近50 年来祁连山及河西走廊地区极端降水的时空变化研究

利用1960~2009年的日降水量资料,选用13项极端降水指数,采用线性趋势、10年趋势滑动、Mann-kendall等方法,对祁连山及河西走廊地区极端降水的时空变化特征进行了研究。结果表明：极端降水日数呈增多趋势,极端降水强度呈减小趋势,极端降水总量呈增加趋势,连续干旱日数、连续湿润日数呈减少趋势,一日最大降水量、五日最大降水量呈增大趋势;极端降水变化存在一定区域差异,走廊平原中西部的降水明显增加,降水变率在减小,走廊平原中部极端降水的日数在增多,降水极值在增大,走廊平原祁连山东部的降水在增加,降水极值在增大,但连续极端降水的总量在减少,祁连山中部的降水在明显增加,降水的极端性在明显增大,对气候变暖的响应最敏感;不同极端降水指数分别在20世纪60年代中期、70年代中期、80年代初期、80年代中后期、90年代中期发生了突变,这些突变点与东亚季风、南亚季风、西风环流等大尺度环流系统强弱变化的时间点是一致的。

Spatial and Temporal Change of Precipitation Extremes in Qilian Mountains and Hexi Corridor in Recent Fifty Years

Based on the daily precipitation of 18 weather stations in Qilian Mountains and Hexi Corridor in 1960-2009, the temporal and spatial changes of precipitation extremes were analyzed by using methods of linear trend, ten moving trend and Mann-Kendall and thirteen indexes of precipitation extremes. The results indicated that the day numbers and amounts of precipitation extreme are on increasing, and this is contrary to intensities of precipitation extremes. Consecutive dry days and consecutive wet days are on decreasing, but max one day precipitation amount and max five day precipitation amount are on increasing. The change trends of precipitation extremes existed certain regional differences that the precipitation amount increased obviously and the variability of precipitation decreased gradually in the middle and west of Hexi Corridor, that the day numbers and the degrees of precipitation extremes increased in the middle of Hexi Corridor, that the amounts and the degrees increased in the east of Hexi Corridor and Qilian Mountains, and that the amounts and the degrees increased obviously in the middle of Qilian Mountains where it is most sensitive to global warming than other regions. The indexes of precipitation extreme changed abruptly in the middle of 1960s, the middle of 1970s, the first of 1980s, the middle and later of 1980s and the middle of 1990s. The abrupt spots are consistent to the times of the strong and weak change of East Asia Monsoon, South Asia Monsoon and Westerly Wind circulation.