Lidar observations of long-range transported Saharan dust over Sofia, Bulgaria: a case study of dust mixed with local aerosols

Two-wavelength (1064/532 nm) lidar observations of long-range transported Saharan dust present in the atmosphere over Sofia, Bulgaria, during a 4-day dust intrusion event in winter 2010, are reported. Aged desert aerosols are detected at altitudes up to 4 km above the sea level, within and above the boundary layer as mixed with other aerosols-representing the particular case under consideration. Optical, microphysical, and dynamical properties of dust aerosols are obtained and analyzed. Special attention is paid to retrieving and vertical profiling of dust backscatter-related Antrom exponents(BAEs), as well as to determining their frequency-count distributions. Obtained BAE values in the range 0.3 to 0.6 (+/- 0.2) indicate domination of coarse particles in the near overmicron size range. Reasonability of coarse-mode-dominated dust size composition is substantiated, based on measurement and transportation-history analysis. The performed frequency-count statistics reveals dust BAE distributions asymmetrically extended to multimode distribution shapes, resulting from dust mixing with finer local aerosol fractions. Peculiarities and patterns of the aerosol dynamics at different stages of dust-loading event are revealed and discussed. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)