The Latest Evidences of a Warm–Wet Climatic Shift in Hexi Corridor, Gansu

Based on the daily precipitation data from 19 weather stations in Hexi Corridor of Gansu province from 1981 to 2011, the change characteristic of precipitation, rain days and precipitation intensity were analyzed. It is found that autumn precipitation increases significantly in the Corridor and winter precipitation has an increasing trend from the east of Jiuquan to Zhangye; rain days reduce significantly in summer, but increase in autumn; precipitation intensity increases dispersedly in autumn. The proportions of precipitation in autumn, spring and winter to annual precipitation rose by 9. 4% , 3. 9% and 1. 8% , respectively, in 2000s as compared with that in the 1990s. Thus it was still with a warm-wet tendency in these seasons, especially in autumn. However, the proportion of precipitation decreased by 15. 3% in summer, showing a warm-dry changing tendency. The extreme weather events of the three analyzed factors had increased markedly in the 2000s; From the aspect of season, the highest frequency had been in autumn , accounting for about 80% of the total extreme factors events, followed by that in summer and winter, accounting for 60% both.Viewing form the factors, rain day frequency, nearly 70% , was the highest, precipitation frequency, 60% , it was second, and precipitation intensity frequency, 50% , it was the least. Compared with those in the 1990s, the 200 hPa and 500 hPa height fields in the 2000s had obvious decadal variation, so did the relative humidity and specific humidity at 700 hPa, which were beneficial to autumn precipitation and unbeneficial to summer precipitation in the 2000s.