Mineral dust over west and central Sahel: Seasonal patterns of dry and wet deposition fluxes from a pluriannual sampling (2006-2012)
2017
Marticorena, B. | Chatenet, B. | Rajot, Jean-Louis | Bergametti, G. | Deroubaix, A. | Vincent, J. | Kouoi, A. | Schmechtig, C. | Coulibaly, M. | Diallo, A. | Kone, I. | Maman, A. | Ndiaye, T. | Zakou, A. | Institut Pierre-Simon-Laplace (IPSL (FR_636)) ; École normale supérieure - Paris (ENS-PSL) ; Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X) ; Institut Polytechnique de Paris (IP Paris)-Institut Polytechnique de Paris (IP Paris)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS) | Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA (UMR_7583)) ; Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS) | Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12) | Institut d'écologie et des sciences de l'environnement de Paris (iEES) ; Institut National de la Recherche Agronomique (INRA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS) | SRAC ; Institut d'Economie Rurale (IER) | US191 Instrumentation, Moyens Analytiques, Observatoires en Géophysique et Océanographie (IMAGO) ; Institut de Recherche pour le Développement (IRD [France-Ouest]) | Institut de Recherche pour le Développement (IRD [France-Ouest]) | European Community's Sixth Framework Research Programme; Observatoire des Sciences de l'Univers EFLUVE; French national program [AMMA-2]; DRUMS (DeseRt dUst Modeling: performance and Sensitivity evaluation) research program - ASTRID fund call of the French Agence Nationale de la Recherche (ANR) [ANR-ASTRID-DRUMS-2012] | ANR-12-ASTR-0029,DRUMS,Modélisation des aérosols désertiques : Evaluation des Performances et de la Sensibilité(2012)
Total and wetmineral dust deposition has beenmonitored since 2006 at three Sahelian stations in Senegal, Mali, and Niger, respectively at the weekly and the event time scale. Average annual deposited mass fluxes range from 75 to 183 gm(-2) yr(-1), from west to east. Deposition fluxes exhibit a clear seasonal cycle in Mali and Niger. High wet deposition fluxes result from an optimum phasing between dust concentration and precipitation: the maximum occurring at the beginning of the wet season, after the maximum of dust concentration and before the precipitation maximum. The contribution of wet to total deposition varies from 67% in Mali to 8% in Senegal. It is the main factor of variability of the deposition fluxes from year to year and at the seasonal scale in Niger and Mali. Wet deposition fluxes in Mali and Niger are mainly due to the wash out of dust emitted by convective systems. In Senegal, the deposition fluxes are lower and dominated by dry deposition (92% of the annual deposition flux). This is due to the low occurrence of convective systems producing local dust emissions and intense wet deposition. The dry deposition fluxes are primarily driven by the variability of the dust concentration. The dry deposition velocities derived from our measurements are consistent with those estimated by theoretical models. Scavenging ratios computed from the measured wet deposition fluxes, dust concentrations, and precipitation are anticorrelated with precipitation amounts. This suggests that most of the atmospheric dust is scavenged at the very beginning of the precipitation events.
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