中国西北地区大范围极端高温事件的大气环流异常特征

Atmospheric Circulation Anomalies of Large-scale Extreme High Temperature Events in Northwest China

利用中国西北5省(区)90个台站1961—2005年的逐日气温资料,分析了西北五省(区)发生大范围极端高温事件时的大气环流异常特征。结果表明,当出现大范围极端高温事件时,100hPa南亚高压强度偏强并北移至西北地区上空,副高脊线偏北,同时500hPa高度场上有一与温度暖中心相匹配的闭合高压单体控制着西北地区,西北地区上空大气高(中低)层为负(正)温度距平。此外,西北地区上空下沉气流强度明显偏强,下沉运动加强中心在300hPa高度左右。与此同时,除了新疆西南部,西北其他地区的散度场形势都是大气上层辐合,下层辐散,并且辐合辐散强度都偏强,其中的辐合带主要位于150～300hPa高度,辐合中心及其加强中心在200hPa高度左右。

By using the daily temperature data of 90 stations in northwest China from 1961 to 2005,the atmospheric circulation anomalies of large-scale extreme high temperature events in this area were analyzed.The results show that when large-scale extreme high temperature event occurred,the South Asia High became strong and moved to the northwest China,and the Subtropical High Ridge shifted to the north,and the high cell with warm centre at 500 hPa controlled this area,and there were negative（positive） temperature anomalies at upper levels（middle and lower levels） over northwest China.Besides,the downdraft enhanced and its abnormal positive centre was at 300 hPa.The atmosphere was convergent at upper levels and divergent at lower levels in northwest China except for southwest Xinjiang,and the convergence and divergence were strong,and the convergence zone was mainly located between 150 hPa height and 300 hPa height,and the center of convergence and its positive anomalies were approximately situated at 200 hPa height.