西太平洋副热带高压的年际变率及其与ENSO的相关性

WEST PACIFIC SUBTROPICAL HIGH'S INTERANNUAL VARIABILITY AND RELATIVITY TO ENSO

利用NCEP资料定义了西太平洋副高的强度指数、脊线指数,并对这两种指数进行功率谱分析,且分别与Nio 3指数作相关性分析,发现副高强度指数、脊线指数都存在年际尺度的变率,而且与Nio 3指数在年际尺度上存在很好的相关性。在此基础上,对可能引起副高年际变率的机理作了尝试性探讨:在年际尺度上,副高脊线位置首先出现异常南移,同时副高强度减弱,副高南侧正的西风距平加强了赤道纬向西风;异常的西风使得暖水向东传播,约2个月后Nio 3区海温异常升高并西传,其后约1个月中太平洋海表温度异常升高,中太平洋海水升温的同时加热大气,在Hardly环流作用下,约3个月以后,副高开始增强。

The intensity index and the ridge index of Western Pacific Subtropical High are defined with NCEP data in this paper. These two indexes are analyzed with wavelet, before each is applied with correlation analysis to Ni駉 3 index. It is shown that these two indexes all have interannual variability. In addition, there is marked correlation between Ni駉 3 index and intensity or ridge index on the interannual scale. Based on the above conclusion, a possible mechanism is discussed: On the interannual scale, the ridge line of the WPSH first has anomalous southward moving and its intensity decreases so that positive westerlies anomalies on the south of the WPSH strengthens the equatorial latitudinal westerlies; anomalous westerlies push warm water eastward and result in the anomalous rise and westward propagation of SST in Nio 3 region about two months later and the anomalous rise of SST in the surface-layer in the central part of Pacific after another one month; under the effect of the Hardly cell, the increased SST in the central Pacific is also heating the atmosphere and the WPSH begins to strengthen about 3 months later.