北半球冬季南太平洋海表温度异常的主要模态及其与ENSO的关系

利用新版本的NOAA扩展重构的海温资料,研究了1950/1951年-2008/2009年北半球冬季(12月-翌年2月平均)南太平洋海温异常的主要模态,并探讨了海温主要模态在年际和年代际时间尺度上与ENSO的关系。研究结果表明:北半球冬季南太平洋海温变化主要存在两个模态,第1模态基本反映了南太平洋海温异常南－北的反相变化特征,第2模态基本反映了南太平洋海温异常东－西的反相变化特征。两个模态的年代际周期均比其年际周期显著,其中第1模态的主要年代际周期为11~16 a,第2模态的主要年代际周期为18~24 a。主要模态与ENSO关系的分析表明,第1模态与同期ENSO事件的关系最显著,主要显示其对ENSO的响应,而第2模态对滞后其1 a的ENSO事件存在一定的影响。为进一步研究它们的年际和年代际关系特征,分别对它们进行滤波后的分析表明,在年际时间尺度上,南太平洋海温两个主模态同ENSO事件的关系与滤波前的基本一致;在年代际时间尺度上,第1模态的年代际变化可能对ENSO的年代际变化存在一定的响应,而第2模态可能不仅对前期的ENSO事件存在一定的响应,还可能对后期的ENSO事件存在一定程度的影响作用。

Principal modes of the boreal wintertime SSTA in the South Pacific and their relationships with the ENSO

Based on the monthly-mean Extended Reconstruction sea surface temperature data (ERSST. V3) from NOAA, the primary modes of the boreal wintertime (December-next year’s Feburary) SST anomalies (SSTA) from 1950/1951 to 2008/2009 in the South Pacific and their relationships with ENSO are studied. The results show that there are two dominant modes in the boreal wintertime of South Pacific, and the first mode with a periodicity of 11-16 a represents an interdecadal fluctuation with response in the north part of South Pacific and out of phase fluctuations of moderate amplitude in the south part of South Pacific,the second mode with a periodicity of 18-24 a also has an interdecadal nature with larger response in the west of South Pacific and out of phase fluctuations of smaller amplitude in the east of South Pacific. The interannual timescale characteristic of the two modes aren’t evident. The first mode coincides well with the occurrence of the ENSO event, and the second mode has an impact on the occurrence of ENSO in the next year. In order to study their interannual and interdecadal characteristic, their time series have been high-pass filtered and low-pass filtered respectively. After filtering, the relationship between the two modes and ENSO is consonant with the relationship before filtering in the interannual time scale. In the interdecadal time scale, the interdecadal variations of the first mode may respond to the interdecadal variations of ENSO event, and the second mode may not only have response to the former ENSO event but also have impact on the latter ENSO event to some extent.