The analysis of solar UVB radiation as a function of solar global radiation, ozone layer thickness and aerosol optical density

Incident solar radiation (insolation) is attenuated by two different phenomena, (i) atmospheric scattering by air molecules, water vapor and aerosols, and (ii) atmospheric absorption by ozone, water and carbon dioxide. The degree of terrestrial solar radiation attenuation is a function of its optical path length, i.e., the distance the Sun’s ray traverse through the Earth’s atmosphere prior to being incident on the its surface. The attenuation by atmospheric scattering, irrespective of source, is an inverse function of the wavelength. Absorption of insolation in the atmosphere is due mainly to ozone in the ultraviolet range and water vapor in the infrared range of the solar spectrum. Ozone absorption decreases with increasing wavelength and above 350 nm there is no absorption. Thus, a priori, any changes in either the ozone layer thickness (OLT) and/or aerosol optical density (AOD) will have a greater effect on ultraviolet radiation, in general, and on UVB in particular. An empirical correlation that determines the UVB radiation intensity as a function of solar global radiation, OLT, AOD and optical path length as represented by the air mass is presented and validated by an independent database. In addition, a parameter sensitivity study was performed on the empirical correlation using two different methods. The application of the empirical correlation as a function of hour type (i.e., clear, partially cloudy and cloudy) was also investigated.