Estimation of Evapotranspiration in Beijing using Modified SEBAL

摘要

Without direct consideration of the terrain factors (slope, aspect and elevation), the original SEBAL (Surface Energy Balance Algorithm for Land) is applicable mainly to plain area. Variables such as roughness length for momentum transport and soil heat flux are computed based on the relationship with surface temperature, NDVI (Normalized Difference Vegetation Index) and surface albedo. However, in the original SEBAL, a uniform empirical formula is utilized for the whole study area, which cannot fully reflect the variation of underlying surface. In this study SEBAL is improved by successfully coupling Digital Elevation Model (DEM) into the model for topography correction and formulated empirical formulas which vary with land use/cover types. Based on the landsat TM images, daily ET on June 23, 2005 in Beijing was estimated. The results indicate that retrieval ET by the modified SEBAL is more reasonable in the spatial distribution, being consistent with the complexity of land use/cover.