中文摘要：

利用19602008年中国693个站逐日降水资料和NCEP／NCAR日平均再分析资料，采用统计分析方法，分析了中国南方春季降水强度和位置的年际变率及其与大气环流的关系。结果表明：在年代际尺度上，江南春季降水在20世纪60年代中、后期偏少，70年代中期到80年代初偏多，90年代初开始减少；在年际尺度上，当春季西太平洋副热带高压和青藏高原东侧的低层低压系统加强，并且异常中心分别位于20°N以南和30°N以南时，异常西南风主要位于长江以南地区，在异常西南风逐渐减弱区出现明显的辐合，伴随着该地区低层空气质量辐合、对流层上升运动和水汽辐合加强，造成江南地区降水偏多，此时来自西太平洋的异常水汽到达南海后，没有在南海聚集，而是转向北输送到江南；当春季西太平洋副热带高压以及青藏高原东侧低压系统加强且异常中心位于30°N以北时，异常西南风盛行在中国东部大部分地区，此时低层异常空气质量辐合、对流层异常上升运动以及异常水汽通量辐合区都向北移到江淮地区，使江淮地区降水增加，而华南地区为异常空气质量辐散、异常下沉运动以及异常水汽通量辐散，伴随着降水减少，这时异常水汽主要来自西太平洋副热带地区。由于上述观测结果与通过改变东亚和周边海域海一陆热力差异的数值试验结果有很好的一致性，因此，这里观测到的降水和大气环流异常可以被东亚区域热力差异异常激发出来。

英文摘要：

Using the daily accumulated precipitation data from Chinese 693 rain gauge stations and the daily National Centers for Environmental Prediction-National Center for Atmospheric Research （NCAR/NCEP） reanalysis data during 1960- 2008, the interannual variations of spring rainy-season precipitation in intensity and position over southern China and the associated atmospheric circulation anomalies were investigated by means of the statistical analysis methods. The results show that on the interdecadal time scale, the spring rainy-season precipitation to the south of the lower valley of the Yangtze River was less in the middle and late 1960s and was more in the middle 1970s to the early 1980s. It began decreasing from the early 1990s again. On the interannual time scale, when the subtropical high over the western North Pacific and the low-level low-pressure system to the east of the Tibetan Plateau strengthen and their anomalous centers appear to the south of 20°N and 30°N in spring respec- tively, anomalous southwesterly winds mainly prevail to the south of the Yangtze River valley. Remarkable convergence of air mass appears over the region where southwesterly winds gradually weaken, accompanying the local strengthened low-level convergence of air mass, the tropospheric ascending motion, and the low-level convergence of water vapor. These anomalies lead to the increase of precipitation over there. At this time, the water vapor coming from the western North Pacific arrives at the South China Sea, not causes the local convergence, and turns northwards into southern China. While both the subtropical high and the low-pressure system strengthen and their anomalous centers appear to the north of 30°N, anomalous southwesterly winds prevail over most of eastern China, with the anomalies of low-level convergences of air mass and water vapor flux and of the tropospheric ascending motion shifting northward to the valleys of the Yangtze-Huai Rivers. Accordingly, more precipitation appears over the valleys. Meanwhile, the an