Aspects of the Fine-Scale Climatology Over Lake Tanganyika as Resolved by a Mesoscale Model |
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| Authors: | Hannu Savijärvi Simo Järvenoja |
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| Institution: | (1) Department of Meteorology, University of Helsinki, FI;(2) Finnish Meteorological Institute, Helsinki, Finland, FI |
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| Abstract: | Summary An hourly averaged climatology at 0.05 ° horizontal resolution over the Lake Tanganyika region was created by making simulations
with a mesoscale model (HIRLAM) using a high resolution physiography to represent the surface. Initial and boundary values
were interpolated from ECMWF analyses. Climatologies for a typical dry season month (July 1994) and wet season month (March
1994) were created by 7-day segmenting. Model results were validated by utilizing a special coastal observation network. A
number of experiments were made with changes to the physiography (mountains/no mountains, lake/no lake).
The results reveal local channelling and blocking effects of the near-surface southeasterly trade winds by the high mountain
chains in the region of the East African rift. Furthermore, surface winds display regular diurnal cycles in many places, due
to slope winds over hills and lake-land-type breezes near the coast. The diurnal coastal winds (defined by the observation
network) are reasonably well simulated. Precipitation patterns display the semi-annual march of the ITCZ across the area,
plus considerable topographic effects. There is high evaporation from lakes and wetlands during the windy dry season, while
evaporation from the moist land surface dominates the rainy season.
Received October 15, 1998/Revised September 2, 1999 |
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