江南雨季降水季节内演变及其年际、年代际变化特征

利用1961—2008年逐日降水资料,在对比我国东南部各地区气候态降水特征的基础上,着重探讨了江南地区(110~120°E、24~30°N)雨季降水的季节内变化特征及其年际、年代际变化规律。结果表明:1)江南雨季气候态降水的季节内变化具有明显的双峰型特征,两个峰值集中期分别是4、6月中旬前后。4月中下旬第一个降水峰值率先出现在江南地区,之后峰值降水南移,于6月上中旬华南地区达峰值集中期,之后强降水才逐渐北移,6月中下旬又回至江南地区,使江南地区降水达第二个峰值集中期。2)我国江南地区区域平均的双峰降水与4—6月的实际降水之间的相关系数达0.69,这表明双峰型降水确实反映了江南雨季降水的季节内演变特征。3)江南雨季降水双峰型的季节内变化特征具有明显的年际、年代际变化周期。年际变化周期为2~3 a,强信号主要集中在20世纪60年代后期到70年代中期以及80年代中期到21世纪初;年代际变化周期约为8~10 a,在整个时间域上都存在,最强信号集中在80年代初到90年代末期。4)年代际尺度上,江南雨季降水的季节内变化特征(双峰型态)具有隔代显著的特征,即20世纪60、80年代及21世纪初双峰型特征显著,而20世纪70、90年代双峰型特征不显著。

Intraseasonal evolution of precipitation in the Jiangnan rainy season and its interannual and interdecadal variations

In this study,the characteristics of intraseasonal evolution of precipitation in the rainy season of Jiangnan(24-30°N,110-120°E) and its interannual and interdecadal variations are researched,using daily precipitation data for the period of 1961-2008,based on the analysis of climatic characteristics of precipitation over southeastern China.The results are as follows:1)A significant twin-peak feature in the intraseasonal evolution of precipitation in Jiangnan is demonstrated,with mid-April and mid-June as the twin-peak periods.The peak precipitation first appears in Jiangnan in mid-to late April,then extends southward.Southern China reaches its peak precipitation period in early to mid-June,after which the heavy precipitation center moves northward,and Jiangnan experiences the second precipitation peak in mid-to late June.Meanwhile,the precipitation in the Jianghuai area(32-35°N) shows a single peak type.The first peak of the Jiangnan rainy season appears very early,and this is the first sign of the rainy season in eastern China.The second peak is the performance of the main rain belt moving northward.2)The correlation coefficient between the regional averaged twin-peak precipitation in Jiangnan and actual precipitation is 0.69,which indicates that the twin-peak precipitation shows the intraseasonal evolution features of the Jiangnan rainy season.The precipitation intensity of the Jiangnan rainy season mainly depends on the precipitation intensity of the bimodal peak in the rainy season(April-June),and this also shows that the twin-peak precipitation characteristics in the Jiangnan area can reflect the change characteristics of the actual precipitation.3)The twin-peak precipitation of the Jiangnan rainy season displays significant interannual and interdecadal variations.The interannual periods are found every 2-3 years,and strong signals are mainly centered in the late 1960s to 1970s and mid-1980s to the beginning of the 21st century,while the interdecadal periods are shown every 8-10 years on the whole time domain,and their strong signals are centered in the early 1980s to late 1990s.4)On the interdecadal scale,although the intraseasonal features of precipitation display a significant twin-peak precipitation pattern in the Jiangnan rainy season,the characteristics of the intraseasonal evolution also show skipped-significant features.A twin-peak precipitation pattern is notable in the 1960s,1980s and the beginning of the 21st century,while in the 1970s and 1990s the twin-peak pattern is insignificant.