Orographic influences on the annual cycle of Namibian stratocumulus clouds

Abstract

The impact of African orography on the persistence and seasonal cycle of Namibian stratocumulus is examined in the context of an atmospheric general circulation model. A control simulation with realistic orography and simulated stratocumulus is compared to a sensitivity experiment, in which African orography is removed. In the absence of orography, stratocumulus incidence off the Namibian and Angolan coast is significantly reduced during austral winter and spring. It is argued that through the combined effects of obstruction and deflection of atmospheric flow, orography acts to enhance static stability of the lower troposphere over the Atlantic off the Namibian coast, which provides an environment conducive to the development of stratocumulus in that region.