2011年初夏我国长江中下游降水的气候特征及成因  

Climatic Characteristics and Cause Analysis of Precipitation over the Middle and Lower Reaches of the Yangtze River Valley During Early Summer of 2011

作　　者：司东[1] 柳艳菊[1] 马丽娟[1] 王艳娇[1] 王遵娅[1] 唐进跃[1] 

机构地区：[1]国家气候中心,北京100081

出　　处：《气象》2012年第5期601-607,共7页Meteorological Monthly

基　　金：国家重点基础研究发展(973)计划(2010CB950404和2012CB955203);国家科技支撑计划(2009BAC51B02);公益性行业(气象)科研专项(GYHY201006009)共同资助

摘　　要：文章主要分析了2011年初夏长江中下游降水的气候特征及其成因。结果表明:2011年5月长江中下游降水异常偏少,6月转为异常偏多,出现了明显的旱涝转换。长江中下游地区的旱涝转换主要受南海季风、东亚季风强度以及西太平洋副热带高压(副高)的异常快速北跳的影响。研究还发现,6月亚洲中高纬长期维持两槽一脊的环流形势,东北冷涡活动频繁,多次引导冷空气南下。同时,副高异常偏北、偏西,并出现多次西伸过程。由于冷涡的加强南压与西伸的副高相互作用,促使长江以南地区西南气流明显增强,使得冷暖空气在长江中下游地区交汇,最终导致该地降水偏多。The climatic characteristics of precipitation over the middle and lower reaches of the Yangtze River Valley（YRV） during early summer of 2011 and associated causes are examined in this study.It is shown that,during May 2011,the precipitation over the middle and lower reaches of the YRV was below normal,but was above normal during June,and then drought-flood alternation occurs.This droughts-flood alternation is mainly influenced by the intensity of the South China Sea summer monsoon and the East Asian summer monsoon,and the abrupt northward shift of the western Pacific subtropical high（WPSH）. During June 2011,there are two troughs located in the Arabian Sea and the Sea of Japan respectively, and a ridge located in the Lake Baikal over the middle-high latitude Eurasian area.The frequent activities of northeast cold vortex（NECV） bring cold air masses to the middle and lower reaches of the YRV. At the same time,the WPSH extends to the west and north of its normal position,and shifts westward several times in June.It is indicated that it is just the interaction between the NECV and WPSH that leads to the reinforcement of the southwest low-level jet（LLJ） in the lower troposphere.The convergence between the northward warm and wet southwesterly flow brought by LLJ and the southward dry and cold air by NECV is favorable to the positive precipitation anomaly in the middle and lower reaches of the YRV.

关 键 词：旱涝转换 西太平洋副热带高压 东北冷涡 降水 

分 类 号：P426.615[天文地球—大气科学及气象学]