Sensitivity of ultraviolet solar radiation to anthropogenic air pollutants and weather conditions

The main objective of this study is to shed light on the influence of air pollutants on the ultraviolet (UV) radiation reaching the earth surface. A short discussion of the role played by weather conditions in determining the levels of the UV radiation is also given. The atmosphere of Cairo was chosen for the polluted case. On the other hand, Aswan and El-Kharga were chosen for the clarity of the atmosphere. To ensure that the fraction of the seasonal variability induced by the variation of the solar zenith angle (SZA) is removed from the UV time series, all data were separated into subsets of data corresponding to the selected SZA. According to the results obtained, the annual value of the UV radiation tends to decrease as the year pass. This is partly because air pollutants, can reduce the increased levels of UV radiation by 39.6% (relative to background value), and explains why the expected UV increases have not been observed. (C) 2006 Elsevier B.V. All rights reserved.