Comparing actual evapotranspiration rates derived from MOD16 product and simulated using SWAP model (Case study: Corn fields in Qazvin Province)

Nowadays, evapotranspiration, which is an important component of water balance calculations, can be estimated using the technology of remote sensing. MOD16 actual evapotranspiration data are produced using the MODIS sensor imageries and have a spatial resolution of 1 Km. In the present study, MOD16 actual evapotranspiration data are compared with the actual evapotranspiration estimated using SWAP model. Using the measured soil moisture content data during the growing season in two 38.9 and 45.6 ha corn fields located in Qazvin Province, SWAP model was calibrated. The average RMSE values in the two fields under study were, respectively, 0.026 and 0.025. Considering the actual evapotranspiration estimated by the SWAP model as the evaluation basis, the MOD16 data were assessed. In this assessment, the RMSE values in the two fields under study were obtained, respectively, 1.46 and 1.94 mm/day. Also, the r2 values were calculated 0.86 and 0.87. The results of the present study suggest that MOD16 product can be effectively used when the measured data of evapotranspiration are not available.