Construction of a quadratic model using modified Ångstrom coefficients to estimate global solar radiation

In this paper, a new correlation for the estimation of monthly average daily global solar radiation will be presented and compared with the correlations of Rietveld, Benson et al., Ögelman et al., and a recent formulation by Gopinathan. The overal results show that the quadratic form gives better performance in terms of global applicability. The new quadratic model should be preferred for the monthly average global solar radiation estimation when the data for bright sunshine hours are available.