Evaportranspiration Estimation Of Ejina Oasis In The Lower Reach Of Heihe River Basin Based On Remote Sensing

Surface evapotranspiration is an important link between land surface ecosystems and hydrological processes.Evapotranspiration plays a decisive role in water cycle research and water resources management.It has a great influence on the regional climate and the distribution of total water resources and affects the development of regional economy.Therefore,the study of surface evapotranspiration is of great significance.In recent years,the rapid development of remote sensing and GIS technology has greatly promoted the research on evapotranspiration.Based on the SEBS model,Landsat8 satellite imagery of Ejina Oasis in 2014 and 2015 and the observed meteorological data of the meteorological stations in the study area were used to estimate the surface evapotranspiration.Combined with the METRIC method and linear interpolation,the daily evapotranspiration was extended to the monthly and annual evapotranspiration.And then we obtained the characteristics of temporal and spatial distribution of evapotranspiration in the study area,and further analyzed the correlation between evapotranspiration and its influencing factors.(1)The SEBS model can well simulate the evapotranspiration in the study area.The validation of the simulation results using the observation data shows that the overall effect is better.The R2 value of the water body is 0.59,and others above 0.65.(2)Spatial and temporal distribution of evapotranspiration in the study area:The evapotranspiration during the growing season in the study area was significantly larger than that in the non-growth season.In January,February,November,and December,the evapotranspiration of various types was very small and very close,with obvious differences in other months.The peak evapotranspiration of water bodies occurred in June,July and August,and the peaks of evapotranspiration in other regions were almost all concentrated in late July.The spatial distribution of evapotranspiration in the study area was significant.The evapotranspiration of the water body was significantly greater than that of the vegetation area,and the evapotranspiration of the vegetation area was significantly higher than that of the bare land area.(3)The relationship between evapotranspiration and meteorological factors:In 2014 and 2015,the evapotranspiration in the study area increases linearly with the increase of the vapor pressure difference,increases exponentially with the increase of atmospheric temperature,and increases exponentially but relatively slowly with the increase of the net solar radiation.(4)The relationship between evapotranspiration and land surface factors:In 2014 and 2015,the evapotranspiration and normalized vegetation index in the study area showed positive correlations on both spatial and temporal scales;On the above,there was a non-linear correlation,and the evapotranspiration showed a trend of increasing first and then decreasing with the increase of the temperature vegetation drought index,and the increasing trend was relatively weak.However,they do not show a linear or nonlinear relationship on the time scale.