Precursory influence of the Antarctic Oscillation on the onset of Asian summer monsoon  

作　　者：GAO Hui LIU YunYun WANG YongGuang LI WeiJing 

机构地区：[1]National Climate Center,China Meteorological Administration

出　　处：《Chinese Science Bulletin》2013年第6期678-683,共6页

基　　金：supported by the National Basic Research Program of China (2012CB417205);the International Cooperation Program of Ministry of Science and Technology of China (2009DFA23010);the Special Research Fund of Public Welfare Project (Meteorology:GYHY200906018 and GYHY201306070);the National Science & Technology Supporting Program (2009BAC51B)

摘　　要：The Asian summer monsoon(ASM) begins firstly over the Indo-China Peninsula in early May and over the South China Sea(SCS) in mid-May.The different monsoon onset dates can exert distinct effects on the summer rainfall in Asia.Statistical results indicate that the Antarctic Oscillation(AAO) in the boreal winter has a significant precursory influence on the ASM onset dates.In stronger AAO years,both the Mascarene high and the Australia high in March are stronger owing to the "see-saw" structure of atmospheric circulation over the subtropics and higher latitudes in the Southern Hemisphere,and the tropical intertropical convergence zone(ITCZ) is deeper.Thus,the pressure gradient between the subtropical and tropical regions increases in spring.As a result,the Somalia cross-equatorial flow(SCEF) occurs earlier,strengthens,and enhances the westerlies over the tropical Indian Ocean.The enhanced westerlies impel an eastward withdrawal of the western Pacific subtropical high and intensify the convergence and rising motion at the lower troposphere,accelerating the burst of ASM.Differently,weaker AAO weakens the pressure gradient between the tropical and subtropical regions and delays the establishment of SCEF,resulting in a delayed onset of ASM.This study extends the leading time of seasonal forecast of ASM onset from the previous spring to winter and provides useful information about precursory signals in climate prediction operation.The Asian summer monsoon （ASM） begins firstly over the Indo-China Peninsula in early May and over the South China Sea （SCS） in mid-May. The different monsoon onset dates can exert distinct effects on the summer rainfall in Asia. Statistical results indicate that the Antarctic Oscillation （AAO） in the boreal winter has a significant precursory influence on the ASM onset dates. In stronger AAO years, both the Mascarene high and the Australia high in March are stronger owing to the ＂see-saw＂ structure of atmospheric circulation over the subtropics and higher latitudes in the Southern Hemisphere, and the tropical intertropical con- vergence zone （ITCZ） is deeper. Thus, the pressure gradient between the subtropical and tropical regions increases in spring. As a result, the Somalia cross-equatorial flow （SCEF） occurs earlier, strengthens, and enhances the westerlies over the tropical Indian Ocean. The enhanced westerlies impel an eastward withdrawal of the western Pacific subtropical high and intensify the conver- gence and rising motion at the lower troposphere, accelerating the burst of ASM. Differently, weaker AAO weakens the pressure gradient between the tropical and subtropical regions and delays the establishment of SCEF, resulting in a delayed onset of ASM. This study extends the leading time of seasonal forecast of ASM onset from the previous spring to winter and provides useful information about precursory signals in climate prediction operation.

关 键 词：亚洲夏季风 前兆信号 南极涛动 发病 亚热带地区 马斯克林高压 西太平洋副高 中国南海 

分 类 号：P425.42[天文地球—大气科学及气象学] P315.7