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Isolated deep convections over the Tibetan Plateau in the rainy season during 2001–2020

Atmospheric and Oceanic Science Letters 2024年第5期17卷 16-21页

作者： Ying Na Chaofan Li Riyu Lu School of Atmospheric Science and Remote Sensing Wuxi UniversityWuxiChina Key Laboratory of Ecosystem Carbon Source and Sink China Meteorological Administration(ECSS-CMA)Wuxi UniversityWuxiChina Center for Monsoon System Research Institute of Atmospheric PhysicsChinese Academy of SciencesBeijingChina State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijingChina College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijingChina

The Tibetan Plateau(TP)is a prevalent region for convection systems due to its unique thermodynamic *** study investigated isolated deep convections(IDCs),which have a smaller spatial and temporal size than mesoscale convective systems(MCSs),over the TP in the rainy season(June-September)during 2001–*** authors used satellite precipitation and brightness temperature observations from the Global Precipitation Measurement *** show that IDCs mainly concentrate over the southern *** IDC number per rainy season decreases from around 140 over the southern TP to around 10 over the northern TP,with an average *** initiation time of IDCs exhibits an obvious diurnal cycle,with the peak at 1400–1500 LST and the valley at 0900–1000 *** IDCs last less than five hours and more than half appear for only one *** generally have a cold cloud area of 7422.9 km^(2),containing a precipitation area of approximately 65%.The larger the IDC,the larger the fraction of intense precipitation it *** contribute approximately 20%–30%to total precipitation and approximately 30%–40%to extreme precipitation over the TP,with a larger percentage in July and August than in June and *** terms of spatial distribution,IDCs contribute more to both total precipitation and extreme precipitation over the TP compared to the surrounding plain *** over the TP account for a larger fraction than MCSs,indicating the important role of IDCs over the region.

关键词： Isolated deep convection Tibetan plateau Climatological characteristics Precipitation contribution Extreme precipitation

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The basic equation for target detection in remote sensing

arXiv

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arXiv 2017年

作者： Geng, Xiurui Ji, Luyan Zhao, Yongchao Key Laboratory of Technology in Geo-Spatial Information Processing and Application System Institute of Electronics Chinese Academy of Sciences Beijing100190 China School of Electronic Electrical and Communication Engineering University of Chinese Academy of Sciences 100049 China Ministry of Education Key Laboratory for Earth System Modeling Department of Earth System Science Tsinghua University

Our research has revealed a hidden relationship among several basic components, which leads to the best target detection result. Further, we have proved that the matched filter (MF) is always superior to the constrained energy minimization (CEM) operator, both of which were originally of parallel importance in the field of target detection for remotely sensed image. Copyright © 2017, The Authors. All rights reserved.

关键词： Remote sensing

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Can Eurasia Experience a Cold Winter under a Third-Year La Nina in 2022/23?

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Advances in Atmospheric Sciences 2023年第4期40卷 541-548页

作者： Fei ZHENG Bo WU Lin WANG Jingbei PENG Yao YAO Haifeng ZONG Qing BAO Jiehua MA Shuai HU Haolan REN Tingwei CAO Renping LIN Xianghui FANG Lingjiang TAO Tianjun ZHOU Jiang ZHU International Center for Climate and Environment Science(ICCES) Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics(LASG) Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China Center for Monsoon System Research(CMSR) Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China CAS Key Lab of Regional Climate-Environment for Temperate East Asia(RCE-TEA) Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China Nansen-Zhu International Research Centre(NZC) Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China CMA Earth System Modeling and Prediction Center Beijing 100081China Department of Atmospheric and Oceanic Sciences&Institute of Atmospheric Sciences Fudan UniversityShanghai 200438China

The Northern Hemisphere(NH)often experiences frequent cold air outbreaks and heavy snowfalls during La Nina *** 2022,a third-year La Nina event has exceeded both the oceanic and atmospheric thresholds since spring and is predicted to reach its mature phase in December *** such a significant global climate signal,whether the Eurasian Continent will experience a tough cold winter should not be assumed,despite the direct influence of mid-to high-latitude,large-scale atmospheric circulations upon frequent Eurasian cold extremes,whose teleconnection physically operates by favoring Arctic air invasions into Eurasia as a consequence of the reduction of the meridional background temperature gradient in the *** the 2022/23 winter,as indicated by the seasonal predictions from various climate models and statistical approaches developed at the Institute of Atmospheric Physics,abnormal warming will very likely cover most parts of Europe under the control of the North Atlantic Oscillation and the anomalous anticyclone near the Ural Mountains,despite the cooling effects of La *** the same time,the possibility of frequent cold conditions in mid-latitude Asia is also recognized for this upcoming winter,in accordance with the tendency for cold air invasions to be triggered by the synergistic effect of a warm Arctic and a cold tropical Pacific on the hemispheric ***,how the future climate will evolve in the 2022/23 winter is still subject to some uncertainty,mostly in terms of unpredictable internal atmospheric ***,the status of the mid-to high-latitude atmospheric circulation should be timely updated by medium-term numerical weather forecasts and sub-seasonal-to-seasonal prediction for the necessary date information and early warnings.

关键词： Eurasian climate seasonal forecast La Nina winter cold climate

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Long-term change in low-cloud cover in Southeast China during cold seasons

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Atmospheric and Oceanic Science Letters 2022年第6期15卷 9-14页

作者： Zhe Chen Minghuai Wang Haipeng Zhang Shuheng Lin Zhun Guo Yiquan Jiang Chen Zhou Institute for Climate and Global Change Research School of Atmospheric SciencesNanjing UniversityNanjingChina Department of Atmospheric and Oceanic Science&Earth System Science Interdisciplinary Center University of MarylandCollege ParkMDUSA School of Atmospheric Sciences Sun Yat-sen UniversityZhuhaiChina Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) ZhuhaiChina State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijingChina

Southeast China has comparable stratus cloud to that over the oceans,especially in the cold seasons(winter and spring),and this cloud has a substantial impact on energy and hydrological ***,uncertainties remain across datasets and simulation results about the long-term trend in low-cloud cover in Southeast China,making it difficult to understand climate change and related physical *** this study,multiple datasets and numerical simulations were applied to show that low-cloud cover in Southeast China has gone through two stages since 1980—specifically,a decline and then a rise,with the turning point around *** regional moisture transport plays a crucial role in low-cloud cover changes in the cold seasons and is mainly affected by the Hadley Cell in winter and the Walker Circulation in spring,*** moisture transport was not well simulated in CMIP6 climate models,leading to poor simulation of the low-cloud cover trend in these *** study provides insights into further understanding the regional climate changes in Southeast China.

关键词： Low-cloud cover Large-scale circulation Hadley cell Pacific walker circulation

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Identification of soybean in Argentina using Sentinel-2 composite images

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International Journal of Agricultural and Biological Engineering 2024年第5期17卷 266-274页

作者： Linsheng Huang Yue Chen Yuhao Pan Zihang Lou Shijun Zheng Xiaoyang Zhang Le Yu Shengwei Liu Dailiang Peng National Engineering Research Center for Agro-Ecological Big Data Analysis&Application Anhui UniversityHefei 230601China Key Laboratory of Digital Earth Science Aerospace Information Research InstituteChinese Academy of SciencesBeijing 100094China Research Area of Ecology and Biodiversity School of Biological SciencesThe University of Hong KongPokfulamHong KongChina College of Environmental and Resource Sciences Zhejiang UniversityHangzhou 310058China Department of Earth System Science Ministry of Education Key Laboratory for Earth System ModelingInstitute for Global Change StudiesTsinghua UniversityBeijing 100084China Geospatial Sciences Center of Excellence Department of Geography&Geospatial SciencesSouth Dakota State UniversityBrookingsSD 57007USA Ministry of Education Ecological Field Station for East Asian Migratory Birds Beijing 100084China Tsinghua University(Department of Earth System Science)-Xi’an Institute of Surveying and Mapping Joint Research Center for Next-Generation Smart Mapping Beijing 100084China School of Surveying and Land Information Engineering Henan Polytechnic UniversityJiaozuo 454000HenanChina

Soybean is one of the most important oil crops, and Argentina is the third-largest soybean producer in the world, accounting for 17% of the global soybean yield. Timely and accurate information on soybean spatial distribution is critical for ensuring global food security. Sentinel-2 multispectral data and machine learning classification models are used to investigate the potential of soybean identification in the early stage of the growing season in Argentina, with the help of Google earth Engine (GEE). The earliest time window and optimal feature set for soybean identification are explored. Results are as follows: 1) the random forest (RF) classification model demonstrated the highest level of classification accuracy compared to the backpropagation neural network (BPNN), support vector machine (SVM), and naive Bayes (NB) models;2) Soybean can be accurately identified as early as the end of February (filling stage), which is approximately one month before harvest;3) The optimal feature-subset can reduce the amount of input data by 80% while maintaining high classification accuracy. The overall accuracy (OA) of the RF classification model is 85.87%, and the relative error between the estimated soybean planting area and the agricultural statistics is 3.45%. This study provided a high-precision method for early-season identification of soybeans over large scales. The results can provide a data support for early futures trading and agricultural insurance, as well as a reference for policy-making to ensure global soybean food security.

关键词： soybean machine learning time window feature selection Sentinel-2 Google earth Engine

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Dominant atmospheric circulation patterns associated with the rapid intensification of summer flash droughts in Eastern China

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Science of the Total Environment 2024年 957卷 177416页

作者： Ma, Feng Yuan, Xing Li, Hua Key Laboratory of Hydrometeorological Disaster Mechanism and Warning of Ministry of Water Resources/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science and Technology Nanjing210044 China School of Hydrology and Water Resources Nanjing University of Information Science and Technology Jiangsu Nanjing210044 China Key Laboratory of Earth System Numerical Modeling and Application Institute of Atmospheric Physics Chinese Academy of Sciences Beijing100029 China

Flash droughts (FDs), which are characterized by rapid intensification, occurred frequently over Eastern China, posing great challenges for drought forecasting and preparation on subseasonal timescale. However, the drivers of the rapid development of FDs are not well understood. By comparing with slow droughts (SDs), this study investigates the dominant physical processes responsible for FDs in four different regions over Eastern China through diagnosing moisture budgets and further linking them to large-scale atmospheric circulation patterns. Results reveal that the rapid intensification of FDs in the four regions are dominantly driven by stronger and more persistent subsidence than those for SDs, which suppress precipitation and heat the atmosphere, leading to rapid soil drying. Further analyses indicate that stronger and more stable atmospheric circulation systems are conductive to the rapid intensification of FDs. Specifically, in Northeast China, the persistent subsidence is strongly related to the maintenance of high over area south to Lake Baikal, which is associated with enhanced subtropical jet stream. In North China Plain, the upper-level cyclonic anomalies associated with the negative phase of the circumglobal teleconnection, together with more southward East Asia summer monsoon (EASM) rain belt, are responsible for the stronger sinking motions. In southern China, droughts can be attributed to simultaneous expansions of the South Asia high (SAH) and western Pacific subtropical high (WPSH). While the persistently joint control of the SAH and WPSH and larger area under the control of the two systems are crucial for FDs in Yangtze River basin and South China, respectively. The SDs are often related to the less organized circulation patterns and inconsistent shift of the EASM rain belt during the development phase. Our findings suggest potential source of predictability for summer FDs in Eastern China. © 2024 Elsevier B.V.

关键词： Drought

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Trends in extreme high temperature at different altitudes of Southwest China during 1961–2014

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Atmospheric and Oceanic Science Letters 2020年第5期13卷 417-425页

作者： XUE Yuting CHEN Quanliang ZHANG Jiayu HUANG Ping College of Atmospheric Sciences Chengdu University of Information TechnologyChengduChina Center for Monsoon System Research Institute of Atmospheric PhysicsChinese Academy of SciencesBeijingChina Earth System Modeling Center and Climate Dynamics Research Center Nanjing University of Information Science and TechnologyNanjingChina State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Chinese Academy of SciencesBeijingChina

This study analyzed the trends in extreme high temperature in Southwest China based on the observed daily maximum temperature and average temperature data from 410 Chinese stations recently released by the China Meteorological *** authors found that the trends in extreme high temperature at different altitudes of Southwest China exhibit staged variations during a recent 50-year period(1961–2014).The trends in mean temperature and maximum temperature also exhibit phase *** temperature-related variables increase gently during the period 1975–94,whereas they increase dramatically during the recent period of 1995–2014,with a rate that is approximately two to ten times more than that during 1975–*** addition,the trends in mean temperature,maximum temperature,and the frequency of extreme high temperature in the low altitudes transit from negative to positive in the two periods,while they increase dramatically in the mid-and high-altitude areas during 1995–2014,the well-known global warming hiatus *** particular,the maximum temperature increases much faster than that of average *** result implies that the regional temperature trend could be apparently different from the global mean temperature change.

关键词： Southwest China extreme high temperature trend change altitude

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“Mega-sandwich pattern”of interdecadal precipitation variations and its regional manifestation in the Asian summer precipitation region

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Science Bulletin 2024年第17期69卷 2656-2659页

作者： Fahu Chen Lingxin Huang Dianbin Cao Jie Chen Shengqian Chen Shuai Ma Tianjun Zhou Alpine Paleoecology and Human Adaptation Group(ALPHA) State Key Laboratory of Tibetan Plateau Earth SystemEnvironment and Resources(TPESER)Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China Key Laboratory of Western China’s Environmental Systems(Ministry of Education) College of Earth and Environmental SciencesLanzhou UniversityLanzhou 730000China State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China University of the Chinese Academy of Sciences Beijing 100049China

The Tibetan Plateau(TP)is an important link between the South Asian monsoon(SAM)region,the East Asian monsoon region,and the drylands of Central *** changes within these regions are dominated by both the monsoon and the *** has prompted the scientific community to adopt a broad spatial perspective,proposing concepts such as the"Pan-Third Poleoor"Asian summer precipitationo,to better understand the regional climate dynamics,their driving mechanisms,and the resulting major ecological and environmental impacts.

关键词： Asian monsoon precipitation

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Influence of the North Pacific Victoria mode on the tropical Pacific summer ITCZ

Influence of the North Pacific Victoria mode on the tropical...

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第一届中国大地测量和地球物理学学术大会

作者： Ruiqiang Ding Jianping Li Yu-heng Tseng State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics(L College of Global Change and Earth System Sciences(GCESS) Beijing Normal UniversityBeijingChina Climate and Global Dynamics Division NCARBoulderColorado

In this paper,we demonstrate the close connection between the second dominant mode of spring SST anomalies (SSTAs) in the North Pacific poleward of 20°N,referred to as the Victoria mode (VM),and the interannual variability of the Pacific ITCZ precipitation during the following *** analysis shows that strong positive VM cases are followed by positive precipitation anomalies over the central–eastern Pacific ITCZ region,in association with negative precipitation anomalies over the ITCZ regions of the tropical western Pacific and eastern North *** influence of the spring VM on the Pacific ITCZ summer precipitation is independent of the effect of ENSO from the previous winter,and they may together act as effective predictors of Pacific ITCZ summer *** hypothesized physical mechanism through which the spring VM induces the Pacific ITCZ summer precipitation anomalies is generally consistent with the seasonal footprinting mechanism (SFM).During strong positive VM cases,positive SSTAs associated with the VM persist until summer in the subtropics,where low-level convergence and divergence caused by SST gradients give rise to enhanced precipitation over the central–eastern Pacific ITCZ region,and to reduced precipitation over the ITCZ regions of the tropical western Pacific and eastern North *** thermodynamic ocean–atmosphere coupling between the ITCZ and SSTAs associated with the VM in the subtropical Pacific may play a vital role in the initiation of ENSO events.

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Contribution of El Nino amplitude change to tropical Pacific precipitation decline in the late 1990s

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Atmospheric and Oceanic Science Letters 2019年第5期12卷 355-360页

作者： GUO Suqi WU Renguang Center for Monsoon System Research Institute of Atmospheric PhysicsChinese Academy of SciencesBeijingChina College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijingChina State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijingChina

Equatorial central Pacific precipitation experienced a prominent decline in the late 1990 *** change was previously attributed to a La Nina-like mean sea surface temperature(SST)change in the Pacific Ocean associated with a phase switch of the Interdecadal Pacific ***,using a series of model experiments,the authors reveal that the El Nino-related interannual SST anomalies contributed largely to the precipitation decrease over the equatorial central *** El Nino SST effect was due to the change in the amplitude of El Nino events in the late 1990 *** 1980-98 decade had more large-amplitude El Nino events than the 1999-2014 *** nonlinear precipitation response to SST anomalies resulted in a larger decadal mean precipitation in the 1980-98 decade than in the 1999-2014 *** results highlight the importance of El Nino amplitude change in future climate change related to global warming.

关键词： Tropical Pacific precipitation decline Interdecadal Pacific Oscillation phase switch interannual SST effect large-amplitude El Nino events

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