Evolution Characteristics and Driving Mechanisms of Actual Evapotranspiration in the Middle and Lower Reaches of the Yangtze River Basin
In order to better understand the spatial and temporal evapotranspiration(ET)evolution characteristics of the six sub-basins in the middle and lower reaches of the Yangtze River,as well as the impacts of the changes in climate and sub-surface factors on the changes in ET,the actual ET sequences of the six sub-basins in the middle and lower reaches of the Yangtze River were reconstructed based on the GRACE gravity satellite observation data and the water balance method.Three ET datasets were evaluated and merged to obtain high-precision monthly ET from 1992 to 2015.The trend of annual and seasonal ET in 6 sub-basins was analyzed,and the comprehensive index of land use degree(La)was introduced.Based on path analysis,the direct and indirect effects of climate and underlying surface factors on the change of ET in each sub-basin were quantitatively evaluated.The results are as follows.Firstly,the applicability of the three datasets in the middle and lower reaches of the Yangtze River Basin is better,and the data fusion method based on the least-squares weigh-ting method reduces the mean difference and root-mean-square error of ETrecon and ETNOAH and ETGLEAM,and reduces the standard deviation of ETNOAH and ETCR.Secondly,the average ET in the middle and lower reaches of the Yangtze River Ba-sin is 728.7 mm,increasing spatially from northwest to southeast.The ET of the six sub-basins showed an increasing trend in different seasons,and the increase was the largest in spring and summer.Thirdly,the increase of annual ET in each sub-basin was mainly caused by the enhancement of La and the increase of air temperature,and the indirect effects of air temperature,La and vegetation cover caused the effect of the decrease of wind speed on ET in the Taihu Lake basin to change from positive to negative.Fourthly,the increase of temperature promoted the positive effect of NDVI on the increase of EV in spring and summer in 6 sub-basins.The increase of precipitation in autumn and winter in the Taihu Lake basin,the middle and lower reaches of the Yangtze River weaken the effect of radiation reduction on ET change,while the increase of wind speed is the dominant factor for the slight increase of ET in winter in the Dongting Lake basin and the middle rea-ches of the Yangtze River.The research results will provide theoretical and scientific basis for water resources management,drought prediction and ecological function assessment in the middle and lower reaches of the Yangtze River Basin.
actual evapotranspirationunderlying surfaceclimate changedriving mechanismthe middle and lower rea-ches of the Yangtze River Basin
万方数据
维普
