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Numerical Simulations of the Role of Land Surface Conditions on the Climate of Mt. Kilimanjaro Region

Sean Heuser & Fredrick Semazzi
Newsletter of the Climate Variability and Predictability Programme, December 2008

A series of WRF-ARW model simulations have been carried out to examine the impacts of changing albedo during the short rains of East Africa for the year 2000. Three simulations were performed with a default albedo, an albedo reduction from 0.22 to 0.18, and an albedo increase from 0.22 to 0.25. The changes show small impacts on the seasonal temperature values near the top of the mountain with temperatures decreasing in both cases (0.12% in the 0.25 scenario and 0.02% in the 0.18 scenario). However, precipitation changes are more significant with a 6.6% decrease in the 0.18 case and a 2.5% increase in the 0.25 case. The changes in precipitation are influenced significantly by the amount of shortwave radiation absorbed at the surface. The increase in shortwave radiation in the 0.25 case triggered more convection leading to more precipitation. The opposite effect is noticeable in the 0.18 scenario. These changes led to an increase in latent heat flux which we believe would tend to accelerate sublimation atop the mountain. Our modeling results support our hypothesis that the response of precipitation to land use change is significantly greater than that of temperature, and therefore a more likely factor for modulating the glacial volume over Kilimanjaro summit. Initially we have focused on changes in albedo as a proxy for land use change.

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