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Abstract
Based on a novel combination of approaches and instruments, this article presents campaign-based results from atmospheric boundary layer (ABL) height and aerosol optical depth (AOD) measurements carried out at two different experimental sites in Sofia, as well as from three-point measurements of aerosol number concentrations. Several instruments (lidar (developed by the IE), ceilometer, aerosol particle counter, sun photometer and meteorological sensors) were used in this study. Based on joint interpretation of the instruments' data we assess the influence of the atmospheric aerosol in the planetary boundary layer and the significant influence of aerosol layers and high clouds on AOD values. Measurements of AOD in the city basin gave values in the range 0.22–0.41 for cloud-free skies, and up to around 0.8 under partly cloudy conditions. The information obtained during the two campaigns indicates that aerosol particle concentrations were lower in park areas than along heavy-traffic thoroughfares in the city, but higher than in the mountain area. In conclusion, our study demonstrates the potential of employing a broad array of instruments for the study of boundary layer and aerosol over large, valley-situated and heavily urbanized city areas.
Acknowledgements
This work was carried out within the project ‘City versus Mountain Tropospheric Ozone: The Sofia-Plana region in an air quality and ecological sustainability perspective’ (contract DO 02-127/08). Parts of the lidar results are within the framework of the Atmospheric Composition Change: the European Network (ACCENT) and European Aerosol Research Lidar Network – Advanced Sustainable Observation System (EARLINET-ASOS) Project. LPC measurements were partly funded by the Kalmar University Faculty of Natural Science and Technology.