Net radiation (Rn) is one of the effective inputs for controlling soil heat flux, thermal convection, moisture flux exchange, and reference crop evapotranspiration (ET0) rate. In this research, the accuracy of some empirical and semiempirical Rn models is examined for different climates of Iran versus the recommended net radiation model as proposed in the Penman–Monteith Food and Agricultural Organization of the United Nations 56 standard (FAO 56) model for the period 1980–2007. For estimating daily net radiation, various net radiation models [Wright, basic regression model (BRM), Linacre, Berliand, Irmak, and Monteith] were examined. Model evaluations were implemented for four climate types. On regional averages, the linear BRM had the superior performance in generating the most accurate daily ET0. Results showed that for 70% of the study sites, the linear Rn models can be reliable candidates instead of sophisticated nonlinear Rn models, which are proposed in the reference FAO 56 model. For some sites, with low altitude and high relative humidity (e.g., coastal humid sites), the Irmak model suggested the minimum deviations from the reference FAO 56 model. Using the best-performing Rn models is recommended for the agricultural sites where comprehensive weather data are not available. DOI: 10.1061/(ASCE)IR.1943-4774 .0001080. © 2016 American Society of Civil Engineers.
