Optical properties of desert and urban aerosol

Aerosol optical properties are of high importance in understanding the evolution of radiative balance; they can also explain the atmospheric evolution and then the climate change. This study is focused on the data analysis of aerosol optical characteristics: aerosol optical depth, particle size distribution, aerosol radiative forcing and single scattering albedo registered by the network AERONET/PHOTONS for urban and desert sites .The monthly average of volume concentrations records larger amplitudes for fine and coarse mode for Ilorin (Nigeria) for which the total volume concentrations of an atmospheric column reach 424 10-3µm3 /µm2 and confirm the importance of urban aerosols. In other way, desert aerosol where coarse mode dominates like Tamanrasset registers 265 10-3µm3 /µm2. The seasonal cycle of optical thickness in visible and infrared show the highest values for the desert sites especially in spring and summer, a maximum reach 3,6 at Mezaira (UAE), These largest values are associated with the highest values of SSA in visible and infrared that reach 0, 93. The atmospheric radiative forcing seems with the same importance for both urban and desert sites, maximum reaches +84 W/m2 recorded in Tamanrasset (Algeria) and +79 W/m2 in Ilorin (Nigeria). The results confirm the warming tendency of the Atmospheric radiative forcing under both urban and desert sites.