General circulation model experiments with surface albedo changes

In 1975, Charney proposed a biogeophysical feedback mechanism to partly explain the droughts that occur in desert border areas. He showed that a perturbation of albedo (due to a natural or anthropogenic decrease of vegetation) can be unstable and lead to a variation of precipitation in the region where albedo is changed.Several numerical experiments have been achieved with general circulation models to study the sensitivity of climate to surface albedo. We compare the GLAS and LMD model results for the Sahel. For all models, rainfall decreases when albedo increases and net radiative heating of soil decreases. We show the variations of circulation simulated by the LMD model that we obtain when albedo is increased. These changes are compared to the weakening of Easterly Jet at 200 mb observed during dry years.