Effects of vegetation map change in MM5 simulations of southern Africa's summer climate

A regional climate model is used to assess potential climatic impacts of altering the vegetation map of southern Africa from an estimated natural state to present-day conditions. The Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model (MM5) is integrated from I August to 28 February for 1988/1989, 1991/1992 and 1995/1996 for two spatial vegetation representations: (1) potential natural vegetation as predicted by the Sheffield Dynamic Global Vegetation Model, and (2) current conditions given by the United States Geological Survey land-surface classification. Significant impacts on mean September-November (SON) and December-February (DJF) surface climate arise from the change in vegetation, the most notable of which is cooling over large parts of the continent in SON, which gives rise to increased large-scale subsidence and decreased moisture convergence. Resultant decreases in rainfall causes a hydrological feedback through reduced latent heat flux which mitigates the initial cooling and weakens the positive geopotential height bias in DJF. The increase in geopotential height extends vertically up to 500 hPa, which potentially has important implications for regional moisture transport over southern Africa. Copyright (c) 2008 Royal Meteorological Society