This PDF file contains the front matter associated with SPIE Proceedings Volume 11916, including the Title Page, Copyright information, and Table of Contents.

Estimation of contribution of new theoretical lines of water vapor monomer from the POKAZATEL calculations to the absorption of solar radiation in the UV spectral region is made. The atmospheric transmission is calculated with use of different broadening parameters of H₂O absorption lines.

Calculations of reflected solar radiation in crystal clouds composed of horizontally oriented plates or Parry columns are presented. The radiation intensity was simulated for a limited set of observation and illumination conditions using the optical characteristics of clouds calculated by the geometric optics method for particles with shape parameters 0.1 (plates) and 2.5 (Parry columns).

Modern models of water vapor continuum are compared in the atmospheric transparency windows of 3-5 and 8-12 μm. The longwave radiative fluxes at the top and bottom of cloudless atmosphere are calculated. The differences in the upward and downward radiative fluxes caused by uncertainties in water vapor continuum models are estimated.

The paper discusses calculations of vibrational energy levels for radioactive oxygen isotopologues of water vapor H₂^XO (where X=11,...,26). A full range of possible water vapor oxygen isotopologues considered. The vibrational levels were calculated in two ways: using the DVR3D variational nuclear motion program and the isotope substitution technique were used. Vibrational energy levels for H₂ ¹¹O, H₂ ¹²O, H₂ ¹³O, H₂ ¹⁴O, H₂ ¹⁵O, H₂ ¹⁶O, H₂ ¹⁷O, H₂ ¹⁸O, H₂ ¹⁹O, H₂ ²⁰O, H₂ 2^1O, H₂ ²²O, H₂ ²³O, H₂ ²⁴O, H₂ ²⁵O и H₂ ²⁶O are presented.

The report provides an overview of the results of work on the systematization of scientific plots characterizing the spectral functions related to the continuum absorption of carbon dioxide. Systematized plots are available for researchers in the W@DIS information system (wadis.saga.iao.ru) and can be used for comparison, both among themselves and with the results of calculations or measurements by users of this system. The work is a continuation of work on the systematization of graphic resources describing the continuum absorption by atmospheric molecules and contains dozens of little-known plots from publications of Soviet researchers in Russian.

The work is aimed at measuring the depolarization ratio of the ν₁ Raman band of methane in nitrogen and carbon dioxide media at a pressure of 50 atm. To improve the accuracy of estimating the ν₁ intensity in the depolarized spectrum, we used the simulation of the ν₃ band. It was found that the environment of nitrogen and carbon dioxide has a negligible effect on the depolarization ratio of the ν₁ Raman band of methane.

The study presents a method for fast modeling of the ν₂ Raman band of methane at any pressure of the medium and spectral resolution of the spectrometer. For this purpose, the spectra of methane with a resolution of ~ 0.4 cm^-1 in the range of 1240- 1850 cm^-1 at a pressure of 1-20 atm were recorded and fitted by Voigt profiles. It was shown that the error of this method using the obtained parameters did not exceed 5% at a pressure more than 5 atm. The demonstrated algorithm can be used in fast data acquisition methods for methane-bearing media by Raman spectroscopy applications.

We present the first results of our numerical study aimed at identifying the possible effects of the atmospheric evolution of biomass burning (BB) aerosol on the aerosol direct radiative forcing (DRF). We used a microphysical box model, which implements different parameterizations of the organic aerosol evolution within the volatility basis set framework, along with the Mie theory and radiative transfer calculations to simulate the dynamics of the physical, optical and radiative properties of polydisperse carbonaceous aerosol in an isolated BB smoke plume. We found that atmospheric transformations of the organic fraction of BB aerosol can result in major changes in the BB aerosol DRF. These changes are related to the underlying variations in the aerosol optical depth and single scattering albedo in a nonlinear manner and are especially strong in optically dense plumes.

The water vapor line broadening and shifting coefficients for the H₂¹⁷O lines in the 8,550-9,164 cm^-1 spectral region induced by oxygen pressure are measured with a spectral resolution of 0.01 cm^-1 at room temperature by a Fourier transform spectrometer. Measurements were carried out using Bruker IFS-125M Fourier spectrometer with a 60 cm multipath cell, with a path length of 1920 cm. In order to prepare the H₂¹⁷O vapor, liquid water enriched to 86% with H₂¹⁷O produced by Sigma-Aldrich Company was used. H₂¹⁶O and insignificant amount of H₂¹⁸O make up the remaining 14% of the sample. The volume of the cell is 2.765 L. The absorption spectra of the H₂¹⁷O isotopologue were recorded at pressure of 23 mBar and oxygen pressures of 0, 171, 422 and 655 mBar.

The absorption time-resolved profiles of ozone and emission signals near 567 nm in O₃-N₂ mixture after the 266 nm laser photolysis were investigated. The unknown effect of rapid ozone decomposition was observed. It was shown that the main contribution into the loss of О₃ in the postphotolysis zone is made by the reaction О₃ + O₂(a¹▵_g, v>2). O₂(a¹▵_g, v>2) is produced as a result of collisional relaxation of the atomic oxygen recombination O + O + N₂ products. It was demonstrated that the rapid depletion of O₃ occurs in the presence of О₂(c¹Σu^-). On the basis of this fact a new mechanism of ozone loss kinetics was proposed.

The global processing of a set of observed positions of spectral lines in the A²Σ⁺→X²П, B²Σ⁺→A²Σ⁺, and A²Σ⁺→A²Σ⁺ electronic transitions, collected from available literature has been performed. The analysis is based on a global model, which assumes the vibrational dependence of the parameters of the effective Hamiltonian for a given electronic state. As a result of processing a more extensive data set, new parameters of the "Dunham" type were obtained for the A²Σ⁺ electronic state, which make it possible to simulate the vibrational-rotational energy levels for the OH radical in the A²Σ⁺ electronic state.

The paper presents the first results of comparative study of the optical turbulence at the sites of the Fuxian Lake Solar Observatory (FSO) and the Baikal Astrophysical Observatory (BAO). The distributions of the probability of the Fried parameter estimated from Shack-Hartmann wavefront sensor measurements are analyzed.

The possibilities of the remote detection of continuous the ring laser beam propagating in the scattering continental and coastal atmosphere at its registration in off-axis zone are discussed. In approaching of the single scattering the estimations of the beam radiance in the point of registration are done, these estimations are compared to threshold characteristics of the available photodetectors in visible and infrared spectral range. It is shown, that the beam of laser radiation is reliably registered in the range of scattering angles (0–180)° in meteorological visibility range (5–20) km at night. In the twilight under same conditions the detection possibilities are essentially reduced.

The possibilities of the remote detection of continuous laser beam propagating in the scattering continental and coastal atmosphere at its registration in off-axis zone are discussed. The significant increase of the beam radiance contrast of laser radiation (LR) at its divergence decrease experimentally (in a field experiment) was shown. It was demonstrated that the dispersion at the border of the laser beam aperture plays an important role along with the multiple scattering. The decrease of the beam radiance contrast under twilight conditions is observed. The beams with divergence of 2’ and 4’ become discoverable at angles of scattering (80–90)° and (60–70)° correspondingly. The contrast difference can reach a decade.

The paper presents the results of the numerical simulations of binary phase Fresnel zone plates (FZP) of the mesowavelength sizes and large aperture angles (NA ~ 1) to reveal the main regularities of the formation of the spatial optical near-field structure, as well as to optimize FZP design for obtaining the most intense focus. We show the dimensional parameters of FZP focal region are sensitive both to the depth of phase zones etching and to the type of structural design of the plate. An increase in the number of Fresnel zones leads to the formation of external local focus with a greater intensity.

We propose the operating principle of a nanophotonic highly sensitive microsensor for a wide range of applications in technology, electronics, medicine as a sensor of pressure, temperature, vibration, blood pressure, etc. Computer simulation of the visible radiation interaction with the sensor nanostructure was carried out using the author's software product. The software is based on the modern mathematical apparatus of the vector finite element method.

The purpose of the work was to build a regional algorithm for reconstructing the vertical diffuse attenuation coefficient at 380, 443, 490, 510, 555, 590 and 620 nm for Lake Baikal based on quasi-synchronous in situ measurements and the standard ocean color Level-2 OLCI product. For the first time, the spatial distribution of the diffuse attenuation coefficient was obtained at seven wavelengths in the upper layer of Lake Baikal.

In this paper a structural scheme of a telecentric lens for a thermal imaging camera without a protective case allowing to carry out a passive athermalization when the operating temperature changes in the atmosphere is proposed. The relationship between the parameters of lenses and the characteristics of materials, which make it possible to limit the number of materials to two, has been found. It is shown that the requirement for the temperature coefficient of linear expansion of the device case material is determined by the thermo-optical constants and the coefficients of the average dispersion of the lens materials. The results of the development of an athermalized objective lens having a relative aperture equal to f /1 are presented.

Laser guide stars (LGS) are becoming essential tool for adaptive optics in large ground-based telescopes. We discuss the limitations of LGS, which is the indetermination of the tilt of the incoming wavefront. Because laser guide star is usually formed with a focused laser beam directed from a telescope (from the ground), it is actually a spherical wave with a random center. Taking this into account, the residual distortions of phase fluctuations are calculated. The analytical calculation carried out in the approximation of the Huygens-Fresnel method.

Possibilities of atmospheric optical communication on scattered radiation in the UV wavelength range are studied. The wavelength from the range λ = 200–400 nm at which the signal-to-noise ratio (SNR) is maximum is determined depending on the baseline distance and the observation conditions. The estimate is obtained for daytime and night communications. To calculate the signal-to-noise ratio, the impulse response (IPR) of the communication channel should be known. It has been calculated by the Monte-Carlo method with local and modified double local estimates at collision points.

The quality of astronomical observations is strongly related to the quality properties of the atmosphere. The studies of the atmosphere above observing sites are important for observation planning, instrument optimization, adaptive optics development. The high-altitude distributions of wind speed over the 6-meters Big Telescope Alt-Azimuthal of Special Astrophysical Observatory of Russian Academy Science for astronomical site characterization and the development of adaptive optics techniques are study. The data used from the NCEP/NCAR and ERA-Interium reanalysis, which is widely acknowledged as being reliable. Seasonal behaviors (mean, median, quantiles) of vertical distributions of wind speed are presented. Statistical analyses of the 200-mbar wind speed used as useful parameter for ranking astronomical sites in term of their suitability for adaptive optics is performed. The long-time trend of V200 is presented.

A method for estimating the radius of the effect of broken cloudiness on the accuracy of reconstructing the reflection coefficients of the Earth surface areas observed through gaps in the cloudy field is proposed. To estimate the radius, the process of radiation propagation in broken cloudiness is simulated by the Monte-Carlo method with averaging of the ascending light flux intensities over realizations of the cloudy field. The method is tested using the results of passive sensing of the Earth surface with the MODIS equipment.

The main processes during the propagation of high-power femtosecond laser pulses in air are analyzed. The theoretical description of self-focusing and filamentation of laser radiation was performed on the basis of the diffraction-ray tubes method. Using the method of characteristics, the equation for the intensity was modified, and the equation for the power in the diffraction-ray tube was obtained. A relationship for the power balance of various processes in the filamentation domain was established. The mechanisms for replenishing energy losses in the filamentation domain caused by plasma formation was determined. The first of them is the transverse flux from the adjacent tube (so-called energy-replenishing diffraction-ray tube). The second mechanism is associated with the inflow of energy stored in the previous time slices of the laser pulse due to dispersion.

Experimental data on self-focusing and filamentation of high-power ultrashort laser pulses for wide-aperture (centimeter) beams of sub-terawatt power are interpreted on the basis of the diffraction-ray model of single filamentation. The intensity inhomogeneities in the initial transverse profile of the laser beam, the Kerr self-focusing of which leads to the formation of high-intensity light channels, are considered. The parameters of these inhomogeneities are estimated, which is important for numerical simulation of multiple filamentation of ultrashort laser pulses along atmospheric paths.

The paper shows the possibility of reconstructing the structure of an axisymmetric supersonic underexpanded jet from laser sensing data based on the Abel transformation.

The paper presents the results of an experimental study of the characteristics of the intensity fluctuations of a laser beam propagating from the surface of a model body when it is blown by a supersonic air flow arising in the T-313 wind tunnel chamber of the ITAM SB RAS (Novosibirsk).

The results of a statistical analysis of the sea temperature field near the South coast of Crimea in the area of Cape Kikineiz, Katsiveli settlement, in the second half of 2013 are presented. The data of the systematic operational monitoring of the vertical profile of the sea water temperature in the area of the Stationary oceanographic platform were used. The data were obtained using a thermoline developed at the Marine Hydrophysical Institute. A number of parameters have been calculated that characterize the structure of the vertical temperature profiles of sea water in the region. An assessment of the temporal variability of the calculated parameters during the summer and autumn hydrological seasons is given. Several specific cases are considered that characterize the transformation of the vertical structure of water temperature during the development of upwelling and downwelling. The influence is noted of atmospheric factors, such as variability of the alongshore wind component, heat flow through the sea surface, and volumetric absorption of solar radiation, on the temporal variability of characteristics of the vertical water temperature profile in the southern Crimea coastal zone.

Results of outdoor experiments on atmospheric optical communication on scattered radiation are presented in the work. It has been established that in the daytime, the stable communication is possible for a baseline distance of 1.3 km at a wavelength of 255 nm. It has been shown that snowfall influences significantly on the communication quality in the UV range.

The objective of current investigation is development of the method intended to extract useful information from a beam in the wavefront of which optical vortices are present. Developed numerical model corresponds approximately to an optical communication system operating in a turbulent atmosphere under conditions of strong distortions of radiation. Specific feature of this system is that information is also transferred by an optical vortex.

Experimental results of measurements of the threshold power density of stimulated radiation in solutions of the coumarin-30 dye with ZnO nanoparticles irradiated with femtosecond laser pulses are presented. It is shown that the thresholds of stimulated emission in solutions of the coumarin-30 dye with ZnO nanoparticles are approximately three orders of magnitude higher than the thresholds of stimulated emission in solutions of the coumarin-30 dye with ZnO nanoparticles irradiated with nanosecond laser pulses.

The results of experimental works on creation of the closed-loop adaptive optical system intended for the tip-tilt wavefront correction have been described. The control unit with a high-speed microcontroller realizing the management by piezo-electrical stacked actuators of the tip-tilt corrector with the help of stochastic parallel gradient algorithm has been developed. The results of experiments on the dynamic wavefront tip-tilt correction at the system bandwidth of 2 kHz are reported. The basic characteristics of the closed-loop adaptive system are measured.

Numerical investigations of multi-channel laser radiation focusing efficiency through the optically inhomogeneous medium at the phasing on the system output and in the target-in-the-loop technique based on stochastic parallel gradient (SPG) algorithm have been performed. The efficiency of focusing according to the ratio of Fried’s parameter to subaperture size has been investigated.

A brief overview of the scientific literature on the turbulence experimental studies with registered deviations from the Kolmogorov–Obukhov theory predictions relating to the spectral characteristics of turbulence, is presented, as well as a brief literature overview with explanations of such deviations. The explanation of these deviations is given from the standpoint of the coherent turbulence theory.

New results of measurements of the characteristics of the turbulent atmosphere in the mountain conditions of the Sayan Solar Observatory are presented. The results were obtained during long-term observations in 2018-2019. The obtained experimental data are compared with the data of early long-term observations over the territories of high-altitude observatories in conditions of different reliefs, at different seasons, in different climatic and geographical regions. The new mobile hardware and software ultrasonic complex AMK-03-4, designed to measure the characteristics of turbulent weather fields, was used for the measurements. Experimental data are obtained for the turbulent scales of velocity V* (friction velocity) and temperature T*, which are important characteristics of turbulence in the Monin-Obukhov similarity theory. The range of experimentally observed Monin-Obukhov numbers in the positive region, where previously experimental data were not available, is significantly expanded. Comparison of new data for 2018-2019 with the data of early observations, it confirms the propositions of the similarity theory in the anisotropic atmospheric boundary layer. The data obtained are useful for predicting the characteristics of turbulence in mountainous regions.

The results of numerical studies of adaptive compensation of vortex laser beams in turbulent atmosphere caused by the initial aberration of the beam wavefront, based on of the beam backscattered radiation power are discussed. It is shown that the power of backscattered radiation increases with an increase in mode order of a Laguerre-Gaussian beam on a horizontal atmospheric path. On inclined paths, phase distortion compensation is more effective for lower-order modes.

Results of field and laboratory experiments on optical communication based on scattered radiation underwater and in air are analyzed in the present work. The feasibility of implementation of the communication with through the ice interface with an underwater source has been confirmed. It has been shown that transition from the coplanar to the non-coplanar communication scheme leads to a nonlinear growth of the communication errors.

Numerical studies of the phase correction of a laser beam passed the turbulent atmosphere by an adaptive optical system with a Shack-Hartmann wavefront sensor have been performed. Criteria for the correction efficiency have been obtained under different the spatial resolution of an adaptive mirror and the Shack-Hartmann wavefront sensor for various values of the Fried parameter.

The numerical simulation has been carried out concerning the determination of needed number of adaptive mirror’s actuators for the correction of phase distortions accumulated by the laser beam under its propagation through an airway. For this purpose, a set of wavefronts of the laser radiation passed through the airway has been registered by a Shack-Hartmann wavefront sensor. The stacked actuators’ response functions of 107- and 203-element adaptive mirrors have been experimentally determined as well. The dynamic range of adaptive mirrors’ actuators has been considered in the calculations. It is established that the 203-element adaptive mirror is not suitable for correction of the registered aberrations due to the limited dynamic range. Meanwhile by means of 107-element adaptive mirror it is possible to obtain a corrected laser beam with the Strehl ratio St=0.65.

The results of calculating the mass absorption coefficient are presented for deeply supercooled water aerosol of cloud formations at the frequencies 100…300 GHz. The computations were made for the supercooling temperatures of 0…–50 °C. New data were used on the values of the real and imaginary parts of dielectric permittivity, based on measurements of the relaxation frequencies in the centimeter band. The model computations were compared to the results obtained previously by other authors. The results proved to be essentially different for deeply supercooled water at the temperature below –20…–30 °C. A conclusion is made that the formulae used for the real and imaginary parts of dielectric permittivity of water are relevant for the frequencies 200…300 GHz.

A method of active microwave measurements of near-surface aerosol is proposed, aimed at discovering formation of ice 0 in it. This ice is formed, when water temperature proves to be below –23 °C. Its deep supercooling may occur in media having pores of nanometric sizes, for example, in aerosol particles. As ice 0 contacts dielectric, a double electric layer emerges, having high electric conductivity, exceeding the electric conductivity of the contacting media by many orders of magnitude. As a result, the effects of scattering of electromagnetic radiation increase sharply on accumulations of particles, and it becomes possible to detect such formations in different bands, including the IR-band. The proposed method of detecting scattered electromagnetic radiation in cold aerosol caused by formation of ice 0 in it has started.

In this study, field measurements of the thermal radiation of freshwater ice cover in the area of ice hummocks are presented. The studies were made at the wavelengths 8.8 mm and 2.3 cm and in the infrared band at the wavelengths 8– 14 μm. It has been demonstrated that the thermal radiation of ice hummocks compared with the background radiation of ice has primarily increased radiation power in the centimeter band but decreased values in the millimeter and IR-bands. In the IR-band, the satellite images (Landsat-8) show the same effect. Decrease of radio brightness in the millimeter band is related to the effect of radiation scattering on the inhomogeneities of the structure. In the IR-band, the effect may be determined by evaporation of snow from the surface of an ice hummock. This study will be of interest for the specialists investigating sea ice, on which ice hummocks are also formed.

The results of imaging system resolution enhancement of the astronomical objects by using a Rayleigh laser guide star (LGS) have been presented. Correction of the distortions of stellar optical image has been performed by the adaptive optical system. The numerical simulation of registration of radiation from the Rayleigh LGS by a Shack-Hartmann wavefront sensor has been carried out. It has been shown that accurate calculation and subtraction of magnitude of the defocus and tip-tilts allows mitigating the reconstruction error concerned with the finite distance to LGS and the angular position of the telescope. It has been demonstrated in the experiment that angular size of the natural star Scheat decreases by 3 times at the use of Rayleigh LGS at range of 5 km.

The report considers the reflection and scattering of waves in a randomly inhomogeneous multiscale layer. Random irregularities with scales larger and smaller than the wavelength are located in an inhomogeneous deterministic layer with a piecewise linear permittivity profile. The reflected wave field includes waves singly backscattered by small-scale irregularities before or after reflection from a layer with large-scale irregularities. The combination of reflection and backscattering gives rise to two-fold backscattering effects. Asymptotic expressions are given for the frequency coherence function of backscattered wave.

In the given work the results of theoretical researches of prominent features of formation of a Bessel-Gaussian beam of noncoherent optical radiation in a uniform medium and a turbulent atmosphere are presented. The problem analysis is based on the analytical solution of the equation for the transverse second-order mutual coherence function of a field of optical radiation. The behavior of the coherence degree, the phase of the complex coherence degree, the coherence radius and the integral scales of the coherence degree and the squared coherence degree of a noncoherent Bessel-Gaussian optical beam depending on beam parameters are studied: from the radius of the Gaussian factor of a field of a beam and from the component of the wave-vector, which is orthogonal to the direction of propagation of optical radiation.

In the given work the theoretical research of characteristics of coherence of a Laguerre-Gaussian beam of noncoherent optical radiation in a uniform medium is carried out. The behavior of the mean intensity, the coherence degree, the phase of the complex coherence degree, the coherence radius, the integral scale of the coherence degree, and the integral scale of the squared coherence degree of the noncoherent Laguerre-Gaussian beams propagating in a uniform medium is particularly considered. In work it is shown that during propagation of a noncoherent Laguerre-Gaussian beam in a uniform medium the increase in any of mode numbers (both the radial, and angular mode numbers) leads to relative reduction of coherence level of the given beam in comparison with the Gaussian beam.

Analytical equations for mutual spatial coherence functions of counter-propagating laser beams in integrated transmit/receive optical systems are derived. These equations being fourfold integrals allow estimating the diffraction parameters of transceivers and turbulent propagation conditions, under which a cryptographic key can be generated based on the principle of reciprocity. For particular cases, the degree of coherence of counter-propagating beams and the degree of coherence averaged over the receiver aperture are calculated as functions of generalized parameters describing the turbulence intensity and diffraction at the apertures.

In laboratory conditions, the fluorescence spectra of rhodamine 6G were obtained in the domain of post-filamentation channels upon interaction with femtosecond laser radiation. A fluorescence signal was received from a distance of 7.5 m from the aerosol and the droplet according to the lidar sensing scheme.

The effect of the effective frequency of collisions of electrons with neutral particles and ions on the characteristics of normal waves of radio band during oblique propagation in an inhomogeneous magnetoactive ionosphere is considered. The results of the calculation of dispersion curves, refractive and absorption indices, ray trajectories, as well as the phase path and total absorption are presented in the figures and analyzed for each of the normal waves at different angles of the entry of the ray into the ionosphere.

The results of an experiment on adaptive correction of random initial distortions of the wavefront of a collimated laser beam based on the signal of atmospheric backscattering are presented. The backscattered signal was recorded by a receiver with a limited field of view from an additional source at a different wavelength. A coaxial transmitter receiving scheme with a large transmitting and small receiving apertures was used. The quality of the correction was assessed using the Shack-Hartmann sensor, as well as by the two-dimensional distribution of the intensity on the remote screen. It is shown that after adaptive operation, the divergence of the distorted beam decreases.

We investigated the temporal fluctuations of the intensity of a laser beam through a vortex flame - a model of a fire tornado on a laboratory scale. Three equally spaced receivers were used. The spectral functions of fluctuations of the intensity of the laser beam were calculated at several speeds of swirling of the air flow incident on a stationary flame. Several spectral functions were recorded with a feature - a spike in the high-frequency region. Quantitative estimates of the shape of such spikes have been made.

The paper gives a detailed analysis of the bathymetry problem, which is the study of sea-bottom relief. Optical and acoustic methods for obtaining bathymetric data are considered. The inverse problem consisting of the search of a function that simulates the seabed profile is formulated and solved based on the kinetic model. Much attention is given to the acoustic method. A solution to the direct problem in the acoustic approach was obtained in the case of a double scattering approximation with some restrictions of the receiving antenna pattern. Numerical experiments for the inverse problem solution showed a significant effect of double scattering on the seabed reconstruction in the case of focusing surfaces.

The results of experiments carried out on the setup of a fast adaptive optical system are presented. A fan heater was used as a source of wavefront aberrations, the air flow of which was directed perpendicular to the laser beam. The processing of the experimental data consisted in determining the spectral characteristics of the disturbing effect from the dynamics of oscillations of the coordinates of the focal point of the lens array. To ensure sufficient resolution in the frequency domain, a sample of the original data was recorded for 10 s, which provided a resolution along the frequency axis of 1/10 Hz. The graphs of the spectral energy for the full set of wavefront aberrations calculated from the fluctuations of the lens array focal spot are shown. For a more detailed consideration, the wavefront aberrations were expanded in terms of Zernike polynomials, after which a spectral analysis of each aberration was carried out. It is shown that more than 90% of all turbulence energy is concentrated in lower-order aberrations, which makes it possible to use a bimorph mirror as a wavefront corrector, which reproduces well the lower-order aberrations.

The stacked-actuator deformable mirror with a high spatial resolution of the control elements was developed. The key advantage of such a mirror is its simplicity of design, thanks to the use of piezoceramic combs. Each comb consists of 5 piezo actuators arranged in a row. By assembling such combs on a piezoceramic base, it is possible to obtain the desired geometry of the control elements of the piezoactuator mirror. On an aperture of 50 * 50 mm, 100 actuators were placed in a rectangular configuration, on which a reflective substrate with a thickness of 1 mm was glued. A deformation of the mirror of 4.5 μm was obtained under the action of a control voltage of +300 V.

In the optical remote sensing field, the radiance factor of the atmosphere-underlying surface system can be measured. As a matter of fact, light is reflected by the surface itself and the scattering processes in the entire substance bulk. Surface reflection is described by considering the surface as a set of randomly oriented facets (i.e., rough surface), each of them reflects according to the Fresnel equations. Scattering in the substance bulk is subject to the radiation transfer theory, recently formulated in its discrete form. However, mathematically rigorous methods of solving the radiative transfer equation (RTE) are often inefficient in practical applications, mostly due to their high computational burden. Keeping this in mind, several approximate (engineering) methods have been developed which could be used in practice. However, the accuracy and the domain of applicability of these techniques have not been strictly defined. This paper analyzes the accuracy of the basic engineering methods for solving RTE based on a consistent discrete radiative transfer theory. The recommendations regarding using these methods in specific applicability areas are discussed.

The paper presents the results of a study of diffusion combustion of gasoline in the presence of external pressure pulsations with small amplitude. It is found that external pressure pulsations lead to characteristic changes in the temperature field, which are expressed by an increase in the amplitude of the temperature pulsation for certain modes of pressure pulsations. Analysis of the spectra of temperature changes in the entire recorded area showed an uneven distribution of frequency maxima.

Experimental investigations of visible laser radiation focusing through a scattering medium using LCOS-SLM with the resolution 1920x1080 was performed. Optical depth of the scattering medium was varied from 1 to 10, anisotropy factor was equal to 0.9. According to the principle of similarity the medium with such parameters can be considered as an equivalent to the layer of the mid-density fog with the length from 300 m up to 5 km. Experimental investigations of the focusing improvement have demonstrated that it is possible to decrease the diameter of the focal spot by 5-13%.

In laboratory conditions, experimental testing of a passive method for real-time retrieval of the instantaneous value of the crosswind speed and computer correction of images was carried out. The possibility is shown of processing a video data stream with a shooting frequency of more than 100 Hz in order to determine the wind speed.

A scheme of an infrared (IR) -parametric laser complex for remote detection and identification of the gas phase of trinitrotoluene by the method of differential absorption and scattering in real time is proposed. Calculated studies of the IR absorption spectra of trinitrotoluene in the range of 5.34-8.38 μm have been carried out.

twochannel catadioptric system of a navigation video camera of a miniature drone, designed to work in the visual and thermal imaging ranges of the spectrum with two radiation receivers simultaneously, is made of materials that are transparent in these ranges of the spectrum.

In light of the extremely high spatiotemporal variability of meteorological conditions, we propose a method for precipitation observation, which allows us to determine its composition depending on the factors of air mass formation, in order to monitor the processes of distribution and deposition of anthropogenic impurities in the Central Ecological Zone of Lake Baikal. By combining trajectory and chemical analyses, we identified the main factors influencing the formation of the chemical composition of precipitation. All events were divided into groups by the similar conditions of air mass formation and by the chemical composition. The main factors are local background, area of air mass formation, synoptic parameters, and intensity of wildfires.

This article investigates the relationship between the level of environmental pollution and morbidity of the population in the industrial centres of the Southern Baikal region. To determine the level of environmental pollution, a chemical analysis of snow sampled in three large industrial centres of the Irkutsk Region was carried out. The methods of statistical data processing (RStudio programme) revealed the groups of anthropogenic sources that had the maximum impact on the ecosystem of the cities in the Irkutsk agglomeration. We studied the relationships between the main pollutants and diseases associated with them. The variability in the morbidity of the population and the chemical composition of the snow was compared for 2013 and 2020.

This article presents the results obtained during the ship borne expedition throughout the water area of Lake Baikal from 29 July to 11 August 2020. We determined the spatiotemporal heterogeneity in the distribution of PAHs and PM₁₀ in the atmosphere above the water area of Lake Baikal. Aerosol above Lake Baikal consisted of submicron particles with the proportion of more than 90% of the total number concentration. The atmosphere above the water area of the northern basin Baikal showed background values of PAHs and high PM₁₀ concentrations. When the wind direction changed from southwestern to northwestern, the PAH concentrations in smoke plumes from wildfires increased in the central and southern basins of Lake Baikal. Among the 21 priority PAHs, phenanthrene, fluoranthene and benzo(b)fluoranthene prevailed in the aerosol. We estimated the degree of atmospheric pollution with benzo(a)pyrene and PM₁₀ standardized in Russia; they did not exceed the average daily MPCs.

From September 2019 to February 2021, we analysed seasonal and interannual dynamics of the PAH concentrations in the atmospheric air of the city of Irkutsk and the southwest coast of Lake Baikal (the Listvyanka settlement). The comprehensive analysis of weather conditions (wind direction, relative humidity and temperature of the air as well as atmospheric pressure) was carried out. There were high correlations between meteorological parameters and PAH concentrations in the study area. Average PAH concentrations in the anomalously warm 2020 were three times lower than the average values obtained in the cold 2016. The proportion of the anthropogenic aerosol transport from the industrial sources in the Southern Baikal region towards Lake Baikal ranged from 61 to 71%.

The calibration of a mobile IR laser source of a DIAL system near ~ 3400 nm for the study of methane in the atmosphere has been carried out. The technical characteristics of the IR lidar have been determined. The first test experiments to collect the atmospheric response at the calibrated wavelengths (3428.428 and 3431.708 nm) of methane sounding using a mobile IR OPO laser source were carried out.

Results from local measurements of aerosol and black carbon concentrations in marine expeditions are burdened by technogenic impacts onboard research vessel and failures of instruments due to unfavorable operation conditions. In this report, we present an algorithm of automatic data filtering, ensuring the preparation of observation time series for a subsequent physical analysis. In addition, we discuss an artifact of recording negative black carbon concentrations, caused by insufficient aethalometer sensitivity in the region of the lowest concentrations. It is noted that, to overcome this problem, data should be averaged over a longer period of time, without disregarding negative concentrations.

A comparative analysis of measurements of black carbon concentrations in the composition of atmospheric aerosol is carried out using two aethalometry methods: on the basis of collecting aerosol samples on filters and with the use of aethalometer. The two independent techniques for measuring the black carbon concentrations are shown to well agree: the cross-correlation coefficient is 0.87, the standard deviation is 17 ng/m³, and the systematic component is 0.65 ng/m³.

The results of testing of the aerosol model MaexPro for compliance with observed data of the particle size distribution (dN/dr) and aerosol extinction ε(λ) in near-surface layer of coastal atmosphere are given in the paper. It is shown that dN/dr and ε(λ) calculated from the model for the input parameters that most similar to the experiment conditions conform well to the observed data and to the calculations by code MODTRAN.

We discuss the measurements of black carbon concentrations in the composition of atmospheric aerosol over seas of the North Atlantic and European sector of the Arctic Ocean (21 expeditions). A comparative analysis of statistical characteristics, calculated for separate marine regions, is carried out. A higher black carbon content in the atmosphere of the North Sea and in the south of the Barents Sea is noted. We present estimates of the average latitude-longitude distribution of aerosol characteristics, measured in expeditions, in comparison with MERRA-2 reanalysis data.

The special features of hydrooptical signals of airborne polarization lidar sensing of non-uniform water depths are considered. Depth profiles of lidar return signal intensity and depolarization calculated by the Monte Carlo method in the presence of underwater hydrosol layers are compared with the data of their airborne polarization lidar measurements. The results obtained can be used to expand the possibilities of lidar return signal interpretation aimed at profiling of the optical characteristics of water, especially non-uniform water in ambiguous situations.

The results of taken spectral-response characteristics of aerosil in water in the form of colloidal solution are presented in the paper. Spectrogram forms depending on aerosil particle size in water were analyzed and a conclusion was made .

The parameters of condensation activity of submicron and coarse aerosol fractions and the volume scattering coefficient are compared on the basis of the data on the growth of submicron aerosol particles during artificial humidification obtained using an optical counter and an integral nephelometer. To calculate the growth factor and the Hanel parameter of condensation activity for the radii of submicron particles, an original methodological approach was applied, which used data on the dynamics of the variability of the total concentration under artificial humidification. The parameters of condensation activity obtained in spring, autumn and winter of 2020-2021 by the counter and the nephelometer are compared. Monitoring of the number concentrations was carried out in 2020-2021 within the framework of the state assignment of IAO SB RAS. The relationship of condensation activity parameters was analyzed with the financial support of the Russian Science Foundation (agreement No. 19-77-20092).

A technique for calculating the growth factor and the Hanel parameter of condensation activity for the radii of submicron particles is presented. Calculation was carried out on the basis of the data on the dynamics of the variability of the aerosol total concentration under artificial humidification. The data on the total number concentration were obtained using an optical counter of particles. The dependence of the counter readings on the relative humidity was taken into account.

The diurnal variability of the parameters of condensation activity of different aerosol fractions obtained by means of an optical counter at the Aerosol station IAO SB RAS is analyzed. The diurnal behavior of the parameters of condensation activity of individual fractions in spring, autumn and winter 2020-2021 is compared with the parameter of condensation activity for the total scattering coefficient. Monitoring of the number concentrations was carried out in 2020-2021 within the framework of the state assignment of IAO SB RAS. The diurnal behavior of the condensation activity parameters was analyzed with the financial support of the Russian Science Foundation (agreement No. 19-77-20092).

Based on the analysis of the Bio-Argo floats measurements for the backscattering coefficients by particles at 532 nm and 700 nm in the Black Sea waters and a regional ocean color product with the involvement of a physical model, the measurements of these parameters were corrected, the slope of the backscattering coefficients by particles was calculated, and its time function in the photic layer of the Black Sea was plotted.

The data of measurements of meteorological optical range (MOR), relative and specific air humidity at ROSHYDROMET meteorological stations Vnukovo (WMO 27518) and Sheremetyevo (WMO 27515) at the same names Moscow’s airports in 1973-2020 are analyzed. Using NOAA HYSPLIT_4 trajectory model and NCEP/NCAR Reanalysis gridded meteorological data, an array of about 420 thousand 7-days backward trajectories of air particles that arrived in atmospheric boundary layer above the meteorological stations during the hours of MOR measurements was modeled. The Concentration Weighted Method was used to reconstruct the seasonal fields of the mean contribution of long-range transport to MOR at the stations in 1973-2020. The influence of long-range air transport on MOR and specific air humidity in Moscow Region and indifference of relative air humidity to the air transport are shown.

Based on measurements of brightness temperatures in the microwave range from NASA satellites using VASIA2 retrieval algorithm, the daily sea ice concentration (SIC) in the Vilkitsky Strait was reconstructed for all months of summer-autumn navigation along the Northern Sea Route for 1987-2020 period. Variations and linear trends of the monthly SIC, the probability density of the daily SIC and the variation of the SIC probability for three ranges (0-34%, 35-69% and 69-100%) of SIC reconstructed using VASIA2 and NASA Team2 (NT2) algorithms were calculated and analyzed. It was found out that VASIA2 algorithm estimates the SIC in its range of 30-100% more accurately than NT2 algorithm, and so it does it for probabilities of medium and severe (by the SIC) ice conditions at the end of the summer-autumn navigation period on the Northern Sea Route.

We discuss the measurements of aerosol characteristics (aerosol and black carbon concentrations and aerosol optical depth) in 80th cruise of RV Akademik Mstislav Keldysh (August 2020) on the route from the Baltic to Barents Sea. We compare them with results from two previous expeditions (67th and 71st cruises of RV Akademik Mstislav Keldysh) and statistically generalize the data from three marine regions. The average aerosol and black carbon concentrations over the Baltic and North Seas are shown to be a factor of 2-3 larger than over the Arctic seas, i.e., Barents and Norwegian Seas. No significant differences between aerosol characteristics over Arctic seas are revealed. We discuss the average latitude-longitude distributions of aerosol characteristics, calculated on the basis of expedition measurements and MERRA-2 reanalysis data.

Results of 31-year remote spectrometric measurements of the NO₂ vertical distribution at the Zvenigorod Scientific Station of the A. M. Obukhov Institute of Atmospheric Physics of the Russian Academy of Sciences in the western Moscow region are analyzed. Seasonally dependent estimates of linear trends and interannual variations of the NO₂ contents in the stratosphere and troposphere under the influence of various natural factors are obtained.

The data of measurements of the NO₂ content in the vertical columns of the stratosphere and troposphere with the Ozone Monitoring Instrument (OMI) aboard the Aura satellite in 2004–2020 are compared to the results of ground-based spectrometric NO₂ measurements at the Zvenigorod Scientific Station of the A. M. Obukhov Institute of Atmospheric Physisc, Russian Academy of Sciences, The mean annual and seasonally dependent values of the discrepancy and correlations between the data of the satellite and ground-based measurements are obtained. The dependence of the discrepancy and correlation on the cloud cover and on the level of pollution of the atmospheric boundary layer by nitrogen oxides is revealed.

We analyze the annual variations in the total ozone content (TOC) over Tomsk in period of 1994-2017 and integrated aerosol backscattering coefficient (IABC) in period of 2000-2016, obtained using M-124 ozonometer and lidar method respectively. The correlation coefficient between these time series turned out to be -0.23, indicating that, although localized in the same altitude range, these time series are uncorrelated. Study of annual behaviors, formed from these time series, showed that TOC can be fitted by the function sin, while IABC by the function cos. At the same time, both functions depend on a single parameter, i.e., time. These functional relationships constitute the parametric equation of circle on the plane. This allowed us to conclude that the variations of these atmospheric constituents are formed mainly in two perpendicular directions.

In the report we analyze the data from lidar measurements of aerosol optical characteristics over Tomsk. Based on time series of long-term measurements of integrated aerosol backscattering coefficient 𝐵π 𝑎 (see PDF) , for the background state of the stratosphere we constructed the linear regressions for the period of 1986 – 1991 with stratospheric aerosol (SA) content decreasing at a rate of −5.1 ∙ 10⁻⁷sr^-1 per decade; for the period of 2000 - 2006 with SA decreasing at a rate of −6.31 ∙ 10⁻⁸ sr^-1 per decade; for the period of 2012 – 2017 with SA decreasing at a rate of −1.79 ∙ 10⁻⁸ sr^-1 per decade; as well as for the period of 2018 - 2021. After products from 2017 forest fires in North America were observed at SLS in Tomsk, since 2018 SA has started growing at a rate of 4.8 ∙ 10⁻⁷sr^-1 per decade. We corrected the regional empirical model of background stratospheric aerosol, which we developed in 2000-2017, by complementing it with measurements from 2017 to 2021.

A brief analysis of works devoted to the detection of greenhouse gas sources using lidars placed on space platforms is given, and the differential optical depth along the sensing path from a spacecraft is estimated for various models of carbon dioxide sources during IPDA sounding at wavelengths in the region of 1.572 μm.

An analysis is carried out of the intra-centennial variations of the length of day, the global mean sea surface temperature, and the global mean sea level. It is shown that variations of these oceanic parameters and variations of the length of day are consistent with each other simultaneously on the inter-decadal (20–30-year) and multi-decadal (50–80 year) timescales. Estimates of the correlation and delay of intra-centennial variations of the oceanic parameters with respect to variations of the length of day are obtained.

Formulas for the temperature and concentration profiles around two large evaporating in the diffusion mode interacting aerosol drops with arbitrary radii are obtained in the case when the drops are heated due to the absorption of optical radiation falling on them. The corresponding graphs are given for water drops in the air for different distances between their centers.

The results of experimental studies are presented on the variability of mass concentration of organic and element carbon, of carbon isotope composition, and of elemental content in aerosol composition at the polar station “Cape Baranov” (the Severnaya Zemlya archipelago) in 2018. Statistical and comparative analysis of expeditionary data, together with the backward air mass trajectories analysis, makes it possible to estimate the degree of Arctic aerosol pollution, and the role of natural and anthropogenic sources in the formation of high latitude aerosol substances.

Being a natural sink, snow cover accumulates pollutants during the entire winter period, and, thus, it is a cumulative indicator of atmospheric pollution. The study of the snow cover shows that the cities of Irkutsk, Shelekhov, and Angarsk are polluted significantly. To evaluate the level of atmospheric pollution in the industrial centers of Southern Pribaikalye (Irkutsk, Angarsk, and Shelekhov), the elemental composition of the snow cover of 2020 was analyzed. According to the data obtained from the research, the total index of snow cover pollution, which characterizes the effect made by the group of elements, was calculated. The spatial distribution of the index for every single city is shown. The comparative characteristic of the level of atmospheric pollution in these cities is given.

The long-term (1997-2020) comprehensive investigations at the EANET surface water monitoring station Pereemnaya River allowed defining changes of chemical composition of snow and river water on the southeast coast of Lake Baikal. We demonstrated that deicing salts, highway and railway transport as well as the transfer of gaseous contaminants from the Irkutsk-Cheremkhovo industrial zone are the main sources of pollution of the snow cover after the shutdown of the Baikalsk Paper and Pulp Mill. The impact of these sources changed the composition of major ions and reduced the equivalent concentration ratio of major cations and anions as well as pH value of snow water. The multiyear input of acid precipitation to the Pereemnaya River resulted in its acidification. Its water becomes little by little richer in minerals due to intensification of rock erosion under the impact of acid precipitation.

Chemical composition of atmospheric aerosol, atmospheric precipitation, and dry deposition in the industrial center of the Eastern Siberia, town of Irkutsk, in 2019-2020 was analyzed. 2019 is characterized by the record-breaking forest fires in the Siberian Region for the last 10 years. Sulfur and nitrogen streams flowing with atmospheric depositions to the underlying surface in Irkutsk were calculated. Sulfur and nitrogen inputs with atmospheric precipitation were higher than with dry depositions. It is noted that the flows of these substances were more intensive in 2019, especially during the warm season of the year. This study was supported by the State Project 0279-2021-0014.

The paper considers the equipment and methodology for remote determination of the vertical distribution of atmospheric temperature up to altitudes of 90 km. The technique is based on the lidar measurements of the vertical profile of the molecular density of the atmosphere using the Rayleigh scattering effect. The results obtained on the modernized Rayleigh scattering channel of the lidar based on the main mirror of the Siberian lidar station with a diameter of 2.2 m are demonstrated. The atmospheric temperature profile obtained from the lidar data is compared with the temperature profile of a satellite radiometer in the altitude range of 40-90 km.

Lidar observations of aerosol and ozone at Siberian Lidar Station (SLS) of Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences in Tomsk (26° 29’ N; 85° 3’ E) showed the presence of stratospheric aerosol layers over Tomsk during winter 2017-2018, signs of descending air masses, and deficit of ozone. Aura OMI/MLS observations indicated that in December-January 2017/2018 the northern Eurasia had been under the influence of Arctic air masses from the Eastern Hemisphere with low total ozone (TO) content and NO₂ content in the stratosphere, and low temperature in the stratosphere. Analysis of back trajectories and integrated (over MLS profile) TO showed that, due to dynamic disturbance of the Arctic stratosphere in December 2017, cold air masses with excessive reactive chlorine (in view of NO₂ deficit) were exported from within the Arctic circle to the stratosphere over Tomsk. Seemingly, in the Tomsk stratosphere, after being exposed to solar radiation and to the excessive reactive chlorine (in view of NO₂ deficit), and, staying chemically isolated, they evolved into chemically disturbed state, similar in ozone destruction rate to the conditions of the springtime Arctic stratosphere.

The results of multiyear aerosol studies during ten marine expeditions in the North Atlantic and the Arctic Ocean are used to analyze the interrelations in variations of related aerosol characteristics: volumes of particles in fine and coarse fractions, mass concentrations of black carbon, contents of organic and elemental carbons in aerosol samples, and aerosol optical depth of the atmosphere. The main factors, influencing the correlations between aerosol characteristics in high-latitude regions of ocean, are discussed.

A stationary lidar system for atmospheric gas analysis in the spectral ranges of 1800–2120 and 2120–2550 nm has been developed and is being modernized. Variants of the technical design of the near-infrared lidar system are presented. Tuning curves of the lidar radiation source and echo signals on the surface horizontal sounding paths were obtained.

The results of 25-year measurements of the aerosol optical depth of the atmosphere (AOD) at Mirny observatory (Antarctica) are discussed. It is shown that the annual average AOD values in 1996 – 2020 are characterized by statistically significant oscillation with a period of 5 years. The AOT variability is compared with the Antarctic oscillation index and the frequency of occurrence of the three main types of atmospheric circulation in the South Polar Region.

The regional full spectral primary production model accuracy has been assessed based on the comparison results of calculation with the data of measurements of chlorophyll a concentration and primary production (gross) in the surface layer of the western and eastern regions of the sea in September and December curried out in the scientific cruises in the period from 2005 to 2016. The comparison showed a good agreement between measured and calculated primary production data. The assimilation number is considered as one of the criteria for the assessment of the accuracy of the primary production model.

Lunar soil studies are planned on-board the Luna-27 polar landing probe of the scheduled Luna-Recourse mission. A sensor, which is called DLS-L, was designed as an additional analytical unit, integrated into a Gas Chromatography GC-L instrument of a Gas Analytical Package, targeted to study products, pyrolytically evolved from soil samples of a close location near the Lunar probe landing point. Gas Analytical Package for direct study of volatiles in the accessible lunar regolith at the landing site is a complex of three instruments: a TA-L thermal analyzer, a GC-L gas chromatograph, and an NGMS neutral gas mass spectrometer. The DLS-L aims in an independent measurement of pyrolytical output dynamics and integral content of Н₂О, СО₂, and in retrieving of isotopic ratios D/H, ¹⁸O/¹⁷O/¹⁶O, ¹³C/¹²C for isotopologues of Н₂О and СО₂. The DLS-L sensor data would help for further understanding of physics and chemistry of the Lunar body, as original data of polar Lunar soil first-ever direct study.

The elemental composition of near-surface aerosol was determined in Kislovodsk city and on Shatzhatmaz mountain plateau (North Caucasus) in 2010-2017. The accumulation coefficients of chemical elements in components of geochemical high-mountain landscape (surface aerosol, soil) show the increased concentrations of lithogenic elements typical for this region (Al, Na, Mg, Ka, Ca, Fe). In its turn, the technogenic elements (phosphorus, sulfur, heavy metals) are also available both in aerosols, and in soils at both observation points. We analyze the impacts of local anthropogenic sources and pollution transport with air masses from neighboring regions.

A comparative assessment of water productivity was carried out using measurements of the intensity of light radiation of aquatic organisms, carried out by optical methods using high-speed hydrobiophysical devices. The proposed method was used to calculate the integral intensity of bioluminescence of hydrobionts, which made it possible to perform a comparative assessment of the biomass, total abundance of hydrobionts, and the productivity of the coastal waters of Crimea (Black Sea). It was found that the highest integral intensity of bioluminescence of hydrobionts, averaging 37830 pW∙cm^-2∙l^-1, was observed on the southwestern shelf of the Crimea, which confirms the high biological productivity of the waters of this area. In the Kerch pre-strait area, where most of the stations were located in the divergence zone, the water productivity was quite high, yielding only 1.24 times to the value on the shallow southwestern shelf.

Using a closed-type small-angle photometer, experimental data were obtained and a comparative analysis of the diurnal variations of the values normalized to the daily average value of the angular scattering coefficient I(φ) was carried out. The data were obtained in 2010-2020 at the Aerosol Station of the LOA IAO SB RAS located in the suburbs of Tomsk. The complex makes it possible to measure round the clock the angular scattering coefficient I(φ) in absolute units (Mm^-1·sr^-1), in the angular φ=1.2÷20 degrees at a wavelength of 650 nm. The data arrays were formed on the basis of hourly values. The data were divided into subarrays within the framework of the empirical classification of the types of "aerosol weather" and by season. To analyze the seasonal and diurnal variability of the in the coarse (r> 1 μm) and submicron (r <1 μm) particle properties, the angular scattering coefficients at the angles of φ = 1.2‡ and φ = 20° were considered. The diurnal variation of the parameters in four situations: "background", "haze", "smog", and "smoke haze" is analyzed.

Analysis of variations and trends in the total ozone content (TOC) at the Kislovodsk High-Altitude Scientific Station is done based on measurements with the Brewer MkII #043 spectrophotometer in 1989–2020. Seasonally dependent estimates of long-term trends and interannual changes in TOC under the influence of the 11-year solar cycle, the quasibiennial oscillation in the equatorial stratosphere, the North Atlantic Oscillation and the El Nino–Southern Oscillation are obtained. The TOC trend is positive in 1989–2002 (1.6% per decade) and negative in 2003–2020 (–1.2% per decade). The obtained characteristics of ozone variability indicate a special character of interannual and long-term evolution of TOC over the North Caucasus. Particularly, the TOC trends over the North Caucasus region are opposite in sign to the trends of zonal mean TOC values.

The results of reconstructing the distribution parameters from aerosol scattering ratios at two wavelengths of 355, 532 nm are considered from experimental data obtained at a small station of high-altitude sounding. This study is carried out with the aim of improving the measurement techniques at the Small Station of High-Altitude Sounding of the V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Sciences. This study was supported by the Ministry of Science and Higher Education of the Russian Federation (V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Sciences).

Analysis of the data on the annual variability of the vertical-temporal structure of the background aerosol and its integral filling in the stratosphere, obtained at the lidar complex of the high-altitude atmospheric sounding station of the IAO SB RAS in 2020 is studied in this paper in comparison with previous years. Based on the monitoring results, as in previous years, a stable tendency of accumulation of stratospheric aerosol in the cold period of the year was revealed with a maximum content in January and a decrease in the warm period until its practical absence in June-July. In the upper stratosphere (30-50 km), the background aerosol is absent throughout the year.

The paper describes the lidar complex of a small lidar station for high-altitude sounding of the atmosphere of the V.E. Zuev Institute of Atmospheric Optics SB RAS (SLS). The lidar complex is based on a Newtonian telescope with a mirror 1m in diameter and is designed to monitor the vertical stratification of aerosol and the distribution of temperature and density in the middle atmosphere. Its block diagram and technical characteristics are given. A description of both the hardware and software control systems, recording and processing of measurement results is given. The profiles of the vertical distribution of aerosol, temperature and density in the altitude range of 10-7