Seasonal influence of the sea surface temperature on the low atmospheric circulation and precipitation in the eastern equatorial Atlantic

Remi Meynadier 1 Gaëlle de Coëtlogon 2 Marion Leduc-Leballeur 3 Laurence Eymard 4 Serge Janicot 4
1 LA - Laboratoire d'aérologie
2 ESTER - LATMOS
LATMOS - Laboratoire Atmosphères, Milieux, Observations Spatiales
3 LGGE - Laboratoire de glaciologie et géophysique de l'environnement
4 PARVATI - Processus de la variabilité climatique tropicale et impacts
LOCEAN - Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques
Abstract : The air–sea interaction in the Gulf of Guinea and its role in setting precipitation at the Guinean coast is investigated in the present paper. This study is based on satellite observations and WRF simulations forced by different sea surface temperature (SST) patterns. It shows that the seasonal cold tongue setup in the Gulf of Guinea, along with its very active northern front, tends to strongly constrain the low level atmospheric dynamics between the equator and the Guinean coast. Underlying mechanisms including local SST effect on the marine boundary layer stability and hydrostatically-changed meridional pressure gradient through changes in SST gradient are quantified in WRF regarding observations and CFSR reanalyses. Theses mechanisms strongly impact moisture flux convergence near the coast, leading to the installation of the first rainy season of the West African Monsoon (WAM) system. The current study details the mechanisms by which the Atlantic Equatorial cold tongue plays a major role in the pre-onset of the boreal WAM.
Keywords : Air–sea interaction Regional climate Water cycle Eastern equatorial Atlantic
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Remi Meynadier, Gaëlle de Coëtlogon, Marion Leduc-Leballeur, Laurence Eymard, Serge Janicot. Seasonal influence of the sea surface temperature on the low atmospheric circulation and precipitation in the eastern equatorial Atlantic. Climate Dynamics, Springer Verlag, 2016, 47 (3), pp.1127-1142. ⟨10.1007/s00382-015-2892-7⟩. ⟨insu-01229906⟩

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