Influence of Urban Aerosol on Spectral Solar Irradiance

Abstract From a dataset of spectral distribution of global and disuse solar irradiances measured in Barcelona during the last three years, the influence of turbidity caused by urban aerosol on spectral composition of solar radiation and transmissivity of urban atmosphere has been determined for cloudless conditions. The effect of urban aerosol is remarkable, mainly in the ultraviolet (UV) part of the spectrum, where attenuation of global irradiance surpasses 25% on very polluted days. The increases in diffuse UV irradiance caused by aerosols ranges in the interval 4%–50%, while this increase ranges from 20% to 250% for the whole solar spectrum. Comparison of spectral irradiance observed for different turbidities with various models shows a good agreement, mainly in the UV and visible spectral regions. Erythemally effective irradiance, that is, a biological measures of the sunburning power of solar radiation, has also been calculated for different aerosol concentrations, giving values in the range of 0.15–...