The contribution of orographic rainfall to the extreme precipitation in Southeastern Africa in Spring 2000

Extreme rainfall occurs when sufficient atmospheric moisture accompanies significant vertical motion. There are many sources of vertical motion in the atmosphere - frontal lifting, convergence near the surface coupled with divergence aloft, and orographic forcing, to name a few. When multiple sources of vertical motion converge, extreme precipitation may result. We examine the contribution of terrain-induced rainfall to the extreme precipitation events in Mozambique, Madagascar and South Africa during the Jan - Mar 2000 rainy season, by comparing the results of a diagnostic model of orographic rainfall to the observed patterns of precipitation, which were analyzed using the CPC/FEWS blended satellite rainfall estimation method. NCEP/NCAR Reanalysis data is used to drive the orographic model. We also test the potential of using the orographic model to improve current CPC/FEWS rainfall estimation techniques.