春夏东亚大气环流年代际转折的影响及其可能机理

The climatic effect of decadal shift of the East Asian atmospheric circulation in spring and summer and its possible causes

中文关键词:  年代际转折  东亚环流主模态  中国南方降水

英文关键词:Decadal shift in mid-1990s  East Asian circulation leading modes  South China rainfall

中文摘要:

      本文通过多变量联合经验正交分解(MV-EOF)方法揭示了近30年(1979~2010年) 春季和夏季东亚大气环流所发生的年代际转折及其与中国南方降水年代际季节反相变化的内在联系,探讨了局地性大气热源年代际变化影响东亚大气环流年代际转折的可能机理.结果表明:(1)东亚大气环流春季第一模态和夏季第二模态在90年代中期都发生了明显的年代际转折;(2)与春季大气环流第一模态和夏季大气环流第二模态年代际转折相对应的是中国南方降水明显的年代际季节反相变化,即春季降水年代际减少,夏季降水年代际增多;(3)春季青藏高原和夏季贝加尔湖地区大气热源年代际变化对东亚大气环流年代际转折有一定贡献,是造成中国南方降水年代际季节反相变化的直接原因;(4)春季青藏高原大气热源的年代际减弱,使得高原东南侧的西南风减弱,导致中国南方上空水汽输送不足,春季降水减少.夏季贝加尔湖大气热源偶极型分布由“南负北正”转变为“南正北负”,由此在贝湖上空激发高压异常,使得夏季雨带北进受阻而停滞南方,造成中国南方夏季降水增多.

英文摘要:

      Based on the multivariate empirical orthogonal function (MV-EOF) analysis, a decadal turning of the East Asian careulation in the past 30 years was revealed.In this context,the decadal change of the South China precipitation and its possible mechanism were investigated,conclusions are as follows; (1)The first mode of spring and the second mode of summer for the Fast Asian circulation are both of a decadal shift in mid-1990s.(2) The two decadal shift leading modes are closely related with an obvious out of phase seasonal decadal rainfall change in spring and summer over South China; the rainfall reduced in spring and increased in summer.(3) The atmospheric heat source (Q₁)over the Tibet Plateau region in spring and the Lake Baikal region in summer are both decadal changed in mid-1990s.(4)The decadal weakening of the Tibet Plateau heating which do pressed the southwesterly on its southeast side mainly caused the reducing rainfall in spring over South China.While the decadal changing of the dipole distribution of the atmospheric heat source in summer over Lake Baikal excited an anomalous anticy clone, which hindered the summer rain belt moving northward,resulting in increased rainfall in summer over South China.