Evaluating efficiency of empirical estimation reference evapotranspiration (Pan based method) in different climate conditionss (Case Study of Iran)

In this research, daily meteorological data for 15 years (1999-2013) were used in 153 synoptic stations throughout the Iran country to determine the best estimation methods for evapotranspiration of reference plant among pan evaporation methods for different climate conditions. For the total synoptic stations of the country, evapotranspiration was calculated from 12 evaporation pan methods, and the FAO-Penman-Monteith method was used as the standard for evaluating with pan methods. RMSE, MBE, R2 and t tests were used to evaluate the accuracy of the methods. The final results showed that in two arid and semi-arid climates, Mohammad et al , FAO-24 (in dry conditions) and Christensen methods were the most suitable methods and different methods as Schneider, Allen and Prout, Ragvanshi and Waldner were the most inappropriate methods. For the Mediterranean climate condition, Mohammed et al, Konica and Schneider were the most appropriate methods and Pereira's, FAO-24 (in dry conditions), Ragvanshi and Waldner were identified as the most inappropriate methods. In the semi-humid climate, the modified Schneider method, Allen, Prout, and Pryira were the most appropriate methods and Mohammad et al, FAO-24 (in dry condition), Ragvanshi and Waldner and were the most inappropriate methods. In the wet and humid climates conditions, modified Schneider method, (Alan et al 1998) were the best and Pryira, FAO-24 (in dry conditions) and Mohammed et al, Ragvanshi and Waldner methods were the worst methods respectively. Moreover, Finally, comparing the results of lysimetric studies in semi-arid climate confirmed the selected methods.