Simulating The Evapotranspiration Of Bayanbuluk Alpine Meadow By Remote Sensing

This paper combined meteorological data of weather station,digital elevation model data with MODIS data of land surface temperature,normalized difference vegetation index and surface albedo to research the daily actual surface evapotranspiration.We used the Surface Energy Balance Algorithm for Land model to investigate the evapotranspiration of different growing seasons that were concentrated 2000,2007 and 2014 in Bayanbuluk Alpine Meadow located in the middle of the southern slope of Tianshan.Moreover,using the FAO Penman-Monteith equation recommended by Food and Agriculture Organization to verify the evapotranspiration simulated by the SEBAL model.Based on the simulated results,we used coefficient of variation method and correlation analytic method to investigate the spatial pattern of evapotranspiration,characteristics of time variation,spatial heterogeneity and spatial relativity considering the study region.This paper mainly drew five innovative conclusions.1.The R square and root mean square error of evapotranspiration simulated by SEBAL model and FAO Penman-Monteith equation are 0.7047 and 0.3676 respectively.Meanwhile,the mean relative error of different growing seasons ranged from large to small in the order of last growing stage,freezing stage,early growing stage,and growing stage.2.For the spatial pattern of evapotranspiration,there was a significant high and low value center in the region.Under the influence of soil humidity and vegetation coverage,the value of evapotranspiration in the Yultuz Basin and lower mountain belt was higher than that in the Yanqi Basin and higher mountain belt.Moreover,affected by artificial cultivation and irrigation,the spotted evapotranspiration of Yanqi Oasis was high.3.1)For the characteristics of time variation,evapotranspiration over the entire region arranged from high to low were 2000,2007,and 2014.Meanwhile,the evapotranspiration for the entire region showed a slight seasonal fluctuation,the degree of fluctuation ranged from large to small in the order of 2000,2007 and 2014.2)For the part of seasonal variation,the highest average evapotranspiration appeared in July over the three years,that is,the highest level of evapotranspiration was in summer.But the lowest average evapotranspiration appeared in September or October,that is to say,the lowest level of evapotranspiration was in autumn.At the same time,the highest standard deviation of evapotranspiration appeared in July,that is,the highest degree of fluctuation of evapotranspiration was in summer.But the lowest standard deviation of evapotranspiration appeared in September or October,that is,the lowest degree of fluctuation of evapotranspiration was in autumn.3)For the part of vegetation growing seasons,the evapotranspiration was low in the freezing stage,rapidly increased in the early growing stage,was high in the growing stage and rapidly fell off in the last growing stage.4.For the part of spatial heterogeneity of evapotranspiration,the degree of variation in evapotranspiration over the 3 years showed an obvious fluctuation.The proportion of areas with different volatility degree ranged from large to small in the order of higher variations,the unidentified,relatively higher variations,medium variations,relatively lower variations,and lower variations.Moreover,under the influence of seasonal rise and fall of natural vegetation,the higher variations of evapotranspiration mainly in the Yultuz Basin.However,the higher variations of evapotranspiration mainly in the Yanqi Oasis where the leaf area of crops in diverse phenological phase and soil moisture of cultivated land was obviously different.5.For the part of spatial relativity of evapotranspiration.In the first place,there was a negative linear correlation between evapotranspiration and land surface temperature,the interdependency in different growing seasons from large to small follows the order of last growing stage,growing stage,early growing stage,and freezing stage.Secondly,there was a negative linear correlation between evapotranspiration and normalized difference vegetation index in freezing stage,early growing stage and last growing stage.Moreover,the interdependency from big to small are last growing stage,early growing stage,and freezing stage.However,the linear correlation between evapotranspiration and normalized difference vegetation index was obviously positive in growing stage.Finally,there was a positive linear correlation between evapotranspiration and surface albedo.Moreover,the interdependency ranged from large to small in the order of freezing stage,last growing stage,early growing stage,and growing stage.