中文摘要：

利用NCEP和中国台站资料,探讨了华南春季降水和降水季节内振荡（Intraseasonal oscillation,ISO）强度的年代际变化特征。经验正交函数EOF分析结果显示,第一模态显示全国春季降水量以及降水ISO强度较大区域均分布在华南地区。两者间的相关关系比较显著,分别经历了3段年代际变化,即1958—1973年偏少（偏弱）、1974—1990年偏多（偏强）以及1991—2007年偏少（偏弱）。并且,强降水和强降水ISO事件天数和强度也经历了偏少（偏弱）、偏多（偏强）和偏少（偏弱）的变化。但强降水ISO事件天数和强度占总强降水的比率呈现减少的趋势。在不同的年代,大气环流和海温异常对降水和降水ISO强度的变化起了主要作用,但其中的作用又各有不同。在1958—1973年,周边海温、北太平洋年代际振荡（PDO）与大气环流起了共同作用;在1974—1990年,周边海温影响不大,PDO和大气环流起了主要作用;在1991—2007年,PDO和大气环流的相互配置抑制了周边海温的影响。

英文摘要：

Based on the National Centers for Environmental Prediction （NCEP） reanalysis data and precipitation measured from 743 weather stations across China, the interdecadal variation characteristics of precipitation and its intraseasonal oscillation intensity in spring in South China are discussed. The results form EOF analysis show that the strong rainfall and rainfall intraseasonal variability intensity appear over the South China in the first modes. The correlation between the rainfall and its intraseasonal oscillation intensity is very high and significant. They experience obvious three period of decadal variability, namely that, dryer （weaker） in 1958 - 1973, wetter （stronger） in 1974 - 1990 and dryer （weaker） in 1991 - 2007. Moreover, the heavy rain and heavy rain intraseasonal oscillation intensity also take place fewer （weaker）, more （stronger） and fewer （weaker） changes. But, the ratio between the heavy rain ISO and the total heavy rain event days and intensity shows the tendency of decrease. In different decadal time, atmospheric circulation and sea surface temperature （SST） anomaly on the variation of rain and rain intraseasonal oscillation intensity play a leading role, but the effect is different. In 1958 1973, surrounding SST, North Pacific decadal oscillation （PDO） and atmospheric circulation anomaly both play the main role. In 1974- 1990, the main role is attributed to the PDO and atmospheric circulation anomaly. In 1991 -2007, the PDO and atmospheric circulation anomaly suppress the influence of surrounding SST.