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A strong Saharan dust event that occurred over the city of Athens, Greece(37.9° N, 23.6° E) between 27 March and 3 April 2009 wasfollowed by a synergy of three instruments: a 6-wavelength Raman lidar, aCIMEL sun-sky radiometer and the MODIS sensor. The BSC-DREAM model was usedto forecast the dust event and to simulate the vertical profiles of theaerosol concentration. Due to mixture of dust particles with low cloudsduring most of the reported period, the dust event could be followed by thelidar only during the cloud-free day of 2 April 2009. The lidar data obtainedwere used to retrieve the vertical profile of the optical (extinction andbackscatter coefficients) properties of aerosols in the troposphere. Theaerosol optical depth (AOD) values derived from the CIMEL ranged from0.33–0.91 (355 nm) to 0.18–0.60 (532 nm), while the lidar ratio (LR)values retrieved from the Raman lidar ranged within 75–100 sr (355 nm) and45–75 sr (532 nm). Inside a selected dust layer region, between 1.8 and3.5 km height, mean LR values were 83 ± 7 and 54 ± 7 sr, at 355and 532 nm, respectively, while the Ångström-backscatter-related(ABR355/532) and Ångström-extinction-related (AER355/532)were found larger than 1 (1.17 ± 0.08 and 1.11 ± 0.02,respectively), indicating mixing of dust with other particles. Additionally,a retrieval technique representing dust as a mixture of spheres and spheroidswas used to derive the mean aerosol microphysical properties (mean andeffective radius, number, surface and volume density, and mean refractiveindex) inside the selected atmospheric layers. Thus, the mean value of theretrieved refractive index was found to be1.49( ± 0.10) + 0.007( ± 0.007)i, and that of the effectiveradiuses was 0.30 ± 0.18 μm. The final data set of theaerosol optical and microphysical properties along with the water vaporprofiles obtained by Raman lidar were incorporated into the ISORROPIA IImodel to provide a possible aerosol composition consistent with the retrievedrefractive index values. Thus, the inferred chemical properties showed12–40% of dust content, sulfate composition of 16–60%, andorganic carbon content of 15–64%, indicating a possible mixing of dustwith haze and smoke. PM10 concentrations levels, PM10 compositionresults and SEM-EDX (Scanning Electron Microscope-Energy Dispersive X-ray)analysis results on sizes and mineralogy of particles from samples during theSaharan dust transport event were used to evaluate the retrieval

atmospheric chemistry and physics

Optical-microphysical properties of Saharan dust aerosols and composition relationship using a multi-wavelength Raman lidar, in situ sensors and modelling: a case study analysis