Global solar radiation over Pakistan Comparison of measured and predicted data

Abstract

The estimates of global solar radiation on horizontal surface at Karachi, Lahore, Multan, Peshawar and Queta were calculated using Angstrom formula which correlates relative global solar irradiance H/Ho to corresponding relative duration of bright sunshine n/N?. The coefficient of this relationship were obtained by regression analysis using daily global radiation and sunshine data measured in these cities over a period of eighteen to twenty seven years and twenty seven to thirty four years respectively. The estimated values of global solar radiation H were then compared with the measured values both by graphical an statistical methods based on calculation of Mean Bias Errror (MBE), Root Mean Square Error (RMSE), Coefficient of Correlation (r) and Coefficient of Determination (r) and were found in good agreement. Thus the correlation of Angstrom is the best estimator for global solar radiation over Pakistan.