Analysis of the Climatic Characteristics and the Variations of the Rainstorm in Beijing Area

Using the precipitation data in Beijing during 1961－2007, statisitcs rate of the climatic tendency, polynomial curve fitting, and Morlet wavelet method, the climatic characteristics and the trends of the climatic change of rainstroms in Beijing were analysed. The results show that: 1）Rainstorm has obvious monthly variation characteristics, the first 10 days of August(before and after the Beijing Olympic Games opening ceremony)are the most evident stage of the rainstorm days in Beijing. 2）The general trend of the annual rainstorm days has slowly decreased with fluctuation in Beijing during 1961〖CD*2〗2007, the descending rate of the annual rainstorm days at Shahe station is the slightest, that at the Xijiao station is second, and that at Nanyuan station is the most marked among the three stations. 3）The variations of the incremental and reduced rainstorm days have periodic characteristics, and there are absolutely opposite variation trends at Nanyuan station before 1990, in comparison with Shahe station and Xijiao station. 4）The variations of the annual rainstorm days have multiple periodicity in Beijing. Different periodic oscillations of the annual rainstorm days exist at Nanyuan station, Shahe station, and Xijiao station.