ENSO位相转换期北太平洋热带外大气对热带东太平洋海温的影响

ANALYSES OF THE IMPACTS OF EXTRATROPICAL ATMOSPHERE IN THE NORTH PACIFIC ON THE SST AROUND TROPICAL EASTERN PACIFIC DURING ENSO TRANSITION PHASE

利用NCEP/NCAR提供的大气月平均再分析资料、NOAA提供的ERSST.V4资料及ECMWF提供的ORAS4海洋再分析数据集,借助合成分析、相关分析和SVD分解等方法,对ENSO位相转换期北太平洋热带外大气对热带东太平洋海温的影响进行分析。结果表明:(1)6月关键区(155~130°W,10~30°N)存在海平面气压正异常与同期以及后期热带东太平洋出现海温负异常有关,E-L型事件(El Nio次年发生La Nia)在关键区出现海平面气压正异常的概率远大于E-N型事件(El Nio次年不发生La Nia);(2)通过分析北太平洋3—6月海平面气压场和后期12月海温场SVD分解的结果,同样发现关键区海平面气压异常和后期12月热带东太平洋海温异常的负相关关系;(3)6月正位相OKJ波列的传播可能是导致同期关键区海平面气压正异常的原因之一;(4)6月关键区出现海平面气压正异常时,可能通过引起1~3个月后同区域出现更多向南海表层海流流速异常,有助于将中纬较冷的海水向赤道输送,引起12月热带东太平洋海温负异常,对于La Nia的形成起到一定促进作用。

Using the composite analysis, correlation analysis and SVD methods, the impacts of extratropical atmosphere in the North Pacific on the sea surface temperature（SST） around tropical eastern Pacific during ENSO transition phase are analyzed by using the global atmospheric reanalysis datasets from NCEP/NCAR,ERSST.V4 from NOAA and ORAS4 from ECMWF. The results are as follows：（1） The positive SLPA of the key area（155-130 ° W,10-30 ° N） in June are strongly correlated with the negative SSTA around tropical eastern Pacific over the same phase and later. The probability of the positive SLPA in the key area for the E-L type, in which an La Nina occurs in the following year of El Nino, is greater than the E-N type,in which no event occurs in the following year of an El Nino event;（2） The results between the SLP in the North Pacific from March to June and the SST in December by means of SVD methods also confirm the negative correlation between the SLPA in the key area and the SSTA around tropical eastern Pacific;（3）The propagation of the positive phase of OKJ wave train in June may contribute to the positive SLPA in the key area;（4） The positive SLPA in the key area in June may result in more southward surface current velocity anomalies around the key area from July to September, which may contribute to transmit more cold water from the middle latitude to the equator. It may cause the negative SSTA around tropical eastern Pacific in December, to some extent, which may be conducive to the formation of La Nina.