The Record-breaking Mei-yu in 2020 and Associated Atmospheric Circulation and Tropical SST Anomalies  

作　　者：Yihui DING Yunyun LIU Zeng-Zhen HU 

机构地区：[1]National Climate Center,China Meteorological Administration,Beijing 100081,China [2]Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters,Nanjing University of Information Science&Technology,Nanjing 210044,China [3]Climate Prediction Center,NCEP/NOAA,College Park,MD 20740,USA

出　　处：《Advances in Atmospheric Sciences》2021年第12期1980-1993,共14页大气科学进展（英文版）

基　　金：This work was jointly supported by National Key R&D Program of China(2018YFC1505806);Guangdong Major Project of Basic and Applied Basic Research(2020B0301030004);National Science Foundation of China(41875100);the China Meteorological Administration Innovation and Development Project(CXFZ2021Z033),and China Three Gorges Corporation(Grant No.0704181).

摘　　要：The record-breaking mei-yu in the Yangtze-Huaihe River valley(YHRV)in 2020 was characterized by an early onset,a delayed retreat,a long duration,a wide meridional rainbelt,abundant precipitation,and frequent heavy rainstorm processes.It is noted that the East Asian monsoon circulation system presented a significant quasi-biweekly oscillation(QBWO)during the mei-yu season of 2020 that was associated with the onset and retreat of mei-yu,a northward shift and stagnation of the rainbelt,and the occurrence and persistence of heavy rainstorm processes.Correspondingly,during the mei-yu season,the monsoon circulation subsystems,including the western Pacific subtropical high(WPSH),the upper-level East Asian westerly jet,and the low-level southwesterly jet,experienced periodic oscillations linked with the QBWO.Most notably,the repeated establishment of a large southerly center,with relatively stable latitude,led to moisture convergence and ascent which was observed to develop repeatedly.This was accompanied by a long-term duration of the mei-yu rainfall in the YHRV and frequent occurrences of rainstorm processes.Moreover,two blocking highs were present in the middle to high latitudes over Eurasia,and a trough along the East Asian coast was also active,which allowed cold air intrusions to move southward through the northwestern and/or northeastern paths.The cold air frequently merged with the warm and moist air from the low latitudes resulting in low-level convergence over the YHRV.The persistent warming in the tropical Indian Ocean is found to be an important external contributor to an EAP/PJ-like teleconnection pattern over East Asia along with an intensified and southerly displaced WPSH,which was observed to be favorable for excessive rainfall over YHRV.

关 键 词：record-breaking mei-yu western Pacific subtropical high quasi-biweekly oscillation Tropical Indian Ocean warming low-level southwesterly jet blocking high 

分 类 号：P731.11[天文地球—海洋科学] P434