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Ocean Science An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/os-2017-74
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
04 Oct 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Ocean Science (OS).
Impact of intraseasonal wind bursts on SST variability in the far eastern Tropical Atlantic Ocean during boreal spring 2005 and 2006. Focus on the mid-May 2005 event
Gaëlle Herbert and Bernard Bourlès Institut de Recherche pour le Développement (IRD), Laboratoire d'Etudes Géophysiques et Océanographie Spatiale (LEGOS), Brest, France
Abstract. The impact of spring intraseasonal wind bursts on sea surface temperature variability in the eastern Tropical Atlantic Ocean in 2005 and 2006 is investigated using numerical simulation and observations. We specially focus on the few documented coastal region east of 5° E and between the equator and 7° S. For both years, the southerly winds strengthening induced cooling events through i) upwelling processes; ii) vertical mixing due to vertical shear of zonal current; and for some particular events iii) a decrease of incoming surface shortwave radiation. The strength of the cooling events was modulated by subsurface conditions affected by the arrival of Kelvin waves from the west influencing the depth of the thermocline. Once impinging the eastern boundary, the Kelvin waves excited westward-propagating Rossby waves which, combined with the effect of enhanced westward surface currents, contributed to the westward extension of the cold water. A particularly strong wind event occurred in mid-May 2005 and caused an anomalous strong cooling off Cape-Lopez and in the whole eastern Tropical Atlantic Ocean. From the analysis of oceanic and atmospheric conditions during this particular event, it appears that anomalous strong spring wind strengthening associated to anomalous strong Hadley cell activity made the event as a decisive event which prematurely triggered the rainfall coastal onset in the northern Gulf of Guinea. Results show that no similar atmospheric conditions were observed over the 1998–2008 period. It is also found that the anomalous oceanic and atmospheric conditions associated to the event exerted strong influence on rainfall off Northeast Brazil. This study highlights the different processes through which the wind power from South Atlantic is brought to the ocean in the Gulf of Guinea and emphasizes the need to further document and monitor the South Atlantic region.

Citation: Herbert, G. and Bourlès, B.: Impact of intraseasonal wind bursts on SST variability in the far eastern Tropical Atlantic Ocean during boreal spring 2005 and 2006. Focus on the mid-May 2005 event, Ocean Sci. Discuss., https://doi.org/10.5194/os-2017-74, in review, 2017.
Gaëlle Herbert and Bernard Bourlès
Gaëlle Herbert and Bernard Bourlès
Gaëlle Herbert and Bernard Bourlès

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Short summary
The impact of boreal spring intraseasonal wind bursts on sea surface temperature variability in the eastern Tropical Atlantic in 2005 and 2006 is investigated. The cooling events induced by southerly wind bursts are modulated by local and remote forcing. A particularly strong wind event and a strong cooling occurred in mid-May 2005. It appears as a decisive event implied in the West African Monsoon onset. This study emphasizes the need to further document and monitor the South Atlantic region.
The impact of boreal spring intraseasonal wind bursts on sea surface temperature variability in...
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