Influence océanique du golfe de Guinée sur la mousson en Afrique de l'Ouest

Marion Leduc-Leballeur 1
1 ESTER - LATMOS
LATMOS - Laboratoire Atmosphères, Milieux, Observations Spatiales
Abstract : The West African monsoon is a complex interaction between the ocean, the land-surface and the atmosphere. Many studies showed a link between the seasonal cooling of the ocean in the Gulf of Guinea (equatorial upwelling) and the monsoon. The aim of this thesis is to explore the air-sea interaction mechanisms, which act on the coastal precipitation of the monsoon during boreal spring. The study is based on in situ and satellite measurements as well as reanalysis datasets. The 2006 monsoon season is analysed thanks to the vast set of observations collected by the AMMA (African Monsoon Multidisciplinary Analyses) project during this year. This study has led to a description of the marine atmospheric boundary layer in the eastern equatorial Atlantic. Results show that the sea surface temperature (SST) front on the northern boundary of the equatorial upwelling is a key zone for air-sea interactions in this region. Thus, a SST cooling south of the equator is generated by a southeasterly wind burst and intensifies the SST front. Consequently, the surface wind tends to weak above cold SST and to strengthen above warm SST. Then, the effect of southeasterly wind bursts in the Gulf of Guinea on the coastal precipitation is studied with satellite measurements and reanalysis datasets on the 2000-2009 period. Results show that a succession of SST coolings is generated by a succession of southeasterly wind bursts in the eastern equatorial Atlantic. These coolings act on the surface wind and the atmospheric circulation between the front and the Guinean coast and favour convection along the coast. This confirms the key role of the SST front and highlights its influence on the coastal precipitation. Finally, these intraseasonal events seem to play an important role in the seasonal evolution of the precipitation before the onset of the West African monsoon.
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Submitted on : Wednesday, September 5, 2012 - 12:38:56 PM
Last modification on : Friday, April 5, 2019 - 8:22:12 PM
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  • HAL Id : tel-00728272, version 1

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Marion Leduc-Leballeur. Influence océanique du golfe de Guinée sur la mousson en Afrique de l'Ouest. Physique Atmosphérique et Océanique [physics.ao-ph]. Université Pierre et Marie Curie - Paris VI, 2012. Français. ⟨tel-00728272⟩

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