江南5月降水与热带印-太海温及对流的联系

Relationship Between May Precipitation in Jiangnan and Tropical Indo-Pacific Sea Surface Temperature and Convection

本文将1980-2021年江南5月降水作为研究对象,采用美国国家气候预测中心(Climate Prediction Center,CPC)降水、美国环境预测中心(National Center for Environmental Prediction,NCEP)大气环流以及英国气象局哈德莱中心(Met Office Hadley Centre)海表面温度等资料,对江南5月降水年际变化特征及其与热带印度洋、太平洋的海表面温度异常(Sea surface temperature anomaly,SSTA)以及对流异常的可能联系进行了分析。结果表明,偏涝年通常伴随有自年前秋季开始发展的热带印度洋暖SSTA,5月同期对流层850 hPa在热带东印度洋至中国南海一带出现东风异常,同时热带印度洋上空对流活动旺盛,通过Hadley环流增强了在西北太平洋的下沉气流,共同增强了西北太平洋异常反气旋(Northwest Pacific anomaly anticyclone,WNPAC),促进了水汽向江南地区输送。热带印度洋中东部的冷SSTA自偏旱年前的冬季开始不断发展,在5月同期的热带印度洋异常冷洋面上空表现为对流抑制,与偏涝年相反的异常Hadley环流促使副高减弱东退,撤出南海,不利于水汽向江南地区输送。除热带印度洋外,热带太平洋和海洋性大陆地区的SSTA及其上空的对流活动异常与WNPAC和江南5月降水异常在一些年份也存在一定的关系,但较热带印度洋复杂。

Taking the May precipitation in Jiangnan from 1980 to 2021 as the research object,this paper uses the data of CPC precipitation,NCEP atmospheric circulation and sea surface temperature in Hadley Centre to analyze the interannual variation characteristics of precipitation in May in Jiangnan,and its possible relationships with sea surface temperature anomaly(SSTA)and convective anomaly on the tropical Indian Ocean and Pacific Ocean.The results show that the pluvial years are usually accompanied by the tropical Indian Ocean warm SSTA that has developed since the autumn of the previous year,and the easterly wind anomaly in 850hPa on the tropical eastern Indian Ocean to the South China Sea in the same time of May,while the convective activity over the tropical Indian Ocean is strong,which enhances the sinking air flow in the northwest Pacific Ocean through the Hadley circulation,which jointly leads to the enhanced westward extension of the WNPAC and promotes the transport of water vapor to the Jiangnan region.Since the winter before the dry years,the cold SSTA in the central and eastern parts of the tropical Indian Ocean has been developing continuously,showing significant convective suppression over the tropical Indian Ocean corresponding to the cold SSTA in the same period of precipitation.The abnormal Hadley circulation opposite to the dry years has promoted the development of abnormal cyclones in the Northwest Pacific and Indochina Peninsula,which is not conducive to the transport of water vapor to the Jiangnan region.In addition to the tropical Indian Ocean,the SSTA in the tropical Pacific Ocean and the Maritime Continent,and the convection anomaly over sea surface is also related to the anomalous anticyclone in the northwest Pacific Ocean and the precipitation anomaly in May in Jiangnan in some years,but it is more complex than the tropical Indian Ocean.