近50 年来祁连山及河西走廊降水的时空变化

利用1960-2009 年的日降水量资料,采用线性趋势、5 年趋势滑动、IDW 空间插值、Morlet 小波分析、Mann-Kendall 突变检验等方法,对祁连山及河西走廊地区不同等级降水日数和降水强度的时空变化特征进行了研究。结果表明:不同等级降水日数和降水强度的多年平均在空间上既表现出东西分异,也表现出南北分异;不同等级降水日数的年际变化在绝大部分区域呈增多趋势,且自东向西增幅减小,大雨强度的年际变化在绝大部分区域呈增大趋势,其它等级降水强度为部分区域呈增大趋势,部分区域呈减小趋势;小雨、中雨日数的年际变化呈显著增多趋势,大雨日数呈明显增多趋势,暴雨日数呈不明显增多趋势,小雨、大雨强度的年际变化呈不明显减小趋势,中雨、暴雨强度呈不明显增大趋势;不同等级降水日数变化的周期集中在2a、5a、8a、11a、19a,不同等级降水强度变化的周期集中在2a、5a、11a、15a、25a;除小雨强度突变减小外,其它等级降水日数均突变增多,降水强度均突变增大,降水量的增加主要是降水日数的增多造成的,其中小雨、中雨日数的增多贡献最大。

Temporal and Spatial Changes of Precipitation in Qilian Mountains and Hexi Corridor during 1960-2009

Based on daily precipitation data of 18 weather stations in Qilian Mountains and Hexi Corridor during 1960 to 2009, the spatial and temporal changes of day number and intensity for different grades of precipitation were analyzed by the methods of linear trend, five-year moving trend, IDW, Morlet wavelet and Mann-Kendall. The results indicated that the spatial distributions of day number and intensity for different grades of precipitation changed from east to west and from south to north. In the last 50 years, the annual variations of day number of different grades of precipitation were increasing in most of the regions and the increasing scales are decreasing from east to west, which is consistent with the intensity of heavy rainfall events. However the annual variations present an increasing trend in some parts or decreasing in other parts in terms of the intensities of light rain, moderate rain and extreme rain. The annual changes of day number of different grades of precipitation showed an increasing trend, and they are significant for light rain, moderate rain and heavy rain. Intensity of light rain and heavy rain prohibited an unobvious decreasing trend, but it is opposite to intensities of moderate rain and extreme rain. The main change cycles of day number of different grades of precipitation have quasi-periods of 2a, 5a, 8a, 11 a and 19a, and those of intensity of different grades of precipitation have quasi-periods of 2a, 5a, l la, 15a and 25a. Except for the abrupt decrease in intensity of light rain, the day number and intensity of different grades of precipitation increased abruptly.