Enhancement of Interdecadal Climate Variability in the Sahel by Vegetation Interaction.

The role of naturally varying vegetation in influencing the climate variability in the West African Sahel is explored in a coupled atmosphere-land-vegetation model. The Sahel rainfall variability is influenced by sea-surface temperature variations in the oceans. Land-surface feedback is found to increase this variability both on interannual and interdecadal time scales. Interactive vegetation enhances the interdecadal variation substantially but can reduce year-to-year variability because of a phase lag introduced by the relatively slow vegetation adjustment time. Variations in vegetation accompany the changes in rainfall, in particular the multidecadal drying trend from the 1950s to the 1980s.