中文摘要：

采用美国气候预测中心1961—2014年逐月土壤湿度资料以及国家气象信息中心降水格点数据,分析了青藏高原土壤湿度的时空分布特征,以及高原春季土壤湿度对长江中下游6、7月降水的影响。结果表明：青藏高原年和不同季节的土壤湿度空间分布特征基本一致,均呈现从东南向西北减少的趋势。区域平均的土壤湿度显示出高原土壤春季最为干燥,秋季和夏季较为湿润的分布特征;近50年来青藏高原大部的年、季节土壤湿度均呈缓慢增加趋势,年、季土壤湿度从20世纪60年代至90年代基本上呈减少趋势,21世纪00年代开始则呈缓慢增加趋势。青藏高原春季土壤湿度与长江中下游降水量基本呈负相关关系。通过信度检验的负相关区在6月位于高原东北部和西南部,7月位于高原南部,且高原西北部分区域春季土壤湿度与7月降水量存在显著正相关。高原春季土壤湿度通过对高原地表温度的作用,进而影响到高原热力特征、大气环流以及长江中下游降水的分布特征。

英文摘要：

Soil moisture has been widely recognized as one of the main drivers of the water and carbon cycle in the climate system. It plays an important role in the interactions between the atmosphere and the land surface with climate change through its influence on the surface albedo and vegetation. To understand the temporal and spatial distribution of soil moisture over the Qinghai-Tibetan Plateau and its influence on the precipitation in the midlower reaches of Yangtze River Basin,with monthly dataset of soil moisture derived from Climate Prediction Center（CPC） and monthly precipitation obtained from National Meteorological Information Center（NMIC） of Chinese Meteorological Administration（CMA） from 1961 to 2014,the distribution of soil moisture over the Qinghai-Tibetan Plateau has been investigated along with its effect on the precipitation in June and July over the mid-lower reaches of Yangtze River Basin. Result shows that seasonal distributions of soil moisture are consistent with the annual distribution and the soil moisture decrease from the southeast part to the northwest part of the Qinghai-Tibetan Plateau. The regional soil moisture presents that it is extremely dry in spring while the moisture is quite humid in autumn and summer over the plateau. Considering the most parts of the plateau,the annual and seasonal soil moistures exhibit slightly increasing trend during the past 50 years. The annual and the seasonal soil moisture basically indicate decreasing trend from 1960 s to 1990 s,and they increase gradually with small magnitude from twenty-first century to the present years. The precipitation in the mid-lower reaches of Yangtze River Basin is negatively related to the spring soil moisture over the plateau. The negative relation areas which exceed the significance level are mainly located in the northeast and southwest parts of the plateau in June. The negative areas are situated in the southern plateau while the positive areas are located in the northwest part of the Plateau in July. The spring