Research Of Evapotranspiration In Qitai County, Xinjiang Based On MODIS Data

It is a very complicated problem to estimate the evapotranspiration of large area. In order to make the regional distribution map of evapotranspiration, this article takes Qitai as an example, based on DEM and remote sensing image (MODIS), combining ARCGIS with remote sensing software (ENVI), meanwhile, considers influent factors, such as terrain, latitude and elevation to carry on the comparatively accurate space inserting value. This article offers the comparatively accurate space data of evapotranspiration for the agriculture, land utilization, climatic divide of Qitai County.In the process of estimating the area evapotranspiration, we can get a lot of meaningful components, these components have the following aspects: Characteristic parameter of earth's surface (NDVI, surface albedo, surface temperature); the earth's surface radiation balances (surface shortwave radiation, surface longwave radiation, atmospheric longwave radiation, surface net radiation); The earth's surface energy balance (soil thermal flux, sensible heat flux, latent heat flux). At the same time, it draws the distribution map of its each components and discusses these distribution maps, these make people have an ocular and comprehensive understanding about regional surface characteristic, surface radiation and energy balance of Qitai county.By analysing the distribution maps of evapotranspiration, we can get following conclusions as follows: The distribution of evapotranspiration has clear zonality. The high value zone of evapotranspiration is mainly in the Northeast and the south of hilly region in studying area where has higher Vegetation Coverage, Irrigation areas of farming region, the artificial Vegetation protection area of desert and Gobi; The low value zone of evapotranspiration is mainly in desert and Gobi, the distributive characteristics of these components in the areas differ from arounding region. This research still finds the vegetation coverage has a large influence on the evapotranspiration of underlaying surface.In a situation that there has no test evapotranspiration (ET) data, in this paper, we use the result that calculated by FAO-PM equation as comparison.