Evolution characteristics of the precipitation in the Yangtze River delta based on the probability density
基于概率密度分析长江三角洲降水随时间的演变规律

The dryness/wetness (DW) grade data of the Yangtze River delta are transformed in this paper 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 more than a century quasi-periodic changes, and the periods are all significant at 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 narrates the significant impact of the climatic evolution as a background state upon the occurrence of SPEs, which will play an instructional role in climatic prediction theory and in raising the accuracy of climatic prediction.