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Your search keyword '"Yves Pomalegni"' showing total 2 results
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1. Stratospheric Sulfate Aerosols Impacts on West African Monsoon Precipitation Using GeoMIP Models

Author

Frédéric Bonou, Casimir Yelognisse Da‐Allada, Ezinvi Baloitcha, Eric Alamou, Eliezer Iboukoun Biao, Josué Zandagba, Ezéchiel Obada, Yves Pomalegni, Peter James Irvine, and Simone Tilmes

Subjects
West Africa, monsoon precipitation, climate change, geoengineering, GeoMIP, G3, Environmental sciences, GE1-350, Ecology, QH540-549.5
Abstract

Abstract Stratospheric Aerosol Geoengineering (SAG) is proposed to offset global warming; however, the use of this approach can an impact on the hydrological cycle. We used simulations from Coupled Model Intercomparison Project (CMIP5) and Geoengineering Model Intercomparison Project (G3 simulation) to analyze the impacts of SAG on precipitation (P) and to determine its responsible causes in West Africa and Sahel region. CMIP5 historical data were first validated, the results obtained are consistent with observational data. Under the Representative Concentration Pathway scenario RCP4.5, a slight increase is found in the West Africa Region relative to present‐day climate. The dynamic processes especially, the monsoon shifts are responsible for this precipitation change. Under RCP4.5, during the monsoon period, reductions in P are 0.86%, 0.80% relative to the present‐day climate in the Northern and Southern Sahel, respectively, while precipitation is increased by 1.04% in the West African Region. Under SAG, we find a 3.71% decrease of precipitation in the West African Region while the precipitation decrease is 17.4% and 8.47% respectively in the North Sahel and South Sahel. This decrease in monsoon precipitation is mainly explained by changes in dynamics, which lead to weakened monsoon circulation and a shift in the distribution of monsoon precipitation. This result suggests that SAG deployment to balance all warming can be harmful to rainfall in WAR if the amount of SO2 to be injected into this tropical area is not taken into consideration.

Published
2023
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2. Seasonal and interannual variability of salinity in a large West-African lagoon (Nokoué Lagoon, Benin)

Author

Alexis Chaigneau, Yves Morel, Zacharie Sohou, Thomas Stieglitz, Yves Pomalegni, Daouda Mama, Victor Olaègbè Okpeitcha, Université d’Abomey-Calavi (UAC), Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), International Chair on Mathematical Physics and Applications ICMPA-Unesco Chair, UAC, Bénin (ICMPA-Unesco Chair), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Institut de Recherches Halieutiques et Océanologiques du Bénin, Université d’Abomey-Calavi = University of Abomey Calavi (UAC), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)

Subjects
0106 biological sciences, Wet season, Salinity, Soil salinity, 010504 meteorology & atmospheric sciences, Stratification (water), Nokoué lagoon, Inflow, Aquatic Science, Oceanography, 01 natural sciences, stratification, Dry season, 14. Life underwater, 0105 earth and related environmental sciences, Shore, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], geography, geography.geographical_feature_category, seasonal and interannual variations, 010604 marine biology & hydrobiology, box model, tropical lagoon, 6. Clean water, 13. Climate action, Environmental science, Seawater
Abstract

International audience; Nokoué Lagoon in the South of Benin is a large intermittent coastal water body in West Africa, which supports one of the largest inland fisheries of the region. The seasonal and interannual variability of its salinity was studied, based on 3 years of monthly surveys (Dec 2017-Dec 2020). This dataset allows us to identify fine-scale salinity structures and to better understand the salinization/desalinization processes at seasonal scales. During the rainy season from May to November, under the influence of large freshwater inflows from the rivers on its northern shores, the lagoon desalinizes to a salinity of zero in October-November. During the dry season from December to April, under the effect of the ocean tide, Nokoué lagoon becomes progressively saltier, reaching typical salinities of ~25 in April. On average, the Nokoué lagoon is saltier in its southwestern part and fresher towards the river's mouths. Vertical salinity stratification is largest in December at the beginning of the main dry season. The lagoon displays a very marked interannual variation with mean surface (bottom, respectively) salinity of 25 (25) in April 2018 and 2020, respectively, against 16 (18) in April 2019. In the absence of river inflow data, a box model shows that the average salinity of the lagoon is very sensitive to small changes in river inflow (or discharge), with observed interannual differences in salinity induced by small variations of 10-15 m 3 s-1 in inflow during the dry season. During the salinization phase, the model suggests that ~30% of the seawater entering the lagoon during flood-tides remains trapped and enhances the Nokoué lagoon salinity. This model also indicates that a complete desalinization of the lagoon occurs for river inflow greater than ~50-60 m 3 s-1. The general mixing time scale of the lagoon is of 30-40 days.

Published
2021
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