Uses of sunshine duration to estimate the global solar radiation over eight meteorological stations in Egypt

The climatological Angstrom regression coefficients have been determined by three methods and used to predict the global solar radiation over eight meteorological stations. Each of the three methods depends on the correlation between two ratios. The first ratio is between the long period of monthly average sunshine duration (s) over bar and the corresponding maximum of daily sunshine duration (day length) N, and the second ratio is between the measured monthly average daily global solar radiation (H) over bar and the corresponding monthly mean daily extraterrestrial solar radiation on the horizontal surface (H) over bar(0). A comparison between the measured data and the estimated values has been done. The t-statistics is used as a statistical indicator to choose the coefficients of the best method that gives a percentage of error less than 10%. (C) 2000 Elsevier Science Ltd. All rights reserved.