This PDF file contains the front matter associated with SPIE Proceedings Volume 12780, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

The measurements of the angular distribution of two-photon-excited fluorescence of a dye solution in an aqueous aerosol are reported. It is shown that the fluorescence of an aerosol with a dye is one and a half to two times greater in the backward direction than in the forward direction.

This paper presents the results of theoretical studies of the coherent properties of partially coherent vortex Bessel-Gaussian optical beams propagating in a turbulent atmosphere. The coherence degree of these optical beams depending on the length of the propagation path, propagation conditions and optical beam parameters: the radius of the Gaussian optical beam cofactor, the topological charge of a vortex optical beam and the transverse coherence length of the optical source field, is particularly studied. It is shown that when a partially coherent vortex Bessel-Gaussian optical beam propagates in a turbulent atmosphere, not two (one due to the influence of turbulence, and the second due to the influence of partial coherence of the optical source), but one ring dislocation of the coherence degree is formed. Moreover, the ring dislocation of coherence degree is formed only for partially coherent vortex Bessel-Gaussian beams whose the transverse coherence length of the optical source field is greater than the radius of the first Fresnel zone.

The theoretical study of the coherence distribution in the cross-section of a partially coherent vortex-free Bessel optical beam during propagation in a uniform medium has been performed. The paraxial approximation of the second-order transverse mutual coherence function of a partially coherent vortex-free Bessel optical beam obtained using the Huygens–Fresnel principle is analyzed. The dependence of the coherence degree of the partially coherent vortex-free Bessel optical beam on the parameters of the problem (in particular, on the transverse coherence length of the field of an optical source) is studied. It is found that if a partially coherent vortex-free Bessel optical beam has the property of axial symmetry, then the coherence degree of this beam at the optical axis has the same property. However, when the observation points are shifted from the optical axis of the partially coherent vortex-free Bessel optical beam, a dependence of the coherence of this beam appears both on the magnitude of the sum coordinate of the observation points and on the mutual orientation of the vectors of the sum and difference coordinates of the observation points.

The results of experiments on the phase correction of a laser beam propagating in a turbulent atmosphere are presented. A scheme was used in which the laser beam of the main radiation, formed using an adaptive optics system, propagated along a horizontal atmospheric path. To ensure the operation of the AO system, a signal was used from a reference source generated by cw-laser radiation at a wavelength of 0.532 μm, which propagated towards the main one. At the transmitter, the optical beam from the main laser is formed using the adaptive optics system and directed into the atmosphere by the Newton telescope. The main radiation laser is focused through the atmospheric layer into the receiving plane. A reflecting screen, a photodetector based on the small astronomical telescope Celestron, and a reference laser, which propagated towards the main one, were located in this plane.

The cross-correlation coefficient of image jitter of a laser guide star (LGS) and a plane wave in the focal plane of the telescope is calculated. The calculation showed that such a cross-correlation function of image jitter consists of two terms. In this case, the first (main) term does not take into account the integral correlation of fluctuations in the displacement of the laser beam with the field of the dielectric permittivity of the medium, and the second one takes into account this correlation according to the Furutsu-Novikov formula. The Kolmogorov-Obukhov turbulence spectrum was used in the calculations. As a result, it turned out that the monostatic LGS has residual jitter, and this signal can be used to correct the "global" tilt of the wavefront in telescopes. Moreover, for medium-sized telescopes operating in conditions of strong turbulence, the magnitude of this random jitter of the position of the LGS will be sufficient to be used for correcting the tilt of the wave front.

We present some results of our numerical study of the radiative impact of Siberian biomass burning aerosol (SBBA) on clouds in the eastern Arctic. The numerical experiments were performed using the CHIMERE chemistry-transport model coupled with the WRF meteorological model. Based on an original numerical methodology, we examined the radiative impact of SBBA on characteristics of cloudiness, such as the cloud optical depth and cloud cover fraction for low, medium-level, and high clouds, as a function of the duration of the radiative forcing of SBBA. The results of the experiments show that SBBA-induced disturbances in radiative fluxes can lead to significant but variable changes in the cloudiness characteristics. The changes in the characteristics of low and medium-level clouds tend to have opposite signs and are caused predominantly by scattering components of the aerosol particles. Overall, this study contributes to a better understanding of the complex mechanisms of formation of the semi-direct radiative effect of SBBA in the Arctic.

The results of full-scale experiments in the atmosphere with various turbulence state meters are considered. In measurements on horizontal open atmospheric paths of various lengths, three optical meters and an acoustic weather station were used. Based on the test results of the meters, a high correlation of turbulence measurements made by optical differential meters DIT-2 and DIT-M as well as the AMK-03 ultrasonic acoustic weather station was shown. Conclusions are drawn about the accuracy and applicability of the meters used to assess the level of turbulence along the atmospheric paths.

The paper presents the results of a study of the influence of the geometric parameters of the mathematical model of a photonic-crystal (PhC) direct waveguide, based on thin-film lithium niobate on an insulator, on the optical insertion loss. Based on the obtained model of a direct photonic-crystal waveguide, a model of a photonic-crystal waveguide structure with a 60° bend was built, based on thin-film lithium niobate on an insulator, and the model parameters were optimized using the MMA method according to the principle of identifying the boundaries of air holes as a Bernstein polynomial 1 order followed by "stretching", which made it possible to reduce the insertion optical loss by a factor of 76 of a photoniccrystal waveguide structure with a 60° bend relative to a waveguide with a bend without optimizing the parameters.

The line broadening and shift coefficients of the absorption lines of the ¹⁵N¹⁸O molecule induced by air pressure in the region of 5200 – 5500 cm^-1 were measured for the first time. The value of the broadening coefficients for transitions in the 3-0 band was about 0.06 cm^-1/atm and was in a good agreement with the values of the broadening coefficients of the ¹⁵N¹⁶O molecule from the HITRAN database. The line shift coefficients by air pressure lie in the range of 0.005–0.01 cm^-1/atm.

The present work focuses on an algorithm for obtaining data on the positions of the centers of gravity of subimages of sunspots from the Shack–Hartmann sensor measurements. The analysis of the positions of the centers of gravity of subimages formed by spaced subapertures is used in determining the verical profiles of optical turbulence and, specifically, the structural constant of turbulent fluctuations of the air refractive index C²_n . The characteristics of optical turbulence determine the quality of astronomical images obtained on ground-based telescopes.

In this paper, wide-field adaptive optics systems for ground-based solar telescopes are discussed. The features of constructing adaptive optics systems based on layer- and object-oriented approaches are considered. It is shown that the optimal adaptive optics system for the Large Solar Vacuum Telescope (LSVT) should be created on the basis of optical conjugation of deformable mirrors with turbulent layers of the atmosphere, the system for determining wavefront aberrations should be based on the use of a set of a narrow field of view sensors conjugated with telescope aperture, as well as a multi-directional wavefront sensor for turbulence tomography, designed on the basis of an object-oriented approach (measurements of wavefront aberrations in different directions). The schemes of pupil imagers that provide optical conjugation of the LSVT wavefront sensor with heights of 3 km as well as the upper atmospheric levels are considered. Direct optical conjugation of the Shack-Hartmann sensor with a turbulent layer is limited by a height of about 3 km (due to significant vignetting).

The passage of electromagnetic radiation in the visible range through a plate of Ih ice with a condensed film of ice 0 on it was studied. Ice 0 is a recently discovered transitional form of crystalline ice from supercooled water at temperatures below –23 °C to Ih or Ic ice. The existence of significant attenuation of radiation in the temperature range from –80 to – 23 °C has been established. The effect is associated with the appearance of a layer with high electrical conductivity at the boundary between Ih ice (dielectric) and ice 0 (ferroelectric). Attenuation is determined by scattering and absorption of electromagnetic radiation propagating through the sample due to plasmon resonance in nanometer-sized films.

Currently, there are no such image registration systems that would provide perfect quality. Therefore, an important stage in the tasks of computer vision and the development of image analysis systems is preprocessing. At this initial stage, it is necessary to use various techniques to improve the image quality acceptable for further analysis and processing. The methods of image pre-processing are considered, both “classical”, element-by-element, and modern, based on the use of artificial intelligence methods, designed to eliminate various kinds of distortions. This study was supported by the Ministry of Science and Higher Education of the Russian Federation.

The 1-meter Large Solar Vacuum Telescope (LSVT) is main instrument of the Baikal Astrophysical Observatory (BAO) of the Institute of Solar-Terrestrial Physics of Siberian Branch of Russian Academy of Sciences (ISTP SB RAS). The in-depth understanding of the Sun’s physics require optical observations of the Sun with higher and higher angular resolution. Therefore the development of adaptive optics is going for 1-meter LSVT. We present characterizations of free atmosphere from atmospheric ERA-Interim reanalysis data above BAO. The aim is estimation of the heights of turbulent layers above LSVT to select the heights of conjugation of deformable mirrors in the development of a multi-conjugated adaptive optics system. The profiles of inverse Richardson number (1/Ri), Brunt–Väisälä frequency, gradient of potential temperature and the total vertical wind shear are calculated for detection of heights in free atmosphere where most probably turbulence generation.

The design of adaptive optics (AO) is largely determined by atmospheric conditions above the telescope site, such as optical turbulence and wind speed. Besides the requirements to laser for LGS formation are related to atmospheric parameters. In this case, the main goal is to provide a sufficient return photons flux from LGS for measurement by the wavefront sensor. The return flux from sodium laser guide star (LGS) is determined by the characteristics of the sodium layer, atmospheric transmission, geomagnetic field parameters, and the spot size of LGS in the mesosphere. The resonance fluorescence of sodium atoms in the mesosphere is affected by such atmospheric parameters, as temperature, wind, atmospheric density of molecules at height of LGS formation. The parameters listed above depend on location of telescope and have seasonal variations. The study discusses these characteristics for astronomical observatories in the Russian Federation located in middle latitudes.

In the conditions of the Sayan Mountain Solar Observatory and the urban environment of Tomsk, long–term observations of the main characteristics of the turbulent atmosphere in the Monin-Obukhov similarity theory were carried out using the AMK-03-4 ultrasonic station. The paper presents the results of measurements of the spatial correlation of fluctuations of the surface longitudinal wind velocity in a thermally stratified turbulent atmosphere. It is shown that during the transition from unstable to stable stratification, on average, the spatial correlation of longitudinal wind fluctuations in the surface atmosphere increases (the average scales in instability are about 14 m, in neutrality – about 40 m, and in stability – about 32 m).

On the basis of long-term measurements in the surface layer, the dependences of the histograms of the distribution of temperature values T and the longitudinal component of the horizontal wind velocity u on the stratification of the turbulent atmosphere are obtained. Experimental data on the time-continuous duration distributions of various stratifications of the atmosphere have been obtained. Long-term measurements were carried out in 2019 in the mountainous conditions of the Sayan Solar Observatory and in 2021 on the territory of the experimental complex of the V.E. Zuev Institute of Atmospheric Optics SB RAS (Tomsk). It is shown that the histograms constructed from the measurement data under typical conditions realized in the surface layer of the Earth's atmosphere basically correspond to the normal (Gaussian) probability density distribution. In cases of highly unstable or highly stable stratifications of the atmosphere, histograms may deviate from the center of the normal distribution curve, significant asymmetry coefficients appear in histograms, characterizing the deviation from the center of the normal distribution, asymmetry appears on the far wings of experimental distributions and negative excesses.

In order to develop the method, the possibilities of determining the type of atmospheric turbulence (Kolmogorov, coherent, etc.) based on meteorological measurements data, receiving from a weather station in real time were researched. To do this, a spectral analysis of successive samples is carried out by a time sliding-window from the continuously replenished assembly of meteorological elements values. The air temperature was selected from the meteorological elements to work out the method. The criterion for changing the types of turbulence is the value of the slope of the inertial interval of the temperature fluctuation spectrum, which is equal to «–5/3» under Kolmogorov turbulence, and «–8/3» under coherent turbulence. Using the method, it is possible to estimate the spatial dimensions of turbulence regions of a certain type based on information about wind velocity and duration of the registration time.

The calculations have been carried to estimate the possibility of phase correction of the simplest Laguerre-Gauss vortex mode in an adaptive optical system without the wavefront sensor. The operation of bimorph adaptive mirrors with square and axisymmetric actuator packing under the control of the stochastic parallel gradient (SPG) algorithm has been simulated. As a result of SPG correction, the power fraction in the near-axis pinhole as well as the Strehl number increased to the level of 0.55-0.6 of the possible maximum.

Statistical characteristics of optical vortices have been analyzed in the paper. As was shown such vortices appear in the radiation wavefront if the initial phase is set as a mathematical raw formed by Zernike polynomials or by a phase screen simulating atmospheric turbulence with a spectrum of the index of refraction fluctuations prescribed by a von Karman formula. In both examples considered here the statistical properties of the vortex distribution satisfy the requirements of the Central limit theorem, and acceptable correspondence is also observed between parameters of beams formed by polynomials and by a phase screen.

Using previously derived formulas describing wave reflection and scattering in a reflective multiscale inhomogeneous layer, we examine the effect of random irregularities on the sounding signal structure. It is shown that, unlike scattering in a homogeneous medium, scattering by small-scale irregularities in a plane-stratified medium depends on the location of these irregularities relative to the reflection point. This largely determines the scattered pulse structure and the applicability of the geometrical optics approximation to its description

A technique for providing apochromatic correction in the wavelength range from 3 to 12 μm, which makes it possible to substantiate the choice of materials and optical powers in an optical system with components separated by an air gap, is discussed. Using numerical methods, it is shown that the solutions found can serve as starting systems for the development of dual-band lenses that provide a stable position of the image plane in the ranges of 3-5 and 8-12 μm, coupled with uncooled dual-band infrared detectors. The results are illustrated by the calculation of a dual-band infrared lens with a focal length of 50 mm and a relative aperture of 1:1.2.

The deviations of the spectral composition of air density fluctuations in a supersonic flow from that predicted by the developed turbulence model, recorded in experiments in wind tunnels, require a revision of the estimates of the disturbance of optical waves propagating through the flow. This article demonstrates a significant dependence of the statistical characteristics describing the degradation of the phase structure and amplitude distribution of laser radiation during the passage of a shock wave near the surface of a supersonic aircraft, on the parameters of the power model of the turbulence spectrum and, in particular, on the exponent. Analytical estimates of the coherence radius and relative dispersion of intensity fluctuations of a plane wave and the results of numerical simulations confirming their correctness are presented.

The paper presents an analysis of the efficiency of using bimorph deformable mirrors and mirrors on piezoactuators for the problem of focusing scattered laser radiation. In this paper, we study the efficiency of a piezoactuator deformable mirror with 61 piezopackets and an aperture of 60 mm, as well as a bimorph mirror with 48 electrodes and an aperture of 50 mm. It is shown that such mirrors can be used to optimize the focal spot formed by scattered radiation in the far-field.

The paper discusses the issues of choosing a site for a new large ground-based radio telescope. One of the most important characteristic that determines the optical atmospheric thickness, in particular, the precipitable water vapor in the atmosphere, is considered. We estimated reference precipitable water vapor height scale in the atmosphere at a number of reference sites within region perspective for creation of ground-based radio telescope. Using the method for correction of precipitable water vapor values, we showed that the sites in the vicinity of the lake Karakul are suitable for placement of large ground-based radio telescope.

This paper is aimed at finding suitable sites for a large ground-based millimeter/submillimeter telescopes. We discuss the most promising regions in the world in terms of low values of precipitable water vapor. A separate issue is the regions with low values of precipitable water vapor within Russia, China and Uzbekistan.

Necessity of miniaturize and to create reliable components for wavefront correctors leads to reduction of the cross-section of the control elements in deformable mirrors. Moreover, such elements should provide reasonable stroke to compensate for wavefront aberrations of the laser radiation propagated through turbulent atmosphere. In this work we simulated the possibility of reducing the cross-sectional area of piezoactuators from 16 mm2 to 5 mm2 in order to hold up the local stroke as 5 microns in the cartridge-type deformable mirror for correction of large- and small-scale phase fluctuations of laser radiation. To increase the reliability of deformable mirror design, the gap structure was used for wiring of electrodes instead of interdigitated commutation.

The paper describes a modernized optical scheme of the LEF3M-1 laser ellipsophotometer with the possibility of automatic determination of the surface microrelief of various materials in situ. Experimental results of registration and processing of ellipsometric patterns reflected from a surface with a microrelief are presented; digital processing was carried out using wavelet analysis methods.

Non-line-of-sight (NLOS) atmospheric optical communication between an unmanned aerial vehicle (UAV) and a ground-based receiver is analyzed The experiments were conducted in nighttime at a wavelength λ = 450 nm with baseline distances up to 150 m and UAV altitudes up to 20 m. It is shown that if the altitude of UAV with a transmitter is 10 m, stable optical communication is possible with the symbol error rate no higher than 0.0002 at baseline distances up to 75 m. If the UAV altitude is 20 m, communication is possible with the symbol error rate of 0.015-0.031 at baseline distances up to 100 m.

Using a fast-acting Shack-Hartmann wavefront sensor (WFS) under the conditions of artificially created pavilion turbulence, the possibility of registering and recording the phase front of laser radiation with a high temporal resolution has been experimentally demonstrated. A FPGA has been used as a control element of the WFS that provides an operation frequency of the WFS and recording information about the wavefronts of 4 kHz. Analysis of the reconstructed dynamics of the wavefront of the laser radiation makes it possible to determine in detail various spatiotemporal phase characteristics and to identify non-Kolmogorov features of turbulent distortions.

In the region of 5100 – 5400 cm^-1, the absorption lines of the HD¹⁶O molecule broadened by the CO₂ pressure were registered on the Fourier spectrometer IFS 125 HR. The parameters of HDO absorption lines belonging to two vibration-rotational bands, ν₂+ν₃ and ν₁+ν₂, are determined. The measurements were carried out at room temperature with a spectral resolution of 0.01 cm_–1. The absorption lines were approximated using a modified Voigt profile, which takes into account the dependence of broadening on the velocities of colliding molecules.

Model estimates of short-wave solar radiation fluxes for summer conditions in the southern part of Western Siberia in the presence of single-layer of the low and high-level clouds are presented. The cloudiness characteristics were obtained on the basis of statistical models based on long-term satellite MODIS observations: the ranges of variability of the optical thickness and effective particle radius were 1.5-40 and 7.5-25 mkm for liquid clouds and 1-5 and 15-50 mkm for ice clouds, respectively. These low-level clouds characteristics variations lead to changes in the average daily radiation fluxes in the range of 150-300 W/m² at the bottom (BOA) and 130-230 W/m² at the top (TOA) of the atmosphere and for ice clouds 230-310 W/m² at the BOA and 140-220 W/m² at the TOA. At a fixed optical depth, there is a relatively weak dependence of the average daily radiation fluxes on the effective particle radius.

The absorption spectra of the mixtures of water vapor and air at different partial pressures of both gases have been recorded using a Fourier spectrometer IFS 125 HR in the 3500−5670 cm^–1 spectral region. The multispectrum fitting procedure has been applied to these spectra to recover the spectral line parameters. The traditional Voigt and quadratic speed-dependent Voigt ones were used. Particular attention was paid to the analysis of the broadening and shift coefficients of the H₂O absorption lines. The significant difference between the obtained and literary data was shown. The atmospheric transmission was simulated with the H₂O absorption lines from the HITRAN and GEISA spectroscopic databases and with new lines parameters obtained in this work.

Line-of-sight optical communication channels are characterized by the high data rate, but they cannot provide stable data transmission in the presence of obstacles in the communication line. Non-line-of-sight (NLOS) optical communication is free of this shortcoming and can be multicast. We have created an optical-electronic system for NLOS communication at a wavelength λ=850 nm. It is shown that in the evening, NLOS communication is possible at a baseline distance of 75 m and receiver azimuth angles 0-40° with the symbol error rate no higher than 0.009. At a baseline distance of 1300 m and receiver azimuth angles of 0 5°, NLOS communication with the symbol error rate no higher than 0.236 is possible.

The downward and upward fluxes of IR radiation are calculated with use of three versions of the HITRAN spectroscopic database (release of 2008, 2012, 2020) and GEISA (2020 version) for meteorological conditions, typical for summer and winter of mid latitudes. The dependent two-sample t-test is used to analyse discrepancies in the radiative fluxes. It is shown that maximal differences in the fluxes at the top and bottom of atmosphere due to use of latest versions of the spectroscopic databases HITRAN2020 and GEISA2020 are not too large (less than 0.54 W/m²) but they are statistical significant.

In the paper, we describe the results of a Monte Carlo simulation of a short laser pulse scattering in a crystal cloud. Simulation results show that expanding light rings can appear in cirrus clouds for a short time, when a laser pulse passes through a thin cloud layer. We compare simulation results for water drop and ice clouds, paying attention to the difference in irradiance at the boundaries of the cloud layers and specific features of the laser pulse scattering processes.

In the report, the review of works carried out in Russia and devoted to experimental and theoretical investigations of nonline- of-sight optical communication in air and water environments is presented. The main results of field, laboratory, and numerical experiments in the visible and UV wavelength ranges are given. In the laboratory experiments, a water-glycerin mixture and atmospheric air were used. In the field experiments, communication was carried out in the surface layer of the atmosphere and in artificial and natural water reservoirs (including through ice). Investigations were carried out for coplanar and non-coplanar schemes of communication channels.

The UAV-surface and surface-UAV channel of non-line-of sight atmospheric optical communication is considered. The communication quality is estimated from values of path loss, the minimal energy per pulse, at which the signal-to-noise ratio in the receiving system is higher than 10, and the duration of the received useful signal.

It is demonstrated how the energy is redistributed and the law of conservation of energy is fulfilled when optical radiation reflecting in a turbulent atmosphere. It is found that the mean intensity of an optical beam, scattered by a point reflector or by an ensemble of point reflectors in a turbulent atmosphere, increases in the strictly backward direction (backscatter amplification (BSA) effect) at the expense of overflow of the energy from a huge area several orders of magnitude exceeding the BSA effect localization area.

The mechanical properties of multilayer thin-film piezoceramic structures have been studied. The results of simulation of multilayer piezoelectric actuators are presented.

The work presents the results on the influence of the temperature of a turbulent layer on the transverse energy structure of femtosecond (multi-ring and Gaussian) laser beams. Gaussian and multi-ring beam profiles exhibit a monotonous growth in the number of intense light maxima with increasing the strength turbulence of air jet and increasing laser pulse energy. The formed intense light channels (~ 10¹¹ W/cm²) make it possible to excite two-photon fluorescence of dyes with a signal level that makes it possible to take at a distance of 100 m.

The propagation of high-power femtosecond laser radiation through an aerosol is studied experimentally and theoretically. In the course of experimental studies, the effect of aerosol on the characteristics of the radiation filamentation region was shown. On the basis of experimental data, the time dependence of the degree of inhomogeneity of the high-power femtosecond laser radiation field due to the spreading of the aerosol cloud is found. A theoretical model is proposed that makes it possible to reproduce experimental patterns not only qualitatively, but also quantitatively.

The phase characteristics of radio waves during oblique propagation in a weakly anisotropic parabolic ionospheric layer are considered in the short-wave radio range. The case of polarization degeneracy of waves is analyzed. The correction to the wave eikonal due to the smallness of the anisotropy is calculated by the perturbation method. The two-valuedness of the solutions corresponds to two normal waves. The figures show the form of these solutions under different conditions of layer probing.

The paper presents the results of studies of diffusion combustion of gaseous methane in the presence of external pressure pulsations with low amplitude on the flame plume. The analysis of the temperature field and the stabilization time of the combustion mode has been carried out. It is established that the presence of pressure pulsations leads to characteristic changes in the temperature field, which are expressed by a growth of the temperature pulsation amplitude, corresponding to the frequency of external influences. A characteristic time for stabilizing the combustion regime from the moment when there is no external influence to their appearance is determined.

By using the Monte Carlo method, we study the dependence of the lidar temporal echo signals on the thickness of the cloud layers. We propose a new technique to reconstruct the optical depth of atmospheric clouds based on the returns of monostatic ground-based and spaceborne lidars with different values of the receiver field of view and laser pulse length.

The numerical simulation of adaptive optical system operation with two sequentially located adaptive mirrors has been carried out. The control of the adaptive mirrors has been realized by the stochastic parallel gradient algorithm. The radiation power within the diffraction angle is the criterion functional of the algorithm. Two variants of system operation have been considered: in the first variant the mirrors have the joint control unit and the criterion functional sensor, and in the second one each mirror is situated in the independent contour. The similar adaptive systems can be applied to the correction of phase distortions of the radiation caused by turbulence of the atmosphere. It is shown that the efficiency of correction of phase aberrations by such adaptive system is high in the case of the independent contours at supplying relatively small stochastic voltages to the first adaptive mirror.

The results of application of the technology for MODIS satellite data processing using the RTM method and the software developed on its basis for obtaining temperature maps and searching for high-temperature objects (HTOs) are presented. The Baikal region in the period of July 2022 is taken for analysis. Atmospheric thematic MODIS products are obtained, and atmospheric correction of satellite measurements is carried out. The corrected data are used to draw the temperature maps of the ground surface, and HTOs of temperature anomalies are identified with a threshold algorithm. Comparison of fire data provided by ground services with those obtained from satellite HTO data demonstrates a good agreement.

One of the problems that arises when restoring the reflectivity of the target surface from the echo pulse of a navigation lidar is the effect of the tilt of the reflecting target surface on the broadening of the echo pulse. In this paper, a model is proposed that describes the broadening of the reflected echo pulse of a short-range lidar at different angles of incidence of the laser beam on the target. This model also takes into account the main parameters of the lidar, the atmosphere, the reflecting surface of the target and its inclination, which allow calculations to be made in a wide range of conditions.

The cloud adjacency effect (CAE) on retrieved values of ground surface reflectance is assessed. The assessment method employs the software for statistical simulation of radiation transfer in the atmosphere with a stochastic cloud field including a deterministic gap of a given radius, and then the simulated results are used in an interpolation formula. Masks of cloudless pixels, for which the cloud adjacency effect changes retrieved reflectances by values greater than 0.005, are constructed. The coefficients of correlation of the CAE radius with the initial data show that the major contributors are the cloud optical thickness, cloud cover index, and surface reflectance.

Numerical calculations of focusing a laser beam on a remote receiver through the turbulent atmosphere using an adaptive optical system have been carried out. The adaptive optical system has been realized the phase conjugation of the outgoing laser beam to a reference one. The adaptive phase correction of both laser and reference beams assume to be imperfect. The research is devoted to obtaining simple estimations of laser intensity at the receiver, which would agree with calculation results. It is proposed to conduct these estimations on the basis of information on the parameters of both laser and reference partially corrected beams. Since there is no way to associate the laser intensity at the receiver with an angular divergence of corrected beams, it has been proposed to estimate the on-axis laser intensity at the remote receiver basing on the correlation characteristics of residual phase of both laser and reference beams.

Mathematical modeling helps to investigate the water basin and forecast the consequences of economic activity when experimental investigation is difficult due to economic and technological reasons. A mathematical model of a river flow based on unsteady turbulent shallow water equations is presented. Monotonic well-balanced high-order accurate finite volume approximations for the equations of the model are built. Accuracy of the numerical method suggested is evaluated on test cases with analytical solutions exist. The flow in the section of Tom river where ice jams often form during the spring breakup and cause localized flooding was modeled and the results were compared to the patterns observed in this area.

We consider the possibilities of information transmission in free space optical communication systems based on encoding with the help of the polarization structure of the synthesized laser beam. To control the polarization structure of beams, an approach based on the fiber array coherent combining with the possibility of changing the direction of subbeam polarization is used. On the basis of numerical simulation, the influence of atmospheric turbulent distortions, as well as the possibility of their adaptive compensation, is analyzed. Situations with different directions of subbeam polarization are considered. It is shown that, for the problems of information transmission, the most stable are the synthesized beams formed at the azimuthal or radial polarization of the subbeams.

ZnGeP2 crystals with different thermal spraying of the chemical elements on the crystal surface studied in this work. The Raman spectra of the crystals were obtained using the inVia Reflex system with an excitation wavelength of 785 nm. Good separation between ZnGeP2 and Ca/Mg samples by first principal component points to the significant differences in corresponding Raman spectral features. Proposed machine learning pipeline include principal component analysis and support vector machine with non-linear radial based function kernel. High area under curve values also reflects good pairwise separability of the samples.

The results of studies of the chemical composition of the snow cover on the northeastern coast of Lake Baikal, the Republic of Buryatia, are presented. Snow samples were taken along the Ulan-Ude – Kurumkan route, in the delta region of the Barguzin River, from the ice of Barguzin Bay and northern Baikal. Groups of sources affecting the composition of atmospheric fallout in the background regions of the Baikal region were determined using the statistical methods of data processing. Based on the calculation data for the dispersion of anthropogenic impurities from large source cities during the period of stable snow cover (November 2021 – February 2022), the percentage of adverse weather conditions, in which emissions could reach the northeastern coast, was obtained. The features of the spatial distribution of marker substances in the background regions of the Baikal region were studied, and the accumulation of chemicals in the snow cover was visualized on maps.

The paper presents the results of studies of petroleum products content in snow water and shows their spatial distribution in the BPT during the winter period of 2022. The highest concentrations of petroleum products were found in the industrial cities of the Baikal region. The conclusion about the local nature of the spread of petroleum products from the source of emission is performed. The assessment of the degree of contamination of snow water with petroleum products in accordance with the sanitary and hygienic standards for water bodies of fishery purposes was carried out. The levels of accumulation in the snow cover of petroleum products on the underlying surface of BNA and Lake Baikal were calculated. Petroleum products accumulation on the lake surface during the winter period is about 11 tons.

The results of the calculation of atmospheric transmission spectra and modeling of lidar signals in the informative range of greenhouse gases sounding (CO₂, H₂O) on horizontal tropospheric paths by using a two-channel infrared lidar system under development are presented. It is shown that the spectral range of operation of the lidar system 4878–4894 cm^-1 (2043–2050 nm) is preferable for simultaneous probing of CO₂ and H₂O, in which the level of lidar signals is in the range of 10^-6 –10^-10 W and exceeds the equivalent noise power photodetector. Several configurations of the lidar system with the generation of nanosecond radiation pulses in the selected informative range of sounding the trace gases under study are proposed.

Methane (CH₄) is a greenhouse gas which directly influences climate changes on the planet. One of the sources of methane emissions in the atmosphere during human agricultural activities is the decay of animal manure and organic components of agricultural effluents. Therefore, remote control and measurement of the concentrations of agricultural products (mainly methane), which are essentially an anthropogenic factor of the impact on the atmosphere, is important. Here, we consider a possibility of creating a mobile laser absorption complex for methane monitoring at cites with agricultural effluents.

The paper analyzes the results of automatic monitoring of the content of sulfur dioxide and nitrogen dioxide in the surface layer of the atmosphere of the Baikal region for the period 2021–2022. It was shown that the average daily concentrations of sulfur dioxide varied from 1 μg/m³ to 11 μg/m³ in summer and from 3 μg/m³ to 39 μg/m³ in winter. The highest content was registered in the cities of Angarsk and Irkutsk and the village of Listvyanka. In Gusinoozersk, Ulan-Ude, and Selenginsk, sulfur dioxide concentrations were 2–3 times lower than in the cities of the Irkutsk agglomeration. The share of SO₂ emissions from stationary sources remained in urban areas and reached various areas of the South Basin. For the cities of the Irkutsk agglomeration, this percentage varied from 2.1% to 6.8%, and for the southern basin of the lake, from 1.3% to 3.1%. It is calculated that from 1 to 3% of nitrogen dioxide emissions from the sources of the Irkutsk agglomeration reaches the water area of southern Baikal.

The possibilities of using broadband sources, as well as an additional wavelength of 630 nm in a lidar-balloon experiment on sensing stratospheric aerosol, are considered, a modification of the calculation procedures according to the Mie theory is carried out, taking into account the parallelization of calculations by wavelengths and particle radii using the tensorflow library, a visual and correlation analysis of the efficiency of using lidar wavelengths and broadband LED sources. The study was supported by the Russian Science Foundation grant No. 23-27-00057, https://rscf.ru/project/23-27-00057.

The paper considers the constructive implementation of the nanophotonic sensor of comprehensive application, proposed by the authors earlier and investigated using computer simulation. Here we investigate one of the constructive solutions of a supersensitive pressure sensor based on nanostructures, providing miniaturization of sensors and their application in various technical products. Based on the previously conducted mathematical simulation of the process of high-frequency electromagnetic radiation propagation through a nanocones array, which is the essential element of the proposed design, justified decisions about the overall dimensions of the structure, its internal structure, and the optimal frequency of the field excitation source are made. This work solves, in particular, the problem of protecting the sensor’s internal structure from external electromagnetic fields. Employing solid-state modeling, the linearly reciprocating motion of the sensor plates under external loading in the proposed device design is confirmed.

The paper considers the problem of solving the inverse problem of retrieval of the vertical distribution of atmospheric temperature from a Rayleigh scattering lidar signal in a high spectral resolution lidar. It is shown that the lidar signal, filtered from the aerosol scattering signal using a molecular filter, acquires a parasitic dependence on the atmospheric temperature due to a change in the width and shape of the Rayleigh scattering line contour. Signal distortions have a significant effect on the result of retrieval of the vertical temperature distribution and do not allow using the standard signal processing technique. To eliminate the influence of the signal filtering effect, the advanced temperature retrieval algorithms should be applied.

A lidar response simulator has been created that makes it possible to generate an optical signal close in shape and intensity to a real lidar signal in the temperature measurement channels at the main lidar of the Siberian Lidar Station. An experimental evaluation of the linearity range of the photodetection system has been carried out. The paper shows a block diagram of a stand for experimental evaluation of the linearity range of a lidar photodetection system with the ability to synthesize a pulsed optical signal. It is shown that when a signal is recorded in the photon counting mode, nonlinear distortions are observed at an average counting pulse arrival frequency of 2.5 MHz.

Differences and similarities of the chemical composition (ions, trace elements, PAHs) of the driven atmospheric aerosol collected in the autumn period of 2022 along the routes 89^th and 90^th cruises of the R/V "Akademik Mstislav Keldysh" in the Kara Sea area were revealed. (RSF) № 21-77-20025.

The first data on spatial and temporal distribution of carbon-containing (soot) aerosol in the atmosphere over Lake Baikal based on the results of comprehensive expeditions 2021-2022 and at the atmospheric monitoring station in Listvyanka settlement are presented

The cases of the passage of frontal cloud systems with embedded convection in Western Siberia were identified, for which the selection and processing of various satellite data with their subsequent analysis were carried out. The threshold values of some characteristics of the embeddedconvection over Western Siberia from active satellite sounding data were revealed, and the statistical dependences between the products of active and passive satellite sounding were evaluated by the method of data approximation.

In this work, long observation time series of the integrated aerosol backscattering coefficient, obtained at the Siberian Lidar Station in Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, Tomsk were used to show that the stratospheric aerosol starts growing at a rate of 1.08 ∙ 10⁻³ sr^-1 per decade after 2018. Comparison of the seasonal regional empirical model of background stratospheric aerosol for 2000-2018 and seasonal average profiles for 2018-2023 showed a significant increase in stratospheric aerosol throughout the stratosphere over the last five-year period; the maximal deviations of the scattering ratio reached 0.1 for summer and 0.2 for winter in the lower stratosphere. It is hypothesized that the aerosol in the stratosphere could increase due to the global effect of explosive eruptions of the volcanoes Raikoke in June 2019 and the submarine volcano Hunga Tonga-Hunga Ha’apai in January 2022.

Lidar returns of a mobile three-channel IR lidar system which is currently designed are simulated in the spectral ranges informative for sounding greenhouse gases (CH₄, CO₂, and H₂O) along horizontal and slant tropospheric paths. The configuration of the lidar system is described.

The laser generation wavelengths were calibrated by experimental measurement of the transmission spectra of the gas mixture in the cell. The program for automatic formation of the tuning curve of a laser with parametric generation of light and the program for automatic measurement of the dependence of the pulse energy on the generation wavelength were developed. Using the developed programs, a number of experiments were carried out to measure the efficiency of laser radiation generation, based on the results of automatically generated tuning curves. The control program for the spectrograph for recording lidar signals with its use were developed, and a test recording of the emission spectrum of a laser diode were carried out.

An approach of a technique for estimation of the content of aerosol matter with different volatility in individual fractions of atmospheric aerosol is discussed. The estimated are performed on the basis of the results of measurements of the number density of particles in 6 size ranges from 0.3 to 5 μm at artificial heating of the atmospheric air under analysis from 25 to 200°C. The number density of particles was recorded by AZ-10 optical counter at temperatures of 25, 100 and 200°C.

A variant of computer modeling of a multichannel mirror-lens system (lens) made of transparent plastic in several spectral ranges for remote devices is considered. The optical system operates using two radiation receivers that are sensitive in the visual and infrared ranges of the spectrum

The results of the study of the chemical composition of the snow cover in Ulan-Ude and the background area of the Republic of Buryatia in 2022 are presented. It was established that the snow melt waters in Ulan-Ude belonged to the sulfate class, calcium group. The maximum concentrations of major ions and compounds of nitrogen and phosphorus were determined near thermal power facilities. The relative content of the suspended form of total phosphorus in snow melt water was significantly higher than the content of its dissolved form. Nitrate nitrogen was the predominant form of mineral nitrogen. The accumulation of most pollutants in the snow cover in Ulan-Ude was significantly higher than in the background area.

The studies have shown that the distribution of suspended particulate organic carbon in the seas of the Russian Arctic is characterized by сircumcontinental and vertical zonalities. These zonalities are manifested in decreasing concentrations and therefore fluxes (mgC/m² /day) of suspended particulate organic carbon in the transition from the near-continental to pelagic areas of the Arctic Ocean, as well as from the surface photic layer to the near-bottom layer by two orders of magnitude, which is confirmed by instrumental data of sedimentation traps and correlates with the zoning of bio-production processes.

The report presents the results of observations of horizontally oriented crystalline particles in the clouds of the upper levels using a scanning polarization lidar. The measured dependence of the lidar signal on the lidar inclination angle is described by an exponential distribution and corresponds to the distribution of particle inclinations relative to the horizontal plane (flutter). Diffraction on the contour of the particles appears as a smoothing of the top of the measured distribution and depends on the size of the crystals. The effect of diffraction is significant for narrow distributions over tilt angles.

The paper presents the results of laser sounding of the atmosphere over of Lake Baikal in the summer ship expedition in 2022. Based on the data obtained using the LOSA-A2 lidar, the spatiotemporal variability of the vertical structure of aerosol fields was studied. This makes it possible to reveal the features of the formation and transport of atmospheric aerosol in a given region. Based on the results of the studies, it was found that during the expedition, either background values of the aerosol content in the atmosphere or a weak filling of the lower troposphere with aerosol due to local sources of pollution were observed.

A change in the frequency spectrum of a person's pulse under the influence of light of different wavelengths has been established. It has been shown that in the light stimulation phase, different colors cause functional changes in the internal organs in the subjects. At the same time, the effects of the photostimulus on the internal organs are not equivalent and depend on the initial functional state and the typology of the subject. Depending on the type of exposure, the same photostimulus can cause contrasting changes in the frequency parameters of pulse signals recorded on the radial arteries of human wrists.

Using the Automated pulse diagnostic system (APDS), the possibility of a quantitative assessment of correcting the functional state of a human organism by the method of spectral analysis of pulse waves (while the subject is exposed to light of different wavelengths) has been revealed. It has been shown that photostimuli have unequal effects on the internal organs, which depends on the functional state of the subject. At the same time, the extreme phtostimuli (blue and red) provide either toning, or relaxing effect on the psychophysiological state of the subject. The contrast effect of light on the human body is one of the promising technologies for managing the functional psychophysiological state.

We present the results of a comparison of high-level cloud (HLC) episodes with different ice crystal orientations from EARLINET ground-based lidar measurements and MODIS satellite data for the period 2015-2022. Cloud particles with total attenuated backscatter values greater than 5-10^-6m ^-1 -sr^-1 are considered preferentially oriented in the horizontal plane if the volume linear depolarization coefficient is less than 0.1, and randomly oriented if it is greater than 0.4. The following parameters of HLC with different orientation of ice crystals were considered: optical thickness, effective particle radius, waterpath, cloud-top height, reflection ratio, and effective emissivity ratio. The results of comparing the features of HLC with different particle orientations from ground-based and satellite data are discussed. It was found that over Europe (as well as over Western Siberia) HLC with reflection ratios greater than 0.15 and effective emissivity ratios greater than 0.5 consist of preferentially oriented ice crystals in the horizontal plane. The typical values of HLC parameters with different particle orientations over Europe were found. We present the analysis results of HLC with specularly reflecting layers having anomalous values of reflection ratios and effective emissivity ratio.

The aerosol optical characteristics in the wavelength range of 0.46-0.87 μm were calculated on the basis of an empirical model of the aerosol optical characteristics in the summer background haze of Western Siberia. The Monte Carlo method was used to estimate the sensitivity of the model to uncertainties in measuring the input parameters: angular light scattering coefficient at a wavelength of 0.53 μm at an angle of 45°, mass concentration of the absorbing substance, and parameters of its lognormal size distribution, relative humidity of air. The relative errors in the reconstructed scattering, extinction, and absorption coefficients, single-scattering albedo, asymmetry factor, and lidar ratio are analyzed.

An algorithm for processing time series of meteorological parameters is proposed, which makes it possible to establish the limits of applicability of the power-law model for the spectra and structure functions of turbulent fluctuations and to determine the values of its parameters - the exponent, the structural characteristic, and the inverse outer scale. The results of experimental data processing, demonstrating a good agreement between the power-law model and the measurement results over most of the observation interval. At the same time, significant deviations of the exponent of power dependence from Kolmogorov one were found, are presented. The measurements also contain intervals lasting several hours with an estimate of the spectrum index close to and less than 1, when the model does not work and its modification is necessary to ensure the suppression of the high-frequency region of the spectrum.

The results of reconstructing the radial dependence of the gas density in the core of a fire tornado model based on the results of laser transillumination are presented. It is shown that the position of the energy gravity centroid of the beam passing through the flame is quite sensitive to regular spatial density variations in the tornado core. Estimates of the transverse size of the core and the temperature in the combustion region are obtained, which correspond to the results of measurements by other methods

Previously, we built a database for a single particle with a random polyhedral shape. The solution was obtained for a size range from of 10 to 300 microns at a wavelength of 0.532 microns. The particle selected was the one closest to the average in the ensemble of generated particles. In this work, a different approach to building the database is implemented: an arbitrary particle with a random shape and size is generated from the range of particle sizes attached to the database. The report examines the differences between the two approaches in building the database.

Laser polarimetric remote sensing is successfully used to study optical characteristics of the atmosphere. Measurements of the elements of full scattering matrix provide an adequate description of optical and morphological parameters and orientation of particles in the atmosphere. A matrix polarization lidar (MPL) operating on the main laser emission lines of 355, 532, and 1064 nm is proposed. The solution is based on the use of not only birefringence, but also optical dispersion of crystals used for the selection of orthogonal components of received backscattering radiation. Experimental results and modeling show the prospects of the chosen direction of development of the matrix polarization lidar.

A 25-year long series of observations of the parameter of aerosol condensation activity in the near-ground layer of the suburb atmosphere of Tomsk is analyzed. The regularities of inter-annual variations of its average monthly values are determined, as well as the dates of the spring maximum of condensation activity.

This paper presents a short-term experimental results pressure surge effect on the pyrolysis plant combustible materials (PCM) zone. It was found that as a result of exposure there is the combustion flame mode interruption, causing a decrease in the PCM elements surface temperature involved in combustion, which during further forced cooling leads to a combustion complete cessation.

The paper presents a comparison of numerical solutions for the problem of light scattering on ice particles using methods of geometric and physical optics. The solutions were developed for irregularly shaped particles ranging in size from 10 to 100 μm, with a wavelength of 0.532 μm. The results of the comparison of the light scattering matrix over the entire direction sphere indicate that the solution within the framework of geometric optics approximation is in good agreement with the solution within the framework of physical optics over the entire scattering sphere, except for the vicinity of scattering in the forward and backward directions.

Measurements of gases desorbed by the vacuum method from the disc ring wood of deciduous trees were carried out. The analysis of gases was performed using a photoacoustic gas-analyzer with a tunable CO₂ laser. The chronologies of residual CO₂ and (CO₂+H₂O) gases of some trees that grew in and around Tomsk (West Siberia) have been obtained. Correlation coefficients of chronologies with temperatures and precipitations for the vegetation period are determined. All the chronologies have cycles with period of 2-4 years. We suppose that the distribution of the residual gases in the discs reflects the annual release of the gases from the stems of the deciduous trees into the atmosphere.

The possibilities of using molecular scattering to determine the wind speed from measurements by a pulsed coherent Doppler lidar (PCDL) from an aircraft at altitudes of 10-20 km are numerically studied. The simulation was carried out for probing radiation focused at 500 m at wavelengths of 1 μm and 2 μm, the aperture diameter of the receiving-transmitting telescope was set equal to 10 cm. It is shown that in measurements from an aircraft, in order to exceed the threshold value of the signal-to-noise ratio, the energy in the pulse is much lower than when sounding from the Earth. Modern PCDLs with probing pulse energies of 1–4 mJ, after adding a molecular scattering recording channel, can be used for airborne wind measurements at altitudes of 10–20 km.

A method is described for increasing the efficiency of an laser emitter based on the frequency summation. The emitter is designed to generate narrow-band radiation with a wavelength of λ ~ 589 nm, consisting in continuous automated correction of the established pumping energy levels and the actuation moments of Q-switches. The aim of the work is to reduce the time jitter of the summed radiation pulses and thereby increase the efficiency of generating of the desired frequency.

This study contains a spatiotemporal analysis of remote monitoring data MODIS on individual vegetation fires from 2013 to 2022, and open OSM data in the Russian Far East. An algorithm for determining the anthropogenic vegetation fire hazard during spring and fall periods in the forest district blocks located near roads and settlements was proposed. The study identifies settlements and road section for arranging forest protection measures in the Jewish Autonomous Region.

The seasonal variability of aerosol composition was studied according to three-year field observations in Moscow and one of its suburbs from the autumn 2019 by the autumn 2022. A high correlation has been established between the aerosol concentration of PM_2.5 and PM₁₀ fractions both in Moscow and in the suburb, as well as between these points for each fraction. Taking into account the seasons, meteorological conditions and sources, the level of aerosol pollution of near-surface atmospheric layer, typical for Moscow metropolis and the suburb, has been determined. Two identical groups of chemical elements were identified in the near-surface aerosol for the city and the suburb at any time of the year – terrigenous (Th, Al, U, La, Li, Sr, Ba, Mg, Fe, Cs, Co, Mn, Cr, K, Ca) and non-terrigenous (Mo, Cu, Zn, Pb, Sn, S, Sb, Cd, Se, Bi).

We present an analysis of variations in the total ozone content (TOC); the analysis is based on monitoring data from OMI-based observations. The analysis is confined to the territory of Russian Federation, within which the TOC variations are considered, in both latitude and longitude, with the consideration of specific features of TOC measurements poleward of the polar circle. For certain observation sites we calculated and presented autocorrelation functions, which, like standard deviation (variance), give an idea on TOC variations or TOC nonuniformities.

In winters-springs 2019-2020 and 2010-2011 there were the strongest ozone anomalies in the Arctic in the total satellite era. They were due to extraordinarily strong and long-lived polar vortices, entailing unprecedented chemical ozone destruction. The Aura MLS data indicate that the minimal temperature was 8-13% below normal over the Arctic in 2020 and 8–12% below normal in 2011. The ozone mixing ratios dropped to 4% of the multiyear average at the altitude of 20 km on March 27, 2020 and to 25% at the altitude of 21 km on March 20, 2011 for Eureka; to 3% at the altitude of 20 km on March 27, 2020 and to 26% at the altitude of 21 km on March 21, 2011 for Thule; and to 1% at the altitude of 20 km on April 5, 2020 and to 27% at the altitude of 20 km on March 23, 2011 for Summit.

Based on multiyear (2007-2022) model MERRA-2 reanalysis data, we analyze the seasonal variations in the content of absorbing substance (black carbon) in Eurasian sector of the Arctic Ocean. Average concentrations of black carbon over six Arctic seas (from the Greenland to Chukchi Sea) are presented for different months. We discuss the specific features of latitudinal and longitudinal distribution of the black carbon concentrations in separate periods of the year. It is noted that model data show no winter-spring maximum and overestimate the summertime concentrations in the Asian sector of the Arctic Ocean.

We discuss the specific features of the spatiotemporal variations in aerosol characteristics in the Arctic atmosphere on the routes of 89th and 90th cruises of RV Akademik Mstislav Keldysh (September – November 2022). We present the average (over the period of expeditions) values of the studied characteristics: the aerosol optical depth of the atmosphere, the aerosol and black carbon concentrations, as well as the chemical composition of aerosol samples, i.e., the concentrations of the main elements, the concentrations of organic and elemental carbon, and the isotopic composition of carbon. Based on multiyear (2013-2022) data from expedition measurements, we present the results from a statistical generalization of aerosol characteristics for the atmosphere of the Kara Sea and southern part of the Barents Sea.

Based on multiyear (2007-2022) MERRA-2 reanalysis data, we discuss the specific features of the average spatial distribution of absorbing substance (black carbon еВС) in aerosol composition in Eurasian sector of the Arctic. Main attention is devoted to the spatial distribution of the concentrations еВС in the period of expedition measurements (July- October). It is noted that outflows of smokes from massive forest fires in Siberia influence markedly the spatial distribution of еВС in Arctic regions. We present statistical characteristics of the concentrations еВС for six Arctic seas (from the Greenland to Chukchi Sea) and four regions of Northern Eurasia. Latitudinal variations in the concentrations еВС over separate seas are estimated. The model (MERRA-2) calculations are compared with actual multiyear measurements of black carbon concentrations in marine expeditions.

The paper shows the woody vegetation reflectivity dependence on the storage conditions of the samples. The results of leaves and needles samples spectral reflectivity measurements in the range of 0.4-0.9 μm for several days after cutting the samples from trees when storing samples in a special refrigerator and without a refrigerator were presented. It was shown that woody vegetation samples storage in a special temperature-regulated refrigerator make it possible to ensure the stability of the reflectivity for coniferous trees for two or three days and for most deciduous tree species in a time interval ranging from a few hours to one day.

The purpose of the study is to analyze the possibilities of forest areas hyperspectral monitoring. The mathematical modeling of the forest territories elements classification on the created neural network using experimentally measured reflection coefficients is presented. The simulation results show that hyperspectral monitoring in the spectral range of 400-2400 nm allows for classification of forest elements (different species of deciduous and coniferous trees, deadwood, swamps, water bodies, soils without vegetation, different types of mosses and lichens, post-fire areas, different shrubby plants) with the probability of correct classification of more than 0.73 and the probability of incorrect classification of less than 0.037. The use of additional information from the laser altimeter allows to significantly improve the classification. The created neural network, using hyperspectral monitoring data and lidar data on the height of trees, provides the probabilities of correct forest area elements classification of more than 0.8 and the probabilities of incorrect classification of less than 0.025.

The elemental composition of near-surface aerosol in Moscow in the winter periods of 2020 and 2021 are presented according to the data of regular observations of aerosol composition at A.M. Obukhov Institute of Atmospheric Physics RAS. Reliable differences in meteorological conditions (air temperature, wind direction) of these winters are confirmed by statistical tests. The use of statistical methods made it possible to identify groups of elements with similar or opposite indicators characterizing their nature and/or processes forming their concentrations in near-surface air, in particular during the transition period from winter to spring seasons.

The study investigates the transition process from a ground fire to a crown fire. The studies were carried out in seminatural conditions on the territory of the Base Experimental Complex (BEC) of the IAO SB RAS. Previously, reconstruction of the forest canopy was carried out. The emergence of a crown fire occurred due to the transition of a ground fire to the bottom layers and further to the crowns of trees. Non-contact diagnostic methods (IR thermography) were predominantly used to measure combustion front parameters.

Using a pulsed coherent Doppler lidar, the effect of an internal gravity wave (IGW) propagating in a thermally stable atmospheric boundary layer on the shape of the spectral density of the vertical component of the wind velocity vector is experimentally studied. It has been established that the presence of IGW causes a significant change in the shape of the velocity spectrum at frequencies below the frequencies of the turbulence inertial subrange. In this case, between the IGW frequency and the lower frequency boundary of the inertial subrange, the spectrum has a power-law dependence on frequency. By analyzing the data of 700 lidar estimates of the spectral density of the vertical wind speed, it was found that the exponent is on average -3.

An preliminary experiment of lidar sensing of the intensity of optical turbulence was performed in Tomsk city. The work was done using a micro pulsed UV turbulent lidar BSE-5, operating by the backscattering enhancement effect, which made it possible to evaluate the structural characteristic of the refractive index C_n². The lidar was located in the Institute building on the eastern outskirts of Tomsk. In winter time the sounding path was either horizontal or had a slight slope, and crossed the city in a north-west direction. Several series of measurements were carried out. Meteorological support included measuring wind speed and temperature at two levels. The experiment made it possible to localize intense turbulent zones over the city and explain the increase in the intensity of turbulence at night. Another part of the experiment with scanning over the city was in summer time to study the spatial-temporal transformation of the intensity of turbulence in the surface layer of the atmosphere. The local increase in the intensity of turbulence over industrial facilities is due to the turbulent removal of heat generated by the city.

The paper examines the features of aerosol optical depth (AOD) variations over the Baikal region. The data from expeditionary measurements conducted between 2018 and 2022 were used, obtained using a portable photometer called SPM, developed at the Institute of Atmospheric Optics of the SB RAS. The study analyzes the AOD optical characteristics, the fine and coarse AOD components, the Ångström parameters, and the retrieved aerosol microstructure parameters. It is demonstrated that aerosol pollution during the summer season is caused by an increase in the concentration of fine aerosol particles. The mean/modal AOD values in the short-wavelength range of the spectrum exceed the mean AOD values for the Baikal region by a factor of 3-8.

In this paper the results of the study of diurnal and annual behavior of concentrations CO₂ and CH₄ are presented. This study is based on monitoring data using gas concentration analyzers in the surface layer of the atmosphere in urban and background observation sites in the Middle Urals in 2021 – 2022. Two maxima and two minima in the annual behavior of CH₄ concentration are observed for urban area (maxima: December – January and August; minima: May-June and October- November). One maximum in January and one minimum in May and summer months in the annual behavior of CH₄ concentration are detected for background region. The annual variations of CO₂ are differing in two areas: the highest values were recorded in December to January for urban site and in July for background monitoring point. The diurnal variation CH₄ concentration is maximal in July and August in the urban area. The changes from minimal to maximal CH₄ concentration are ∼20% The highest diurnal variability of CO₂ is observed in July at the background area (∼47%).

In this paper, authors propose a method for determining middle (4-7) and high (8-10) Cu amount using an unshaded pyranometer data and provide examples of its determination.