Evolution characteristics of the precipitation in the Yangtze River delta based on the probability density

Abstract

In this paper the dryness/wetness (DW) grade data of the Yangtze River delta is transformed into the temporal evolution of precipitation probability (PP) and its hierarchically distributive characters are revealed. Research results show that the precipitation of the Yangtze River delta displays the interannual, interdecadal, as well as longer quasi-periodic changes than a century and all the periods have a confidence level of more than 0.05. In the DW grade series of 530 years, although the frequency of the small probability events (SPEs) of drought/flood in each area of the Yangtze River delta is different, the frequency of the SPEs triggered by the climatic background state is yet the same. This research result fully shows the significant impact of the climatic evolution as a background state upon the occurrence of SPEs, which will be instructive in climatic prediction theory and in raising the accuracy of the climatic prediction.