西北四省区降水的时空变化特征分析

Analysis on Spatial-temporal Variation Characteristics of the Precipitation in Four Provinces of the Northwest China

[目的]分析西北四省区降水的时空变化特征。[方法]利用陕西、甘肃、青海、宁夏西北四省区113个地面观测站1961～2008年降水资料,采用线性回归、Morlet小波变换等方法,对该地区48年降水空间格局的变化、降水量的变化趋势和周期特征进行了分析。[结果]西北地区四省降水量存在明显的年际、季节变化特征;年降水量呈下降趋势,春、秋季降水量变化趋势与年降水量变化趋势一致,其变化幅度小于年降水量的变化幅度,夏、冬季的降水量逐年略有增加,变化趋势不明显。西北四省降水变化存在明显的区域差异,增加幅度明显的区域在唐古拉山地区、柴达木盆地、祁连山东部山脉两侧,减少幅度明显的是在陇东和陕南、陕北地区。西北地区四省的东、西部区域降水呈反位相变化的特点,东部地区的降水呈减少趋势,而西部大部分地区的降水呈增多趋势;全区、东区、西区的降水波动普遍存在3～5年的短周期,且为主要周期;一些区域也存在8年周期和15年左右的中周期;不同时间尺度上,干、湿交替和突变点有所差异。[结论]该研究为西北地区的气候变化提供理论依据。

[ Objective] The research aimed to analyze temporal-spatial change characteristics of the precipitation in four provinces of the Northwest China. [ Method] Based on precipitation data at 113 ground observation stations in four provinces （Shaanxi, Gansu, Qinghai and Ningxia） of the Northwest China from 1961 to 2008, by using linear regression and Morlet wavelet transformation, spatial pattern change, change trend and period characteristic of the precipitation in the zone in 48 years were analyzed. [ Result] Rainfall in four provinces of the Northwest China had obvious interannual and seasonal change characteristics. Annual, spring and autumn rainfalls all presented decline trends. Summer and winter rainfalls both had slight increase trends, but change trend wasn＇ t obvious. Precipitation change in four provinces of the Northwest China had obvious regional difference. Increase amplitudes in Tanggula Mountains, Tsaidam Basin and east Qilian Mountains were obvious. Obvious decrease amplitudes existed in east Sichuan and south and north Shaanxi. Precipitation in east and west areas of the four provinces in Northwest China presented anti-phased change characteristics. Precipitation presented decrease trend in east and increase trend in most areas of west. Precipitation in the whole district, east district and west district generally had 3 - 5-year short period. It was main period. Precipitation also had 8-year and 15-year medium periods in some areas. Under different time scales, dry and wet alteration and muta- tion point had difference. [ Conclusion] The research provided theoretical basis for climate change in Northwest China.