Abstract: Based on the daily precipitation data from 19 meteorological stations in Baoding during 1974 to 2012, the spatial and temporal distribution characteristics of rainstorm and its variation were analyzed using methods of a linear trend analysis, a Mann-Kendall test, a wavelet analysis and a power spectrum. The results show that more rainstorms occur in the north and less in the south and most are in the northeast region. Rainstorm usually appears in the flood season (June to August), especially in the main flood season (July to August). Rainstorm frequency increases slowly since the middle ten days of May, then increases sharply in the last ten days of June, and it reaches the peak value in the last ten days of July. The annual rainstorm frequency is in a decreasing trend in the recent 39 years, especially in August. An abrupt change of rainstorm frequency from less to more during the main flood season occurs in 1980 s, while it is in the late of 1990 s that the rainstorm frequency changes from more to less.

Key words: Wavelet transform, Mann-Kendall test, Power spectrum