Remote Sensing Estimation Of Evapotranspiration In Qilian Mountains Based On Landsat - 5

Evapotranspiration on the underlying surface is the basic of interactions betweenatmosphere and waters, and is important to the biosphere of earth evolution anddevelopment. Efficient estimation of regional evapotranspiration is very important tounderstand the water cycle and energy balance in a region. Remotely sensed datacombined with some amounts of meteorological data for estimating regionalevapotranspiration is considered to be a viable method that efficient and fast estimatethe actual evapotranspiration.This article based on the energy balance model and Landsat5-TM image data forestimation and analysis of daily evapotranspiration in Qilian Mountains.Understanding the distribution of water and energy distribution regularity of QilianMountains in depth, and water resources, meteorology and relevant research resultshas been further improved, then promote the rational use of water resources inresearch area, and provide basic information for the study about Qilian Mountainsecological water demand and other related research. It will contribute to scientificallyand roundly understand the natural environment of Qilian Mountains in the WestChina and predict its change tendency. It also plays an important role to the ecologyand rational management of water resources in Qilian Mountains protection.Using energy balance model as the regional remote sensing estimateevapotranspiration method, can requires less relative parameters, only needs imagesdata of remote sensing，DEM data and small numbers of meteorological data, and itwill accurately estimate instantaneous surface evaporation at the time of remotesensing image acquisition, and then obtains day steamed bulk volume of researchdistrict through the expansion of the time scale.After studying the regional evapotranspiration of Qilian County in2007/8/13,2009/7/17and2010/8/5, energy balance model for diurnal evapotranspiration ofinversion in the region were more exactly, its precision evaluation is4.23%, requiredthe demand on accuracy of evapotranspiration in the region, can be used in theestimation of evapotranspiration in the region.Through the analysis of the daily evapotranspiration results found that theregional evapotranspiration has the obvious temporal variation characteristics. The evapotranspiration estimates value in flat flood plains of Tuole River region betweenTuole Mountains in northwest and Tuole Nan Mountains and the evapotranspirationestimates value in flood plains of Hei River between Central Corridor Nan and TuoleMountains is lower, the evapotranspiration estimates value in region of ZhamashengRiver in Northeast is high; the Distribution of evaporation in the mountains top ishigher than in the lower region.Different land use pattern has the different evapotranspiration. the evaporation inthe different land use type is different, for specific performance,the evaporation in icesnow is more than in swamp, in woodland, in bare soil bare rock gravel, in waters, ingrassland, in farmland, in urban and rural. Among them, the evaporation in ice snowand bare soil bare rock gravel have obvious changes, its daily evapotranspirationreduced with glaciers shrink. The daily evapotranspiration of cultivated land related tothe crop growth cycle, and is same as the grass in the normal growth, but is lower thanthe grass after the harvest.The evaporation is also has obvious relationship with the slop direction. Throughthe zonal statistics of evaporation by aspect, the evaporation in direction from240to270is reach to the maximum.The correlation between evapotranspiration in region and the surfacecharacteristic parameters is obvious. The study found that the daily evapotranspirationand surface emissivity have positive correlation relationship, and the coefficient ofassociation is0.5. The correlation relationship between the daily evapotranspirationand NDVI is same to the above-mentioned. But between the daily evapotranspirationand surface temperature has negative correlation, the coefficient of association is-0.9and-0.4.The daily evapotranspiration and surface albedo have same negativecorrelation.