A SIMPLE-MODEL FOR ESTIMATING MONTHLY MEAN DAILY SUMS OF SOLAR IRRADIATION AND ITS LOCAL-DISTRIBUTION

This paper deals with linear correlations between solar irradiation su ms and sunshine duration for mapping global, diffuse and direct irradi ation. All values represent long-term averages of monthly mean daily s ums. The first part of this paper describes a set of fourteen correlat ion equations based on an earlier study. The constants of all correlat ions depend on a common numerical triple that describes the climatic c onditions. The constants, correlation coefficients and the triple are determined and discussed with reference to the example of two stations in the Federal Republic of Germany. In the second part, a general met hod for generating solar irradiation maps is proposed and applied for the state of North-Rhine Westphalia (FRG). The distribution of global and diffuse irradiation in terms of yearly averages is shown and discu ssed. (C) 1997 by John Wiley & Sons, Ltd.