Vertical and near-horizontal scanning lidar observations of aerosol loads over Sofia, Bulgaria, in the presence of Saharan dust

Abstract

Intrusions of extraneous aerosols and their interactions with locally produced aerosols result in serious climatic, ecological and health effects and consequences. In this work, we analyze results of lidar observations during Saharan dust loads in the atmosphere above the city of Sofia. Two types of measurements are described, namely, vertical lidar sounding and near-surface aerosol mapping by quasi-horizontal lidar scanning. The temporal dynamics of the aerosol density vertical distribution is displayed by color-mapped time series of range-corrected lidar signals. The resulting time-averaged profiles of the backscattering coefficients at two lidar wavelengths (532 nm and 1064 nm) were retrieved and the topological parameters of the detected aerosol fields were determined. The aerosols’ microphysical characteristics and their height distribution were estimated by calculating the backscatter-related Ångström exponent. Presented and analyzed are results of vertical profiling of the total and mode volume concentration for the aerosol/dust fractions obtained by using the inversion code LIRIC-2 based on combined synergistic use of data from the CALIPSO satellite on-board lidar and sun-photometer data. The quasi-horizontal mapping of near-ground aerosols was carried out over a large urban area of the city of Sofia of about 25 km2 within a 50° angular sector in a south-western direction. The results presented in the work demonstrate the capabilities of the combined approach including lidar, radiometer, satellite measurements and theoretical modeling in conducting effective ecological monitoring of the atmospheric aerosol pollution.