Regional modelling of Saharan dust biomass-burning smoke: Part 2: Direct radiative forcing atmospheric dynamic response

Abstract

The direct radiative forcing dynamic atmospheric response due to Saharan dust biomass-burning aerosol particles are presented for a case study during the SAMUM-2 field campaign in January February 2008. The regional model system COSMO-MUSCAT is used. It allows online interaction of the computed dust smoke load with the solar terrestrial radiation with the model dynamics. Model results of upward solar irradiances are evaluated against airborne radiation measurements in the Cape Verde region. The comparison shows a good agreement for the case of dust smoke mixture. Dust smoke particles influence the atmospheric dynamics by changing the radiative heating rates. The related pressure perturbations modify local synoptic scale air-flow patterns. In the radiative feedback simulations, the Hadley circulation is enhanced convergence zones occur along the Guinea coast. Thus, the smoke particles spread more than 5° further north the equatorward transport is reduced. Within the convergence zones, Saharan dust biomass-burning material are more effectively advected towards the Cape Verdes. Given the model uncertainties, the agreement between the modelled observed aerosol distribution is locally improved when aerosol-radiation interaction is considered. © 2011 The Authors Tellus B © 2011 John Wiley & Sons A/S.