Multi-year wind dynamics around Lake Tanganyika
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Lake Tanganyika is the second largest freshwater lake in the world by volume and is of prime importance for the regional economy in East Africa. Although the lake is recognized as a key component of the regional climate system, little is known about atmospheric dynamics in its surroundings. To understand this role, we analyze winds around Lake Tanganyika as modeled by a high resolution (7 km) regional climate model (Consortium for Small-scale Modeling in Climate Mode) over the period 1999–2008. Modeled surface wind speed and direction are in very good agreement with high resolution (12.5 km) Quick Scatterometer (QuikSCAT) satellite wind observations during the dry season. Comparison of a control run with a model simulation where all lake pixels are replaced by representative land pixels indicates that mean surface wind speed over Lake Tanganyika almost doubles due to lake presence. Furthermore, a region of higher surface wind speed in the central part of the lake is identified and confirmed by QuikSCAT observations. A combination of wind channeling along valley mountains and wind confluence on the upwind side of the lake is responsible for this speed-up. The lower wind speeds in the rest of the lake result from blocked conditions due to more pronounced orography. Finally, the model captures a zone of higher wind speed at around 2 km height, associated with the low-level Somali jet. These results demonstrate that high resolution climate modeling allows a detailed understanding of wind dynamics in the vicinity of Lake Tanganyika.
KeywordsLake Tanganyika Wind Regional climate model Orography
We would like to thank Y. Cornet and N. Poncelet for the interesting discussion concerning lake surface water temperature over the African Great Lakes. We also thank I. Gorodetskaya for her input during group discussion. We sincerely thank the editor and two reviewers for their constructive remarks which helped to improve the manuscript. D. Docquier is funded by the Belgian Science Policy Office (BELSPO) through the research project EAGLES. W. Thiery and S. Lhermitte are funded by the Research Foundation Flanders (FWO). The computational resources and services used in this work were provided by the Flemish Supercomputer Center (VSC), funded by the Hercules Foundation and the Flemish Government—department EWI.
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