中国干旱气候分区及其降水量变化特征

利用中国614个气象台站1974～2006年历年月平均降水资料，计算各站的降水量距平百分率及其干旱等级序列，采用REOF等方法，对干旱等级序列进行气候分区，并分析各区域50a左右干旱等级的时间演变特征。结果表明：全国降水量具有显著的年代际变化特征，尤其西北地区年代际变化十分突出，其中新疆西部地区在21世纪以来降水量的增加非常明显，增加的程度也是近33a中最强的。根据干旱等级序列的旋转载荷向量将中国划分为11个区域，它们各自具有不同的旱涝特征。干旱等级序列和代表站资料反映出近50a东北、华北及河套地区的干旱明显加重，而西北大部分地区降水量有显著的增加。

PrecipitationVariation Characteristics and Arid Climate Division in China

The percentage of precipitation anomalies and the drought grades(DG) were calculated by using the monthly mean precipitation data for the period of 1974-2006 from 614 stations in China.The climate regions are divided according to DG based on REOF,and the temporal evolution characteristics of DG in each region were studied.The results show that there is obvious interdecadal variability in annual precipitation in China,especially in northwest China.Since the 21st century,a sharply increasing rainfall trend appeared in the west of Xinjiang.The first eleven rotated loading vector fields of DG represent eleven principal precipitation anomaly areas,and each marked by a dryness/wetness trend of its own.DG and the data at the representative stations show that annual total precipitation has obviously decreased in northeast China,north China and Hetao area,but significantly increased in northwest China in the recent 50 years.