The role of bright desert regions in shaping North African climate

Abstract

Albedo changes have long been recognized as an important element of land surface - climate interaction in the North African region, despite a general lack of adequate albedo data. Here, a new broadband surface albedo data set derived from a geostationary satellite with a recently developed bidirectional retrieval algorithm is used in a series of two climate simulations with the ECHAM4 general circulation model. We find that compared to traditionally assumed albedo values, the new data improve simulated precipitation over North Africa considerably when compared to observations. The results suggest that a series of large, extremely brigth desert areas suppress the northward advance of the North African monsoon, considerably reducing summer rainfall of the southern Sahara desert margins and the Sahel. The unusually high albedo of the southern Sahara thus implies an even larger impact of desert albedo to the climate of North Africa than previously assumed.