Evapotranspiration Simulation And Driving Force Analysis Of SWH Dual-Source Model In Hetao Irrigation District,Inner Mongolia

Evapotranspiration（ET）is a key parameter of water cycle and energy exchange in land and atmosphere system,and also an important factor affecting the surface water and heat balance.Hetao Irrigation Area in Inner Mongolia belongs to plateau landform,and the climate conditions change dramatically.Under the special terrain and climate conditions,the surface evapotranspiration process shows a very complex regional correlation.The results are as follows:1.To explore the applicability of SWH（Shuttleworth Wallace Hu）dual source model in Hetao Irrigation District,Inner Mongolia,and to provide experimental data and theoretical support for the research of climate evolution,rational allocation of water resources and natural ecological protection.Based on 14 meteorological stations data and MODIS remote sensing data of Hetao irrigation area from January,March,may,July,September and November 2017 to 2018,this study estimates plant transpiration and soil evaporation respectively based on SWH dual source model to obtain the surface evapotranspiration of Hetao irrigation area.Based on the verification of the estimation results,the spatial and temporal distribution characteristics of evapotranspiration in Hetao irrigation area are summarized step by step.The main driving factors of evapotranspiration in Hetao irrigation area are calculated by using the mathematical statistical methods such as correlation analysis and principal component analysis.The specific conclusions are as follows;（1）The average relative error of evapotranspiration data measured by SWH model is7.71%,5.89%and 7.86%respectively,which shows that the evapotranspiration estimation of Hetao Irrigation Area in Inner Mongolia can be realized based on SWH model.（2）The main driving data of SWH model are analyzed in time and space distribution.The spatial distribution of normalized vegetation index（NDVI）,photosynthetic effective radiation（PAR）,temperature,relative humidity and precipitation are basically consistent in the same month.The values are all in the trend of"peak type"in the year,but the wind speed is not obvious.（3）The distribution of time-space variation of evapotranspiration results estimated by SWH model is obviously"seasonal".The daily evapotranspiration in January is0.083mm·D^-1,that of March is 0.37mm·D^-1,that of May is 3.72mm·D^-1,that of July is5.36mm·D^-1,that of September is 2.17mm·D^-1,and that of November is 0.94mm·D^-1,and the fluctuation of the same month’s daily evapotranspiration is lower than 1mm·D^-1.（4）The correlation analysis results of the main driving data of SWH model and the estimated evapotranspiration of the model show that the average temperature and evapotranspiration are highly correlated,Pearson correlation coefficient is 0.802,relative humidity and normalized vegetation index（NDVI）are strongly correlated with the evapotranspiration,and Pearson correlation coefficient is 0.622 and 0.624 respectively.（5）The main driving data of SWH model and the main component analysis of the estimated evapotranspiration of the model show that the average temperature,NDVI and relative humidity are the main driving factors affecting the evapotranspiration in Hetao irrigation area.