Temporal and spatial characteristics of precipitation in Tongzhou District, Beijing

Daily precipitation data at 17 weather stations in Tongzhou District from 1973 to 2018 were used to calculate frequency of occurrence and precipitation cumulative value of four grades of light rain, moderate rain, heavy rain, torrential rain, and spatial distribution characteristics of different grades of precipitation were analyzed. Percentile threshold method, moving average method and other methods were used to analyze extreme precipitation threshold, temporal and spatial evolution of extreme precipitation. The 95% threshold range of Tongzhou District was found to be 44.1~50.2 mm, 99% threshold range 74.5~93.5 mm. The 99% threshold was found more representative of extreme precipitation events. Extreme precipitation of 99% threshold was found to occur from June to September, mainly in early August, mid-late July, end of June and beginning of July. Extreme rainfall events were found to be more likely to occur in northern part of Songzhuang Town and eastern part of Xiji Town. In sub-center, extreme rainfall events were found to be more likely to occur in northwestern part of Zhangjiawan Town and northwestern part of Lucheng Town. The frequency of extreme precipitation was found to decrease as a whole, but increase in the north and east, decrease in the southwest, with a clear spatial dividing line. In the east of Xiji Town, precipitation frequency, extreme precipitation and contribution rate of extreme precipitation were found to be not only at a high value, but also showed an increasing trend of interannual change, therefore it should be the focus area.