基于MOD16产品的塔里木河流域蒸散量时空分布特征

Spatio-temporal Variation of Evapotranspiration in the Tarim River Basin by Using MOD16 Products

蒸散量的时空格局分析不仅对理解气候变化对区域水资源和能量平衡的影响具有重要的意义,且为探讨旱涝灾害成因以及区域生态需水量研究提供一定的理论依据。以塔里木河流域为研究区域,利用MODIS全球蒸散产品MOD16数据,通过趋势分析法和相对变化率,统计分析了2000-2014年塔里木河流域地表实际蒸散(AET)与潜在蒸散(PET)的年际和年内时空变化特征与趋势。结果表明:MOD16-PET产品在塔里木河流域的验证精度达到极显著相关(R^2=0.81),能够满足蒸散量时空变化分析的要求;在年尺度上,塔里木河流域AET与PET的年际变化波动不大,AET为306.54~383.77 mm、PET为1 551.97~1 744.85 mm,多年平均AET与PET值分别为345.04 mm和1 641.52 mm,月尺度上,AET与PET呈先增大后减少的变化特征,夏季AET与PET之差最大,导致流域处于极端干旱、缺水状态;多年平均AET与PET的空间分布格局体现出从盆地中心往外环状分布的特征,且AET与PET值的增减趋势正好相反,流域外围天山、阿尔金山、昆仑山、帕米尔高原等边疆山区AET较高,PET较低。环塔里木盆地的山脚绿洲平原区AET较低,PET较高;2000-2014年,塔里木河流域AET总体上处于减少趋势,PET处于增加趋势,说明该地区近15 a内干旱加重。

A quantitative analysis is made of spatio-temporal distribution and evolution of surface AET. PET in Tarim River Basin is essential for evaluating the energy balance and water conditions,it provides a certain theoretical basis for the estimation of ecological water requirement. In this paper,the spatio-temporal characteristics and variation trend of actual evapotranspiration（ AET） and potential evapotranspiration（ PET） are studied by using MOD16 data products during 2000-2014 in the Tarim Basin,Xinjiang,China. The results show that： the accuracy of the MOD16-PET-data（ R^2= 0.81） can meet the requirements of statistical analysis,and can be used to examine the spatio-temporal distribution of surface ET. The average annual AET fluctuation range is 306.54 ～ 383.77 mm,with a mean value of 345.04 mm,the average annual PET fluctuation range is 1 551.97 ～ 1 744.85 mm,with a mean value of 1 641.52 mm. The big gap between AET and PET show that the land surface is drought in Tarim River Basin. Furthermore,the monthly variation of AET and PET show a pattern that increases first then decreases,such a gap difference between AET and PET in summer indicates that the land surface is extreme dry. The mean AET and PET show an annular spatial distribution characteristics centering the Tarim Basin. AET increases with the distance from the center,while PET keeps an opposite trend. The spatial distribution of AET is higher,while PET is lower in the mountainous areas（ Tianshan,Altun,Kunlun,and Pamir）. The spatial distribution of AET is lower and PET is higher in the oasis of the Tarim Basin. During2000-2014,AET is in a decreasing trend,while PET is in an increasing trend,showing that the drought in Tarim River Basin has been aggravated in the past 15 years.