Study On Spatial And Temporal Distribution Characteristics Of Surface Evapotranspiration And Its Influence Factors In Southern Slope Of Qilian Mountains

Evapotranspire,which plays a important role in water cycle and water resource management,is a important surface parameters in ecological process.Surface evapotranspiration is a important link between terrestrial ecosystem and hydrologic process,and has great influence to local climate,total water resources distribution,and local economy.Therefore,studying the surface evapotranspiration based on remote sensing has important meaning and research value.Using the theory of surface energy balance system from SEBS model,based on the remote sensing data of southern slope of Qilian Mountains on the year of 2000,2005,2010 and 2015,and the observed meteorological data around the study area,this study figured out surface physical parameter and land surface heat fluxes of the southern slope of Qilian Mountains and estimate its surface evapotranspiration.And then,using FAO Penman-Monteith model,calculated the reference evapotranspira t io n of the study area,and verified calculation results by SEBS model.At last,analyzed the spatial and temporal distribution characteristic and the influence factor of surface evapotranspiration.(1)The spatial and temporal distribution characteristic of the annual surface evapotranspiration of study area: as for temporal distribution,the annual surface evapotranspiration of study area generally show a “V” shape,which means the largest evapotranspiration appeared in summer,followed by spring and autumn,and winter.As for spatial distribution,the spatial distribution characteristic of the annual surface evapotranspiration in the southern slope of Qilian Mountains is roughly the same,overall performanced as lowered from southeast to northwest.The half year from summer to autumn and to winter,the low value area expand to southeast gradually.(2)the spatial and temporal distribution characteristic of the interannual surface evapotranspiration of study area: as for temporal distribution,the highest surface evapotranspiration of study area appeared in 2005,and then 2010,the lowest value appeared in 2015,showed a declining trend.As for spatial distribution,the spatial distribution characteristic of the interannual surface evapotranspiration in the southern slope of Qilian Mountains is overall performanced as lowered from southeast to northwest.(3)The influence factor of the spatial and temporal distribution characteristic in study area: within a certain period,the surface evaporation has positive correlation with precipitation.The surface evaporation is increased with the raise of elevation within the range of 2200m~2500m,the area which elevation is higher than 2500 m,the surface evaporation is declined gradually with the raise of elevation,and exists small range of fluctuations at the same time.The area which slope is within 0-45,the surface evaporation is increasing with the raise of slope.The area which slope is above 45,the surface evaporation is declined with the raise of slope.The southeast and northwest of study area is the high surface evaporation value area,and the northeast and southwest is low value area.(4)This paper use the calculation results of meteorological stations in study area by FAO Penman-Monteith model and the calculation results by SEBS model to make accuracy test.The result shows that the error is around 20%.Therefore,using SEBS model to study surface evaporation inversion has certain feasibility.