Long-term simulations (2001–2006) of biomass burning and mineral dust optical properties over West Africa: comparisons with new satellite retrievals

Abstract. The West African region is characterized by large concentrations of smoke and biomass burning aerosols, which could significantly modify the regional radiative budget and the hydrological cycle. Here, we propose long-term (2001–2006) RegCM simulations of aerosol optical properties over West Africa together with their spectral dependences. Results of simulations are evaluated at local and regional scale by using surface network (AERONET/PHOTON) and remote sensing observations (MODIS, MISR, OMI) especially during the dry season, December-January-February, DJF. New original satellite retrievals are tested and compared to RegCM simulations. Concerning AOD, we obtain values in agreement with AERONET/PHOTON observations at the local scale but some differences clearly appear between simulated AOD and regional MISR, OMI and MODIS view, especially over (1) the central Africa and (2) the gulf of Guinea during DJF. Concerning simulated SSA (for visible wavelengths), our results display (1) comparable values with level 2 AERONET/PHOTON local observations together with (2) non negligible differences with satellite (MODIS Deep blue, OMI and MISR products) observations. In most cases, satellite SSA is found to be higher than those simulated by RegCM and retrieved through AERONET/PHOTON network. In parallel, we also note significant differences on retrieved SSA from each satellite (OMI, MISR, MODIS Deep Blue) remote sensing techniques over this specific region. Finally, our work highlights that the spectral dependence of aerosol optical properties is a useful parameter to adapt so that modeled simulations should be be better evaluated and constrained.