Optical and Microphysical Properties of Aged Biomass Burning Aerosols and Mixtures, Based on 9-Year Multiwavelength Raman Lidar Observations in Athens, Greece

Mean optical and microphysical aerosol properties of long-range transported biomass burning (BB) particles and mixtures are presented from a 9-year (2011-2019) data set of multiwavelength Raman lidar data, obtained by the EOLE lidar over the city of Athens (37.58 & DEG; N, 23.47 & DEG; E), Greece. We studied 34 aerosol layers characterized as: (1) smoke; (2) smoke + continental polluted, and (3) smoke + mixed dust. We found, mainly, small-sized aerosols with mean backscatter-related (355 nm/532 nm, 532 nm/1064 nm) values and & ANGS;ngstrom exponent (AE) values in the range 1.4-1.7. The lidar ratio (LR) value at 355 nm was found to be 57 & PLUSMN; 10 sr, 51 & PLUSMN; 5 sr, and 38 & PLUSMN; 9 sr for the aerosol categories (1), (2), and (3), respectively; while at 532 nm, we observed LR values of 73 & PLUSMN; 11 sr, 59 & PLUSMN; 10 sr, and 62 & PLUSMN; 12 for the same categories. Regarding the retrieved microphysical properties, the effective radius (reff) ranged from 0.24 & PLUSMN; 0.11 to 0.24 & PLUSMN; 0.14 mu m for all aerosol categories, while the volume density (vd) ranged from 8.6 & PLUSMN; 3.2 to 20.7 & PLUSMN; 14.1 mu m(-3)cm(-3) with the higher values linked to aerosol categories (1) and (2); the real part of the refractive index (mR) ranged between 1.49 and 1.53, while for the imaginary part (mI), we found values within 0.0108 i and 0.0126 i. Finally, the single scattering albedo (SSA) of the propped particles varied from 0.915 to 0.936 at all three wavelengths (355-532-1064 nm). The novelty of this study is the provision of typical values of BB aerosol properties from the UV to the near IR, which can be used in forecasting the aerosol climatic effects in the European region.

Automated summary

This study presents the optical and microphysical properties of biomass burning (BB) aerosols transported over long distances, based on a 9-year data set of multiwavelength Raman lidar data in Athens, Greece. Different aerosol categories were identified, with typical values of backscatter, Ångstrom exponent, lidar ratio, effective radius, volume density, and refractive index provided. The findings can be used to forecast the aerosol climatic effects in the European region.