Study On Estimation Of Evapotranspiration In Western Taihu Area Based On MODIS Data

Evapotranspiration is an important process of water cycle and energy cycle, and it is a very efficient and effective way to use remote imagery estimate evapotranspiration of watershed.We select the western lake area as the study area, and choose2009’s MODIS imagery and meteorological data to estimate evapotranspiration of this area through SEBS model. The precision validation results between observed data of weather station and our estimation data show that this SEBS model is suitable for Taihu Lake evapotranspiration estimation work. Meanwhile, we analysis the estimation parameters and the spatial and temporal (S&T) varying pattern of this area. The main conclusions are as follows:(1) We use the split window algorithm to estimate the surface temperature and use Owe formula to compute surface emissivity ratio. Meanwhile, we use the formula proposed by Liang to calculate surface albedo ratio and use the near-infrared band and visible red band to count NDVI figure. Based on the above calculations, we tracked out the surface factors’spatial and temporal distribution features of western lake area.(2) Besides the DEM data, we also use slope, aspect correction and regression analysis to revise surface net radiation, surface temperature and average temperature from topography influence.(3) Relying on SEBS model principle, we use the Matlab software to realize the computation of sensible heat flux, surface net radiation, soil heat flux, latent heat flux and other parameters. Based on that computation results, we calculate the evapotranspiration of western lake. After that, we use the monitoring data of Liyang and Changzhou station to testify the veracity, it turns out that the coefficient indexes are very high (0.73and0.76). Meanwhile, we also use the MODIS evapotranspiration data to testify the veracity, it turns out that the coefficient indexes are also very high (0.61and0.58). At last, the results show that Lakes evaporated most in the research area, and the maximum data can go to5.5mm per day. The second most evaporated areas are the beach, irrigated land, woodland and farmland of Yili County. The conurbation of the study area has the minimum evaporation amount.