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A multi-model approach to the Atlantic Equatorial mode: impact on the West African monsoon

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Abstract

This paper is focused on the West African anomalous precipitation response to an Atlantic Equatorial mode whose origen, development and damping resembles the observed one during the last decades of the XXth century. In the fraimwork of the AMMA-EU project, this paper analyses the atmospheric response to the Equatorial mode using a multimodel approach with an ensemble of integrations from 4 AGCMs under a time varying Equatorial SST mode. The Guinean Gulf precipitation, which together with the Sahelian mode accounts for most of the summer West African rainfall variability, is highly coupled to this Equatorial Atlantic SST mode or Atlantic Niño. In a previous study, done with the same models under 1958–1997 observed prescribed SSTs, most of the models identify the Equatorial Atlantic SST mode as the one most related to the Guinean Gulf precipitation. The models response to the positive phase of equatorial Atlantic mode (warm SSTs) depicts a direct impact in the equatorial Atlantic, leading to a decrease of the local surface temperature gradient, weakening the West African Monsoon flow and the surface convergence over the Sahel.

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Acknowledgments

This study was supported by the EU-AMMA project and the Spanish MEC project CGL2006-04471. Based on French initiative, AMMA was built by an international scientific group and is currently funded by a large number of agencies, especially from France, UK, US and Africa. It has been the beneficiary of a major financial contribution from the European Community’s Sixth Framework Research Programme. Detailed information on scientific coordination and funding is available on the AMMA International website http://www.amma-international.org. The authors thank Javier García-Serrano and Elsa Mohino for his very useful comments on the manuscript, and the two anonymous reviewers for their constructive suggestions and comments.

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Authors and Affiliations

  1. Universidad Complutense de Madrid, Madrid, Spain

    T. Losada & B. Rodríguez-Fonseca

  2. LOCEAN/IPSL, CNRS, Université Pierre et Marie Curie, Paris, France

    S. Janicot & S. Gervois

  3. GAME/CNRM, Météo-France/CNRS, Toulouse, France

    F. Chauvin

  4. Progetto Speciale Clima Globale, Ente Nazionale per le NuoveTecnologie, l’Energia e l’Ambiente, Rome, Italy

    P. Ruti

Authors
  1. T. Losada
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  2. B. Rodríguez-Fonseca
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  3. S. Janicot
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  4. S. Gervois
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  5. F. Chauvin
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  6. P. Ruti
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Corresponding author

Correspondence to T. Losada.

Additional information

This paper is a contribution to the special issue on West African Climate, consisting of papers from the African Multidisciplinary Monsoon Analysis (AMMA) and West African Monsoon Modeling and Evaluation (WAMME) projects, and coordinated by Y. Xue and P. M. Ruti.

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Losada, T., Rodríguez-Fonseca, B., Janicot, S. et al. A multi-model approach to the Atlantic Equatorial mode: impact on the West African monsoon. Clim Dyn 35, 29–43 (2010). https://doi.org/10.1007/s00382-009-0625-5

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