Abstract:

Rainfall is a key factor of urban flooding,which has great effect on social safety.The research on rainfall characteristics could provide significant guidance in flooding control.The climate of Shanghai is complicated, which is deeply influenced by disaster rainfalls such as rainstorms and typhoons.According to the data from national basic weather station,Baoshan Staion,the precipitation change and the characteristics of disaster rainfalls in Shanghai during the last 40 years were analyzed.The results showed that the annual precipitation in Shanghai increased with a rate of 509 mm/10 a and the annual precipitation days decreased with a rate of 3 d/10 a.In terms of precipitation and rainfall intensity,rainstorms and short intense falls are viewed as disaster rainfalls.Annually,3 days of rainstorms could contribute one fifths of the annual precipitation. Usually，rainstorms in large area are caused by typhoons.In recent years,the frequency of short intense falls that exceed the drainage standard tend to aggregate.Furthermore,the flood season,as the peak of the disaster rainfalls,should be considered as the critical period in flooding control