The SEBAL Model For Estimating Evapotranspiration In The Jing He Oasis In Xinjiang

Evapotranspiration is an important basis for the allocation and utilization of water resources,and is also the basis for surface water interaction. Estimate intensity of evapotranspiration activity within the region, it has a very unusual significance and plays an important role in analyzing the energy balance of the process of surface water activities and land surfaces within the region.Combining meteorological measuring data with satellite remote sensing data to retrieval evapotranspiration is a feasible method to get regional actual evapotranspiration rapidly,and it was identified by many researchers.Taking JingHe River Oasis as the study area, based on September 25,1998, September 18, 2007,September 13, 2011 three Landsat₅ TM image data,using remote sensing technology to build model SEBAL, inversing evapotranspiration of spatial variation in area,trends and its mainly impacting factors.Research indicates:（1） Using Landsat₅ TM image inversing model needs some surface parameters :normalized difference vegetation index（NDVI）,surface emissivity,sueface albedo and land surface temperature, theirs values are: normalized difference vegetation index（NDVI）-0.01-0.99,surface emissivity 0.906-1.01,surface temperature 285.6-339.4K,surface albedo 0.02-0.51.And analysis temporal distribution characteristics of these four parameters, Surface emissivity,surface temperature, and surface reflectance minimum value in Aibi Lakes,normalized difference vegetation index（NDVI） and surface emissivity highest in the middle of the study area.（2） Model-based SEBAL, Inversion satellite transit time（September 25, 1998, September 18, 2007 and September 13, 2011） fluxes of energy balance, Analysis spatial distribution and pixel distribution histogram of the four fluxes. In the study area, surface net radiation flux and latent heat flux are higher,thermal flux are lower. Mean value of the four flux are: surface net radiation flux 947.9 w / m2,917.7 w / m2,914.9 w / m2; soil heat flux 62.03 w / m2,89.12 w / m2,85.62 w / m2; thermal flux 363.79 w / m2,431.47 w / m2,382.39 w / m2; latent heat flux 517.5 w / m2,392.3 w / m2,442.1 w / m2. According to inversed parameters and fluxes, getting the date spatial distribution of evapotranspiration in study area by the time-scale expanded.（3） Precision verification of inversion daily evapotranspiration was by Penman – Monteith,results show that the error is within a reasonable range, then analyzed the temporal and spatial variability of daily evapotranspiration.Combining land use classification map, analyzed features of daily evapotranspiration in different land use types, Day evapotranspiration of Jinghe Oasis is now published: adequate moisture, maximum daily evapotranspiration is in surface temperature stable Aibi Lakes, minimum daily evapotranspiration is in place which less vegetation covered or without vegetation covered.Natural factors normalized difference vegetation index（NDVI） and regional relations instantaneous evapotranspiration basic parabola, surface temperature and surface albedo and evapotranspiration study area is inversely related to the instantaneous relationship, show the Water is the decisive factor indicates of evapotranspiration in the arid zone. Human Factors in human activities have more and more influence on the land surface area of land use types, moisture and demographic factors increasing,Small area of local water status, the impact surface temperature and vegetation cover,caused changes in the small area evapotranspiration.