东亚冬季风指数的定义及其年际年代际异常

Definition of a East Asian Winter Monsoon Index and Its Variation Characteristics

利用NCAR/NCEP再分析资料,通过相关分析方法分析了多种可以表征东亚冬季风活动的气象要素指数的相关性特征,选取地面温度、海平面海陆气压差和500hPa高度3个要素,综合定义了一个东亚冬季风指数。结果表明,该指数表征的东亚冬季风有明显的QTO和QFO周期振荡特征,这一特征与冬季风年代际背景有关,强冬季风年代背景下的振荡比弱冬季风年代背景下的振荡显著,同时该指数能很好地表征东亚冬季风活动的各个方面。对强弱冬季风年的大气环流的结构及其相应的低纬度对流活动、海洋和高低层大气热力状况的分析表明,强弱冬季风活动不仅表现在中高纬度高低层大气环流变化的差异,在局地Hadley环流和赤道附近Walker环流、低纬度对流活动、海洋和大气的热力状况的变化方面也表现出了显著的差异。

A new East Asian winter monsoon（EAWM） index （IEAWM） is defined in this paper compositely by the surface temperature, sea level pressure （SLP） and 500 hPa geopotential height from the NCEP/NCAR reanalysis dataset. It is found that the index may well represent the activity of EAWM, and its quasi-three year oscillation and quasi-five year oscillation are close related to the decadal background of EAWM ; the oscillations are more significant under the strong decadal background of EAWM than that under the weak decadal background, and furthermore, the index under the strong decadal background is able to better characterize various aspects of the activity of EAWM. Besides, the results also show that the EAWM variation involves not only the atmospheric circulation in mid-high latitude regions, but also the Walker circulation, Hadley circulation, convection activities, sea surface temperature （SST） and thermal anomalies in low latitude regions.