长江中下游梅雨与春季南半球年际模态(SAM)的关系分析

THE RELATIONSHIP BETWEEN MEIYU IN THE MID-AND LOWER REACHES OFTHE YANGTZE RIVER VALLEY AND THE BOREAL SPRING SOUTHERN HEMISPHERE ANNULAR MODE

关键词:  梅雨  SAM指数  关系

Key words:  Meiyu  SAM index  analysis

摘要:

利用1951～2000年中国160站梅汛期(6～7月)月平均降水资料和南半球月平均海平面气压资料,对全国梅汛期降水与其前期春季(4～5月)南半球年际模态进行了统计分析,结果表明:长江中下游梅雨与春季SAM指数存在显著的正相关,东亚梅汛期大尺度大气环流异常同样与春季SAM指数有着紧密的联系,强SAM春季对应着后期弱东亚夏季风,西太平洋副高加强西伸,以及长江中下游地区垂直上升速度的增加,这些为长江中下游梅雨的增加提供了有利的大气环流和水汽条件,而弱SAM春季情况则正好相反。春季南半球年际模态的异常为长江中下游

Abstract:

Based on the precipitation of 160 stations in China during the Meiyu period and monthly mean sea level pressure of the Southern Hemisphere from 1951 to 2000,the relationship between the Meiyu and the boreal spring Southern Hemisphere Annular Mode(SAM) is examined with statistical methods.Here are the results.There is a significantly positive correlation between the boreal spring SAM index and the following Meiyu rainfall in the mid-and lower reaches of the Yangtze River.The large-scale atmospheric circulation anomalies during the Meiyu period over East Asia are also related to the boreal spring SAM index.A strong SAM in boreal spring is followed by a weakened East Asian summer monsoon,a strengthened and westward-expanded Western predicting Meiyu precipitation in the mid-and lower reaches of the Yangtze River.Pacific Subtropical High,as well as increased ascending vertical velocity.These situations provide necessary circulation and water vapor conditions for the increase of Meiyu precipitation in the mid-and lower reaches of the Yangtze River valley,and vice versa.The boreal spring SAM variation provides a potential valuable signal for predicting Meiyu precipitation in the mid-and lower reaches of the Yangtze River.