南极绕极波动及其与中国夏季降水异常的关联

利用NCEP／NCAR逐月SLP再分析资料，通过复经验正交函数展开(CEOF)，借助其第1模态恢复场研究了1952-1998年期间南极绕极波动的年代际变化和传播特征。结果表明，东南太平洋是研究南极绕极波动(ACW)的关键区，并由此定义东南太平洋ACW活动指数(EPAI)。相关分析揭示了秋季EPAI与次年中国夏季降水有着密切的关系，当秋季EPAI出现异常正位相时，即当东南太平洋SLP距平出现正异常时，次年春、夏季澳大利亚高压偏强，进而由于越赤道气流的增强及西太平洋副高调整引起次年夏季中国出现华南多雨、江淮少雨的雨型分布，证实了ACW是另一个与中国夏季降水异常有密切关联的年际变化强信号。

Antarctic Circumpolar Waves and Its Association with the Abnormality of Summer Rainfall over China

Based on the NCEP/NCAR monthly SLP reanalysis data,the interdecadal changes and propagating features of the Antarctic Circumpolar Wave(ACW) during 1952-1998 are studied in this paper by use of the first recovered field of the complex empirical orthogonal function(CEOF) expansion.The results show that the southeast Pacific is a key area for researching ACW.Then the activity index of ACWs over the southeast Pacific(EPAI) is defined.It is revealed that there is a close relation between the EPAI in autumn and the next summer rainfall over China.When the autumn EPAI appears an abnormally positive phase,namely while the positive SLP anomalies occurs over the southeast Pacific,the Australian high becomes stronger than normal in the next spring and summer.Furthermore,the enhancement of the cross-equatorial flow and the shift of the west Pacific subtropical high lead to the summer precipitation pattern of more rainfall in South China and less rainfall in the Changjiang-Huaihe valley in the next year,thus confirming that the ACW is a strong interannual variation signal for the abnormality of summer rainfall over China.