Evaluation of smoke mass concentration within the PBL based on observations of fluorescence lidar with several discreet channels

Abstract. Elevated concentrations of smoke within the planetary boundary layer (PBL) represent a significant health hazard, making its monitoring essential. This study demonstrates that a multi-channel fluorescence lidar can effectively analyze smoke–urban aerosol mixtures and retrieve smoke mass concentration. The method is based on the fundamentally distinct fluorescence spectra of the two aerosol types, with an estimated detection threshold on the order of 0.1 µg · m^-3. Measurements performed over Moscow with a five-channel fluorescence lidar in 2023–2024 captured numerous smoke episodes across a wide altitude range from spring through autumn. In 2024 alone, smoke was detected in 59 out of 67 measurement sessions between April to October. Back-trajectory analysis indicates that most events were associated with long-range transport over Atlantic, with only 12 episodes originating from fires in southern Russia. Focusing on smoke within the PBL, the results show that long-range transported smoke from North American wildfires can descend and mix with this layer, contributing mass concentrations on the order of 1 µg · m^-3. In contrast, regional wildfires in southern Russia led to substantially higher concentrations, with smoke mass in the PBL reaching up to 50 µg · m^-3 during observed episodes.