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CR 52:97-113 (2012)  -  DOI:

Contribution to the CR Special: 'The regional climate model RegCM4'

Radiative and climatic effects of dust over West Africa, as simulated by a regional climate model

Fabien Solmon1,*, Nellie Elguindi1, Marc Mallet2

1The Abdus salam International Center for Theoretical Physics, Strada Costiera 11, 34100 Trieste, Italy
2Laboratoire d’Aerologie, CNRS, Universite de Toulouse, 14 av. Edouard Belin, 31400 Toulouse, France

ABSTRACT: We used the Regional Circulation Model (RegCM) to investigate the direct effect of dust aerosol on climate over West Africa, with a specific focus on the Sahel region. First, we characterized the mechanisms linking dust radiative forcing and convective activity over Sahel and the net impact of dust on precipitation: The mean effect of dust over 11 summer seasons is to reduce precipitation over most of the Sahel region as a result of strong surface cooling and elevated diabatic warming inhibiting convection. However, on the very northern Sahel and in the vicinity of dust sources, a relative increase of precipitation is obtained as a result of enhanced diabatic warming in the lower atmosphere associated with high dust concentrations at low altitude. In the second part of the paper, we investigated the robustness of this signal with regards to different modeling conditions that are thought to be sensitive, namely the extension of the domain, the effect of dust on sea surface temperature, the land surface scheme, the convective scheme and the dust single scattering albedo. The simulated dust induced precipitation anomaly over West Africa is consistent and robust in these tests, but significant variations over the northern Sahel region are nevertheless pointed out. Among different factors, single scattering and surface albedo, as well as the nature of the convective scheme, have the greatest influence on the simulated response of West African climate to dust forcing.

KEY WORDS: Dust · Aerosol · Sahel · West Africa · Regional climate · Radiative effect · Single scattering albedo · Convection

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Cite this article as: Solmon F, Elguindi N, Mallet M (2012) Radiative and climatic effects of dust over West Africa, as simulated by a regional climate model. Clim Res 52:97-113.

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