Estimate of the direct radiative effect of mineral dust

The assessment of the direct radiative effect of mineral aerosols requires the use of a radiative transfer code initialized by the vertical profiles of their concentrations, physico-chemical (composition, size and shape) and optical (scattering and absorption) properties. The physico-chemical properties can be determined from measurements at the ground or onboard research aircraft during intensive campaigns. This was especially conducted in West Africa in the AMMA project and associated campaigns [McConnell et al., 2010]. These properties can also be inferred by inversion of remotely-sensed data: for example, the inversion of measurements of the sun photometer from the AERONET network has been used to study the seasonal variability of aerosol in Cairo and its radiative impact [El-Metwally et al., 2009; 2010].

The distributions of radiative forcing at the surface (RFBOA) and the top of the atmosphere (RFBOA) derived from photometric measurements carried out in Cairo and Alexandria (Egypt) illustrate the cooling effect linked to the presence of high concentrations of desert aerosols in this region. (From El-Metwally et al., 2010)