冬季热带西太平洋海平面气压与后期亚洲夏季风的关系

利用月平均的NCEP/NCAR再分析资料(1958-1996),基于一个新的冬季热带西太平区域环流指数,研究了冬季热带西太平洋环流的极端异常及其随时间的演变。研究发现,冬季热带西太平洋环流异常与北半球亚洲大陆高纬度地区的气候变化有紧密的联系。随着季节发展,冬季出现在热带西太平洋的一个反气旋(气旋)环流异常逐渐向东北方向移动并向西扩展,其东西方向的轴线逐渐被拉长。因此,位于反气旋(气旋)环流异常南部的异常东风(西风)连续向西伸展到印度半岛,导致南亚夏季风减弱(增强)。同时,随着季节发展,源于热带西太平洋的气压异常逐渐移近并最终占据亚洲大陆,进而影响夏季亚洲大陆热低压。

Relationship between Sea Level Pressures of the Winter Tropical Western Pacific and the Subsequent Asian Summer Monsoon

Using monthly mean National Center for Environmental Prediction/National Center for AtmosphericResearch (NCEP/NCAR) reanalysis data for the period 1958-1996, based on a new circulation index inthe tropical western Pacific region, this paper investigates extreme winter circulation conditions in thenorthwestern Pacific and their evolution. The results show that the extreme winter circulation anomalyin the northwestern Pacific exhibits a strong association with those appearing in the high latitudes of theNorthern Hemisphere including the northern Asian continent, part of the Barents Sea, and the northeasternPacific. As the season progresses, an anticyclonic (cyclonic) circulation anomaly appearing in the north-western Pacific gradually moves northeastwards and extends westwards. Its axis in the west-east directionis also stretched. Therefore, easterly (westerly) anomalies in the southern part of the anticyclonic (cyclonic)circulation anomaly continuously expand westwards to the peninsula of India. Therefore, the South Asiansummer monsoon would be weaker (stronger). Simultaneously, another interesting phenomenon is theevolution of SLP anomalies. As the season progresses (from winter to the following summer), SLP anoma-lies originating from the tropical western Pacific gradually move towards, and finally occupy the Asiancontinent, and further influence the thermal depression over the Asian continent in the following summer.