Spatial And Temporal Distribution Of Flood Season Rainfall Pattern And Heavy Rain Days, And Its Causes

In this paper, We analyzed the corresponding relationship between the precipitation pattern of flood period and the distribution trend of the anomaly of rainstorm frequency over China, their inter-annual/inter-decadal change of rule, the response to ENSO. It was mainly studied the inter-annual change features of the numbers of rainstorm day in Yangtze Valley and the south area of Yangtze . And by power spectrum and wavelet analysis we revealed the periodic variation of rainstorm frequency over Yangtze Valley. We also discussed the large-scale circulation background of the heave rainstorm system in the middle reach of Yangtze River, and the sensitivity area at 500hPa and 100hPa. Furthermore, it was comparatively analyzed that the SSTA precursor features during December to February in the Pacific Ocean producing the heavy rain year and the slight rain year in the Yangtze River.From the analyses, we found the following significant facts: Main precipitation pattern of flood period in the middle-east of China has close relation to anomaly of rainstorm frequency; The precipitation pattern's 80% discontinue, and only 20% persists for two years; The frequent appearance of rainstorm in the middle reach of Yangtze River have close relationship not only with the persistent stability and strong of western Pacific subtropical high, South China sea subtropical high ,North America subtropical high at SOOhPa during the same term, but also with the persistent stability of South Asia high and America high at 1OOhPa.