Abstract
Identifying the shortwave solar radiation, R-s, is very important in various fields of science which is calculated by mathematical models if not measured experimentally. These models depend on the coastality factor, k(r). Several equations are developed to calculate k(r) but with errors of estimation. The aim of this paper was to develop a local formula to calculate k(r) from temperature range. Based on the 30-year climate data for 29 weather stations throughout the Kingdom of Saudi Arabia (KSA), monthly temperature ranges were calculated. The hyperbolic equation was derived based on the best-fit analysis and the resulted errors of four statistical parameters were compared with any other established formula. The average of the absolute percent error was estimated as 2.1% as compared with 6-11% of the various published models. Results show that k(r) is inversely proportional to the distance from the coast and the altitude. In addition, it was found that urbanization has a considerable effect on k(r) and the noncoastal but high-population cities behaved similar as coastal cities. It is recommended to use the proposed equation due to its accuracy for the KSA instead of using other models. More research is needed to further investigate the effects of urbanization on the k(r).