LAUSR

Abstract. We report results of lidar studies of the atmospheric aerosols present above the city of Sofia during four episodes of wintertime Saharan dust intrusions in the last decade. The optical and microphysical properties of the detected aerosols, as well as the aerosol layering and dynamics, are retrieved and characterized. By combining lidar results with in situ PM10 concentration measurement data and air-transport modeling/forecast data, the effects of mixing and interaction of desert aerosols with local ones are analyzed as dependent on the altitude range, phase, and intensity of the dust load events. Included in the analysis are also meteorological radiosonde data, which allow us to ascertain the direct and strong influence of the desert air and aerosols on the local atmospheric conditions and meteorological parameters and thus, indirectly, on essential components of the local weather, such as the seasonal thermal regime and the regimes of cloud formation and precipitation. Using online resources, color maps of air temperature anomalies in the region for the days of lidar measurements are also provided based on climatological data over the three preceding decades. The results presented are in conformity with previously published statistical data of other authors and indicate that the wintertime intrusions of warm air masses from North Africa carrying Saharan dust to Europe, and particularly to the Balkans, rare and atypical until recently, nowadays show a trend of increasing in terms of frequency and intensity, pointing to deviations in the seasonal regime of the involved intercontinental air circulation systems.