Evaluation of 24 models of reference evapotranspiration in different climates of Iran

There are various methods for estimating evapotranspiration, in which the performance of these equations varies in different climatic conditions. The purpose of this study is investigate different methods of evapotranspiration of reference plant in different climates of Iran and validate these methods by FAO-Penman-Monteith method. For this, 30-year weather data (1988-2017) were used in nine cities (Shahrekord, Urmia, Mashhad, Zahedan, Bandar Abbas, Ahvaz, Gorgan, Rasht and Sari). Initially, evapotranspiration was obtained by the FAO-Penman-Monteith method on a daily basis. Then reference evapotranspiration values were calculated with 24 other methods. Using RMSE, (MAE), (MR) and (PE) with the method FAO-Penman-Monteith. The results showed that in cold and semiarid, cold, moderate, warm and dry, cold and dry, warm and humid conditions, there were Urmia, Shahrekord, Zahedan, Mashhad and Ahwaz, modified Makking models, in warm and humid climate of Bandar Abbas, respectively. The Voluntzas model and in the Mediterranean, semi-wet and humid climates including Gorgan, Sari and Rasht, the Druggerz and Allen model had a better and closer estimate by the FAO-Penman-Monteith method.Regarding the scores given to each method based on the MAE and RMSE evaluation index, modified Makking models, Derrgger and Allen, Valiantzas and Hargreaves Samani and based on the index PE models and Reynolds and Allen, McQueen modified, Valiantzas and Hargreaves Samani were selected as superior models.