北太平洋涛动和东亚冬季风对ENSO影响差异分析

北太平洋涛动(NPO)和东亚冬季风(EAWM)二者是热带外重要的气候系统,不仅对我国甚至对整个东亚气候都有重要影响,对厄尔尼诺-南方涛动(ENSO)的影响也越发受到关注。本研究利用HadISST海温资料以及美国国家环境预报中心(NCEP)月平均气象场再分析资料,采用相关回归等统计方法分析研究了冬季NPO和EAWM对次年冬季ENSO发生、发展影响的差异,并分析了产生差异的可能原因。结果表明,冬季NPO和EAWM对次年冬季ENSO的影响无论是从相关性大小还是触发的ENSO强度上来说都存在明显的差异;进一步分析冬季NPO和EAWM回归的海表面温度(SST)场相关的降水和风场的季节演化特征发现:在热带太平洋区域,冬季NPO和EAWM通过激发赤道西太平洋区域西风和降水异常建立起了相应的海气正反馈机制,而这种正反馈机制在强度和位置上的不同,造成了对ENSO影响的差异。冬季NPO和EAWM年代际变化上的差异可能是另一原因。

Different influence on ENSO caused by East Asian Winter Monsoon and North Pacific Oscillation

The North Pacific Oscillation (NPO) and East Asian Winter Monsoon (EAWM), as significant extra tropical climate modes, have meaningful impacts not only on the climate of China and even the entire East Asia, but also on the global scale system of ENSO. With HadISST re-analysis data and NECP-NCAR monthly mean atmospheric circulation and precipitation data, this paper analyzes the different influences between winter NPO and EAWM on the ENSO of following winter, and the possible mechanism of the differences with statistical methods. The results show that the effects of winter NPO and EAWM on the subsequent winter ENSO are significantly differences, both in correlation and the intensity of the ENSO triggered. Further the evolutionary features of sea surface temperature (SST) anomalies, 850 hPa winds and precipitation obtained by correlation and regression upon the normalized winter NPO and EAWM indexes are studied. It shows that in the tropical Pacific region, winter NPO and EAWM have established corresponding responses by stimulating westerly winds and precipitation anomalies in the western equatorial Pacific region. The positive air-sea feedback mechanism and the difference in strength and location of this positive-feedback mechanism causes different influences on ENSO. Besides, different interdecadal variations of NPO and EAWM in winters may be another reason.