东亚地区大气环流的季节划分及其时空变化特征

利用NCEP-DOE Reanalysis 2 1979-2009年位势高度场、温度场、湿度场和风场逐日再分析资料,采用考虑面积权重的区域多要素最优分割法,对东亚地区大气环流的季节进行划分,并分析了四季起始时间的时空变化特征.研究结果表明:1)东亚地区春季最早始于中高纬地区的平流层和副热带的对流层中下层;夏季最早始于中高纬的平流层和副热带、中纬度地区的对流层中上层;秋、冬季开始最早的地区集中在东亚地区东部和东北部的对流层中低层,以及中高纬的平流层. 2)季节变化与环流形势密切相关,且对流层各个层次的夏季和冬季起始时间的分布均有较好的垂直一致性,平流层与对流层各季节起始时间分布有较大的差异性,平流层中层和下层也并不一致. 3)华北地区四季平均起始时间距平序列的逐年演变特征表明近30年该地区出现了6个四季起始时间异常偏早的年份,与El Niño活跃年份相一致,反映了海温等外强迫对大气环流季节变化的影响. 关键词： 季节划分 东亚地区 区域多要素最优分割法

Season division and its temporal and spatial variation features of General atmospheric circulation in East Asia

Using the NCEP-DOE Reanalysis 2 data of air temperature, geopotential height, relative humidity and wind field of 17 pressure levels from 1979 to 2009, and the Multi-factor Fisher optimal dissection method, the seasons of the general atmospheric circulation in East Asia are diuided. The main results are as follows. (1)The seasonal establishment of atmospheric general circulation is initiated from subtropic of the stratosphere in East Asia. In the troposphere the spring and the summer first start from the tropical regions, and then extend into middle latitudes. The autumn and the winter first start from middle latitudes, and then extend into low latitudes. (2) In the troposphere the seasonal establishment of atmospheric general circulation is more consistent, and it is very different from that in the stratosphere. And the seasonal establishments of the middle and the low level of the stratosphere are not very consistent. (3)In the past 30 years, the four seasons have started much earlier in about 6 years, in which years some stronger El Niño phenomena just happened. That implies that the El Niño phenomenon causes abnormal seasonal variation.