关键词: 夏季极端降水事件, 面雨量, 时空特征, 长江流域

Abstract:  Based on daily precipitation data at 700 meteorological stations of the Yangtze River basin from June to August during 1961-2017, the areal precipitation in each sub-zone was calculated by using Thiessen polygon method, and converted to normal distribution by using Box-Cox transformation. The thresholds of extreme precipitation events in summer were determined by using percentile method in each sub-zone of the Yangtze River basin. And on this basis, the temporal and spatial distribution characteristics of summer extreme precipitation events in each sub-zone and their spatial relationships of precipitation among sub-basins were studied. The results are as follows：(1) The decadal characteristic of summer extreme precipitation events in the Yangtze River basin was obvious. The extreme rainless events occurred frequently in the 1960s and 1970s, and the extreme rainy events dominated in the middle and lower reaches of the Yangtze River, while the extreme rainless events dominated in the upper reaches in the 1980s and 1990s. Since the 21st century, the large-range extreme rainless events dominated and occurred mainly in the upper reaches, while the extreme rainy event was easily to occur in Shigu of Jinsha River and above. (2) The first mode of summer extreme precipitation decomposed by EOF was consistently negative in most parts of the Yangtze River basin except for the east of Mintuo River, the north of Jialing River and the south of Poyang and Dongting Lakes during 1961-2017, vice versa. The second mode appeared opposite phases in the north and the south of the Yangtze River basin. (3) When the precipitation was extremely more in summer in the Yangtze River basin, the spatial distribution of summer precipitation had obvious differences and appeared four kinds of patterns, but the precipitation was easily more in the main streams of the Yangtze River. When the extreme rainless events occurred in summer, the precipitation was consistently less in most sub-zones, while for Mintuo River and Jialing River or the south of two lakes it was more.

Key words: summer extreme precipitation events, areal precipitation, spatio-temporal distribution characteristics, the Yangtze River basin