Distribution feature of time series of extreme precipitation over the Yangtze River Basin

Abstract

Based on daily precipitation data of 147 stations in the Yangtze River Basin during the flood season (April to September) for 1960-2005, extreme high precipitation (percentile95th) and its time gap, days with precipitation 1.27mm/d and its duration were calculated. Accordingly, spatial distributions and temporal sequences of extreme precipitation events had been analyzed, and the probability model was established. Research results showed that Sichuan Basin in the upper reaches and southeastern Lake Poyang Catchment in the mid-lower reaches were the high precipitation center of the Yangtze River Basin with centralized extreme event. Total number of days with precipitation1.27mm/d is more in the mainstream section, Minjiang-Tuojiang Catchment and upper Wujiang Catchment than any other area of the Yangtze River Basin. However, due to shorter lasting period of events with 1.27mm/d, it did not create serious drought situation in theses areas. Whereas, areas in the upper and lower Jinshajiang(upper reaches of the Yangtze River) Catchment, Lake Dongting Catchment, southeastern Lake Poyang Catchment, and lower main stream section, were more likely to be stricken by prolonged events with 1.27mm/d and droughts caused. By applying Weibull model with the method of maximum likelihood estimator on the time gap of extreme high precipitation and lasting period of 1 27mm/d, it was proved that Weibull-Ⅱcan simulate well the probability distribution of timing of extreme precipitation events over the Yangtze River Basin. Changes of Weibull-Ⅱparameter can reflect well the spatial and temporal variation of timing of extreme precipitation events.