Abstract:Based on the summer precipitation data of 20 stations in Beijing and its urban development statistical data during 1971-2010, and defining the 95th percentile as the threshold of extreme precipitation for each station, the characteristics of the spatio temporal distribution and the linear trend of extreme precipitation events with different durations and city effect of local precipitation are analyzed. The results indicate that the extreme precipitation event frequency shows a gradual decreasing trend from west to east, which is remarkably different from the precipitation distribution. There exist distinctive spatial differences in the distributive features and changes of the threshold values, frequencies, and rainfall of extreme precipitation events. The averaged intensity and frequency of extreme precipitation in Beijing Area show a descending trend in the past 40 years and have significant difference at interannual and interdecadal changes. The impact of urbanization on the intensity and frequency of extreme precipitation has become more and more apparent. Urbanization can not only enhance rain island effect but also make an influence on precipitation in downwind areas; moreover, urbanization can also increase the intensity and frequency of local extreme precipitation.