亚澳越赤道季风环流的年际变化特征

Interannual Variability of the Asian-Australian Monsoonal Cell

利用1948~2004年美国月平均NCEP/NCAR(National Center for Environmental Prediction/National Center for At-mospheric Research)再分析资料,采用谐波分析和功率谱分析的方法,根据经向风的垂直切变定义了亚澳越赤道季风环流指数(IAAM),分析了亚澳季风(AAM)系统中越赤道季风环流的年际变化特征。结果表明:AAM的年际变化主要以2~3 a和准5 a周期振荡为主。利用合成分析,探讨了年际尺度上亚澳越赤道季风环流的空间分布特征。环流异常主要表现为整个东亚季风区冬季风环流的异常减弱和热带季风区夏季风跨赤道季风环流的异常加强,以及夏季赤道沃克环流和南亚高压的减弱。

The interannual variation of the Asian-Australian monsoonal cell(AAMC) was analyzed by using the method of harmonic analysis and power spectrum analysis based on the NCEP/NCAR(National Center for Environmental Prediction/National Center for Atmospheric Research)reanalysis data from 1948—2004.The index of the AAMC was defined by the vertical shear of the across-equatorial meridional wind to reveal the feature of the vertical-meridional circulation over the AAM areas.It is shown that the AAMC mainly has notable characteristics of interannual variability with a period of 2-3 years and quasi-five years.The spatial characteristics at the interannual timenscales of the AAMC were analyzed by way of harmonic filtering and composite analysis,in order to investigate the behavior of the summer AAM circulation anomaly.The AAMC interannual variability is represented by weakening of the anomalous monsoonal circulation in winter over the East Asia monsoon region,and strengthening of the tropical across-equatorial AAMC,as well as weakening of the equatorial Walker circulation and the South Asia High in summer.