GMD Geoscientific Model Development GMD Geosci. Model Dev. 1991-9603 Copernicus Publications Göttingen, Germany 10.5194/gmd-7-317-2014 Understanding the performance of the FLake model over two African Great Lakes Thiery W. https://orcid.org/0000-0002-5183-6145 1 Martynov A. 2 3 Darchambeau F. 4 Descy J.-P. 5 Plisnier P.-D. 6 Sushama L. 2 van Lipzig N. P. M. 1 Department of Earth and Environmental Sciences, University of Leuven, Leuven, Belgium Centre pour l'Étude et la Simulation du Climat à l'Échelle Régionale (ESCER), Université du Québec à Montréal, Montréal, Canada Institute of Geography and Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland Unité d'Océanographie Chimique, Université de Liège, Liège, Belgium Laboratoire d'écologie des Eaux Douces, University of Namur, Namur, Belgium Royal Museum for Central Africa, Tervuren, Belgium 18 02 2014 7 1 317 337 Copyright: © 2014 W. Thiery et al. 2014 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://gmd.copernicus.org/articles/7/317/2014/gmd-7-317-2014.html The full text article is available as a PDF file from https://gmd.copernicus.org/articles/7/317/2014/gmd-7-317-2014.pdf

The ability of the one-dimensional lake model FLake to represent the mixolimnion temperatures for tropical conditions was tested for three locations in East Africa: Lake Kivu and Lake Tanganyika's northern and southern basins. Meteorological observations from surrounding automatic weather stations were corrected and used to drive FLake, whereas a comprehensive set of water temperature profiles served to evaluate the model at each site. Careful forcing data correction and model configuration made it possible to reproduce the observed mixed layer seasonality at Lake Kivu and Lake Tanganyika (northern and southern basins), with correct representation of both the mixed layer depth and water temperatures. At Lake Kivu, mixolimnion temperatures predicted by FLake were found to be sensitive both to minimal variations in the external parameters and to small changes in the meteorological driving data, in particular wind velocity. In each case, small modifications may lead to a regime switch, from the correctly represented seasonal mixed layer deepening to either completely mixed or permanently stratified conditions from ~ 10 m downwards. In contrast, model temperatures were found to be robust close to the surface, with acceptable predictions of near-surface water temperatures even when the seasonal mixing regime is not reproduced. FLake can thus be a suitable tool to parameterise tropical lake water surface temperatures within atmospheric prediction models. Finally, FLake was used to attribute the seasonal mixing cycle at Lake Kivu to variations in the near-surface meteorological conditions. It was found that the annual mixing down to 60 m during the main dry season is primarily due to enhanced lake evaporation and secondarily to the decreased incoming long wave radiation, both causing a significant heat loss from the lake surface and associated mixolimnion cooling.

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