SATELLITE CLIMATOLOGY OF AFRICAN DUST TRANSPORT IN THE MEDITERRANEAN ATMOSPHERE

A daily analysis of African dust concentrations in the Mediterranean a tmosphere has been made between June 1983 and December 1994 using the International Satellite Cloud Climatology Project (ISCCP-B2) archive o f Meteosat visible (VIS) channel images. The ISCCP-B2 archive of Meteo sat infrared (TR) images has also been used to determine the frequenci es of dust mobilization over the continent, north of 30 degrees N. Des pite a large daily variability, climatological results show a clear se asonal cycle with a maximum during the dry season: dust transport begi ns over the eastern basin in spring and spreads over the western basin in summer. These patterns are shown to be related to both cyclogenesi s over North Africa and rainfall over the Mediterranean Sea. Indeed, t he frequency of dust mobilization over the continent and of dust outbr eaks over the sea are strongly related to the climatology of depressio ns affecting North Africa. Precipitations appear to be an important fa ctor explaining both the seasonal east-west shift in transport locatio n and the south-north gradients of dust concentrations over the Medite rranean.