亚太地区冬季海平面气压异常的偶极型结构及其与海温的关系

The Dipole Mode of Asia-Pacific Sea Level Pressure Anamalies in Winter and Its Relation to SST

利用全球月平均海平面气压资料以及海表温度资料,采用旋转经验正交函数分解(REOF)、Morlet小波分析、相关分析及合成分析等方法研究了亚洲—太平洋地区(20°N^70°N,40°E^120°W)冬季海平面气压异常的空间结构与时间演变特征,并进一步分析了该地区冬季海平面气压异常与全球海温异常的关系。结果表明:亚太地区冬季海平面气压场异常既存在近乎纬向的偶极型(反位相)分布,也存在明显的经向的偶极型(反位相)分布。冬季海平面气压变化最显著的区域主要有4个,分别位于亚洲东北部地区(60°N^70°N,110°E^150°E)、北太平洋副热带地区(25°N^35°N,150°E^170°W)、我国西北部地区(35°N^45°N,85°E^110°E)及阿留申群岛一带(50°N^60°N,170°E^165°W)。亚洲东北部地区与北太平洋副热带地区之间,以及我国西北部地区与阿留申群岛地区之间分别存在显著的负相关,即冬季海平面气压异常存在一个经向的偶极子振荡和一个纬向的偶极子振荡。两个偶极子存在明显的年际变化,变化特征都具有显著的3~4年周期;而纬向偶极子指数还有16年左右周期的年代际变化。偶极子指数与海温异常(SSTA)的相关系数分析,以及对应强正(负)偶极子指数所作的合成SSTA分析一致表明,太平洋和印度洋的SSTA对亚太地区冬季海平面气压的异常有重要影响,不同的海温异常型将导致不同型的海平面气压场偶极子振荡模的出现。冬季北太平洋的SSTA从赤道东太平洋到堪察加半岛南有"-、+、-、+"式("+、-、+、-"式)波列状分布特征,以及在西北太平洋近岸海区均为负(正)海温异常,将有利于亚太地区冬季海平面气压场出现经向型振荡的正(负)位相模。冬季北太平洋40°N附近(北太平洋西风漂流区)的明显SSTA负(正)异常,以及热带太平洋—印度洋海温异常联合模的正(负)特征,有利于亚太地区冬季海平面气压场出现纬向型振荡的正(负)位相模。

The anomaly mode of the Asia - Pacific （20°N - 70°N, 40°E - 12°W） sea level pressure in winter is studied, using the methods of rotated empirical orthogonal function decomposition （REOF）, Morlet wavelet analysis, correlation analysis, and synthesis analysis on the global monthly-average Sea Level Pressure （SLP） and Sea Surface Temperature （SST）. Then the relationship between SLP anomaly （SLPA） and SST anomaly （SSTA） is studied. The results show： The Asia- Pacific winter SLP has a nearly-zonal dipole （anti-phase） distribution, as well as an obvious meridional dipole （antl-phase） distribution. The most significant anomalies of winter SLP are in the four areas which locate in Northeast Asia （60°N - 70°N, 110°E - 150°E）, subtropical North Pacific （25°N- 35°N, 150°E- 170°W）, northwest of China （35°N- 45°N, 85°E- 110°E）, and the Aleutian Islands （50°N- 60°N, 170°E- 165°W）. There is a significant negative correlation of SLP between Northeast Asia and the subtropical North Pacific, as well as Northwest China and the Aleutian Islands, which shows the existence of meridional dipole oscillation and zonal dipole oscillation. Two dipoles obviously change at interannual scale with a period of 3 - 4 a, while zonal dipole index has a cycle of 16 a or so at interdecadal scale in addition. The correlation coefficient analysis between dipole indices and SSTA, and the synthesis analysis of the SSTA corresponding to the strong positive （negative） years of dipoles all indicate that the SSTA of Pacific and Indian Ocean both have important impacts on the Asia - Pacific SLPA in winter. Different types of SSTA will lead to differ- ent types of SLP dipole oscillation modes. When the North Pacific SSTA in winter takes on the character of ＂-, ＋, -, ＋ （ ＂＋, -, ＋, -＂） wave-like distribution from the equatorial eastern Pacific Ocean to the Kamchatka peninsula, and negative （positive） SSTA are found in the Northwest Pacific coast, then the positive （negative） phase mode of meridional oscillation will be conducted in the winter Asia- Pacific SLP field. On the other side, sig- nificantly negative （positive） anomalies taking place in the vicinity of the North Pacific 40~N （North Pacific westerly drift region） in winter, and the positive （negative） characters of the tropical Pacific - Indian Ocean temperature anomaly mode, are conducive to the positive （negative） phase mode of zonal oscillation in the winter Asia- Pacific SIP field.