Abstract:

The Southwest region is one of the most serious areas of mountain hazards in China, and the shortterm extreme precipitation is one of the critical control factors for the evolution of mountain hazards. In this paper, daily precipitation data of 110 meteorological stations in Southwest China from 1960 to 2011 were employed, with the 95th percentile of the annual rainfall as threshold of daily extreme precipitation was established, spatial analysis of GIS technology and linear trend, MannKendall trend test and Morlet wavelet analysis method were used to study the spatial and temporal variation of the extreme precipitation events in Southwest China. The results show as follows. Since the 1960s, extreme precipitation frequency increased with a rate of 0017/10 a in Southwest China, and the proportion of extreme precipitation in total precipitation was increasing. Extreme precipitation frequency changed in different decades. The significant increase area showed a patchy distribution, and reduce area in the region showed a pronounced banded distribution. Southwestern of Yunnan, most areas of Guizhou and central of Sichuan Basin are the high incidence of extreme precipitation area, while the border of Yunnan and Sichuan at YuanmouHuili and northern mountainous areas of Sichuan Basin are less likely to occur. Extreme precipitation frequency showed a significantl increasing trend with a rate of 0031 times/10 a during the summer monsoon, and a decreasing trend with a rate of -0014 times/10 a during the winter monsoon. There was no obvious abrupt year in summer monsoon and annual extreme precipitation frequency. However, there were three abrupt years in winter monsoon, 1969, 1983 and 1994 respectively; summer monsoon and annual extreme precipitation showed periodic oscillations of 27, 15 and 7 years time scale, while the cyclical oscillation on the winter monsoon is mainly concentrated in the 27 and 12 years time scale