A differential absorption lidar (DIAL) system designed on the basis of optical parametric oscillators (OPO) with nonlinear KTiOAsO₄ (KTA) and KTiOPO₄ (KTP) crystals is described. The crystals allow laser radiation tuning in the infrared region (IR) wavelength region. The measurements in the 3.30–3.50 μm spectral range, which includes a strong absorption band of methane, are carried out. Lidar backscattered signals in the spectral band 3.30–3.50 μm has been measured and analyzed along the horizontal path in the atmosphere. Based on the experimental results, CH₄ concentrations ~2.085 ppm along a 800 m surface path are retrieved in the spectral range under study with a spatial resolution of 100 m.

The change of the global climate is most pronounced in the Arctic, where the air temperature increases 2 to 3 times faster than the global average. This process is associated with an increase in the concentration of greenhouse gases in the atmosphere. There are publications predicting the sharp increase in methane emissions into the atmosphere due to permafrost thawing. Therefore, it is important to study how the air composition in the Arctic changes in the changing climate. In the Russian sector of the Arctic, the air composition was measured only in the surface atmospheric layer at the coastal stations or earlier at the drifting stations. Vertical distributions of gas constituents of the atmosphere and aerosol were determined only in a few small regions. That is why the integrated experiment was carried out to measure the composition of the troposphere in the entire Russian sector of the Arctic from on board the Optik Tu-134 aircraft laboratory in the period of ​​​​​​​4 to 17 September of 2020. The aircraft laboratory was equipped with contact and remote measurement facilities. The contact facilities were capable of measuring the concentrations of CO₂, CH₄, O₃, CO, NO_x​​​​​​​, and SO₂, as well as the disperse composition of particles in the size range from 3 nm to 32 µm, black carbon, and organic and inorganic components of atmospheric aerosol. The remote facilities were operated to measure the water transparency in the upper layer of the ocean, the chlorophyll content in water, and spectral characteristics of the underlying surface. The measured data have shown that the ocean continues absorbing CO₂. This process is most intense over the Barents and Kara seas. The recorded methane concentration was increased over all the Arctic seas, reaching 2090 ppb in the near-water layer over the Kara Sea. The contents of other gas components and black carbon were close to the background level. In bioaerosol, bacteria predominated among the identified microorganisms. In most samples, they were represented by coccal forms, less often spore-forming and non-spore-bearing rod-shaped bacteria. No dependence of the representation of various bacterial genera on the height and the sampling site was revealed. The most turbid during the experiment was the upper layer of the Chukchi and Bering seas. The Barents Sea turned out to be the most transparent. The differences in extinction varied by more than a factor of 1.5. In all measurements, except for the Barents Sea, the tendency of an increase in chlorophyll fluorescence in more transparent waters was observed.

Lidar and searchlight instruments and techniques for atmospheric research developed at the V.E. Zuev Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, in recent years are described. Key results obtained using these techniques are presented.

A differential absorption lidar (DIAL) system based on optical parametric oscillators (OPO) with nonlinear KTA and KTP crystals is designed. The crystals allow laser radiation tuning in the IR wavelength region. A series of experiments on remote monitoring of methane along a horizontal surface sounding path in the 3300–3430 nm spectral range was carried out. Based on the experimental results, the CH₄ concentrations are retrieved along a surface 800-m path in the spectral range under study with a spatial resolution of 100 m.