中文摘要：

利用1979-2007年全球月平均的积雪水当量资料,定义了春季积雪水当量增量指数,该指数可以较为直观地反映春季融雪的情况.通过这一纽带,分析了欧亚大陆春季融雪与长江流域夏季降水之间的联系.研究表明：欧亚大陆春季融雪与中国长江流域夏季降水是负相关关系,这与高原积雪的影响是不一致的.春季融雪量的减少,使得欧亚大陆北部夏季剩余积雪偏多,夏季融雪增多.融雪的局地效应使得土壤湿度增加,加大了欧亚大陆南北热力差异.从而,夏季中纬度的纬向风切变增大,对流层上层的副热带西风急流增强,副热带高压增强西伸,但是北抬受到抑制.长江流域位于异常西南暖湿气流与冷空气的辐合带上,上升运动活跃,有利于降水偏多.

英文摘要：

Based on the monthly snow water equivalent data during 1979-2007 provided by the Nation- al Snow and Ice Center, a snow water equivalent increment index directly reflecting the spring snowmeh was defined, by which the possible linkage between the spring snowmelt over Eurasia and the summer rain- fall in Yangtze River valley was investigated. Results show that the summer rainfall in Yangtze River valley has negative correlation with the Eurasian spring snowmelt, so it is different from the snow over plateau. The increased summer soil moisture, the heat distribution difference between northern and southern Eura- sia, the increased zonal wind shear in the mid-latitude, the stronger subtropical westerly jet in the higher troposphere as well as the enhanced and moving westward subtropical high caused by the decrease of the spring snowmelt and increase of the following summer snowmelt over northern Eurasia are all the reasons why the summer rainfall is increased. Furthermore, Yangtze River valley located in the convergence zone between the warm and cold air flow would also lead to the strong ascending motion and more precipitation.