青藏高原冬春雪深年代际变化与南亚高压可能联系

Possible Connection between Interdecadal Variations of Snow Depth in Winter and Spring over Qinghai-Xizang Plateau and South Asia High in Summer

利用1978-2006年SSMR和SSM/I卫星遥感雪深反演资料和同期NCEP/NCAR再分析月平均值资料,采用经验正交函数分解EOF、合成分析和相关分析等方法,分析了青藏高原冬、春季积雪深度(下称雪深)的时空分布演变特征,并在此基础上研究了青藏高原冬、春季雪深的年代际变化与夏季南亚高压的可能联系。结果表明,青藏高原冬、春季雪深EOF分析第一模态呈现出全区冬春一致性的年代际变化特征,即:1987(1988)年之前青藏高原冬(春)季大部分地区少雪,1987(1988)年之后则多雪。青藏高原冬、春季雪深EOF分析第一模态时间系数与南亚高压东伸指数、强度指数相关显著。进一步分析表明,高原冬、春季积雪少(多)主要增强(减弱)了夏季高原南部对大气的加热作用,从而引起高原上空对流层的上升运动明显加强(减弱),有(不)利于热量向高空输送,致使高原对上空对流层加热作用增强(减弱),从而造成了南亚高压较强(弱),东脊点偏东(西)。

By using monthly SSMR and SSM/I satellite retrieved snow depth as well as NCEP/NCAR reanalysis data during 1978-2006,the spatial and temporal variations of snow depth anomalies in winter and spring over the Qinghai-Xizang Plateau were investigated with statistical methods such as EOF,correlation and composite analysis.And the connection between interdecadal variations of snow depth in winter and spring over the Qinghai-Xizang Plateau and summer South Asia High are further explored.Results show that the leading EOF modes of winter and spring snow depths exhibt consistent spatial and temporal variations and significant inter-decadal variations.Less winter（spring） snow appears in most areas before 1987（1988）,while more snow exists after that.There are evident correlation between the time coefficients of the first EOF mode of snow depth and the characteristic index of the South Asia High.Further analysis suggests that light（thick） snow in winter and spring tends to enhance（reduce） the surface heating,especially in the south part of the Qinghai-Xizang Plateau and intensify（weaken） the vertical motion over the Qinghai-Xizang Plateau,resulting stronger（weaker） and eastward（westward） summer South Asia High.