in Recent Decades over Tanzania Following the 2011 Abrupt Change

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Journal of Geoscience and Environment Protection 2024年第3期12卷 110-130页

作者： Charles Yusuph Ntigwaza Wen Wang Key Laboratory of meteorological Disaster of Ministry of Education (KLME)/International Joint Research Laboratory of Climate and Environment Change (ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of meteorological Disasters (CIC-FEMD) School of Atmospheric Sciences Nanjing University of Information Science & Technology Nanjing China Tanzania meteorological Authority Dodoma Tanzania National meteorological Training Centre Kigoma Tanzania

The present study explored how the indian Ocean Dipole (IOD) influences October-November-December (OND) rainfall over Tanzania in recent decade following the 2011 abrupt change. The study spans 50 years, from 1973 to 2022. Notable abrupt changes were observed in 1976 and 2011, leading us to divide our study into two periods: 1976-2010 and 2011-2022, allowing for a close investigation into the existing relationship between OND IOD and OND rainfall and their associated large-scale atmospheric circulations. It was found that the relationship between OND IOD and OND rainfall strengthened, with the correlation changed from +0.73 during 1976-2010 to +0.81 during 2011-2022. Further investigation revealed that, during 1976-2010, areas that received above- normal rainfall during positive IOD experienced below-normal during 2011- 2022 and vice versa. The same pattern relationship was observed for negative IOD. Spatial analysis demonstrates that the percentage departure of rainfall across the region mirrors the standardized rainfall anomalies. The study highlights that the changing relationship between OND IOD and OND rainfall corresponds to the east-west shift of Walker circulation, as well as the north-south shift of Hadley circulation. Analysis of sea surface temperature (SST) indicates that both positive and negative IOD events strengthened during 2011-2022 compared to 1976-2010. Close monitoring of this relationship across different timescales could be useful for updating OND rainfall seasonal forecasts in Tanzania, serving as a tool for reducing socio-economic impacts.

关键词： Sea Surface Temperature (SST) Percentage Departure of Rainfall Atmos-pheric Circulations Walker Circulation Hadley Circulation

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ResoNet:Robust and Explainable ENSO Forecasts with Hybrid Convolution and Transformer Networks

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Advances in Atmospheric Sciences 2024年第7期41卷 1289-1298页

作者： Pumeng LYU Tao TANG Fenghua LING Jing-Jia LUO Niklas BOERS Wanli OUYANG Lei BAI Shanghai Artificial Intelligence Laboratory Shanghai 200072China Zhejiang meteorological Observatory Hangzhou 310002China Institute for Climate and Application Research(ICAR) Nanjing University of Information Science and TechnologyNanjing 210044China Technical University of Munich Potsdam Institute for Climate Impact ResearchPotsdam 14473Germany

Recent studies have shown that deep learning(DL)models can skillfully forecast El Niño–Southern Oscillation(ENSO)events more than 1.5 years in advance.However,concerns regarding the reliability of predictions made by DL methods persist,including potential overfitting issues and lack of interpretability.Here,we propose ResoNet,a DL model that combines CNN(convolutional neural network)and transformer architectures.This hybrid architecture enables our model to adequately capture local sea surface temperature anomalies as well as long-range inter-basin interactions across oceans.We show that ResoNet can robustly predict ENSO at lead times of 19 months,thus outperforming existing approaches in terms of the forecast horizon.According to an explainability method applied to ResoNet predictions of El Niño and La Niña from 1-to 18-month leads,we find that it predicts the Niño-3.4 index based on multiple physically reasonable mechanisms,such as the recharge oscillator concept,seasonal footprint mechanism,and indian Ocean capacitor effect.Moreover,we demonstrate for the first time that the asymmetry between El Niño and La Niña development can be captured by ResoNet.Our results could help to alleviate skepticism about applying DL models for ENSO prediction and encourage more attempts to discover and predict climate phenomena using AI methods.

关键词： deep learning ENSO CNN transformer

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Characterization and Propagation of Historical and Projected Droughts in the Umatilla River Basin, Oregon, USA

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Advances in Atmospheric Sciences 2024年第2期41卷 247-262,I0020-I0028页

作者： Sudip GAUTAM Alok SAMANTARAY Meghna BABBAR-SEBENS Meenu RAMADAS School of Civil and Construction Engineering Oregon State UniversityCorvallisOR 97331USA School of Infrastructure Indian Institute of TechnologyBhubaneswarOdisha 752050India

Climate change is expected to have long-term impacts on drought and wildfire risks in Oregon as summers continue to become warmer and drier. This paper investigates the projected changes in drought characteristics and drought propagation in the Umatilla River Basin in northeastern Oregon for mid-century(2030–2059) and late-century(2070–2099) climate scenarios. Drought characteristics for projected climates were determined using downscaled CMIP5 climate datasets from ten climate models and Soil and Water Assessment Tool to simulate effects on hydrologic processes. Short-term(three months) drought characteristics(frequency, duration, and severity) were analyzed using four drought indices, including the Standardized Precipitation Index(SPI-3), Standardized Precipitation-Evapotranspiration Index(SPEI-3), Standardized Streamflow Index(SSI-3), and the Standardized Soil Moisture Index(SSMI-3). Results indicate that short-term meteorological droughts are projected to become more prevalent, with up to a 20% increase in the frequency of SPI-3drought events. Short-term hydrological droughts are projected to become more frequent(average increase of 11% in frequency of SSI-3 drought events), more severe, and longer in duration(average increase of 8% for short-term droughts).Similarly, short-term agricultural droughts are projected to become more frequent(average increase of 28% in frequency of SSMI-3 drought events) but slightly shorter in duration(average decrease of 4%) in the future. Historically, drought propagation time from meteorological to hydrological drought is shorter than from meteorological to agricultural drought in most sub-basins. For the projected climate scenarios, the decrease in drought propagation time will likely stress the timing and capacity of water supply in the basin for irrigation and other uses.

关键词： Umatilla drought SPI SPEI SSI SSMI

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What induced the trend shift of mixed-layer depths in the Antarctic Circumpolar Current region in the mid-1980s?

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Acta Oceanologica Sinica 2024年第1期43卷 11-21页

作者： Shan Liu Jingzhi Su Huijun Wang Cuijuan Sui Key Laboratory of Marine Hazards Forecasting National Marine Environmental Forecasting CenterMinistry of Natural ResourcesBeijing 100081China Center for Earth System Modeling and Prediction of CMA Beijing 100081China Collaborative Innovation Center on Forecast and Evaluation of meteorological Disasters Nanjing University of Information Science&TechnologyNanjing 210044China Nansen-Zhu International Research Center Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China

An obvious trend shift in the annual mean and winter mixed layer depth(MLD)in the Antarctic Circumpolar Current(ACC)region was detected during the 1960–2021 period.Shallowing trends stopped in mid-1980s,followed by a period of weak trends.The MLD deepening trend difference between the two periods were mainly distributed in the western areas in the Drake Passage,the areas north to Victoria Land and Wilkes Land,and the central parts of the South indian sector.The newly formed ocean current shear due to the meridional shift of the ACC flow axis between the two periods is the dominant driver for the MLD trends shift distributed in the western areas in the Drake Passage and the central parts of the South indian sector.The saltier trends in the regions north to Victoria Land and Wilkes Land could be responsible for the strengthening mixing processes in this region.

关键词： mixed layer depth trend shift Antarctic Circumpolar Current(ACC) flow axis

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Spatial Variation and Trend of Extreme Precipitation in Africa during 1981-2019 and Its Projected Changes at the End of 21^st Century

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Journal of Geoscience and Environment Protection 2024年第3期12卷 192-221页

作者： Fabien Habiyakare Tong Jiang Ibrahim Yahaya Daudi Ndabagenga James Kagabo Buda Su School of Atmospheric Sciences Key Laboratory of Meteorological Disaster of Ministry of Education Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science and Technology Nanjing China Rwanda Meteorology Agency (Meteo Rwanda) Kigali Rwanda Institute for Disaster Risk Management/School of Geographical Sciences Nanjing University of Information Science & Technology Nanjing China Department of Geography Gombe State University Gombe State Nigeria

This study comprehensively examines the patterns and regional variation of severe rainfall across the African continent, employing a suite of eight extreme precipitation indices. The analysis extends to the assessment of projected changes in precipitation extremes using five General Circulation Models (GCMs) from Coupled Model Intercomparison Project Phase 6 (CMIP6) under four Shared Socioeconomic Pathways (SSPs) scenarios at the long-term period (2081-2100) of the 21st century. Furthermore, the study investigates potential mechanisms influencing precipitation extremes by correlating extreme precipitation indices with oceanic system indices, specifically Ni?o 3.4 for El Ni?o-Southern Oscillation (ENSO) and Dipole Mode Index (DMI) for the indian Ocean Dipole (IOD). The findings revealed distinct spatial distributions in mean trends of extreme precipitation indices, indicating a tendency toward decreased extreme precipitation in North Africa, Sahel region, Central Africa and the Western part of South Africa. Conversely, West Africa, East Africa and the Eastern part of South Africa exhibit an inclination toward increased extreme precipitation. The changes in precipitation extreme indices indicate a general rise in both the severity and occurrence of extreme precipitation events under all scenarios by the end of the 21st century. Notably, our analysis projects a decrease in consecutive wet days (CWD) in the far-future. Additionally, correlation analysis highlights significant correlation between above or below threshold rainfall fluctuation in East Africa and South Africa with oceanic systems, particularly ENSO and the IOD. Central Africa abnormal precipitation variability is also linked to ENSO with a significant negative correlation. These insights contribute valuable information for understanding and projecting the dynamics of precipitation extreme in Africa, providing a foundation for climate adaptation and mitigation efforts in the region.

关键词： Extreme Precipitation Mann-Kendall Trend Projections Oceanic System Africa

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The Monsoon Low-Level Jet:Climatology and Impact on Monsoon Rainfall over the West Coast and Central Peninsular India

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Journal of meteorological Research 2023年第1期37卷 112-125页

作者： Rohit THAPLIYAL meteorological Centre India Meteorological DepartmentUttarakhand 248005India

The monsoon low-level jet(MLLJ)originates at Mascarene high and after traveling thousands of kilometers enters India from the western boundary causing deep convection,cloudiness,and rainfall.Although its core lies at 850 hPa,it has a large vertical extent;therefore,different meteorological parameters at different levels have a large influence on the indian summer monsoon rainfall.This study aims to examine the upper-air climatology of 9 stations on the west coast and central Peninsular India and to find out the effects of various parameters at different standard pressure levels on the indian summer monsoon rainfall variability.We used the 34-yr(1971–2004)actual upper-air radiosonde/radio wind and standard synoptic surface observations data from these 9 stations and reported some new aspects of the MLLJ.The NCEP/NCAR and ECMWF reanalysis wind data have also been used to holistically study the features of MLLJ over sea and land areas.This study,as opposed to some recent studies,confirms the splitting of MLLJ into two branches,which can be seen on a few days during the monsoon season.Further analyses show that the change in geopotential height between 800 and 900 hPa has a strong bearing on the strength of MLLJ.The change in the upper-air pressure gradient force over the indian landmass can cause a change in the wind speed of MLLJ during the monsoon season.

关键词： monsoon low-level jet(MLLJ) heavy rainfall MLLJ splitting MLLJ climatology Somali low-level jet

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