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Validation and calibration of solar radiation equations for estimating daily reference evapotranspiration at cool semi-arid and arid locations

Tabari, Hossein, Hosseinzadehtalaei, Parisa, Willems, Patrick, Martinez, Christopher
Hydrological sciences journal 2016 v.61 no.3 pp. 610-619
equations, evapotranspiration, models, semiarid zones, solar radiation, Iran
In this work, the applicability of 12 solar radiation (R S) estimation models and their impacts on daily reference evapotranspiration (ET ₒ) estimates using the Penman‐Monteith FAO-56 (PMF-56) method were tested under cool arid and semi-arid conditions in Iran. The results indicated that the average increase in accuracy of the ET ₒ estimates by the calibrated R S models, quantified by the decrease in RMSE, was 2.8% and 6.4% for semi-arid and arid climates, respectively. Mean daily deviations in the estimated ET ₒ by the calibrated R S equations in semi-arid climates varied from −0.283 mm/d ⁻¹ for the Glover‐McCulloch model to 0.080 mm/d for the El-Sebaii model, with an average of −0.109 mm/d ⁻¹, and in arid climates, they ranged from −0.522 mm/d ⁻¹ for the Samani model to 0.668 mm/d for the El-Sebaii model, with an average of 0.125 mm/d ⁻¹.