A correlation for estimation of global solar radiation

We present a simple Angstrom-type correlation for estimating the monthly average daily horizontal global radiation. We have developed this correlation using the bright sunshine and global radiation data of 48 locations around the world, with varied meteorological conditions and a wide distribution of geographical locations. Our study shows that this correlation provides good estimates of solar radiation. We have also statistically compared the performance of our correlation with Rietveld's equation, which is believed to be applicable anywhere in the world and has been found by Ma and Iqbal (1984) to give better estimates than other published correlations. Our correlation yields better estimates than Rietveld's equation for a majority of the stations considered.