ENSO发生发展阶段赤道西太平洋西风异常长时间维持的分析  

The Persistent Maintenance of the Strong Westerly Anomalies over the EquatorialWestern Pacific during the Onset and Development Phase of ENSO

作　　者：刘长征[1] 薛峰[2] 

机构地区：[1]中国科学院大气物理研究所 [2]中国科学院大气物理研究所北京100029

出　　处：《气候与环境研究》2008年第2期161-170,共10页Climatic and Environmental Research

基　　金：国家自然科学基金资助项目40475036和40221503

摘　　要：根据NCEP/NCAR再分析资料和美国气候预测中心提供的赤道太平洋信风指数,发现在ENSO年3-5月（MAM）和8-10月（ASO）,赤道西太平洋存在两次显著的西风异常盛行期,并分析了这两次西风异常长时间维持的原因。研究结果表明,南北两半球中低纬度异常经向风向赤道西太平洋地区的输送,以及海气耦合模态中反Walker环流的自维持,是这两次西风异常维持的主要原因。其中,经向风输送在MAM时期以北半球为主,而在ASO时期以南半球为主。在上述两个时段,作为对赤道西太平洋西风异常的响应,赤道印度洋呈现为东风异常。此外,南太平洋中高纬存在一正压结构的气压偶极子模态,该模态在MAM时期由海冰异常维持,其部分气流向赤道辐散,并汇入赤道西太平洋西风异常中,因此对西风异常有直接贡献。而在ASO时期,这一模态由西风异常引起的赤道太平洋海水变暖所激发的大气遥相关波列维持,因此它是对热带ENSO信号的响应。Based on NCEP/NCAR reanalysis data and the trade wind indices provided by the Climate Prediction Center,it is revealed that during the onset and development phase of ENSO,the equatorial western Pacific westerly anomalies（WPWA） prevail during March-April-May（MAM） and August-September-October（ASO）,respectively.The following two factors are responsible for the maintenance of WPWA.One is the equatorward transport of the anomalous meridional wind from middle-to-low latitudes of the two hemispheres into the equatorial western Pacific,and the other is the self-maintenance of the anomalous Walker Circulation associated with ENSO.It is also found that the equatorward transport is dominated by the Northern Hemisphere meridional flow during MAM.In contrast,it is maintained mainly by the Southern Hemisphere meridional flow during ASO.Besides,the easterly anomalies prevail over the equatorial Indian Ocean as a response to WPWA during the two periods.Moreover,there exists a barotropic dipole mode in sea level pressure over mid-high latitudes of the South Pacific.This mode is maintained by sea ice anomaly during MAM,one branch diverges equatorward and joins the WPWA.During ASO,however,it is maintained by the atmospheric teleconnection pattern associated with the warming over the tropical Pacific,so it is a response to the ENSO signal associated with WPWA.

关 键 词：ENSO 西风异常 赤道西太平洋 

分 类 号：P461[天文地球—大气科学及气象学]