Aerosol characterization in Northern Africa, Northeastern Atlantic, Mediterranean Basin and Middle East from direct-sun AERONET observations [Discussion paper]

• Main Authors: Basart, Sara, Pérez García-Pando, Carlos, Cuevas Agulló, Emilio, Baldasano, José María, Gobbi, Gian Paolo
• Format: Report
• Language: English
• Published: European Geosciences Union 2009
• Subjects: Aerosol characterization; AErosol RObotic NETwork (AERONET); Direct-sun observations; Observación solar directa; Aerosoles; Aerosol Robotic Network
• Online Access: https://hdl.handle.net/20.500.11765/6496

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 to track and discriminate different aerosol types and quantify the contribution of mineral dust. The method relies on the combined analysis of the Ångström exponent (α) and its spectral curvature δα. Plotting data in these coordinates allows to infer aerosol fine mode radius (Rf) 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 found to be the most important constituent in Northern Africa and Middle East. Under specific meteorological conditions, its transport to Southern Europe is observed from spring to autumn and decreasing with latitude. We observe "pure Saharan dust" conditions to show AOD>0.7 (ranging up to 5), α<0.3 and δα<0 corresponding to η<40% and (Rf)~0.13 μm (.) This work was funded by the project CICYT CGL2006-11879 of the Spanish Ministry of Education and Science.