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Scanning lidar LOSA-M3 makes it possible to measure the polarization characteristics of backscattering signals from aerosol and clouds at wavelength 532 and 1064 nm. The lidar transceiver is placed on a scanning column, which allows changing the direction of sounding within the upper hemisphere at a speed of 1 degree per second. The polarization characteristics of the transmitter (linear or circular polarization) can be changed by rotating the phase plates synchronously with the laser pulses. Conical scanning of the lidar allows identifying cloud areas with preferential zenith or azimuthal orientation of the crystal particles. The article presents the results of observations of the cloud polarization structure carried out in Tomsk. Methods of the calibrations of lidar polarization channels are described.

Airborne lidar measurements were carried out over Siberia in July 2013 and June 2017. Aerosol optical properties are derived using the Lagrangian FLEXible PARTicle dispersion model (FLEXPART) simulations and Moderate Resolution Imaging Spectrometer (MODIS) AOD. Comparison with Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aerosol products is used to validate the CALIOP aerosol type identification above Siberia. Two case studies are discussed : a mixture of dust and pollution from Northern Kazakhstan and smoke plumes from forest fires. Comparisons with the CALIOP backscatter ratio show that CALIOP algorithm may overestimate the LR for a dusty mixture if not constrained by an independent AOD measurement.

The paper presents the results of studies aimed at the analysis and assessment of atmospheric pollution over the Lake Baikal in the summer. This information is necessary to create physical models of the formation and transfer of atmospheric aerosol fields, taking into account the physical and geographical features of the Baikal region. Measurements were carried out by a lidar «LOSA-A2» installed on the scientific-research vessel «Academician V.A. Koptyug». The vessel’s route passed along the South, Middle and Northern Baikal, from July 15, 2018 to July 26, 2018. At the same time, observations were conducted using lidar «LOSA-M2». It was located in the background area at Boyarsky stationary site (51.84° N, 106.06° E), in the south-eastern part of the lake. The results of changes in the spatial structure of atmospheric aerosol fields in background conditions and during forest fires are shown.

The paper presents the preliminary results of the lidar&radiometer measurement campaign (LRMC-2017), estimation of statistical relations between aerosol mode concentrations retrieved from CALIOP and ground-based lidar stations and case study of fire smoke events in the Eurasian regions using combined ground-based and space lidar and radiometer observations.

Pulsed radiation propagating through a layer of a scattering medium undergoes distortions caused by multiple scattering. The results of numerical calculations of pulse waveforms for media with different scattering phase functions are presented. It is demonstrated that the scattered radiation waveform is not described by diffusion theories even for sufficiently large optical thicknesses ([tau] [approximately equal to] 10- 20) but is described, as a rule, by a bimodal distribution. Only when the optical thickness significantly increases ([tau] > 100-150), the photon distribution over the free paths acquires the unimodal diffusion form. OCIS codes: 010.1300, 290.4210.

The results of seawater sensing by use of an airborne lidar with a changeable field of view (FOV) are presented, together with the results of numerical simulation of lidar operation by the Monte Carlo method. It is demonstrated that multiple scattering and wind-driven sea waves have opposite effects on the measured attenuation coefficient. At small FOVs the wind-driven sea waves cause the lidar signal decay rate to increase compared with the size of the plane surface and hence result in an overestimation of the retrieved attenuation coefficient. Inefficient operation of lidars with small FOVs is caused by strong fluctuations of lidar signal power that cannot be described by a normal distribution. Specific features of the fluctuations can be interpreted as manifestations of the well-known effect of backscattered signal amplification caused by the double passage of radiation through the same inhomogeneities. As for the plane air-water interface, multiple scattering is significant for large FOVs and compensates for the effect of wind-driven sea waves. The applicability of simple sea-surface models to a description of lidar signal power fluctuations is discussed. OCIS codes: 010.4450, 010.3640, 290.1350.

A method of lidar data collection by simultaneous registration of signals from the anode and several dynodes of the photomultiplier is suggested. The dynamic range of the receiver has been extended as many as 5 orders of magnitude in the case of cloud sensing. The stable operation under strong background illumination is possible without losses in fine signal structure. OCIS codes: 040.5250, 120.0280, 230.5160, 280.3640.