92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Wednesday, 25 January 2012
The Meteorology of Kilimanjaro Over One Year At One Kilometer
Hall E (New Orleans Convention Center )
Jonathan G. Fairman Jr., The University of Alabama in Huntsville, Huntsville, AL; and U. S. Nair and S. A. Christopher

Global circulation models often utilize coarse grid spacing that is incapable of adequately resolving terrain generated circulation patterns. In this context, it is important to understand the relationship between differing synoptic scale meteorological parameters and terrain generated weather patterns. Such knowledge is important for Kilimanjaro, located in equatorial East Africa where the climate is highly reliant on oscillations of the Intertropical Convergence Zone. This study utilizes the Regional Atmospheric Modeling System to simulate meteorology of Kilimanjaro for the period of July 2007 through June 2008 at one kilometer grid spacing. Simulations show adequate performance compared to regional and local scale meteorological observations as well as satellite derived cloud cover. Analysis of flow patterns show the blocking caused by the mountain changes over the course of the year, dependent on the slope and cross section of the mountain normal to the prevailing wind. Local scale precipitation shows the elevation of maximum precipitation of around ~800 m higher then previously reported, while following existing function fits with elevation. The blockage caused by the topography interacting with wind patterns causes a mean 0-1000m wind of < 3.5 ms-1 greater then 25% during months in the dry seasons, whereas the number of points with low wind speeds is much smaller (<10%) during months in the wet seasons. There is a distinct signal in the thermal circulation between each season causing differences in the patterns of cloud formation, leading to higher cloud bases during certain seasons, in agreement with conceptual models. Dependence on local processes due to synoptic scale features are examined, and these local processes are found to contribute >60% of the precipitation from elevations ranging from 2000 m to 4000 m, and contribute 20% of the precipitation at the peak.

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