1962—2009年天山北部湿润指数变化的区域差异

湿润指数揭示了地表干湿变化趋势,与降水变化相比,它更能客观地诠释在全球增暖背景下区域干湿演变特征及变化趋势。本文运用消除趋势波动分析、样条函数法和最小二乘法等方法,对天山以北5个不同区域1962—2009年的地表湿润指数的时空变化趋势和降水、气温变化趋势的空间分布进行统计,以分析各分区的不同年份、季节气候干湿变化特征。结果表明:各分区分季节湿润指数序列在48年的时间尺度上具有微弱的Hurst效应,即具有较弱的长期持续性和较强的随机性,并且各分区不同季节差异较明显;近48年来天山北部荒漠绿洲区降水整体呈现统计意义上的增加趋势,但地表湿润指数变化趋势差异较大;干化趋势最显著的地区与增暖最强烈的地区对应,干化趋势最显著的地区在伊犁谷地及其周围地区,准噶尔西部山地和东部边缘地区干化趋势次之;干湿变化表现出明显的季节差异,干化趋势最显著的季节为冬季和秋季,春季次之,夏季全区表现为明显的变湿趋势。

Regional differentiation in the variations of surface moisture index in north Tianshan Mountains in 1962-2009

Surface moisture index is more objective than precipitation in describing regional drying-wetting feature and its changing trend under the background of global warming.Based on the meteorological data from 21 stations in 1962-2009,and by using detrended fluctuation analysis,spline interpolation,and least square fitting,this paper analyzed the spatiotemporal variations of surface moisture index,precipitation,and air temperature in different sub-regions of north Tianshan Mountains,Xinjiang of Northwest China in 1962-2009.During the past 48 years,the temporal pattern of the moisture index showed a weak Hurst’s effect,i.e.,the moisture index exhibited relatively weak persistence and relatively strong randomness through the time.There was a significant seasonal difference among the sub-regions.In desert oasis sub-region,the annual precipitation had an overall increase,but the moisture index varied spatially.The sub-regions that experienced significant drying also experienced significant warming,and the sub-regions with the most significant drying were the Ili Valley,followed by the west mountainous area and the eastern edge of Junggar basin.The ground surface drying-wetting also varied seasonally,with a trend of becoming drier in winter and autumn,followed by in spring,and wetter in summer.