Optical properties of desert aerosol –I–

The desert aerosol plays a very important role in the atmospheric evolution as well as in the climate change. In this study, we present the results of the optical thickness, the single scattering albedo and radiative forcing of desert aerosol. These main optical parameters will be analyzed for six sites covering the main desert areas such as, Ouarzazate and Oujda (Morocco, North Africa), Tamanrasset (Algeria, North Africa), Dalanzadgad (Mongolia, Asia), Birdsville (Australia) and Frenchman-Flat (Nevada, West of United States). The annual cycle of the aerosol optical thickness daily averages shows variable values due to the changeable weather and the Sahara source. The maximum values were recorded at the Sahara site (Ouarzazate, 3.04; Tamanrasset, 2.76). The single scattering albedo daily averages ranges from 0.36 to 0.99 at Ouarzazate and Birdsville, and registers high proportional values at Oujda and Tamanrasset. The daily averages of Aerosol Radiatif Foricng at surface ranged from -375W/m² to -2W/m², being larger in spring and summer than in the rest of season. The seasonal ARF evolution was inconsistent with seasonal aerosol optical depth variation due to the effects induced by other aerosol parameter such as the single scattering albedo. The ARF at top of the atmosphere changed from +40 W/m² to -75 W/m². These results suggest that the Simpson dust caused local atmospheric heating over the Birdsville and also Saharan dust over Ouarzazate.