三峡大坝运行后长江中下游流域气温与植被变化特征及原因分析

基于长江中下游流域120个气象站点1971-2015年日值气温数据，2006-2015年ERA-Interim土壤湿度再分析资料和2006-2015年MODIS卫星遥感植被指数产品MOD13A3，研究了在考虑全球变暖背景下，长江中下游流域春、夏、秋、冬4个季节平均气温在三峡大坝运行前后的变化，采用百分比阈值方法量化最高和最低气温并进行MK突变检验，并分析三峡大坝运行后的长江中下游流域四季土壤湿度和增强型植被指数（EVI）的变化。结果表明：长江中下游流域四季平均气温在三峡大坝运行以后出现明显变化，江南地区主要出现增温现象，江北地区主要出现降温现象；MK突变检验结果显示，江南地区的高温日和江北的低温日均在2006年左右发生突变，与三峡大坝完全运行的时间相符；长江中下游流域土壤湿度在三峡大坝运行后出现南湿北干的变化趋势；EVI在江南地区诸多区域出现显著增加趋势，其中冬季最突出（33.06%），而江北地区诸多区域则出现显著减小趋势，其中夏季最明显（5.11%），EVI与平均气温的空间变化在春、夏、冬3个季节显著相关。

Analysis on Characteristics and Causes of Temperature and Vegetation Changes in the Middle and Lower Reaches of the Yangtze River After the Three Gorges Dam Operation

Using daily temperature data of 120 stations in the middle and lower reaches of the Yangtze River during 1971-2015, the variations of average temperature before and after the operation of Three Gorges Dam in four seasons (spring, summer, autumn and winter) were analyzed after removing the impacts of global warming background, the mutation times of high and low temperature days were investigated by the MK test method. Furthermore, the change in soil moisture was investigated by utilizing ERA-Interim soil moisture reanalysis data during 2006-2015, and the vegetation response to the temperature variations was analyzed by utilizing MODIS dataset during 2006-2015. The average temperature in the middle and lower reaches of the Yangtze River showed significant changes after the operation of the Three Gorges Dam, warming phenomenon occurred in the southern study area while cooling phenomenon occurred in the northern study area. The MK test results indicated that the high temperature days in the southern study area and low temperature days in the northern study area both mutated around the time when the Three Gorges Dam began to fully operate. Soil moisture obviously increased in the southern study area. The spatial distribution of the enhanced vegetation index (EVI) trend was consistent with the change of the average temperature in spring, summer and winter, the EVI increased in the southern study area, most significantly in winter (33.06%), but decreased in the northern study area, most significantly in summer (5.11%).