Estimation of land surface evapotranspiration using MODIS data

Evapotranspiration (ET)affects the transportation of the water and energy of land surface. Based on the principle of the atmospheric radiative transferring, the instantaneous solar radiation was estimated firstly with an atmospheric transmittance model and the content of ozone, water vapor and aerosol optical thickness at 550 nm provided by MODIS products. The root mean square error(RMSE) of the incident solar radiation was 61.4 W/m2, while it was 112.1 W/m2 with FAO-56 transmittance function. Based on the transmittance model, land surface temperature, vegetation index of MODIS products were used to estimate land surface evapotranspiration. The results show that the instantaneous sensible heat flux has a good agreement with the observation of large aperture scintillometry (LAS) in Zhengzhou, and the RMSE was 29.9 W/m2. The RMSE of daily ET estimated with atmospheric transmittance model was 73.2 W/m2, while it was 107.1 W/m2 with FAO-56 transmittance function. The precise estimation of transmittance can obviously improve the precision of ET estimation.