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.
Highlights
The rise in the mean annual atmospheric temperature of Earth’s climate system, known as global warming, has shown a distinct and sustainable trend over the last few decades,[1] being at present clearly evident even on regional and local scales
Cases of the presence of Saharan dust in the atmosphere above Europe in winter months have multiplied, as proven by satellite, in situ, and lidar observations conducted during the last several years.[8,11,14,15,16,17,18,19,20,21,22]
We present results of lidar observations of unusual winter penetrations of dustrich air masses from the Sahara Desert into the atmosphere over Sofia, Bulgaria, performed on the 17th, 24th, 1st, and 18th of February in the years 2014, 2017, 2018, and 2019, respectively
Summary
The rise in the mean annual atmospheric temperature of Earth’s climate system, known as global warming, has shown a distinct and sustainable trend over the last few decades,[1] being at present clearly evident even on regional and local scales. Along with the greenhouse gasses, mineral aerosols (dust) play an important role in the phenomenon.[2] Dust emissions into the atmosphere result from various natural processes and human activities. The European continent is predominantly invaded by cold frontal systems from the north; events of desert dust transport are less probable and, as a rule, rare.[5,6,7,10] cases of the presence of Saharan dust in the atmosphere above Europe in winter months have multiplied, as proven by satellite, in situ, and lidar observations conducted during the last several years.[8,11,14,15,16,17,18,19,20,21,22]
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