Home – Home – Jornals – Atmospheric and Oceanic Optics 2025 number 12

The article presents the results of a study of the problem of propagation regimes of narrow (millimeter) laser beams in a Kerr-nonlinear turbulent medium, which is a model of evolution of the light inhomogeneities generated at multiple filamentation of high-power laser pulses in the corresponding media. We used methods of diffraction beam tubes and diffraction beams in the theoretical study. It was found that there are three propagation regimes for laser beams with certain parameters in a turbulent medium: self-focusing with generation of a nonlinear focus (beam collapse), self-channeling over a limited distance, and turbulent propagation. An analytical relationship for the square of the beam's effective radius was derived, which is of interest for practical applications in nonlinear atmospheric optics.

This work is devoted to the development and experimental verification of effective methods for compensating for the dynamic atmospheric distortions of a laser beam propagating through a turbulent medium. The paper presents the results of a laboratory experiment on the correction of wavefront distortions of laser radiation propagating along a turbulent path in a pavilion. Turbulence was simulated using a fan heater supplying warm air perpendicular to the beam propagation. Distortion compensation was performed using an adaptive optics system, including a wavefront tilt corrector and a bimorph deformable mirror. The system efficiency was assessed by analyzing the far-field intensity distribution. It is shown that the generated turbulent distortions are spectrally similar to Kolmogorov turbulence with a bandwidth of about 30 Hz. It is found that for effective compensation of wavefront aberrations, the operating frequency of the adaptive optics system should be 20-30 times higher than the turbulence bandwidth. At a system operating frequency of 1 kHz, the beam divergence was reduced to 1.4 of the diffraction limit, and by increasing the frequency to 2 kHz, a beam stabilization accuracy of 5 mrad can be achieved using an FPGA. The results of this work can be used to design high-performance systems related to the propagation of laser radiation in a turbulent medium.

Determining the isotopic shift of vibrational energy levels of molecules is a challenging task in molecular spectroscopy. Detailed knowledge of the vibrational-rotational energy spectrum is necessary, for example, for laser isotope separation. In this paper, a calculation method based on high-order perturbation theory and summation of series by the method of quadratic Padé-Hermite approximants is proposed. The method is applied to determine the isotopic shifts of vibrational energy levels of all stable hydrogen sulfide isotopologues. Calculations were performed using ab initio intramolecular potential function within a simple quartic force field model. To refine the results, corrections were introduced to account for the error in ab initio data. The results of summation of perturbation theory series coincide with the levels determined by the variational method with accuracy of 10^-10-10^-2 cm^-1. The corrections reduced the root-mean-square error in the available experimental level values to 3.5 cm^-1 (0.3%).

This article presents an improved internet-accessible expert system, SLON, for analyzing high-resolution molecular spectra. It was developed in the Laboratory of Molecular Spectroscopy at Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences. The SLON expert system is based on a neural network model capable of making independent decisions when analyzing combination differences formed by groups of molecular transitions from different rotational sublevels of the ground state to the same excited vibrational-rotational state. The set of features by which the neural network distinguishes the correct variant of a combination difference from random realizations has been improved. Restrictions on the size of the analyzed spectrum have been removed. The format of the databases used is now universal and enables expanding the class of molecules under study. A modern multi-platform user interface allows this program to be compiled for Windows and Linux systems. The operating principles, operational experience, and prospects for the development of the created expert system are described.

The problem of aerosol pollution of the atmosphere and associated climate change has become increasingly relevant. Of particular interest are physicochemical properties and structure of atmospheric aerosols. Being an important component of polluted air, aerosols affect various atmospheric processes, the environment, and human health. Analysis of the morphology and composition of aerosol particles allows us to identify the features of their behavior in the atmosphere and determine their origin. This paper studies the composition and morphology of ground-level atmospheric aerosol particles at a year-round monitoring station (Irkutsk) in different seasons of 2024 using scanning electron microscopy and X-ray spectral analysis. The main types of aerosol particles (soot, fly ash, mineral, and biogenic particles) are identified, and their shapes and sizes are determined. It has been established that mineral and biogenic particles predominate in the composition of ground-level atmospheric aerosol in Irkutsk during the warm season, while fly ash and soot particles predominate during the cold season. Brochosomes (fullerene-like structures of biological carbon-containing particles) were detected for the first time in the surface aerosol at the urban Irkutsk station. The results of this study expand our understanding of the morphological properties and composition of individual particles in surface atmospheric aerosol in the urbanized area of the Southern Baikal region.

Atmospheric ions play an important role in the formation of aerosol particles and affect public health. At the same time, measurements of their concentration in Russia are extremely insufficient. To fill the gap, the Fonovaya observatory began monitoring the ion content in July 2019. Analysis of the data obtained showed that from July 2019 to May 2024, the concentrations of both positive and negative aeroions were in the range 220-720 cm^-3. Negative ions have a trend of +7%/year, and positive ions have a trend of -1.2%/year. Ions of both signs have a pronounced annual cycle with a maximum in summer and a minimum in winter. The long-term average daily cycle revealed that the concentrations of ions of both signs change synchronously. The minimum of their concentration is observed in the morning hours and the maximum in the afternoon. The results allow us to clarify the role of ions in atmospheric processes.

Snow cover in the temperate and northern latitudes of Eurasia accumulates atmospheric precipitation during winter. The analysis of the trace element composition of snow cover makes it possible to estimate the level of aerosol pollution of the atmosphere. The estimations are usually made relative to the average background concentrations of elements. However, in a poorly studied region, the selection of background points may be incorrect. We suggest using the upper limit of geochemical baseline variation (ULBL) as a norm. It considers the natural and controlled anthropogenic input of an element and is defined as the sum of the 75-quantile of the distribution of element concentration and the difference between the 75- and 25-quantiles multiplied by 1.5. Using the suggested approach we have detected contamination with Ag, Sn, and Hg in places a priori considered background; a zone of heavy metal contamination at a distance of 9-26 km from the industrial zone; and conventionally "clean" points, where the concentrations of trace elements do not exceed the ULBL. The use of ULBL as a norm enables objective estimation of air pollution over a territory from the results of a single snow survey.

The paper presents the results of lidar measurements of the vertical distribution of optical characteristics of dust aerosol from the Gobi Desert in the free troposphere of Vladivostok. The instrument used is an aerosol-Raman lidar with a cross-polarization channel, which provides vertical profiles of a set of (3β + 2α + δ). High values (δ_а = 0.13÷0.24), typical of submicron dust aerosol particles, are noted in the altitude range 3.00-4.25 km. This altitude range was also characterized by low values of the Ångström parameter (Å = 0.5) and high values of the single scattering albedo ω = 0.98÷0.99. The values of complex refractive index ( m = m _r + im_i ) in the dust layer were characteristic of dust particles: m _r = 1.48÷1.56, m_i = 0.001. The effective radius ( r _eff) varied within 0.2-0.4 μm with a maximum at an altitude of 3.8 km. The particle size distribution function in the dust layer had a well-defined bimodal structure with a slight excess of the coarse mode over the fine one. The modal radii of the fine and coarse fractions r _f = 0.18 μm and r _c = 0.8 μm, respectively.

Stratospheric aerosol, the main component of which is volcanic emissions, is one of the main factors influencing global climate. The role of aerosol formed during wildfires and injected into the stratosphere is clearly underestimated. Taking into account the influence of stratospheric aerosol generated by wildfires into climate models leads to significant uncertainties and highlights the need for an in-depth study of this phenomenon. This paper presents the results of lidar monitoring of stratospheric aerosol dynamics over Tomsk in 2025, with an emphasis on the study of disturbances in the stratospheric aerosol component caused by wildfires. Ground-based lidar sensing in June 2025 detected aerosol layers in the stratosphere over Tomsk at altitudes of 10-17 km. Using trajectory analysis and satellite data on fires, it was shown that the possible source of the observed aerosol layers could be combustion products, including soot injected into the stratosphere by pyrocumulative clouds formed in late May and early June 2025 in the area of severe wildfires covering parts of Canada and the United States. These results are of interest for climate change research in Western Siberia.

The current global warming is caused by an increase in the concentration of greenhouse gases in the atmosphere. Therefore, the estimation of the potential of different ecosystems for the sequestration of atmospheric carbon dioxide on both regional and global scales is relevant. The balance of natural carbon dioxide fluxes throughout the Sverdlovsk region is considered. An integral assessment of the net CO₂ absorbed from the atmosphere by regional ecosystems for the period 2020-2022 is made based on the original NorthFlux machine learning model, where spectral data from the MODIS satellite sensor, meteorological data from retrospective climate analysis, and satellite data on the classification of the underlying surface vegetation are used as input data. Data on anthropogenic CO₂ emissions are taken from the inventory of greenhouse gas emissions in the Sverdlovsk Region. To assess the transboundary transfer of carbon dioxide, we used a balance equation for CO₂ fluxes in the atmospheric column and data on the average annual rate of increase in the CO₂ concentration in the region's atmosphere obtained from ground-based IR Fourier spectroscopy using the Bruker IFS 125M high-resolution spectrometer at the Kourovka Astronomical Observatory for the period 2012-2024. As a result, it was found that the sequestration of atmospheric CO₂ by the ecosystems of the Sverdlovsk region ranges from 10.9 to 15.2%, and its transboundary transfer outside the region to neighboring regions ranges from 72.5 to 76.7% of the annual industrial CO₂ emissions in the region.

The paper proposes a method for analyzing the quality of wind fields from hydrodynamic model forecasts for a specific transport model. This is done using the results of measurements in the Kincaid tracer experiment. The method involves adding normalized random fluctuations to the wind fields up to an altitude of 4 km and analyzing the maximum values of wind speed and direction to obtain accurate results for the transport of pollutants. The measurements are taken from a dense network of specialized stations.

Imaging in the visible spectrum of processes in media transparent only to IR radiation requires the use of active converters of IR radiation into the visible spectrum. In this work, we simulate the transformation of IR radiation into the visible due to competition between transitions in manganese vapor active media. Our approach is based on the spatio-temporal kinetic model of the active medium. We evaluate the coefficient of the transformation for continuous and pulsed modes an input IR signal for a wide range of its power and various pulse repetition frequencies (from 2 to 20 kHz). We show the pulsed mode and pulse repetition frequency lower than the optimal one in terms of the amplified spontaneous emission power to be optimal for this transformation. The measurable transformation factor is higher than 10 for medium-size GDT. Results confirm than the bistatic scheme of a laser monitor on Mn vapor active media can be used to obtain a negative image of processes in a medium transparent for IR radiation, i.e., to make a pulsed narrowband converter of IR signals into visible ones.

The primary challenge in observing small (inconspicuous) space objects with ground-based optical telescopes is the effect of the atmosphere on the passage of radiation from a small (inconspicuous) space object. This paper examines the specifics of long-exposure observations of small space objects by recording short-exposure images of a laser guide star and then summing them in the telescope's focal plane. Correlation analysis is used to investigate the relationship between random displacements of the observed laser guide star image and the predicted position of the small space object. It is shown that a sufficient condition for determining their relative positions is the ratio of the absolute values of the energy centers of gravity of the images as two jointly correlated Gaussian random variables with a Cauchy probability density distribution. Calculation results for monostatic and bistatic laser guide star formation schemes are presented.