The relationship between total solar radiation and biologically erythematic radiation over urban region of Egypt

Abstract

Abstract This work studies the relationship between the effective of erythematic radiation (EER) and the total solar radiation ( G ) from urban region of Egypt. The measurements of total solar radiation ( G ) and biologically effective erythematic radiation (EER) incident on a horizontal surface at Cairo, Egypt (lat. 30°05′N and Long. 31°15′E), during the period time (1990–2010) are used. The relationship between hourly mean and daily mean of EER and the hourly mean daily mean totals of broadband total solar radiation is presented. The average hourly monthly mean variation of slant ozone Z and UVB transmission K tUVB at the present work are found. The relation between the two variables slant ozone Z and UVB transmission K tUVB show an opposite seasonal behavior, the low values of the slant ozone column during summer time produce high UVB transmission values in this season. The apposite pattern is observed during the winter. The Seasonal Statistical values of regression equations; the slopes ( β ), intercepts ( α ) and the standard errors (SE) for the fitted lines. The minimum slope occurs in winter, indicating that the percentage reduction in EER at higher SZA is larger than G . The variations of the slopes ( β ) during the course of the year ranges from a minimum of 0.2214 in winter to a maximum of 0.2914 in summer, the intercepts also show their minimum and maximum values in cold humid and hot dry months. The temporal variability of the percentage ratio of the total hourly mean daily erythema to total hourly mean daily broadband solar global irradiation (EER/ G ) is presented. The estimated values of UVB solar radiation a good agreement with the measured values of the UVB solar radiation, the difference between the estimated and measured values of UVB solar radiation varies from 2.3% to 3.6%.