Performance Evaluation of Different Radiation Models for Sub Humid Region

This study aimed to Performance of six radiation models. The objective was to determine the most accurate model for estimating solar radiation. Performance Evaluation of all the models on the same basis is prerequisite for selecting an alternative approach in accordance with available data such as air temperature (Tmax, Tmin, Tmean), actual sunshine hours(n) and potential sunshine hours (N). Therefore, recommended Angstrom-Prescott (A-P) model, locally calibrated A-P model, Chen et al. (2004), Ertekin and Yaldiz (1999), Togrul-Onat (1999), Almorox - Hontoria (2004) and Ogelman et al. (1984 ) radiation based model were used to estimate monthly solar radiation (Rs) at Pantnagar (Uttarakhand), India. Further, the performance of all these methods were evaluated by regression and error analysis between standard Rs derived using FAO recommended Angstrom-Prescott (A-P) model and Rs values estimated using all the five models, on monthly basis. On monthly basis, Almorox - Hontoria (2004) model performed best with lowest Root mean square error (0.1178) MJ m−2 day−1 and high coefficient of determination (0.997). Based on overall results it was concluded that the radiation based model provides average monthly accurate estimate of solar radiation compared to other models.