Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 9 2 2009 10.5194/acpd-9-7707-2009 http://www.atmos-chem-phys-discuss.net/9/7707/2009/ http://www.atmos-chem-phys-discuss.net/9/7707/2009/acpd-9-7707-2009.html http://www.atmos-chem-phys-discuss.net/9/7707/2009/acpd-9-7707-2009.pdf 7707 7745 2009-03-24 Aerosol characterization in Northern Africa, Northeastern Atlantic, Mediterranean Basin and Middle East from direct-sun AERONET observations S. Basart sara.basart@bsc.es C. Pérez E. Cuevas J. M. Baldasano G. P. Gobbi Earth Sciences Department, Barcelona Supercomputing Center-Centro Nacional de Supercomputación, BSC-CNS, Barcelona, Spain Izaña Atmospheric Research Center, Meteorological State Agency of Spain (AEMET), Santa Cruz de Tenerife, Spain Environmental Modelling Laboratory, Technical University of Catalonia, Barcelona, Spain Institute of Atmospheric Sciences and Climate, ISAC-CNR, Rome, Italy We provide an atmospheric aerosol characterization for North Africa, Northeastern Atlantic, Mediterranean and Middle East based on the analysis of quality-assured direct-sun observations of 39 stations of the AErosol RObotic NETwork (AERONET) which include at least an annual cycle within the 1994–2007 period. We extensively test and apply the recently introduced graphical method of Gobbi and co-authors in order to track and discriminate different aerosol types and quantify the contribution of mineral dust. The method relies on the combined analysis of the Ångstrøm exponent (α) and its spectral curvature. Plotting data in these coordinates allows to infer aerosol fine mode size (R_f) and fractional contribution (η) to total Aerosol Optical Depth (AOD) and separate AOD growth due to fine-mode aerosol humidification and/or coagulation from AOD growth due to the increase in coarse particles or cloud contamination. Our results confirm the robustness of this graphical method. Large mineral dust is the most important constituent in Northern Africa and Middle East; and under specific meteorological conditions, its transport to Europe is observed from spring to autumn. Small pollution particles are abundant in sites close to urban and industrial areas of Continental and Eastern Europe and Middle East; as well as, important contributions of biomass burning are observed in the sub-Sahel region in winter. Dust is usually found to mix with these fine, pollution aerosols. 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