Spatial and temporal variability of windborne dust in the Sahel-Sahara zone in relation with synoptic environment

Abstract

Windborne dusts have been recognised as climatic indicators in the Sahel region, because of their ability to cause reduction in horizontal visibility. These phenomena have intensified after the exceptionally drought periods in the 1970s over the Sahel region. In this work, we have analysed the spatial and temporal evolution of visibility reduction in the Sahel-Sahara zone between 1957 and 1987. The results showed that windborne dusts were more frequent and severe over the western coast of West Africa. The zone characterised by the maximum variability included largely, the Sahel region (15° to 20°N). Stations in this region were characterised by a progressive reinforcement of suspended windborne dust between 1970 and 1987. Dust emissions in the Sahelian region increased during dry years and were associated with weak monsoon flux, African Easterly Jet (AEJ) reinforcement and weak Tropical Easterly Jet (TEJ).