Estimate of potential evapotranspiration in Freiman using the priestiley-taylor method and remote sensing technique

Evapotranspiration is one of the important components of water balance which is measured and estimated by several methods. Since these methods mainly involve point-by-point measuring and requiring a large amount of grounded data, so they have limitations. In this study, potential evapotranspiration for 8 days in 2014, 2015 and 2016 was estimated using the Priestley-Taylor method and remote sensing technique in Fariman area in Khorasan Razavi province using Landsat 8 Operational Land Imager (OLI). To determine the accuracy of the estimates, the results of this study were compared with the FAO Penman-Monteith method (the reference method for estimating potential evapotranspiration). Comparison of the obtained results by the Priestley-Taylor method with the FAO Penman-Monteith method showed that the R2 and Root Mean Square Error (RMSE) are 0.91 and 0.78 mm/d, respectively. This result indicates that the high accuracy of this method in estimating potential evapotranspiration in a semi-arid climate.