西北干旱区地气温差季节和年际变化特征的分析

Analyses on Characteristic of Seasonal and Interannual Variation of Difference between Surface and Air Temperature (Ts-Ta) in Arid Region in Northwest China

利用西北干旱区49个气象站1961—2000年0cm地温和气温月平均资料，采用逐级归并法、小波分析、经验正交函数（EOF）、旋转经验正交函数（REOF）方法，分析了西北干旱区地气温差的时空演变特征、气候突变和周期振荡。结果表明：西北干旱区地气温差可分为12月～2月、3月、4～6月、7～10月和11月5类，11月和12月～2月呈下降趋势，3月、4～6月和7～10月呈上升趋势，12月～2月下降幅度较大，4～6月上升幅度最大；地气温差受大尺度气候异常的影响，第一载荷向量反映了全区一致的性质；北疆区和内蒙区有异常变化存在；3月和11月的突变点为1977年，12月～2月、4～6月和7～10月的突变点为1981年；周期振荡主要以3～6年为主。

The temporal-spatial evolution features, abrupt climate change and oscillatory period of the difference between land surface and air temperature （simply as the （Ts-Ta）） are analyzed by using the monthly surface temperature and air temperature of 49 weather stations （1961-2000） in the arid region in Northwest China（NWC）, with hierarchical cluster analysis, wavelet analysis, EOF, REOF methods. The results show that （Ts-Ta） in the arid region in NWC can be divided into December～February, March, April～June, July～October and November; （Ts-Ta） reveals the tendency of descent in November and December～February. （Ts-Ta） reveals the tendency of ascent in March, April～June and July～October months; the tendency of descent is the maximum in December～February and the tendency of ascent is the biggest in April～June; （Ts-Ta） is influenced by the large-scale weather systems, the first loading vector reflects the main spatially-anomalous structure; the north of the Xinjiang and the Inner Mongolia area have the exceptionally change existence; the abrupt year in March and November months is in 1977; the abrupt year in December～February, April～June and July～October is in 1981; the periodic oscillation is mainly 346 years.