石羊河流域干旱变化趋势及气候影响因素

摘要

基于Thornthwaite干燥指数概念,采用Sen斜率、敏感性分析和空间分析等方法研究1981-2014年石羊河流域干旱的空间分布特征和变化趋势,分析干燥指数的气候敏感性.结果表明:石羊河流域干燥指数自上游至下游呈增大趋势;研究时段内,干燥指数减小的区域主要分布在乌鞘岭东北、永昌以西及民勤以北,其余地区干燥指数呈增加趋势.石羊河流域干旱对降水、相对湿度和净辐射的变化较为敏感.1981-2014年流域上游山区降水减少导致干旱加重,而相对湿度的增加抑制了陆表蒸散发,一定程度上缓解了旱情的加剧;流域中下游地区干旱减弱主要由降水增加所致.%Based on the determination of the Thomthwaite aridity index (AI),methods of Sen's slope and spatical analysis were used to analyze the spatial and temporal characteristics and variation tendency and climate sensitivity of drought across the Shiyang River Basin from 1981 to 2014.The results revealed that the AI increased spatially from the area of the upper reaches to the lower reaches in the Shiyang River Basin.From 1981 to 2014,there presented a decrease of AI in the area of northeastern Wushaoling,westem Yongchang and the northern Minqin,with an increase in other areas of the Shiyang River Basin.Sensitivity analysis showed that variations of drought in the basin were influenced more by the three key climate factors including precipitation,relative humidity and net radiation.The decrease of precipitation led to aridity in the upper mountainous area to be strengthened,while the weakened aridity in area of the middle and lower reaches was due to an increase of precipitation.The increase of relative humidity in the upper mountainous area led to less evapotranspiration,which,to some extent,remitted the aridification in the area.