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Trends in long-term changes in the annual average and seasonal average temperatures within the atmospheric boundary layer in Siberia over 1981-2020, estimated based on observations at 24 aerological stations in winter, spring, summer, autumn, and for the year as a whole, are analyzed. It has been established that during the 40-year period under study, statistically significant positive trends in the annual average air temperature are observed throughout the atmospheric boundary layer over the Siberian territory; the trend value decreases from north to south and with altitude. The main contribution to the regional warming of the atmospheric boundary layer climate over Siberia is made by the spring, summer, and autumn periods. The warming of the boundary layer has intensified in the past decade, from 2011 to 2020.

Stationary non-laser gas analyzers based on the classical differential absorption method have been designed for continuous measurement of the content of nitrogen and sulfur oxides in exhaust gases of thermal power plants natural gas, coal, and fuel oil. The operation of gas analyzers at Russian thermal power plants based on has shown their high sensitivity, reliability, and ease of maintenance. Based on the method of differential optical absorption spectroscopy and UV LEDs, a prototype of a portable low-power gas analyzer has been designed. It is an effective tool for simultaneous trace measurements of concentrations of a number of atmospheric gases. A mercury analyzer has been created based on the atomic absorption method using a capillary lamp with a natural isotopic composition of mercury with a transverse Zeeman effect as a radiation source. A technique for determining mercury in various media has been developed; the sensitivity of the analyzer is 14 ng/m³. The possibility of its wide use for multi-purpose mercury monitoring is shown.

Information about an angular distribution of emission from the filamentation region is required to select an effective scheme for remote sensing of the aerosol atmosphere by femtosecond laser-induced breakdown spectroscopy. We present the results of a series of experiments on identification of an impurity with the use of femtosecond LIBS. The angular distribution of the emission from the femtosecond radiation filamentation region in the atmosphere for an impurity in water aerosol is estimated in the range from 0 to 180° based on the experimental data. A model of the angular distribution of the emission is suggested, where absorption in the filament plasma is taken into account. The variation in the intensity of the emission line with the impurity concentration is analyzed. It is shown that emission from the filamentation region occurs due to spontaneous emission.

A large-scale comprehensive study of the composition of the troposphere of the Russian Arctic was carried out in September 2020 onboard the TU 134 “Optic” aircraft laboratory. The results of the study of the spatiotemporal variability of aerosol and black carbon (BC) concentrations are considered. The airborne sensing data were used for the analysis of general and particular features of the spatial variability of vertical profiles of aerosol and BC concentrations. The columnar BC concentrations in the arctic and subarctic latitudes were obtained.

The results are presented of atmospheric experiments on compensation for the artificially introduced initial aberrations of the wavefront of a focused laser beam using the aperture sounding method based on an atmospheric backscatter signal from an additional source at a different wavelength. It is shown that adaptive compensation can reduce the amount of wavefront distortions, increase the backscatter signal, and restore the focusing of the main laser beam

The processes of interaction of an expansion wave with the flow in a laminar boundary layer are studied with the use of the theory of free interaction. Numerical solutions of a nonlinear problem are found for various values of the dimensionless velocity of wave motion. Distributions of pressure-induced friction stress on the surface are obtained.

The effects of the water-jet velocity and its angle on the laser-water-jet processing results are studied. It is found that the depth of laser-water-jet processing gradually increases with an increase in the water-jet angle; however, this increasing trend becomes less pronounced as the water-jet angle increases from 60 to 75^°C. As the water-jet velocity increases, the depth of laser-water-jet processing gradually increases.

The problem of generation of two-dimensional unsteady motion in a viscous incompressible fluid of finite depth is investigated here. The motion is generated due to initial disturbances in the form of prescribed surface pressure or displacement at the free surface. The Fourier transform with respect to space and the Laplace transform with respect to time are used to obtain the form of the free surface in terms of multiple integrals. Finally, an asymptotic form of the free surface is obtained using the method of steepest descent.

The problem of the flow of a viscoelastic fluid in a flat channel with permeable walls and a constant flow through the walls is considered. The problem is formulated using the equations of the modified Vinogradov - Pokrovskii mesoscopic model. For the case of the presence of a flow through the walls, a method for setting the boundary conditions is proposed, which ensures that the resulting solution is consistent with the solutions obtained with no account for the flow. A computational algorithm for finding solutions is considered both in the presence of flow through the walls and in its absence.

This paper describes a problem of unsteady flow of an aqueous polymer solution in a strip with a free boundary, the condition on which includes the time derivative of the desired function. A solution to this problem is constructed for a layered flow in a strip of constant width. The dependence of variation of the strip width with time on a parameter proportional to relaxation viscosity is studied.