Lidar observations of massive Saharan dust intrusion above Sofia, Bulgaria, in April 2019

A large-scale massive transport of Saharan dust over all of Europe was observed in the last third of April 2019. As part of the European Aerosol Research Lidar Network (EARLINET) and the Aerosol, Clouds and Trace Gases Research Infrastructure (ACTRIS), Sofia lidar station conducted lidar observations of the atmospheric aerosol load in this period. Some of the results obtained are described in this work. Remote measurements were implemented using two elastic-scatter lidar channels (1064 nm/532 nm). The paper presents results of studying and analyzing the optical and microphysical properties of the aerosols detected, as well as the topological and dynamical features of the aerosol/dust layers observed. The height profiles of the atmospheric aerosol backscattering coefficient are retrieved and discussed. The microphysical properties of aerosol/dust particles are characterized qualitatively based on an analysis of the backscatter-related Ångström exponents profiles and distributions obtained for particular aerosol layers. Dust mixing with other aerosol types of local origin or such captured during the transport is also considered and discussed based on local meteorological radiosonde data and air-transport modeling and forecasting data. Conclusions are drawn concerning the experimentally ascertained and the possible impacts of the massive dust intrusion event on the local tropospheric aerosol structure and meteorological conditions.