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RESEARCH PRODUCT

Les vagues de chaleur au Sahel : caractérisation, mécanismes, prévisibilité.

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The mechanisms controlling Sahelian heat wave (HW) variability are examined on the period 1979-2014 using the GSOD observational database and ERA-Interim reanalyses. HW events are analyzed through all terms of the atmospheric energy balance, showing a predominant role of incoming shortwave radiation on daily maximum temperature (Tx) and atmospheric water vapor on minimum temperature (Tn). The low-frequency warming trend, not explained by the previous terms, is thought to relate to the increase of greenhouse gases concentrations, due to anthropogenic emissions. The predictability of Sahelian HW events is assessed for lead times reaching up to 15 days. The model's skill, biases and uncertainties all highly vary from one event to another. During the very warm 2010 spring, the Tn peaks associated with a moister air mass appears as much more predictable than those concerning Tx and modulated by the cloud fraction and incoming solar radiation.