LIDAR Detection of Aerosols in the Tunnel above the Elbrus Volcano Chamber

300-percent spikes of lidar backscattering are detected for the first time in air of a dead-end underground adit over the Elbrus volcano magma chamber. The adit is at the Baksan Neutrino Observatory (BNO). It is revealed that short bursts (~2 h) of aerosol backscattering over the seasonal decreasing trend coincide well with radon emission ( 222 Rn) and with a pulsed increase in air humidity by 2—3%. An inverted height temperature profile is measured in the BNO adit along with high concentration of heavy magmatic gases ( 12 СO 2 and 13 СO 2 ) emanating from the magma chamber. The measured data indicate that the observed lidar backscattering coefficient increase is due to pulsed generation of evaporation fog around magmatic gas plumes. Hence, the aerosol lidar might be recognized as an instrument highly sensitive to magmatic gas plumes above the volcanic chamber.