This PDF file contains the front matter associated with SPIE Proceedings Volume 12341, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Numerical simulations of longitudinal chromatic aberration in a four-component LWIR continuous zoom lens coupled to an uncooled detector are presented. The results have shown that in schemes containing two optical materials, most solutions involve the outer components made of germanium and the inner components made of materials with lower dispersion coefficients (chalcogenide glasses). The results are confirmed by the developed lens with a zoom ratio of 5X.

The longwave radiative fluxes in the cloudless atmosphere are calculated for meteorological conditions of Lower Volga Region. The radiative forcing due to CO2 concentration increase for the latest 50 years is estimated. Modern models of water vapor continual absorption in the 3-5 and 8-12 􀁐m atmospheric transparency windows are compared. It is shown that the H2O continual absorption reduces the CO2 radiative forcing in case of high concentrations of atmospheric water vapor.

The results of numerical simulation of optical radiation focusing on a mesowavelength Fresnel phase zone plate (ZP) with zones having an inclined profile are presented. In order to reveal the regularities in the formation of the focal spatial structure, the optical field was calculated in the case of diffraction of a monochromatic optical wave by a single ZP. It is shown that the basic parameters of the focal region (intensity, longitudinal and transverse dimensions, focal distance) are sensitive to the angle of inclination of the annular zones of the ZP. By changing the inclination of the edges, it is possible to optimize focusing and achieve its significant enhancement, which, depending on the focal length of the plate, can be up to 40%.

The paper considers the further development of a nanophotonic supersensitive sensor proposed by the authors earlier. The sensor is oriented for a wide range of engineering applications. The main idea of the device is to estimate the external pressure loading of the sensor by the electromagnetic field measurements. The nanophotonic sensor structure is irradiated by the electromagnetic source operating in the frequency domain. The light beam is passing through the internal cone structure of the sensor, and the output electric field is measured. The proposed mathematical modeling gives the opportunity to connect the radius of the inclusion in the sensor longitudinal section and the output electric field intensity in the reference measurement’s point. A 3D simulation of high-frequency electromagnetic wave propagation in a photonic microsensor structure was performed in a formulation close to the real one in the following paper. The mathematical modeling is carried out by the vector finite element method implemented in the author's software. The conducted numerical research allows us to make design decisions about the optimal overall dimensions of the sensor and the operating frequency of the electromagnetic radiation source.

In this paper, we estimate the type of orientation of H₂O molecules adsorbed on the surface of airgel nanopores based on experimental data on the broadening of the vibrational-rotational lines of the H₂O molecule during its collisions with H₂O molecules on the surface of the airgel in their chaotic and ordered orientation. It is shown that the experimental data are consistent with the model of orderly oriented H₂O molecules on the surface of SiO₂ nanopores.

In this paper, the authors propose a method for determining diffuse and direct irradiance under cumulus clouds using an unshaded pyranometer data, and provide an example and practical measurement results.

The current algorithm for retrieval of the optical and microphysical properties of clouds from satellite measurement data involves the use of independent pixel approximation and a model of plane-parallel horizontally and vertically homogeneous clouds for each pixel of satellite image, that in some situations can lead to large retrieval errors. The paper describes an alternative approach based on applying neural networks trained using the results of 3D simulation of solar radiation transfer in the Earth’s atmosphere in the presence of a field of broken horizontally inhomogeneous clouds. To generate a cloud field realization, the fractal multiplicative bounded cascade model is used. The examples of modeling the stratocumulus clouds by means of the bounded cascade model are considered. The model is successfully tested using the MODIS image of stratocumulus cloud scene.

The propagation of high-power ultrashort laser pulses on aerospace paths when laser radiation is sent from the Earth into space is analyzed theoretically. Titanium-sapphire and CO₂ lasers with femtosecond and picosecond pulse durations, respectively, are considered as radiation sources. The effective intensity and effective radius of curvature of the wavefront of high-power laser beams are estimated on the basis of the nonlinear layer model. It is shown that, on the whole, the use of a CO₂ laser makes it possible to achieve more precise focusing of radiation on an object during energy transfer under the conditions of power losses caused by strong molecular absorption. Also, more precise focusing on aerospace paths up to 400 km long is ensured by the use of a laser beam with a lower peak power and a larger initial radius.

The result of measurement of the cross-polarized component of the reflected field from liquids with different permittivity are presented. The cross-polarized component of the field is observed for liquid dielectrics with a large value of the imaginary part of the complex permittivity. The mechanism of excitation of this component is proposed.

The atmospheric transmission of UV radiation was simulated with use of new data on H₂O absorption lines in the 0.25- 0.4 μm spectral region. The transmittance spectra were calculated with the most complete H₂O line list POKAZATEL, its new modification in 2020 by Conway et al, refined databank W2020, and new version of popular spectroscopic database HITRAN2020, in which the H₂O lines were added in the UV region. The intercomparison of the spectra was made. The water vapor contribution to the atmospheric transfer of solar radiation in the UV region was estimated. The radiative transfer was modeled with taking into account of aerosol and Rayleigh multiple scattering and absorption.

The numerical simulations of propagation of high-power femtosecond laser pulses in air under conditions of superposed spatial phase modulation are carried out on the basis of the reduced form of nonlinear Schrödinger equation for time-averaged electric field envelope. Initial spatial modulations are applied to pulse wavefront profiling by a staggered phase mask with variable phase jumps between adjacent elements. It is shown that with specific phase modulations, the pulse filamentation region in air can be markedly shifted further and elongated compared to a non-modulated pulse.

The paper describes the results of measuring the structural parameters of optical turbulence for different altitudes in the atmosphere above the Large Solar Vacuum Telescope of the Baikal Astrophysical Observatory. The structural parameters of optical turbulence we estimated from the measurement data of the Shack-Hartmann sensor for individual atmospheric layers by applying the analysis of wavefront distortions in crossed optical beams. To estimate the structural parameters of optical turbulence, we propose an approach based on statistical averaging normalized dimensionless characteristics of turbulence, the Fried parameter and averaged profile of optical turbulence at a given site.

A description of the stand for an adaptive optics system operating in the mode of emulation of the slopes of the laser radiation wavefront on a turbulent path is given. The potential capabilities of the test bench involve setting the parameters of turbulent distortions characteristic of paths of various lengths, as well as using a piezceramic deflector of wavefront slopes as a source of emulated image distortions in the observation plane. The stand of the adaptive optics system makes it possible to stabilize the jitter of the optical radiation image in the plane of the receiving device with the adaptive correction circuit turned on and off under conditions of various system operation modes.

This development is carried out in the interests of creating a remote optical meter operating on the optical signal of a weak extra-atmospheric source - such as a star. It will allow obtaining data on turbulence for inclined paths at different heights above the underlying surface, and will also make it possible to detect the presence of turbulent layers in the atmosphere, including the presence of non-Kolmogorov turbulence in the atmosphere. For this purpose, it is planned to create two single-channel mock-ups of image jitter meters operating on signals from two different optical sources in a scheme with intersecting lines of sight. Atmospheric experiments have been carried out to compare the results of measurements of atmospheric turbulence by various methods.

For adaptive optics systems, one of the fundamental task to be decided is determination of the frequency characteristics of wavefront distortion variations in the focus of a ground-based solar telescope. It is a classical approach to use the atmospheric coherence time related to the vertical distribution of turbulence and wind speed. Besides, small-scale variations of wavefront induced due to turbulence for understanding the large-scale structure of atmospheric turbulence it is important to estimate frequencies of large-scale (low-frequency) turbulent components. The paper presents the results of the analysis of the frequency characteristics of wavefront distortion variations recorded in the adaptive optics system of the Large Solar Vacuum Telescope of the Baikal Astrophysical Observatory.

We present the results of studying year-to-year changes in the variabilities of the mesopause temperature and the peak electron density from the observational data of the complex of instruments of the Institute of Solar-Terrestrial Physics SB RAS in 2008-2020. The analysis involved data on solar and geomagnetic activity, as well as on variations in the Southern Oscillation Index (SOI). We revealed a correlation between the day-to-day variability of the mesopause temperature and SOI variations, with a peak in the La Niña phase and a minimum in the El Niño phase. An analysis of the ionospheric variability and their comparison with changes in geomagnetic and solar activity revealed, that only day-to-day ionospheric variability correlates unambiguously with geomagnetic activity.

The processes of combustion and flame propagation in various technological devices and during wildfires are carried out, specifically, under turbulence conditions. Turbulent combustion is a non-stationary process of turbulent mixing of combustion products with a fresh mixture and its ignition due to the temperature increase. This article compares estimates of the turbulence scale in a flame during the combustion of forest fuels in laboratory conditions and in a test site.

The paper shows the influence of deviations from the Kolmogorov-Obukhov model in the spectra of refractive index fluctuations in a supersonic air flow on optical radiation propagating through it. It is shown that with an increase in the exponent ( ) in the model of the spectrum of the refractive index of air, the transverse dimensions of the beam propagating through a high-speed turbulent flow increase.

In the present article the influence is considered of phase screen characteristics on the statistical properties of dislocations developed in a beam passed this screen. Analysis was performed with application of numerical experiment methods, and in the developed model the screen represented a thin layer of turbulent atmosphere. Special attention was devoted to assessment of the turbulence inner scale impact on distribution of vortices. We have also shown that this distribution meets the requirements of the central limit theorem.

The results of experiments with the use of a multi-parameter meter of turbulent micropulsations of the components of wind speed, temperature, humidity, pressure, and concentration of aerosol particles in the study of atmospheric turbulence in the lower layers of the atmosphere are discussed. In the process of automated measurements, data were accumulated on the turbulent characteristics of various meteorological parameters in the surface layer of the atmosphere. Based on the obtained experimental information, the synchronous behavior of the statistical characteristics of measured substances and their turbulent flows and some results of their complex processing and analysis were considered.

The parameters of the 190 H₂O absorption lines broadened by the carbon dioxide pressure were determined for the vibration-rotational bands ν₁+ν₃, 2ν₂+ν₃, and 2ν₁ in the 6760–7430 cm^–1 spectral region. The measurements were carried out on a Bruker HR 125 Fourier spectrometer at room temperature with a spectral resolution of 0.01 cm^–1. The values of the broadening and shift coefficients of the H₂O absorption lines are determined for the Voigt profile and the modified Voigt profile which takes into account the dependence of the broadening on the speed of the colliding molecules. The parameters of the H₂O absorption lines obtained in the work will allow more accurate determination of the H₂O concentration in the carbon dioxide atmospheres of the planets.

The water vapor line broadening and shifting coefficients for the HDO-16 and HDO-17 lines in the 6400-7000 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. The volume of the cell is 2.765 L. The absorption spectra of the HDO-16 and HDO-17 isotopologue were recorded at pressure of 23 mBar and oxygen pressures of 0, 171, 422 and 655 mBar. The difference in the broadening coefficients of the HDO-16 and HDO-17 absorption lines for the (101)–(000) band does not exceed 5%.

The formulas derived earlier for the frequency coherence of the field of a wave propagating in a layer with a linear profile of mean permittivity are used to simulate the mean intensity of a radio pulse reflected and scattered from a randomly inhomogeneous multiscale ionospheric layer. This intensity is shown to contain a wide pedestal due to backscattering by small-scale irregularities and a pulse with a smaller width determined by broadening of the pulse during propagation in a medium with large-scale irregularities.

We present the results of studying variations in the concentrations of the CO and H₂O atmospheric constituents over the Baikal Natural Territory from the long-term (2010–2021) data of the MLS Aura satellite measurements. The data were analyzed at the stratospheric heights for pressure levels within 215–10 hPa (~11–32 km) for the locations of Khorinsk (52.17° N, 109.77° E) and Zhigalovo (54.81° N, 105.15° E). We obtained averaged seasonal variations in the concentrations of the analyzed components for each pressure level under day and night conditions for the 2010-2020 period. Comparison of the obtained results with the behavior of the concentrations of atmospheric constituents in 2021 revealed an increased CO concentration for Khorinsk in July–August 2021, when increased smoke from forest fires was observed in the analyzed region.

The structure constant of refractive index fluctuations is one of the most important characteristics of atmospheric turbulence affecting the propagation of optical radiation. However, in a real atmosphere, the conditions of homogeneity and isotropy of turbulence, which are necessary for a correct experimental estimation of the structure constant and its further use in calculations, are not always realized. In 1, to characterize real turbulence, it is proposed to use an equivalent structure constant calculated by introducing a scaling factor depending on the parameters of the spectrum of turbulent fluctuations - the outer scale and the exponent of the spectrum. In order to assess the possibility of using this approach, the report presents the results of calculations of an equivalent structure constant based on spectral processing of sonic weather station data.

ZnGeP₂ crystals with different optical breakdown thresholds studied in this work. The Raman spectra of the crystals were obtained using the inVia Reflex system with an excitation wavelength of 785 nm. It is shown that the obtained peaks at frequencies of 141.6, 203.3, 327.4, and 402.4 cm^–1 correspond to the vibrational frequencies of the ZnGeP₂ lattice for wafers cut parallel to the (100) crystallographic directions and the peaks at frequencies of 119.1, 245, 327.4, 357.1, 384.7, and 408.7 cm^–1 to the (001) crystallographic directions. No correlation with the breakdown threshold was found. This fact confirms the assumption that the breakdown threshold in a given spectral range is determined not by thermal mechanisms, but by the dielectric breakdown of the crystal surface. This work 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).

The article provides the PIN-photodiode semiconductor structure In0.52Al0.48As/In0.53Ga0.47As/InP computer simulation results. The structure was grown on an InP-substrate by the method of molecular beam epitaxy. In modeling, PIN-photodiode mathematical model was constructed, with the help of which photocurrent values were obtained for various thicknesses of the undoped section in photodiode absorbing layer. The photodiode response time values are also obtained.

The results of numerical studies of the possibility and efficiency of intra-cavity phase correction of Cr:CdSe laser radiation with the moving active elements using an adaptive optical system without a wavefront sensor are presented. The beam quality of the Cr:CdSe laser directly depends on the speed of movement of the active element due to the influence of thermal effects. The peak radiation power has determined by the efficiency of the resonator and the cooling system of the active element. It has been shown that the using of intra-cavity adaptive correction in the Cr:CdSe laser can significantly reduce the influence of thermal effects and expand the range of laser operation in single-mode regime.

The numerical study of the efficiency of correction of sinusoidal phase distortions in the adaptive optical system with a finite response time (finite operation speed) has been performed. It has been shown that the operation of the adaptive optical system does not affect the beam quality at the ratio of the adaptive optical system bandwidth to the frequency of sinusoidal distortions ν_AOS / ν_turb < 1, laser beam is not corrected. The exceed of divergence over the initial value is observed as the result of correction at the increasing of ν_AOS / ν_turb from 1 to 6. The increasing of divergence has replaced by its monotonous decline at ν_AOS / ν_turb = 2.5. The decrease in the laser beam divergence relative to the initial value has been observed at ν_AOS / ν_turb > 6. The average Strehl ratio upon correction reaches 0.65, and the divergence of the laser radiation exceeds the diffraction limit by a factor of 2 at ν_AOS / ν_turb =100. Calculations show that phase distortions with the temporal spectrum in the form of a frequency band with a characteristic frequency ν_turb require a lower bandwidth ν_AOS for correction than single-frequency phase distortions with the same ν_turb.

The report considers the possibility of estimation of the profile along the optical path of the transverse wind velocity component from fluctuations in the image of a diffuse target illuminated by a laser beam. An algorithm for processing video images based on the construction of a spatiotemporal correlation function of fluctuations in the intensity of radiation scattered from a target is proposed. The results of testing the proposed technique by means of numerical simulation and in experiments at the IOA SB RAS test site are presented.

The high-altitude distributions of the Richardson number above the 6-meters Big Telescope Alt-Azimuthal of SAO RAS for astronomical site characterization are study. The 1/Ri used as parameter for ranking sites in term regime of stability and relative probability of periods and regions of turbulence. The profiles of the gradients of the potential temperature and the wind speed up to height of 25km for each month of year are calculated. The data used from the ERA-Erratum reanalysis, which is widely acknowledged as being reliable.

The random inhomogeneities of the refractive index due to turbulent motion in the atmosphere cause a significant decrease in the theoretical resolution of an optical telescope, cause such well-known effects as scintillation, jitter, and degradation of the optical images. Adaptive optics (AO) systems with a laser guide star (LGS) are designed to eliminate the negative effects. The main limitation of LGS is the problem of measuring the global tilt. We offer the approach to using the LGS signal. The approach, where initially the LGS is considered as a point source of spherical wave with a random center is considered. The results of analytical and numerical calculations are reported. The estimation of sodium column density and height peak of sodium mesospheric layer above large Russian Observatories are presented also.

The results of experimental studies of the absorption spectra of pure NH₃ at room temperature in the range 6611.6 - 6613.5 cm^-1 and pressure range (up to 0.01 atm.) are presented. The measurements were carried out at the Department of Diode Laser Spectroscopy of the Institute of General Physics on a high-sensitivity high-resolution diode laser spectrometer with a signal-to-noise ratio of ~ 1400. The spectra were analyzed using a Voigt contour. The results of reconstructing the parameters of spectral absorption lines are presented: the positions of centers, intensities, coefficients of collisional self-broadening and shifts. A comparison was made with the parameters of the HITRAN database. A ~ 2-fold difference in intensities was found. Ammonia is one of the most common chemicals in human activity, is a waste product of living organisms and one of the most important products of the chemical industry. Ammonia is used to produce nitric acid, nitrogen fertilizers, explosives, etc. Ammonia is toxic and, along with such molecules as CO, NO, CH₄, ¹³CO₂, is a biomarker molecule^1,4. These circumstances lead to the need to ensure continuous monitoring of ammonia and the development of reliable, low-cost measuring instruments in the environment, food industry and medicine. Currently one of the most highly sensitive and highly selective modern methods of gas analysis is diode laser spectroscopy. However, the realization of the advantages of this method is largely determined by the quality of the spectral data basis used, represented by the HITRAN database. One of the promising spectral ranges for monitoring NH₃ is the region 6604 - 6613 cm^{-1 2}. And another paper presents the results of experimental studies and analysis of the absorption spectra of pure NH₃ in the range 6547 - 6552 cm^-1 at room temperature and pressure range 0-0.04 atm ³.

The work presents the results of laboratory experiments on controlling the filamentation domain of a focused femtosecond laser beam with a spatially structured (using a deformable mirror) wavefront. We studied aberration beams consisting of coherent nested annular subapertures obtained with a specific shape of a deformable mirror determined from theoretical estimates. This makes it possible to create inhomogeneities in distribution of the optical field amplitude during propagation of the laser beam, which can subsequently become seeds for the light filaments formation. This regime of high-power radiation filamentation control does not require compensation for distortions in the initial beam profile, but on the contrary, it is based on the controlled introduction of preliminarily calculated wavefront aberrations.

The paper presents experimental data on determining a level of turbulence over a heated metal surface in the saturated turbulence regime, which cannot be explained by the classical Kolmogovov-Obukhov theory. A spectral behavior of temperature fluctuations is studied. Based on the calculated data of the structural function and the spectrum of temperature fluctuations, the level of turbulence over the heated surface is determined along the height. Estimation of the outer scale of turbulence showed that in the center of the metal surface the outer scale increases with height. At the surface boundary, cascade generation-dissipation of vortices is observed.

The experimental results of the features of formation and path propagation of high-intensity light channels under conditions of distortions of the initial profile of a high-power femtosecond laser beam are presented. The distortions are introduced by amplitude modulation of the laser beam with the help of the masks. The use of amplitude masks allows generation of a given number of high-intensity light channels and their controllable filamentation mainly at short (tens of meters) distances of radiation propagation in air.

We present the results of the turbulent layer influence on the characteristics of the filamentation domain at the path beginning for the beams with a diameter of 2.5 and 5 cm. Addition of turbulence results in the fact that the beginning of the multiple filamentation domain (MFD) to the source coming closer. Decreasing of the distance to the beginning and end of the MFR in the presence of turbulence is inappreciable (<10%). The turbulent layer formed at the beginning of the path leads to a multiple increase in the number of the intense channels (~ 10¹¹-10¹² W/cm2) with a length >100 m.

The results of the experiments on the excitation and detection of two-photon fluorescence of the dyes by the intense light channels generated by controlling the wavefront of the femtosecond laser pulses are presented. Emission of the dyes and the detection of the backward signal were carried out according to the lidar scheme at a distance of 100 m from the source.

The problem of information transmission by modulating the topological charge of the orbital angular momentum (OAM) of beams synthesized by an array of fiber lasers during radiation propagation through a turbulent atmosphere is investigated. The possibility of adaptive compensation for turbulent distortions of a beam in the periodic process of successive phase matching in the receiver plane and phase modulation in the initial radiation plane for information transmission is demonstrated for the first time. A mathematical model of the process of adaptive control for two modifications of the feedback loop and the results of OAM recognition by machine learning methods are presented.

The experimentally obtained dependences of acoustic signals on the energy of femtosecond pulses in the filamentation mode, propagating in a liquid-drop aerosol with nanoparticles of various concentrations imitating Aitken nuclei, are presented. It is shown that, under the action of a femtosecond pulse filament, a water aerosol jet breaks into two jets.

In 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 new results of measurements in 2021 of vertical derivatives of average temperature and average horizontal wind velocity in the turbulent atmosphere of the boundary layer. In measurements in the urban surface layer of the turbulent atmosphere, the range of experimentally observed Monin-Obukhov numbers has been significantly expanded – 227 ≤ ζ ≤ +72572 in the positive region, where experimental data were previously absent. This made it possible, on the basis of the necessary characteristics obtained, to restore the empirical view of the function φ(ζ) with super-strong stable stratification in the range +1 ≤ ζ ≤ +72572. The comprehensive studies of the similarity function performed in this paper based on the measurement data of 2021 can be considered as a new significant result in the Monin-Obukhov similarity theory.

An important task in controlling signal reception, transmission, and processing in photonic integrated circuits is to make a specific EM waveform, which is done with polarization convertors. Today, various waveguide structures based on the effects of birefringence and dichroism are used as polarization controllers that control the electromagnetic waveform. This paper presents the structures of symmetric and asymmetric ridge waveguides that allow polarization control based on the birefringence effect; and the waveguide structure with an asymmetrically arranged metal film that allows polarization control based on the plasmon effect; and also the structure of a dichroic circular polarizer based on nanostructures.

The treatise presents the results that allow assessing the impact of the semiconductor-air interface geometry on the PIN diode characteristics. The study describes the semiconductor InGaAs/InAlAs-structure of the PIN photodiode grown on an InP-substrate and presents its topological scheme. For the study, a mathematical model of the PIN photodiode was built that describes the motion of charged particles and their distribution in the structure on the basis of Fermi-Dirac distribution function and the stimulated absorption of the electromagnetic radiation. The calculations yielded the dependence of the diode photoelectric current on the semiconductor-air interface geometry.

The transverse mutual coherence function of the second order of the field of optical beam propagating in a discrete scattering medium with particles, whose sizes are large compared with a wavelength of optical radiation, is described by the integral equation. It is shown that when certain conditions are met, this integral equation turns into a differential equation. Using the analytical solution of this differential equation, a numerical analysis of the behavior of the mean intensity of the Gaussian, hollow Gaussian, Gaussian beam with a vortex phase and vortex Gaussian beams is performed.

The theoretical possibility of correcting the amplitude-phase distortions of Laguerre-Gaussian beams on atmospheric paths is studied by computer simulation. A dynamic adaptive correction scheme is used based on the principle of phase conjugation of the reference wave from an auxiliary coherent source. By numerically solving the inhomogeneous parabolic wave equation, the split-step method simulates the propagation of beams in a randomly inhomogeneous medium with a power-law spatial spectrum characteristic of atmospheric turbulence. The wave equation is solved using parallel architecture algorithms based on the functions of the Intel MKL and IPP libraries. The influence of atmospheric turbulence on fluctuations of the orbital angular momentum of Laguerre-Gaussian beams is considered, and the efficiency of their suppression in a closed loop of an adaptive optical system is theoretically demonstrated.

The current level of technical development has led to increased number of anthropogenic hazards including emissions from industrial and agricultural enterprises, terrorist threats using chemical and organic components etc. An important factor in ensuring safety is the timely detection, identification, and localization of sources of danger. In this regard, remote methods, including laser ones, become more and more important allowing detecting and identifying danger in real time and at a distance from its source. The paper presents a calculation of the laser radiation absorption by water vapor for the wavelengths of CO₂-laser generation lines. It is shown that absorption caused by H₂O, C₂H₄ and NH₃ at some laser generation lines can significantly affects the results of remote detection of organic components depending on the concentration of these gases in the atmosphere. These results can be useful for specialists that develop instruments and methods for remote detection of organic compounds in the atmosphere.

The paper is devoted to numerical investigation of coherent beam combining of 7-channel laser radiation and its focusing on the remote receiver in dynamic turbulent medium using the two-step stochastic parallel gradient (SPG) algorithm with the double-pass delay included in the step time or in the temporal shift between steps. Dynamic turbulent medium has been modelled using one phase screen approximation based on the Taylor hypothesis. The spatial spectrum of turbulent distortions has corresponded to the von Kármán spectrum and has been characterized by the atmospheric coherence radius (the Fried parameter) r₀. Combining efficiency has been estimated for various ratios of the aperture size d to r₀ and ratios of the phasing frequency νph (reciprocal value of time interval required to achieve the Strehl ratio equaled 0.8 in the nonturbulent medium) to the Greenwood frequency ν_G. The requirements for d/r₀ and ν_ph / ν_G values have been determined, under which the SPG coherent beam combining with taking into account the double-pass delay provides the Strehl ratio level of ~0.7 or higher.

The paper presents the results of numerical simulation of focusing a laser beam with the non-diffraction angular divergence through the turbulent atmosphere using the adaptive optical system. The operation of the adaptive optical system is based on the phase conjugation principle. The adaptive phase correction of the outgoing laser and reference beams is assumed to be imperfect. The numerical calculations of the laser beam propagation to a remote receiver through the turbulent atmosphere under conditions of imperfect phase conjugation have been carried out. It is found that St=St_R·St_L, where St is the Strehl ratio for the laser beam at the receiver, St_R and St_L are the Strehl ratios for reference and outgoing laser beams, respectively. This formula is true for St>0.03.

Paper contains the results of modeling the propagation of monochromatic ultrashort pulses in medium simulating natural waters with suspended mineral, organic particles and air microbubbles taken into account. The role of each component in limiting the information transfer rate is shown.

The characteristics of radio waves with inclined propagation in an inhomogeneous magnetoactive ionosphere are considered, taking into account the altitude dependence of the effective frequency of electronic collisions. The results of the calculation of dispersion curves, refractive indices and absorption, 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 beam entry into the ionosphere.

The numerical simulations of possibility of effective delivery of the speckled laser beam energy through the optical heterogeneous medium onto a target have been carried out. The calculations of speckled beam have been carried out within the framework of a numerical model of integration of the parabolic equation for the laser field amplitude taking into account the turbulence according to the phase screens model. Two approaches for pointing the speckled laser radiation onto the target in far field have been considered: the first approach is concerned with the preliminary scanning of the focal plane by the beam with the subsequent SPG correction of the beam position, and the second approach is the direct tip-tilts SPG correction without scanning. The probability estimation of the performance efficiency of the pointing system has been performed. It is shown that in both cases it is possible to direct the most intensive speckle of the laser beam onto the target with high probability.

The report presents the results of experiments to compensate for the mismatch of the optical axes of the transmitter and receiver based on backscattering of the focused beam radiation. The matching error does not exceed 2.5 arc seconds.

We have developed three types of deformable piezoelectric mirrors with a high density of control elements to compensate for the aberrations of the wavefront of high-power laser radiation that has passed through a turbulent atmosphere: bimorph and piezoactuator types. When creating correctors of the first type, laser engraving and microwelding methods were used, which made it possible to create a 30 mm bimorph mirror with 37 electrodes, compensated for wavefront aberrations up to the 7th order of the Zernike polynomials. The design of the piezoactuator mirrors provided for the possibility of replacing the piezoelectric stacks in the event of their failure, as well as thermal stabilization of the corrector's reflective substrate through the body of the actuators. Main parameters of all types deformable mirrors were investigated and compared.

The work proposes an original algorithm of the Monte Carlo method for simulating the propagation of laser pulses in a cloudy atmosphere taking into account all scattering orders. The results of studying the features of echo signal propagation through the cloud represented by semi-infinity homogeneous layer are discussed. The contribution of multiple scattering to a ground-based and a spaceborne monostatic lidar returns from clear atmosphere obscured by cumulus, stratus or cirrus clouds is assessed at the wavelength of 0.532 μm. The significant presence of multiple scattering in lidar returns and its dependence on the characteristics of the sounded clouds are demonstrated. High anisotropy of scattering in the forward direct ion by polydispersions of large nonspherical ice crystals is the basis of a tangible effect of multiple scattering for small values of the lidar receiver field of view. The radiation scattered by the crystal particles within a narrow cone around the forward direct ion is predominant and is greater than the corresponding values for scattering on water droplets. For cumulus and stratus clouds, the contribution of triple-scattered photons and higher to the total echo signal increases with increasing field of view of the receiver. The magnitude of multiple scattering effects is also seen to be largely determined by the optical depth across the receiver field of view at the cloud.

Carbon-dioxide broadened sulfur-dioxide line widths have been calculated with semi-empirical method at the room temperature (T=296K) for 621 R-branch lines of the ν₁+ν₃ band, rotational quantum numbers J vary in the range from 0 to 70. The computed broadening parameters are compared with the literature data, and good agreement is obtained. Semi-empirical approach is based on analytical expressions of semi-classical impact theory and including a fewparameter correction which can be determined by fitting the broadening coefficients on the experimental data.

Atmospheric monitoring of methane shows that CH₄ concentration growth since 2007 is accompanied by C¹³/C¹² isotopic delta ratio shift to more negative values due to ¹³CH₄ content depletion. In the work, the atmospheric total column amount and vertical profiles of ¹³CH₄ and ¹²CH₄ are retrieved from the ground-based measurements of solar spectra in Kourovka observatory. The CH₄ isotopologues ratio is calculated. The error of the isotopologues content retrieval is estimated for different spectral regions. On basis of the obtained results, optimal spectral windows were found.

New results of measurements of the time correlation scales of temperature fluctuations in a thermally stratified turbulent atmosphere are presented. The results were obtained during long-term observations 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). The mobile hardware-software ultrasonic station AMK-03-4, designed to measure the characteristics of turbulent meteorological fields, was used for measurements. It is shown that the time correlation scales of surface temperature fluctuations are minimal in the indifferent stratification (and do not exceed ten seconds). During the transition to the region of super-strong instability and super-strong stability, on average, an increase in correlation times (up to 50-60 seconds) was noted. It is established that temperature fluctuations are minimal in unstable and indifferent stratifications (where the standard deviation is in the range of 0.1– 0.25 degrees). When moving to the region of stable stratification, the standard deviation of temperature fluctuations increases on average and can reach one degree.

In this work, we used the data of a laboratory experiment on registration of fluctuations in the intensity of a laser beam passing through a vortex flame (model of a fire tornado) to calculate their power spectra. The nature of the decay of the power spectra in the high-frequency region was studied. The dominance of the two-scale decay of such spectra over the single-scale decay is established. The analysis carried out makes it possible to compare the results with the well-known Kolmogorov-Obukhov theory for estimating the turbulence parameters of the free atmosphere and to assume the presence of an inertial interval in the vortex flame.

Until now, a number of issues related to the energy and dynamics of the atmosphere of Venus remain unclear. In particular, this is the phenomenon of superrotation, which consists in the presence of a high-speed wind flow in a narrow high-altitude layer above the upper boundary of clouds in the equatorial atmosphere of Venus. In the framework of the simplified model, the problem of radiation transfer in the spectral lines of infrared CO₂ bands in the planetary atmosphere is considered, taking into account the frequency shift of the volume opacity coefficient due to the Doppler effect. Such frequency shift occurs when there is non-zero value of projection onto the ray pathway of the velocity vector of large-scale winds. For different viewing angles, the variability of the values of the radiation intensity leaving the atmosphere at the upper boundary was studied, depending on a number of parameters of both the model of the vertical gradient of the horizontal wind speed and the spectral parameters of the line (band). The analysis of the present study results allows us to conclude that further investigations of the above mentioned radiative transfer problem for more realistic models would be fruitful.

The non-equilibrium populations of excited vibrational states of the CO₂ molecules in the problem of radiation transfer in infrared bands of carbon dioxide in the middle and upper atmosphere of the Earth are investigated, taking into account changes in the absorption coefficient due to the line-mixing effect. To do this, a carbon dioxide molecule model is used to study non-equilibrium CO₂ emissions in the Earth's atmosphere, which takes into account 206 vibrational states of the 7 isotopologues of CO₂ giving rise 545 radiation vibrational transitions consisting of about 64200 ro-vibrational lines. The line-mixing effect was taken into account only for lines belonging to the spectral range of the 15 μm CO₂ band, using a correction function to the values of the radiation absorption coefficient in this band, which was calculated within framework of the strong collision model with adjusted branch coupling. It is shown that taking into account the deviation of the frequency profile of ro-vibrational transitions in the spectral range of the 15 μm CO₂ band from the sum of Voigt profiles due to the phenomenon of line-mixing leads to only insignificant (less than 2%) changes both in the values of non-equilibrium populations of vibrational states of CO₂ excited in the bending mode of the CO₂ molecule and in the magnitude of the rate of radiative cooling of the atmosphere in the bands of CO₂. The study could be useful for understanding the radiation regime in planetary atmospheres. The results of the work may be used in the development of methods for remote sensing of atmospheric parameters.

The influence of the type of the initial beam profile on the beginning and end of filamentation in a turbulent medium is considered based on a numerical experiment. It is shown that the beginning and length of filamentation can both move away and get close depending on the initial profile of the laser beam amplitude with topological charge increasing. In addition, the filamentation length decreases with increase of a topological charge. The statistical dispersion of the spread of the longitudinal filamentation boundaries decreases monotonically with an increase of the topological charge; in turn, the dispersion of lateral spread does not have a unique dependence on the topological charge value.

The article considers the possibility of using mirror scanners in scanning polarization lidars. Distortions introduced by reflections from mirrors with metal coatings into the state of polarization of scattered radiation are calculated. The measurement errors of the scattering matrix elements, including the depolarization parameter of an ensemble of scattering particles, are discussed.

A variant of computer simulation of a multichannel mirror-lens system (lens) made of a material transparent in several spectral ranges for remote sensing of the Earth by unmanned mini-vehicles is considered. The optical system operates using two radiation receivers that are sensitive in three spectral ranges.

The impact of the number and dislocation scheme of electrodes of piezoelectric bimorph mirror on the efficiency of scattered laser beam focusing was researched. The mirrors with the apertures up to 50 mm and the number of electrodes up to 50 were investigated using the proposed algorithm of numerical focusing. The algorithm used the experimentally measured response functions of each mirror.

The results of experimental determining the morphological and other optical characteristics of the Asian dust show the crucial role of measuring the scattering matrix of particles using a polarization lidar. The accumulated experience of polarization measurements allows the matrix polarization lidar to be designed optimally and the calibration problem to be formulated and solved. Optimality is understood here as simplifying the unit changing the lidar phase plates from four to one plate in the transmitter and receiver. To provide the transition to angular phase plate rotations, the problem of the optimal set of the phase plate states and the problem of measurement sample size are solved. The problem of calibration of the optimal polarization lidar is considered.

This article presents the results obtained during the expedition on board the research vessel throughout the water area of Lake Baikal from 1 to 9 September 2021. We determined the spatiotemporal heterogeneity of the distribution of polycyclic aromatic hydrocarbons (PAHs) and sub-10μm particulate matter (PM₁₀) in the atmosphere above the water area of the lake. Local sources of air pollution along the lake coast and synoptic conditions affected the changes in the concentrations of pollutants. Elevated concentrations of PAHs and РМ₁₀ were recorded near the Nizhneangarsk settlement in the northern basin, at the estuary of the Selenga River in the central basin as well as along the east coast and at the estuary of the Angara River in the southern basin of Lake Baikal. During the observations, the proportion of submicron particles at different sites of the lake water area decreased to 35-29 % of the total number concentration. Among the priority PAHs, fluoranthene > pyrene > benzo(b)fluoranthene predominated in the aerosol. Cyclones operating above the region, which were accompanied by precipitation and intense winds, led to the purification of the atmosphere and a decrease in the concentrations of the studied elements.

At the Siberian Lidar Station in V.E. Zuev Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences in Tomsk (56.5 N, 85.0 E), a lidar is operated to measure the ozone vertical distribution in the upper tropospherelower stratosphere, to study the ozone dynamics in the tropopause region, and to investigate the stratosphere-troposphere exchange. In this work, we compare R7207-01 PMT, operated on this lidar jointly with amplifiers-discriminators C3866 of HAMAMATSU firm for signal recording, against H12386-210 PMT units at the wavelength pair of 299/341 nm. It is shown that the new H12386-210 PMT units are promising for ozone sensing at the wavelength pair of 299/341 nm.

We present the time series of the total ozone content (TOC) over Tomsk, obtained using three independent spectrophotometers, and carry out their comparative analysis. Comparison of measurements by these instruments shows that they well correlate in terms of the pronounced variations, arising in time behaviors; but the amplitudes of the bursts differ. On the whole, we can note that the TOC values, obtained using IAO instrument, exceed those from two other instruments, TOC values from NASA instrument being the lowest. These smallest TOC values are especially apparent for the summer and fall periods.

The research studies the unfavorable meteorological and synoptic situations contributing to an increase in the concentration of sulfur dioxide (SO₂) and carbon monoxide (CO) in the air basin of the Southern Baikal region. Atmospheric impurities and meteorological parameters were registered at the Listvyanka station with SV-320 and R310-A chemiluminescent gas analyzers, as well as a Meteo-2M ultrasonic weather station. General synoptic processes over the region were studied using the Digital Atmosphere software and the HYSPLIT trajectory model. The influence of various meteorological conditions on the atmospheric air over the Listvyanka station in 2020 and 2021 was determined.

The results of computer simulation of the overlap function for a biaxial lidar scheme with different diameters of the receiving part photosensitive zone of the optical system are presented. It is shown at what sizes of the photosensitive zone the full overlap of the telescope field of view and the laser beam is ensured sounding path of up to 1 km. The length of the "dead" zone, when the laser beam propagates parallel relative to the optical axis of the telescope is estimated.

The report provides an analysis of the dependence of the ozone absorption coefficient on the change in temperature and pressure in the atmosphere in the spectral region of 1000-1070 cm^-1. Two spectral sections of the outgoing radiation of the atmosphere (1002-1003 cm^-1) and (1020 -1021 cm^-1) of the ozone absorption band with the opposite dependence of the ozone absorption coefficient on the change in gas temperature were determined. The atmospheric model is presented in the form of homogeneous layers of 100 meters to an altitude of 40 km. The parameters of the layers are determined for the standard atmosphere and the contribution to the outgoing radiation of the atmosphere in the investigated spectral sections of the ozone absorption line 1002-1003 cm^-1, 1020-1021cm^-1 is equal to the contributions to the outgoing radiation of the Earth's surface and all the heterogeneous layers that make them up. A possible method of adjusting the temperature of the Earth's underlying surface and the ozone content is shown by the convergence of the results of simultaneous calculations of the amount of investigated gas in the atmosphere by the outgoing radiation in the investigated spectral areas.

To study the parameters of the condensation activity of individual fractions of atmospheric aerosol with an artificial change in the relative humidity of the air, a prototype was designed in which small particle counters are used as a number concentration analyzer. The advantage of such meters is their small size and low cost. The prototype uses Alphasense OPC-N3 counters. Preliminary results of the evaluation of the studied parameters are presented.

The paper discusses the problem of ensuring the linearity of photo registration of the lidar signal of molecular scattering on the main lidar of the Siberian lidar station (SLS) based on a unique mirror with a diameter of 2.2 m. To reduce the dynamic range of signal changes, it is proposed to use a mechanical shutter based on a disk obturator to cut off the near zone of the lidar signal in the altitude range of 0÷30 km. A high-speed brushless motor was used as an obturator driver. The synchronization signal was generated by a Hall sensor. Bench and full-scale tests of the obturator were carried out. It is shown that the error of the Hall sensor does not affect the delay and duration of the shutter opening.

The paper considers a block diagram of a photodetection system based on a new version of the four-channel photon counter "PHCOUNT-4" used for precision lidar measurements of atmospheric temperature. The results of using the new capabilities of the analog part of the photon counting system, which makes it possible to automatically record the amplitude distribution of single-electron pulses of each of the photodetectors installed in the channels and determine the optimal discrimination threshold, are described. It is shown that setting the optimal discrimination thresholds makes it possible to achieve a small spread in the end-to-end quantum efficiency of each of the channels

The influence of the turbulent combustion model on the position of the flame zone in a swirling flow is analyzed. Three models of turbulent combustion were analyzed: a model of volumetric combustion, a model of turbulent pulsations, and a model of vortex decay. The research results show that the data of the combustion model controlled by turbulent mixing are in the best agreement with the experimental data.

The paper presents the results of quantitative studies of the heart rate variability detected when the subject was exposed to the preferred light stimulus with a wavelength of 460 nm (blue color). The use of the variational pulsometry method showed the possibility of assessing the state of homeostasis, the interaction of sympathetic and parasympathetic regulation circuits. In the course of the experiment, the activity of various links of the regulatory mechanism was assessed and a general picture of the adaptive response of the organism to the preferred blue light was revealed.

The paper presents the results of experimental studies of optical radiation impact of three colors (yellow, green and blue) on the functional state of human internal organs using the method of energy coefficient. It has been shown by quantitative assessment that a biological response of the body is not determined by the properties that are common to all the waves of the visible range, but it depends on the wavelength of optical radiation. Short-term exposure to optical radiation of the visible range does not lead to any significant and stable changes in the functioning of internal organs. The results of the research can be used to develop technologies for managing the mental and physiological state of a person.

An analysis of the differential optical depth from the lidar signals simulated by IPDA on board the space platform in detecting carbon dioxide sources is presented, and estimates of the limiting capabilities and technical characteristics of a possible lidar system are given. 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).

The analysis of the reconstructed differential optical depth from simulated IPDA lidar signals when detecting carbon dioxide sources from a low-flying vehicle (such as an airplane) is given, estimates of the limiting capabilities and technical characteristics of a possible lidar system are given. 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).

Based on the ten-year (2011-2021) measurements of the aerosol optical depth of the atmosphere, and the near-surface volume concentration of aerosol and mass concentration of black carbon (eBC) in the Barentsburg settlement (Spitzbergen Archipelago), we estimate the relationship between the contributions from different time variability scales to their total variations. It is noted that synoptic-scale variations make the main contribution (30-70%) for all characteristics. The effect of the diurnal rhythms, making up about 30%, is just manifested for eBC and concentrations of submicron aerosol. The contribution of seasonal and interannual variations does not generally exceed 10-20%.

We discuss the statistical estimates of how continental outflows influence the aerosol characteristics over the Arctic Ocean using data from marine expeditions over the last 15 years. The analysis was performed based on elevated values of the aerosol optical depth of the atmosphere and mass concentration of absorbing substance in the equivalent of black carbon. The data from trajectory analysis of air mass motion, satellite maps of the temperature anomalies were used to identify the types of the sources of continental aerosol and to systematize them into separate groups.

Corner-reflection effect is the main feature at lidar soundings of cirrus clouds. In this paper, this effect is numerically studied in the case of plate-like quasi-horizontally oriented ice crystals of cirrus clouds. It is shown that the lidar signal as function of lidar tilt relative to the vertical can be used for inferring microphysical properties of ice crystals. In particular, if depolarization ratio at small lidar tilts is a small quantity it means that the crystals are plate-like and the plates are quasi-horizontally oriented. Appearance of a sharp step of depolarization ratio at the tilts of about 30° means that the transversal shapes of the crystals are regular. Otherwise, the transversal shapes are irregular.

The paper presents the phenomenon of negative polarization for large randomly oriented irregular particles what occurs as a result of interference between specific reflected waves associated with geometric optical trajectories of light beams for four refraction/reflection events. All calculations were performed for randomly oriented particles with a convex irregular shape. We used our physical optics approximation computer algorithm where the light scattered inside the particle consists of many plane-parallel beams. It is shown that the appearance of a backscattering peak is characteristic of the trajectories of light beams with any number of refraction/reflection events; however, only trajectories with four events (two internal reflections and two refractions at the exit faces of the particle) create negative polarization.

This study presents the research results of chemical composition of the snow cover in the Baikal region exposed to aerotechnogenic emissions from pollution sources located in the Irkutsk region and the Republic of Buryatia. The samples of snow cover taken along the Irkutsk–Listvyanka route, in the Selenga River delta and in the territory of the Baikal State Natural Biosphere Reserve were analyzed. The features of the spatial distribution of tracers from large industrial centers in the southern Irkutsk region and the Republic of Buryatia along the prevailing air mass transfers were studied. The percentage of unfavorable meteorological situations in which emissions from regional anthropogenic pollution sources could reach the coast of Lake Baikal was determined based on the calculations of spatial distribution of anthropogenic impurities from large cities being sources of pollution (HYSPLIT). The model of spatial distribution of anthropogenic substances from the large industrial centers of the Baikal region along the prevailing air mass transfers was shown.

The paper substantiates the choice of the slope of the spectral characteristic of the Fabry-Perot interferometer (FPI) for an incoherent Doppler lidar. The results of numerical simulation of the relative sensitivity of the FPI transmission with a change in the wind speed in the atmosphere by 1 m/s are presented for various FPI bases.

This paper presents the results of synchronous observations of the ozone concentration and meteorological parameters obtained using an automated system for measuring the characteristics of gaseous impurities and the AMK-02 meteorological complex in the near-air layer of the atmosphere on the southeastern coast of Lake Baikal. The vertical ozone fluxes in the friction layer h = 3 m above the water surface were estimated during the summer period (July- August). Estimation of the rate of dry ozone deposition showed that, in the region of high wind velocity gradients in the friction layer, its distribution depends on the wave parameters and varies over a wide range.

Linear trends in the total, tropospheric, and stratospheric column NO₂ contents obtained from satellite measurements using the Ozone Monitoring Instrument are compared to NO₂ trends obtained from ground-based measurements at NDACC stations. For the Zvenigorod station, where vertical distribution of NO₂ is retrieved from the ground-based measurements, a satisfactory correspondence of the trends calculated from satellite data to the trends calculated from measurements at the station has been obtained. For other stations where only the total column NO₂ contents are measured, the correspondence of the trends calculated from satellite data and trends obtained from ground-based measurements may generally is less satisfactory.

The results of measurements of the mass concentration of black carbon in the near-ground aerosol (eBC) and the aerosol optical depth of the atmosphere (AOD) are compared with the data of the MERRA-2 reanalysis in the region of 45°W ÷ 110°E, to the south of 35°S and observatory Mirny. Shipborne measurements were carried out during the Russian Antarctic Expeditions (2004-2005) during the transition from Africa to the coast of Antarctica. It is shown that the correlation coefficients between the model and expedition data are only 0.1 for eBC and 0.65 for AOD, but the values are statistically significant. 90% of the discrepancies between model and measured data lie in the ranges of - 20÷65 ng/m3 and -0.045÷0.015, respectively. The correlation of measured and modelled AOD in observatory Mirny is 0.18, and 90% of the discrepancies lie in the range –0.04÷0.025.

The results of measurements of the organic and elemental carbon concentration, the carbon isotope composition in atmospheric aerosol samples collected during the marine expeditions – the 83rd and 84th cruises of the RV Akademik Mstislav Keldysh are presented in this paper. The measurements were carried out from June to August 2021 mainly in the waters of the Kara Sea (83rd cruise) and Barents Sea (84th cruise). It is shown that the aerosol in the northern part of the Barents Sea is formed due to anthropogenic and natural sources, while the background aerosol prevails over the Kara Sea.

A pulsed coherent Doppler lidar (PCDL) developed at the Wave Propagation Laboratory of the Institute of Atmospheric Optics SB RAS (WPL lidar) was tested in two experiments conducted in 2021 at the Basic Experimental Observatory of the Institute of Atmospheric Optics SB RAS and on the coast of Lake Baikal. In these experiments, the Stream Line PCDL of serial production from HALO Photonics (Great Britain) was also involved. A comparative analysis of estimates of the average horizontal and vertical wind speeds from measurements by Stream Line and WPL lidars showed good agreement between the results (with a 30-minute averaging of the data, the correlation coefficient of the estimates is 0.98).

In this report we present and generalize the results from lidar measurements of the vertical distribution of the stratospheric aerosol layer at the Siberian Lidar Station in 2021. The description and technique of the stratospheric measurements at multichannel stationary lidar complex in Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, Tomsk are presented. Based on the measurements and analysis of the data obtained, we confirm the regularity of increasing accumulation of background aerosol in the period of fall – winter, followed by its active depletion in summer period.

The long-term variability (2004-2021) of the aerosol parameters in the atmospheric column, were obtained at a location near the city of Yekaterinburg in the Middle Urals using solar photometer CIMEL CE-318 of the ground-based aerosol robotic network (AERONET). In this study, we present the results of analysis of trend of long-term changes of the aerosol optical depth (AOD) and the characteristics of the aerosol microstructure in the atmospheric column. The AERONET measurements show gradual decrease in annual values of AOT at a wavelength of 0.5 μm, fine and coarse components of atmospheric aerosol.

The results of numerical simulation using Ansys Fluent software of the droplets trajectories formed during the atomization of water-coal fuel (WCF) using pneumatic mechanical nozzles are presented. The trajectories of two qualitatively different systems are modeled: coal “particle droplets” and water-coal droplets. It is found that the trajectories of moving “particle droplets” and WCF droplets in the vortex chamber have the form of spirals, while the residence time of burning “particle droplets” and WCF droplets in the furnace is proportional to their diameter, which makes it possible to ensure their near-complete burnout.

A method of probing the profile of the structural characteristic of the refractive index using a micro-pulse turbulent lidar BSE-4 has been tested. The sounding path included a horizontal section 130 m long, located above the roof of the building. A flat mirror directs the laser beam vertically upwards. The high intensity of optical turbulence above the roof contributed to the appearance of fluctuations in the intensity of radiation in the laser beam. Turbulence above the roof was controlled by a scintillometer. Measurements were made at night during three days. An increase in the intensity of fluctuations of the refractive index was recorded in the altitude range from 12 to 18 km at the level of 10^-16 m^-2/3. The intensity of optical turbulence at this altitude regularly increased over time, while the wind speed at an altitude of 15 km, obtained from meteorological observations, regularly decreased. The results consistent with analytical models of vertical profile of the structure parameter of atmospheric refractive index.

Consideration of the results of the interaction of electromagnetic radiation with non-spherical atmospheric particles with anisotropic properties is of both scientific and practical interest. Particular attention should be paid to the interaction of directed optical radiation with spatially oriented atmospheric ice crystals. Failure to take into account the mirror image of optical radiation from an ensemble of spatially oriented atmospheric particles of non-spherical shape can distort model representations, significantly complicate the interpretation of the results obtained and lead to incorrect interpretation of some phenomena observed in the atmosphere. The paper considers some results of observations of the phenomenon of mirror reflection from horizontally-oriented flat crystal parts localized in the atmosphere. This study was supported by the Ministry of Science and Higher Education of the Russian Federation.

An optical scheme of an optical parametric oscillator (OPO) with a common pumping based on a pulsed YAG:Nd³⁺ laser (λ=1.064 μm) with a ring resonator based on an active element made of a lithium niobate crystal (LiNbO3), which performs frequency tuning in the near and mid-IR wavelength ranges, is presented. waves (1.41–4.24 μm). A scheme is described and the technical characteristics of a broadband spectrometer developed on the basis of this OPO for medical research based on differential absorption spectroscopy are described. The results of calculation of spectroscopic parameters of the drug ciprofloxacin are presented. It is shown that the developed spectrometer with a tunable radiation frequency makes it possible to confidently detect a large number of organic formations, to identify in them the presence of an increased content of other hazardous impurities that pose a potential threat to health. This method is also applicable to the analysis of human blood components.

A study was conducted on the relationship of the attenuation coefficient of optical radiation by midges with the meteorological parameters of the atmosphere for the summer conditions of 2018 in Western Siberia. It is shown that the maximum values of the coefficient of attenuation of radiation by the midges are observed at the values of vertical turbulent heat flow from 0 to 60 W/m², air temperature more than 5-7 C and relative air humidity from 30 to 85%. Minimum values of the coefficient of attenuation of radiation by the midges are observed at values of vertical turbulent heat flow more than 100 W/m², as well as at negative values of vertical turbulent heat flow, air temperature less than 20 С and relative air humidity more than 60-70%.

It is shown that in the absence of developed convective turbulence, estimating the mixing layer height from height-time distribution of the Richardson number not always provides correct results. The more correct way is to estimate the mixing layer height from height-time distributions of the turbulence kinetic energy (TKE) dissipation rate by the threshold criterion.

It is shown that zones of clear air turbulence can be indicated remotely both from the variance of radial velocity measured by a coherent Doppler wind lidar and from the structure constant of turbulent fluctuations of the refractive index measured by the lidar capable of determining the intensity of optical turbulence.

Lidar, as an important tool for studying atmospheric aerosol, is widely used in studying the distribution of atmospheric aerosol pollution. In environmental monitoring, especially when using mobile lidar for measurements, it's important to know not only situations of the pollution, but also the coordinates of their sources, and their dynamics distribution . The article introduces a method for calculating the coordinates of the objects locations according to the coordinates of the lidar, the detection direction and the distance between the lidar to the objects. Finally, the programming implementation of the method and its application in the development of auxiliary lidar systems.

This paper presents results of verification of recovered precipitation sums based on GPM IMERG microwave satellite measurements with standard observations at hydrometeorological stations in Western Siberia during summer period. The results revealed good agreement between GPM IMERG data and ground observations at the network of meteorological stations with a correlation coefficient of 0.987. The statistical analysis showed that the average discrepancy between daily precipitation sums according to GPM IMERG data and ground observations for all cases considered is 1.2 mm. The obtained accuracy of GPM IMERG data allows it to be used for most tasks.

Based on satellite and ground-based measurements, the characteristics of the atmosphere during the passage of frontal cloud systems with embedded convection were evaluated. An approach was developed to identify centers of embedded convection in frontal cloud systems, which allows one to identify with high probability mesoscale phenomena in frontal clouds (in the horizontal and vertical planes). Based on the developed approaches and the obtained estimates of atmospheric characteristics, the methodology of automatic detection of the centers of embedded convection using satellite data will be implemented.

A series of simultaneous measurements of the spectral aerosol extinction coefficients at wavelengths of 0.45-3.9 μm, angular scattering and absorption in the wavelength range of 0.46-0.63 μm in pine combustion smokes was carried out in the Big Aerosol Chamber of IAO (BAC) in 2019-2021. Relationships between the aerosol optical characteristics at the initial stage of smoke formation are considered depending on: a) the value of the mass mixing parameter for open flame combustion (generation of black carbon microparticles) and smoldering combustion (brown carbon particles); b) the total mass of the combusted material. The spectral dependences of the aerosol scattering and absorption coefficients of pyrolysis (12 realizations) and mixed (28 realizations) smokes in the wavelength range from 0.45 to 3.9 μm were estimated.

The calculation time and the error of the estimates of the horizontal wind velocity from the data of the conical scan are compared. Various implementations of algorithms for direct and filtered sinusoidal wave fitting, and machine learning algorithms based on boosted decision trees (BDT), are being tested. The paper presents the advantages and disadvantages of these algorithms in numerical simulation and experimental data, obtained during measurements with pulse coherent Doppler lidar.

To validate the proposed algorithm for retrieving the reflection coefficients of the earth’s surface, the results of ground - based measurements at the test area with the coordinates 38.829°N, 8.791°W are compared with the results obtained with the proposed algorithm, the MOD09 algorithm, and the algorithm without atmospheric correction. The comparison shows a good agreement of the results yielded by the proposed and MOD09 algorithms with the ground measurements. The reflection coefficients for the area with the coordinates 38.4-39.3º N, 8.3-9.2º W on May 03, 2016, as retrieved by the proposed algorithm, the MOD09 algorithm, and the algorithm without atmospheric correction are analyzed. For the MODIS channels 1 and 2, the MOD09 algorithm gives negative values of the reflection coefficient for some pixels, while the proposed algorithm does not. The algorithm without atmospheric correction overestimates the reflection coefficient.

A model of an atmospheric channel for wireless optical communication based on scattered radiation between the ground surface and an unmanned aerial vehicle (UAV) in the visible and UV ranges is considered. It is estimated how the path loss, the minimal pulse energy ensuring the stable communication, and the maximal information transfer rate change as functions of the optical and geometric conditions for formation of the communication channel.

Within the Russian Science Foundation (RSF) project 21-79-10051 we developed a mobile lidar system for monitoring of tropospheric ozone and aerosol at the sensing wavelengths 299/341 nm. The lidar system is created on the basis of the QX 500 laser (“SOLAR LS”, Belarus) and Cassegrain telescope with receiving mirror diameter of 0.35 m and focal length of 0.7 m. Balancing and commissioning of laser source are carried out. Tests of receiving-transmitting lidar channel showed that the mobile lidar can cover the altitude range from ~0.1 to 12 km.

We have started using the Suomi satellite data since 2021. In this report, we present an example of comparing lidar and satellite measurements of the vertical distribution of ozone concentration in the upper troposphere – stratosphere, obtained using measurements at differential absorption lidar complex and data from Aura, MetOp, and Suomi satellites. The ozone vertical distribution was retrieved using the vertical temperature distribution according to the data from MetOp meteorological satellite. The spatiotemporal discrepancies are found between measurements at Siberian Lidar Station (SLS) and on Suomi satellite. Figure 1 shows the block diagram of the SLS complex.

The report compares quasi-triennial seasonal model with lidar and satellite (Aura, MetOp, Suomi, TIMED) measurements of the vertical distribution of ozone concentration in the upper troposphere – stratosphere. Lidar measurements are obtained using the laser differential absorption complex with the sensing wavelengths 299/341 nm and 308/353 nm. The ozone vertical distribution was retrieved using the vertical temperature distribution, based on the data from MetOp meteorological satellite. For January 12, 2021 as an example, the report presents the deviations between the quasi-triennial seasonal model and data from lidar and satellite measurements.

The article considers options for using electro-optical modulators as a device for shifting the frequency of the probing signal. Unlike acousto-optic modulators, which do not allow changing the modulation frequency, electro-optic modulators can change it over a very wide range, according to the form specified by the RF generator. At the same time, electro-optical modulators have disadvantages that require a special operating point controller that maintains the state of the modulator in a given position, regardless of environmental conditions.

It is revealed based on the analysis of observations of the 24-year series (1998 – 2021) of the parameter of aerosol condensation activity in the near-ground layer of the atmosphere of Tomsk, that its most significant variation are observed in the annual cycle. Slower variations with a period of 6-7 years were also found.

The relationship between the aerosol hygroscopic properties and the volume fraction of substances evaporating from particles in different temperature ranges during their artificial heating was analyzed by the method of active spectral nephelometry based on the measurement data obtained in 2000-2019. Throughout the year, there is a stable negative correlation between the parameter of condensation activity and the volume fraction of substances volatilizing in the range of 200-250°C. A stable positive correlation is observed in the temperature range from 25-75 to 160-200°C, the boundaries of the interval vary depending on the season.

When studying the condensation growth of atmospheric aerosol, many researchers note the dependence of hygroscopic properties on the particle size. In this work we consider the relationship between the parameter of condensation activity and the parameters of particle size distribution in the nanometer range on the example of test measurements. Due to the small amount of data, the results are preliminary.

Based on the database of the elemental and ionic composition of the tropospheric aerosol according to the data of aircraft measurements in the south of Western Siberia (SWS) in 1997-2020, taking into account the synoptic information about the air masses (AM) prevailing on sounding days and the results of the trajectory analysis, two main trajectorysynoptic samples with cases of the influence of the Aral-Caspian arid region (ACAR) on the SWS and with days without such influence. The chemical components-references of the ACAR aerosol were revealed: silicon, strontium, chromium, silver and magnesium - in the elemental composition, and in the water-soluble fraction - halide anions (fluorides, bromides and chlorides), ammonium and sodium cations. Days with the influence of ACAR are characterized by a 1.5-2- fold increase in the number concentration of aerosol particles with a size of 0.6-4 μm, which is associated with an increase in the volumetric concentration of aerosol in the atmospheric layer of 0.5-7 km by 1.5 times.

The paper presents a complex refractive index in the model of the aerosol optical characteristics in the lower 5-km atmospheric layer of Western Siberia. The model is based on the data of long-term airborne sounding of the vertical profiles of angular scattering coefficients, atmospheric aerosol disperse composition, content of absorbing substance, and condensation activity of aerosol particles. Various algorithms for taking into account the absorbing substance and the aerosol condensation activity are considered.

The optical and microphysical characteristics of smog phenomena in the Akademgorodok of Tomsk in the winter period of 1997-2022 were studied. It was found that since 2011 the number and intensity of such situations has increased. On the example of smog on January 13-14, 2022 it is shown that a significant increase in the concentrations of atmospheric aerosol and equivalent of black carbon develops with temperature inversion and with a wind regime close to calm. There is an increase in both the submicron and coarse particle fractions, but more intense in the range of the submicron fraction. The formation of smog is accompanied by a decrease in the ability of aerosol particles to absorb moisture.

Measurements of polarization scattering phase functions and spectral extinction coefficients were carried out in smoke aerosols formed as a result of thermal decomposition of wood materials, in a big aerosol chamber (BAC) of the IAO SB RAS. The results are presented of reconstructing of the parameters of the microstructure and the complex refractive index of smoke aerosols based on the developed algorithm for inverting optical measurements. Temporal variability of the microphysical characteristics of smoke is studied.

The results of development of an adjustment block for regulating the angular position of output mirror of a lidar in a semi-automatic mode are presented. The possibility of implementing an adjustment block using economical, widely used electronic components, such as an Arduino board and stepper motors, as well as 3D-printed mounting components, is shown. Appropriate software was developed to control this unit. The program for the automatic formation of a tuning curve of the laser with parametric generation of light and the program for the automatic measurement of the dependence of the pulse energy on the generation wavelength was developed.

The results of field experiments on atmospheric optical communication based on scattered laser radiation in the UV range are reported and briefly discussed. In addition, the effect of the ozone concentration on the probability of receiving error symbols is estimated. The characteristics of the transmit/receive equipment used in the experiments and the experimental results obtained with this equipment in daytime at a wavelength λ=255 nm are presented. The stable communication at a baseline distance of 1.3 km in the presence of precipitation in the form of rain and at the high concentration of water vapor in the atmosphere was obtained. A strong positive correlation between the ozone concentration and the symbol-error probability was found.

The paper presents the results of lidar observations of the atmosphere over the water area of Lake Baikal. Integrated shipboard research using the research vessel «Academician V.A. Koptyug», are held annually, using the LOSA-A2 lidar, as well as local means (gas analyzers). Additionally, satellite data and information about the meteorological parameters of the atmosphere during the experiments are involved. The route of the ship goes all over the lake. An analysis is being carried out to identify the main sources of air pollution in the Baikal region.

The effect of the designed antireflection coatings based on Nb₂O₅/Al₂O₃ and Nb₂O₅/SiO₂ pairs of materials on the laserinduced damage threshold (LIDT) of ZnGeP₂ crystals at a wavelength of 2097 nm is shown. The coating was applied using the ion-beam sputtering (IBS) method. The LIDT of the sample coated with Nb₂O₅/SiO₂ was W_0d = 1.8 J/cm². The LIDT of a sample coated with Nb₂O₅/Al₂O₃ is W_0d = 2.35 J/cm². The presence of silicon conglomerates in the antireflection coating leads to a decrease the LIDT of a nonlinear crystal due to local thermomechanical stresses and scattering of the incident laser radiation.

A method for estimating the radius of effect of a cloud field on the error of retrieving the reflection coefficient of cloudless areas of the earth's surface through gaps in the cloud field is considered. Within the framework of the proposed method, an interpolation equation is used to estimate the radius of this effect for various optical and geometric conditions of remote sensing. MODIS data are considered for an area with a radius of 50 km centered at a point with coordinates 53.2849º N, 103.4066º E in the period of July 1-31, 2021. The radius, within which the retrieved reflection coefficient of cloudless areas changes by 0.005 or more, is calculated from these data with the developed interpolation equation. The analysis shows that this radius ranges from 0.5 to 10 km and is highly correlated with the average cloud depth for the considered situations.

The paper presents the light backscattering matrices for crystal particle of an irregular convex shape of the size of 200 micrometers with different refractive indices within the physical optics approximation. The calculation of matrices was carried out at the wavelengths of incident light of 0.532 micrometers, for the case of an arbitrary spatial orientation of particles. The matrices can be used to study mineral dust cloud particles.

The paper presents the results of the mass concentration of PM2.5 and PM10 particles measurements which were carried out using the Atmas dust analyzer (manufactured in Russia) for 2021. The analysis of the results showed that the period with the maximum values of the mass concentration of suspended particles PM10 and PM2.5 was observed in November-December of the year under study. Also, throughout the year the dates with an excess of the average monthly concentrations by more than 2 times were identified and an analysis of atmospheric pollution by suspended PM particles was carried out for them using the SILAM model. The results of modeling the back trajectories of air flow movement performed using the HYSPLIT software package were used to determine the source of PM10 and PM2.5 particle transport.

The use of shock waves as a source of intense impact on the combustion process, in particular, on a wildfire or man-made fire, has been known in science for several decades. The discontinuity surface of hydrodynamic functions, which is the front of the shock wave, can stop combustion, or intensify the fire situation. An experimental setup with shock tube was made to study the effect of shock waves. This article presents the study results of the impact of the charge energy characteristics on the shock tube characteristics.

The article presents the results of a series of mesoscale experiments to study wildfires and their impact on the atmosphere. A change in meteorological parameters, a significant increase in fluctuations of the refractive index, speed of sound and temperature in the vicinity of the experiment, which are a reflection of the occurrence of turbulent processes in the atmosphere, were established, experimental data were obtained on changes in the concentration of methane and carbon dioxide as a result of a fire, and data were obtained on the mechanism of occurrence of crown fire.

The paper examines the effect of low-amplitude pressure pulsations on the temperature field in the flame formed during methane combustion. Using the Ansys Fluent solver, the fields of temperature, velocity, and other flow characteristics in the presence of internal pressure pulsations were analyzed. As a result of the analysis of the obtained data, qualitative estimates of the effect of pressure pulsations on the flame plume were obtained. It is shown that the effect of acoustic oscillations on the flame plume leads to a change in the rate of combustion of fuel.

The main greenhouse gases are ozone and the gas components of ozone cycles. Operational determination of ozone concentration profiles is carried out by lidar methods, which limits the number of measurements obtained. Machine learning methods can be used to build predictive models of the data as well as to approximate them. This paper investigates the possibility of generating data to build robust predictive models of ozone concentration profiles based on generative adversarial neural networks (GAN). Several GAN architectures were proposed and the benefits of each one is discussed.

The paper shows the effect of magneto-rheological (MPO) polishing of a ZnGeP₂ on the surface roughness. The extreme level of surface roughness of the ZnGeP₂ Ra=1.54Å was recorded. Analysis of the topography of the sample surface before and after magnetic polishing showed that after the classical polishing technology, the relief of the surfaces was formed under the influence of multidirectional movement of the working tool, there are single extended scratches up to 1.3 nm deep. The topography of the sample surface after MPO polishing does not contain these scratches and is represented by a less textured profile formed under the influence of MPO fluid.

The paper defines the laser-induced damage threshold from the fluence and the peak power of GaSe and GaSe:In single crystals upon exposure to nanosecond radiation in the two-micron range and assesses the influence of test radiation energy parameters (pulse repetition rate, pulse duration) on the damage threshold. Laser-induced damage threshold was determined with the parameters of the incident radiation close to the pump radiation parameters of promising dual-wavelength optical parametric oscillators (effective pump sources for THz difference frequency oscillators): wavelength is ~ 2.1 μm, pulse repetition rate is 12 and 20 kHz, pulse duration is 18-22 ns.

The article considers the features of the optical and fiber-optic schemes of a pulsed coherent Doppler lidar. Two options for the telescope optical scheme design, as well as the use of an optical hybrid to increase the measurement range, are studied. The noise of the measuring system, which is determined by the active and passive components of the system, is analyzed. Experimental results are presented for the scheme with an optical hybrid and a basic scheme, as well as for a telescope based on spherical and aspherical optics.

A technique is proposed that makes it possible to significantly accelerate the solution of the problem of light scattering in the exact backscattering direction on particles larger than 100 microns within the framework of the physical optics method. The peculiarities of this technique is that the solution is constructed within the vicinity of a small number of nodal points. Then, in the resulting solution, one complete period of interference oscillations is allocated and the light scattering matrix is averaged in this range. The average value is entered into the database. In this way, it was possible to build a complete database of backscattering matrices for atmospheric ice particles with sizes from 10 to 1000 microns for wavelengths of 0.355, 0.532, 1.064, 1.55, 2 and 2.15 microns. The results obtained make it possible to improve the algorithms for interpreting the data of laser sensing of cirrus clouds.

Small-sized mobile lidars mainly use single-frequency sounding with registration of elastic backscattered radiation on aerosols. Mie-Raman lidars are used to correctly reconstruct the optical characteristics of an aerosol. The method most widely used in such lidar measurements for evaluating optical properties is the method of recording vibrational Raman scattering on nitrogen molecules. The disadvantages of this method are the low backscattering cross section and the significant frequency shift of the Raman vibrational component. These problems are solved by using purely rotational Raman scattering, which is characterized by a higher backscattering cross section, and a much smaller frequency shift, which practically eliminates the dependence on the Angstrom exponent. The paper presents the practical implementation of pure-rotational Raman measurements in the mobile lidar "LOSA-A2".

The behavior of the total carbon dioxide content in the atmosphere of the south of Western Siberia (48°–53° N, 60°– 90° E) has been studied using data from the orbital carbon observatories OCO-2 and OCO-3. OCO-2 data analysis was carried out for the period 2014-2021, OCO-3 results have been added to processing since 2019. To describe the seasonal cycle of CO₂ content in the atmosphere of the region, we use an empirical model that was proposed for the interpretation of GOSAT satellite data and verified by the results of measurements of TCCON the global network of ground stations. It was found that for the studied period the increase rate of CO₂ in the atmosphere of the region is about 2.48 ppm/year, and the amplitude of seasonal fluctuations is about 9.3 ppm. The possibility of applying satellite data with sufficient precision, coverage, and resolution to support of works on the carbon polygons in the south of Western Siberia was analyzed.

Terrestrial gross primary production (GPP) is the quantitative equivalent of the total amount of carbon assimilated by vegetation through photosynthesis. The GPP is crucial element for understanding land-atmosphere carbon exchange. In recent years, solar-induced chlorophyll fluorescence (SIF) observed by satellite radiometers has been considered as a new approach to advance research on monitoring of GPP from space. In this paper we presents quantitative estimates of the terrestrial gross primary production for the region of the south of Western Siberia (50º-55 º N, 75º -90º E) obtained using “sun-induced chlorophyll fluorescence” data products from orbital carbon observatories OCO-2 and OCO-3. The analysis of OCO-2 data was carried out for the period 2014-2021, the results of OCO-3 were added to processing from 2019. It was established that GPP reaches a maximum in the summer months and is ~10 − 12 gC m^-2day^-1.

The paper shows an increase in the threshold energy density of laser radiation at a wavelength of 2091 nm as the temperature decreases from 0º С to -60º С until the optical breakdown of a ZnGeP₂ (ZGP) single crystal sample is reached. With a decrease in temperature from 0º to -60º C, a sharp increase in the threshold energy density is observed from 1.6 to 2.6 J/cm², with a laser beam diameter of 270 μm, and from 3.2 to 10.2 J/cm² with a diameter of 100 μm (by 1.5 and 3 times, respectively).

In this study, the processing of MODIS Terra and Aqua satellite imagery data was carried out for the assessment and forecast of fire danger according to weather conditions. The time periods and threshold values of the NDVI vegetation index were determined, at which the greatest number of fires occur during the fire hazard period in the territory of the Russian Far East from 2003 to 2016. A significant correlation of the NDVI vegetation index with the distribution of the number and rate of individual vegetation fires was revealed using the fire hazard season of 2016 as an example in the southern part of the Russian Far East. Statistical analysis of the time series of the vegetation index made it possible to obtain a regression equation for the change in daily air temperature and NDVI vegetation index values for predicting the spread of grass fires based on the MacArthur method in the Jewish Autonomous Region.

This paper presents the results of calculations and analyzes the backscattering matrices of random oriented ice crystals, typical for cirrus clouds. The backscattering matrices were calculated within the physical optics approximation for lidar (wavelength 0.355 μm) and the discrete dipole approximation for 94 GHz radar (wavelength 3189 μm) with the refractive indices of ice – 1.3249+0i and 1.7864+0.0032i respectively. For the first time, it was possible to correctly calculate the ratio of radar and lidar signals in the direction of backscatter, called the radar-lidar ratio. The radar-lidar ratio is obtained for a wide particle size distribution for typical ice crystal shapes in cirrus clouds: hexagonal column and plate, bullet, droxtal, aggregate, bullet-rosette, arbitrary shape and sphere. As a result, it is shown that the radar-lidar ratio can be used to estimate the ice crystals size in cirrus clouds. The radar-lidar ratio for the EarthCARE satellite was unambiguously obtained for an adequate model of the sizes and shapes of ice crystals of a cirrus cloud.

The paper presents a solution to the problem of light scattering by small randomly oriented hexagonal ice crystals of cirrus clouds. The solution was obtained both within the discrete dipole approximation and within the physical optics approximation. The particle sizes ranged from 0.2 to 6 μm. The wavelength of the incident radiation is 0.532 μm, the refractive index is 1.3116. The results of the comparison of the solutions obtained within the framework of the discrete dipole approximation with the physical optics approximation are shown. It is found that the solutions are in good agreement, however, to solve the problem of light scattering in the vicinity of the backward direction, which is important for the interpretation of lidar data, it is necessary to continue the calculations by the discrete dipole approximation up to particle sizes of about 10 μm.

The paper presents the results of comparing numerical solutions to the problem of light scattering on atmospheric ice particles by methods of geometric and physical optics. The solution was constructed for hexagonal shaped particles (hexagonal ice column) and droxtals. The results of the comparison of the light scattering matrix over the entire sphere of the direction showed that in the direction of scattering strictly backward, the use of the geometric optics approximation can lead to significant errors, especially for hexagonal particles, which are characterized by the presence of angular reflection

The degree of influence of the Aral-Caspian arid region on the territory of Russia along its southern border, as well as on the countries of near and far abroad is compared according to measurements of meteorological optical range in 2000- 2020, aerosol optical depth (AOD) of coarse aerosol at AERONET stations in recent two decades and AOD532 of dust aerosol from the CALIPSO satellite in 2006-2020.