【摘要】 利用帕尔默干旱指数(PDSI)全球数据库,提取覆盖中国西北地区的56个PDSI栅格点数据,对1953-2003年间各个季节均值和年均值进行旋转经验正交函数(REOF)分析。REOF空间分区结果发现西北地区各个季节均值和年均值表现出较为一致的主要空间异常型,依据PDSI年均值数据可以将中国西北地区划分为5个空间型:北疆型、南疆型、高原北部型、蒙古西部型以及西北东部型。其中北疆型、南疆型主要位于西北地区西部,高原北部型、蒙古西部型位于西北中部,西北东部型位于西北东部。各个空间型特征点的PDSI序列及二项式拟合对比发现西北东部、西部存在完全相反的干湿变化:西北西部主要受西风带影响,自20世纪80年代开始有逐渐变湿的趋势;西北东部主要受亚洲季风的影响,有逐渐变干的倾向,特别是夏秋季,西北地区东南部变干的趋势更加明显。西北地区受西风带、亚洲季风以及青藏高原的影响明显,在全球变暖的情景下,不同区域的干湿状况的响应存在较大的差异。更多还原

【Abstract】 Using global Palmer drought severity index(PDSI)database,the seasonal and annual PDSI mean values of 56 grid points covering the period 1953-2003 over northwestern China is analyzed by rotated experience orthogonal function(REOF).The results show that the seasonal and annual means display similar anomaly regions,and furthermore there are five main anomaly regions in the northwestern China based on the annual PDSI mean,i.e.,the northern and southern parts of Xinjiang,northern part of plateau,western part of Inner Mongolia and eastern part of northwestern China.The opposite changes of dry-wet conditions are discovered after comparing the curves of feature point series and binomial fit between the eastern and western parts of the northwestern China:The western part of the northwestern China influenced by westerly,a trend of wetting gradually occurred since 1980.On the contrary,a trend of drying gradually occurred in the eastern part of the northwestern China which is mainly influenced by Asian monsoon,and especially in summer and autumn,there is notable trend of drying over the southeastern part of the northwestern China.The northwestern China is obviously affected by westerly,Asian monsoon and Tibetan Plateau.There are differences among the responses of the dry-wet conditions to the global warming in different regions.更多还原