MJO对2020年夏季中国东部持续性降水的维持作用  

Prolonged Effects of the Madden-Julian Oscillation on Persistent Rainfall over Eastern China during Summer 2020

作　　者：赵起帆 周洋 ZHAO Qifan;ZHOU Yang(Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters/Key Laboratory of Meteorological Disaster,Ministry of Education/School of Atmospheric Sciences,Nanjing University of Information Science&Technology,Nanjing 210044)

机构地区：[1]南京信息工程大学气象灾害预报预警与评估协同创新中心/南京信息工程大学气象灾害教育部重点实验室/南京信息工程大学大气科学学院,南京210044

出　　处：《大气科学》2024年第3期1157-1172,共16页Chinese Journal of Atmospheric Sciences

基　　金：国家自然科学基金项目41930969、42175030。

摘　　要：本文利用美国NOAA的CMORPH降水和NCEP的CFSv2再分析资料、欧洲中心ERA-5再分析数据、Wheeler和Hendon的MJO指数等资料和敏感性数值试验分析了MJO对2020年夏季中国东部持续性降水的影响机制。通过相关、回归、波源分析等方法发现:(1)与往年相比,2020年夏季风雨带在我国华南和长江中下游地区长时间维持,使得该地区季风降水具有明显的极端性特征;(2)同时,我国东部大气中高层位势高度出现负异常,伴随着水汽辐合和低层大气不稳定,均有利于2020年夏季强降水的维持;(3)2020年夏季MJO活跃于1、2位相,其振幅在10~30天具有显著的周期。MJO在非洲和印度洋产生显著的Rossby波源,该波源激发的波列沿急流传播,造成了我国东部位势高度负异常的维持,同时也有利于我国东部夏季降水的维持;(4)通过敏感性试验进一步验证,MJO的在10~30天的信号有利于在我国东部500 hPa上空形成负的位势高度异常,有利于该区域降水增加。Using precipitation derived from CPC MORPHing technique(CMORPH)of the US National Oceanic and Atmospheric Administration,the US National Centers for Environmental Prediction Climate Forecast System version 2 reanalysis(CFSv2),ERA-5 reanalysis obtained from the European Centre for Medium-Range Weather Forecasts,and the Madden-Julian Oscillation(MJO)index of Wheeler and Hendon,the effects of MJO on rainfall persistence over eastern China in the summer of 2020 were analyzed.Three major conclusions were made based on the analyses of correlation,regression,and wave source.1)Summer precipitation over eastern China in 2020 was extremely strong compared with rainfall in the previous 21 years.This is because the summer monsoon rain belt has been maintained for a very long time over southern China and the middle and lower reaches of the Yangtze River during 2020.2)A negative geopotential height anomaly in the middle and upper atmosphere,with water vapor convergence between 1000 and 300 hPa and instability at the lower levels,has been maintained over eastern China.Thus,atmospheric circulation favored prolonged rainfall in the 2020 summer.3)During this period,MJO was abnormally active in phases 1 and 2 with significant periods of 10–30 days,indicating that MJO convective centers were sustained over eastern Africa and the western Indian Ocean.Therefore,significant Rossby wave sources have been found over eastern Africa and the western Indian Ocean,which is consistent with the Gill mode.Finally,a Rossby wave train was excited at the sources and transported by a jet stream,which induced the negative geopotential height anomaly over eastern China.Negative geopotential height anomaly over the eastern region maintained and prolonged the rainfall during 2020 because the MJO was sustained in phases 1 and 2.Sensitivity experiments further prove that the 10–30-day signal favors the formation of the negative anomaly of the 500 hPa geopotential height and the positive anomaly of precipitation over eastern China.

关 键 词：Madden-Julian振荡(MJO) Rossby波源 季风降水 中国东部 

分 类 号：P466[天文地球—大气科学及气象学]