• 42.650°N 23.380°E 590 m a.s.l.

Observational platform

Bulgaria

• Institute of Electronics

• Tanja Dreischuh
  Facility PI
• Zahari Peshev
  PI deputy

The ACTRIS national facility in Sofia is a ground-based fixed urban site hosted by the Laser Radars Laboratory of the Institute of Electronics, Bulgarian Academy of Sciences (IE-BAS). It is located in the southeast part of Sofia, right next to a heavy-traffic thoroughfare, at a distance of about 7 km from the city center. Sofia is situated in a heavily urbanized valley (average altitude of about 550 m above sea level), surrounded by mountains on all sides, the largest being the Balkan Mountains on the northeast and Vitosha Mountain on the south. The complex orography, the intricate air-flow pattern caused by the diurnal mountain winds, and high urbanization, as well as the temperature inversions, complicate the natural ventilation and facilitate the trapping of air pollutants. Sofia has a continental climate with a monthly average air temperature varying between -0.5 °C in January and 21.6 °C in July and a mean annual air temperature of 10.9 °C.

The infrastructure at Sofia (IE-BAS) national facility consists of state-of-the-art, ACTRIS compliant, aerosol remote sensing instrumentation, along with additional equipment for measuring cloud base and depth, meteorological parameters and PM mass concentrations. Regular high-power lidar and continuous sun/sky/lunar photometer and ceilometer measurements are performed aimed at studying and characterizing the aerosol climatology, typology, stratification and dynamics, as well as events and phenomena related to loads and presence in the troposphere of specific aerosols, such as desert dust, volcanic ash, forest and/or industrial fire smoke, etc. Substantial and diverse database has been accumulated over the years resulting from the vertical remote sensing observations, as well as from ecologically significant horizontal-scanning and mapping measurements on the aerosol distribution and dynamics in the near-ground atmospheric layer.

• Dreischuh et al. (2016). Lidar Mapping of Near-Surface Aerosol Fields. Aerosols - Science and Case Studies. https://doi.org/10.5772/65274
• Evgenieva et al. (2022). Optical and Microphysical Properties of the Aerosol Field over Sofia, Bulgaria, Based on AERONET Sun-Photometer Measurements. Atmosphere, 13(6), 884. https://doi.org/10.3390/atmos13060884
• Peshev et al. (2022). Large-Scale Saharan Dust Episode in April 2019: Study of Desert Aerosol Loads over Sofia, Bulgaria, Using Remote Sensing, In Situ, and Modeling Resources. Atmosphere, 13(6), 981. https://doi.org/10.3390/atmos13060981
• Peshev et al. (2023). Combined Characterization of Airborne Saharan Dust above Sofia, Bulgaria, during Blocking-Pattern Conditioned Dust Episode in February 2021. Remote Sensing, 15(15), 3833. https://doi.org/10.3390/rs15153833