华南前汛期极端降水年代际异常及其影响因子分析

摘要

Based on the daily precipitation data provided by the National Meteorological Information Center from 89 representative sta-tions in South China,as well as the reanalyzed monthly average 850 hPa wind field from the National Centers for Environmental Predic-tion and the National Center for Atmospheric Research (NCEP/NCAR)and extended reconstructed sea surface temperature (SST)da-ta from 1969 to 2013,the interdecadal variation and the causes of extreme precipitation during the pre-rainy season in South China were analyzed,moreover,the interdecadal abnormal coupling relation among SST,850 hPa wind field and extreme precipitation during the pre-rainy season in South China were also analyzed.The results are as follows:(1 )The “El-Nio-Southern-Oscillation-like”(ENSO-like)positive SST anomaly during 1977-1997 and the corresponding atmospheric circulation anomaly were major cau-ses of less extreme precipitation during the pre-rainy season in most part of South China.However,from about 1997 to 2010,the pre-ceding winter SST presented ENSO-like negative SST,there were more extreme precipitation in most part of South China during the pre-rainy seanson.(2)On interdecadal scales,when it was the ENSO-like positive SST anomaly during the pre-rainy season in South China,there was an anomaly strong anti -cyclonic circulation over the middle -high latitude North Pacific,its western end southern flow was conducive to the South China Sea warm flow transport to South China,meanwhile,the east flow stream coming from mid-latitude Western Pacific was in favour of the wet air transport to South China,the intersection of two section airflow to South Chi-na caused severe pre-rainy season floods in South China.However,the ENSO-like negative SST anomaly was conducive to pre-rainy season less rain in South China.%利用国家气象信息中心提供的华南89个代表站1969～2013年逐日降水资料、NCEP／NCAR 850 hPa月平均再分析风场及NOAA重构延长的逐月海表温度（SST）资料，研究了华南前汛期极端降水年代际异常的时空分布特征，并进一步分析了太平洋海温、850 hPa风场及华南前汛期极端降水三者之间年代际异常耦合关系。结果表明：（1）1977～1997年左右海表温度为“类El NiNo”型，华南前汛期大部地区极端强降水偏少，1997～2010年左右海表温度转为“类La NiNa”型，华南前汛期大部地区极端强降水偏多；（2）年代际尺度上，前汛期太平洋海表温度异常呈“类La NiNa”型时，整个中高纬北太平洋存在一个强大的反气旋性环流异常，其西端的偏南气流有利于南海的暖湿气流向华南地区输送，同时，其南端的偏东气流有利于将中纬度西太平洋上的湿空气输向华南地区，2股水汽在30°N以南附近交汇，极大地增强了华南地区的水汽输送，有利于华南前汛期发生极端强降水，而太平洋海表温度异常呈“类El NiNo”型时，则不利于华南前汛期极端强降水的发生。