Abstract A harmonic analysis of lidar aerosol backscattering, Earth’s crust deformation data (measured by a laser interferometer strainmeter), and meteorological factors (air relative humidity, atmospheric pressure, and air temperature), monitored in the period from August 23, 2019 to June 13, 2020 in the tunnels of the Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences), has been performed. Phase portraits of meteorological factor variations have been constructed, and phase shifts have been calculated with respect to the aerosol backscattering signal measured by the lidar. A high contribution (up to 70%) of external atmosphere humidity to the obscuring of lidar signal modulation is revealed.