利用西南5省161个气象站1996~2015年的气温、水汽压数据资料,以及MODIS产品数据,基于改进的混合型线性双源遥感蒸散模型拟合西南地区的地表蒸散状况,并定义蒸散干旱指数(EDI)分析该区干旱时空变化特征.结果表明:①西南地区近20 a来实际蒸散呈现明显的增加趋势,春、夏两季蒸散量较大,占全年总量的62.3%;春季由东南向西北递减,广西南部以及云南南部实际蒸散量较大;夏季呈现由东向西递减的趋势,由广西、贵州、重庆向云南和四川递减;秋季与冬季则呈现由南向北递减的规律.② 潜在蒸散也呈现增加趋势,季节上存在一致性,春、夏两季蒸散量占全年总量的60.6%,空间上相比实际蒸散而言,变化存在一定规律,潜在蒸散量春季、秋季以及冬季呈现明显的由南向北递减的趋势,具有纬向分异规律,而夏季则表现为由东向西递减的经向分异规律.③年际间的EDI呈现波动趋势,且近20 a来明显下降,但各年EDI均值都大于0.5,说明整体干旱化程度相对严重.%The data of temperature,vapor pressure of 161 meteorological stations in 5 provinces in Southwest China from 1996 to 2015 and MODIS product data were used to fit the surface evapotranspiration in southwest China,based on the improved hybrid linear dual source remote sensing evapotranspiration model. The evapotranspiration drought index (EDI) was defined to analyze the temporal and spatial variation characteristics of drought in the area. The results show that:in the past 20 years,the actual e-vapotranspiration in southwest China has increased obviously,and it is larger in spring and summer,accounting for 62.3% of the annual evapotranspiration. In spring,the actual evapotranspiration descends from the southeast to northwest, and it is larger in southern Guangxi and Yunnan. While, in summer, it shows a decreasing trend from east to west, from Guangxi, Guizhou, Chongqing to Yunnan and Sichuan. In autumn and winter, it decreases from south to north. Potential evapotranspiration also shows an increasing trend and the seasonal variation trends are coincident with the actual evapotranspiration. It also accounted for 60.6% of the total annual evapotranspiration in Spring and summer. However,compared to the actual evapotranspiration in view of spatial distribution,the variation of potential evapotranspiration has certain rules. In spring,autumn and winter,it shows obvi-ous decreasing trend from south to north with a latitudinal differentiation distribution, but in summer, it decreases from east to west with a longitudinal differentiation distribution. The interannual EDI shows a fluctuating and obviously decreasing trend in the past 20 years,but the average EDI of each year is greater than 0.5,indicating that the overall degree of drought is relatively seri-ous.
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