中文摘要：

土壤湿度作为陆面过程的重要因子,对局地及邻近地区的大气环流和天气气候有重要影响.青藏高原的土壤湿度观测站点稀少,时间较短,鉴于此,本文使用经过部分观测站点检验的卫星反演数据,研究了春季高原土壤湿度的年际变化与后期夏季我国东部降水的联系和可能机理.结果表明：在全球变暖的背景下,高原土壤湿度总体呈现出显著增加的趋势,去除该线性趋势后,我们定义了一个高原土壤湿度指数TPSMI来定量表征高原土壤湿度的年际变化特征,发现表层、中层、深层的土壤湿度年际变率趋于一致,且春季土壤湿度与夏季土壤湿度显著相关（相关系数可达0.56）.当TPSMI偏大时,即高原东部土壤湿度偏大,而西部偏小时,夏季在高原东部（西部）存在一个潜热（感热）热源,二者共同作用下,在对流层中高层从高原西部经我国大陆直至东北地区激发出一个气旋—反气旋—气旋波列,该波列呈相当正压结构,有利于东北冷涡的加强及冷空气向南爆发;与此同时,南亚高压加强东伸,西太副高西伸加强,低空南方暖湿气流与北方干冷气流在长江流域汇合,伴随着上升运动加强,从而有利于夏季长江流域降水增多;反之,当TPSMI偏小时,夏季长江流域降水减少.

英文摘要：

As an important factor of surface processes,soil moisture has great influence on atmospheric circulation and weather climate of local and adjacent areas.Because the observation sites of soil moisture in the Tibetan Plateau（TP）are sparse and the observation time is short,we use a set of satellite retrieval data which has validated by field observations,to study the relationship between earlier soil moisture of TP and later precipitation of eastern China and its mechanism.The results indicate that with the global warming,the general soil moisture of TPhas an obvious trend to increase.After removing the linear trend,we define the Tibetan Plateau soil moisture index（TPSMI）to characterize the interannual variation of TP soil moisture.Such variations of soil moisture have great conformance in 0~10cm,10~40cm and 40~100cm,which makes soil moisture interannual signal from spring continue into summer.The correlation coefficient between spring and summer TPSMI is 0.56.When the TPSMI is bigger,which means that the soil moisture of eastern TP is bigger,and when the soil moisture of western TP is smaller,there is a latent heat source（sensible heat source）in eastern（western）TP.The two heat sources together induce a cyclone-anticyclone-cyclone wave train from the west of TP through China mainland to northeast China, which presents a prominent quasi-barotropic structure through the middle and upper troposphere. This has great contribution to the enhancement of Northeast Cold Vortex,which leads to the outburst of cold air.At the same time,the South Asian anticyclone gets enhanced and eastward,while the Sub-tropical anticyclone gets enhanced and westward with the converge of warm moist airflow from south and cold dry airflow from north in the Yangtze River basin.In addition to the stronger rising movement,the summer precipitation of the Yangtze River basin is much more.On the contrary,when the TPSMI is smaller,the precipitation of the Yangtze River basin is much less.