Alban Lazar

Sorbonne Université

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Amadou Thierno Gaye

Cheikh Anta Diop University

Malick Wade

Université Gaston Berger

Xavier Capet

Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques

Emmanuel Mignot

Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques

Gaëlle de Coëtlogon

Laboratoire atmosphères, milieux, observations spatiales

VÉ

Vincent Échevin

Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques

Patrice Brehmer

Institut Universitaire Européen de la Mer

ÉM

Éric Machu

Laboratory for Ocean Physics and Satellite Remote Sensing

Belén Rodríguez‐Fonseca

Universidad Complutense de Madrid

Marta Martín‐Rey

Universidad Complutense de Madrid

Cooperative Institutions

Centre National de la Recherche Scientifique

125

Institut de Recherche pour le Développement

Sorbonne Université

Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques

Institut Pierre-Simon Laplace

Laboratoire d’Études en Géophysique et Océanographie Spatiales

National Oceanic and Atmospheric Administration

Ifremer

Cheikh Anta Diop University

Woods Hole Oceanographic Institution

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Comment on egusphere-2024-818

Clovis Thouvenin-Masson Jacqueline Boutin Vincent Échevin Alban Lazar Jean‐Luc Vergely

Abstract. In tropical regions, the fresh water flux entering the ocean originates primarily from precipitation and, to a lesser extent when considering basin scale averages, from continental rivers. Nevertheless, at regional scale, river flows can have a significant impact on the surface ocean dynamics. Riverine fresh water modifies salinity, and therefore density, stratification and circulation. With its particular coastline, relatively high cumulative river discharge, and the vicinity of Inter Tropical Convergence Zone (ITCZ), the eastern Southern North Tropical Atlantic (e-SNTA) region off Northwest Africa is a particularly interesting location to study the linkage between precipitations, river outflows and Sea Surface Salinity (SSS). Here we focus on the regional e-SNTA SSS seasonal cycle and interannual variability. We quantify the impact of river runoff and precipitation on SSS by means of regional simulations forced by different interannual and climatological river runoffs and precipitation products. The simulated SSS are compared with the Climate Change Initiative (CCI) SSS, in situ SSS from Argo, ships and a coastal mooring, and the GLORYS reanalysis SSS. The analysis of the salinity balance in the mixed layer is conducted to explore the dynamics influencing the SSS variability. Overall, the simulations reproduce well the seasonal cycle and interannual variability despite a positive mean model bias north of 15N. The seasonal cycle is impacted by the phasing of the different runoff products. The mixed layer SSS decrease during the rainy season is mainly driven by precipitation followed by runoff by means of horizontal advection and partly compensated by vertical mixing. In terms of interannual anomalies, river runoffs have a more direct impact on SSS than precipitation. This study highlights the importance of properly constraining river runoff and precipitation to simulate realistic SSS, and the importance of observing SSS in coastal regions to validate such constraints.

10.5194/egusphere-2024-818-rc3

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Equatorial upper‐ocean dynamics and their interaction with the West African monsoon

Atmospheric Science Letters (2010)

Peter Brandt Guy Caniaux Bernard Bourlès Alban Lazar Marcus Dengler

Abstract Zonal wind anomalies in the western equatorial Atlantic during late boreal winter to early summer precondition boreal summer cold/warm events in the eastern equatorial Atlantic (EEA) that manifest in a strong interannual Atlantic cold tongue (ACT) variability. Local intraseasonal wind fluctuations, linked to the St. Helena anticyclone, contribute to the variability of cold tongue onset and strength, particularly during years with preconditioned shallow thermoclines. The impact of cold tongue sea surface temperature (SST) anomalies on the wind field in the Gulf of Guinea is assessed. It contributes to the northward migration of humidity and convection and possibly the West African monsoon (WAM) jump. Copyright © 2010 Royal Meteorological Society

Anticyclone

10.1002/asl.287

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Intraseasonal variability of the ocean - atmosphere coupling in the Gulf of Guinea during boreal spring and summer

EGUGA (2009)

Gaëlle de Coëtlogon Serge Janicot Alban Lazar

New guinea

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Long-term Variability of NorthWest African coastal upwelling

EGU General Assembly Conference Abstracts (2014)

Malick Wade Belén Rodríguez‐Fonseca Alban Lazar

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Is the boreal spring tropical Atlantic variability a precursor of the Equatorial Mode?

Climate Dynamics (2019)

Marta Martín‐Rey Alban Lazar

Kelvin wave

Downwelling

Forcing (mathematics)

Equatorial waves

Madden–Julian oscillation

10.1007/s00382-019-04851-9

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Citations (32)

Tropical Atlantic climate experiment (TACE)

CLIVAR Exchanges (2013)

Peter Brandt Moacyr Araújo Bernard Bourlès Ping Chang Marcus Dengler

Tropical Atlantic

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La branche froide de la circulation thermohaline : sensibilite a la diffusion turbulente dans un modele de circulation generale idealisee

Alban Lazar

La branche froide de la circulation thermohaline oceanique joue un role primordial dans le climat de la planete en assurant le transport meridien et le stockage abyssal de diverses quantites (chaleur, eau douce, traceurs anthropiques et telluriques). Elle anime les trois quarts du volume des mers sous la thermocline principale, a l'abri de l'essentiel de l'action du vent et est de ce fait sujette a un fort controle par les processus turbulents de petite echelle. Cette these est une etude de processus visant a mieux comprendre la physique de sa circulation, en particulier dans le cadre des modele d'ocean basse-resolution utilises pour les simulations climatiques. Diverses simulations issues d'un modele de circulation generale a la geometrie et au forcage idealises ont ete effectuees en faisant varier les parametrisations de la physique sous-maille dans les equations de la temperature et de la salinite. Elles mettent en evidence l'importance de l'effet des tourbillons meso-echelle dans le controle des courants grande-echelle au travers de deux equilibres thermiques qui s'ajoutent a l'equilibre vertical diffusion/advection (stommel et arons, 1969) pour expliquer les principales structures dynamiques du bassin profond sous la thermocline. Les vitesses verticales negatives susceptibles de caracteriser une grande partie de l'interieur, la ou une ascendance est traditionnellement attendue, sont notamment interpretes en ces termes. A l'echelle globale, il apparait que le melange turbulent joue sur l'intensite de la circulation meridienne et du transport de chaleur du fait de son controle de la consommation des masses d'eau qu'equilibrent leur production/advection. Cependant, notre analyse suggere que le role moteur de la diffusion pour la circulation thermohaline est favorise par la geometrie du bassin etudie et que d'autres moteurs semblent etre a l'oeuvre dans l'ocean global.

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Fine scale structure of an Anticyclonic eddy off Cape Verde peninsula observed from Glider

EGUGA (2015)

Nicolas Kolodziejczyk Pierre Testor Alban Lazar Vincent Échevin Gerd Krahmann

Cape verde

Anticyclone

Peninsula

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A numerical study of the South Atlantic circulation at the Last Glacial Maximum

Palaeogeography Palaeoclimatology Palaeoecology (2007)

Gabriel Clauzet Ilana Wainer Alban Lazar Esther C. Brady Bette L. Otto‐Bliesner

Last Glacial Maximum

10.1016/j.palaeo.2007.06.018

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Do SST gradients drive the monthly climatological surface wind convergence over the tropical Atlantic

EGUGA (2018)

Moussa Diakhaté Alban Lazar Gaëlle de Coëtlogon Amadou Thierno Gaye

This article presents a climatological study of the tropical Atlantic surface wind convergence, one of the main drivers of the marine intertropical convergence zone (ITCZ) precipitations, including coastal northeastern Brazilian and West African rainfalls. Climatological monthly mean surface wind convergence budget, as well as that of their month-to-month variations, is analysed over the 2000–2009 decade, using ocean–atmosphere reanalyses and satellite-derived data sets. Sea surface temperature (SST) influence is particularly investigated via comparison of its Laplacian with that of sea level pressure. Results for monthly means reveal that the Lindzen-Nigam paradigm does hold in regions of deep convection but only on their flanks. In deep convection regions, the budget analysis suggests the entrainment due to elevated heating by cumulus convection as the leading term. Elsewhere, over the ‘open ocean ITCZ’ meridional flanks, as well as over the ‘coastal one’ (Gulf of Guinea and northeastern Brazilian coasts), the pressure contribution is positive and largely dominated by its component below the boundary layer closely related to the SST. Horizontal advection is also found important over these areas, but with the pressure as the first-order driver. Otherwise, month-to-month variations of ITCZ are controlled by the geostrophy within the pressure contribution tightly dominated by the free tropospheric component.

Intertropical Convergence Zone

Tropical Atlantic

Entrainment (biomusicology)

Convergence zone

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