Prediction of Clear-Sky Biologically Effective Erythematic Radiation (EER) From Global Solar Radiation (250-2800 nm) at Cairo, Egypt

This work studies the effective of erythematic radiation (EER) from urban region of Egypt. The hourly and daily measured clear-sky global solar radiation (G) and biologically important effective erythematic radiation (EER) incident on a horizontal surface at Cairo, Egypt (lat. 30° 05’ N & Long. 31° 15’ E), during 1995-2005 are used. A linear relationship is established between daily integrated totals of EER and the daily totals of broadband global solar radiation (300-3000 nm). A good linear correlation between the daily G and EER was found. The observed (G) data is a routine meteorological measurement at many meteorological stations and such a relationship would enable estimates of the daily EER to be made from accessible records. The seasonal variability of EER/G is also discussed. The effect of the annual cycles of solar zenith angle (SZA) and total column ozone (TCO) on the ratios (EER/G) are presented and the correction factors are determined for removal of the ozone cycle. The recommended correlation equation enables the prediction of daily values of EER radiation from broadband solar radiation (G) in urban climates, where spectral UV measurement is not available.