冬季北太平洋优势气候模态的转移

The Climate Shift of the Dominant Modes of North Pacific During Winter

采用EOF分解和小波分析,并引入相似度,分析冬季北太平洋的两个主要气候模态,即太平洋年代际振荡(PDO)模态与北太平洋涡旋振荡(NPGO)模态,及其结构特征随时间的演变。结果表明:1988/1989年的气候转移后,冬季海温距平(SSTA)优势模态为NPGO模态的年份越来越多,这种优势气候模态的转移现象表现出准18 a的年代际周期;SSTA与NPGO模态相似度的20年滑动平均在20世纪80年代中后期之后超过了SSTA与PDO模态的相应值,这表明此后SSTA的优势模态发生了转移,由PDO型转换为NPGO型;对典型时间段SSTA的合成分析显示,其优势模态由1988年前的PDO型转变为之后的NPGO型。

Empirical Orthogonal Function （EOF）, wavelet analysis and resemblance analysis methods were used to research the variation of the structure feature of Pacific Decadal Oscillation （PDO） mode and North Pacific Gyre Oscillation （NPGO） mode. The spatial similarity coefficients between the Sea Surface Temperature Anomaly （SSTA） and the PDO mode, NPGO mode were computed separately. The results show that the spatial field of S STA was more and more similar to that of the NPGO mode after 1988/1989, and the climate shift had a period of 18 years. Then, the 20-year moving average of the two similarity coefficients show that the latter one was greater than the former after 1984, which meant that the spatial shift of SSTA occurred about 1984. Lastly, the spatial feature of the averaged SSTA of some special periods also show that the structure feature of SSTA became NPGO- like mode from PDO-like mode after the 1980s.