Home – Home – Jornals – Atmospheric and Oceanic Optics 2025 number 7

The helical symmetry of a permittivity tensor causes Bragg’s reflection at wavelengths close to the screw (helicoid) pitch for circular polarization of light. The study has discovered and explained the resistance of a band gap short-wave boundary to the optical axis tilt towards helical axis (normal to the plane of layers) in helical photonic structures. For a conical helical structure, the long-wavelength boundary of the reflection area changes more than for a structure with a normal cone opening with optical axis perpendicular to helical axis. Still, the wavelength for the edge mode at the short-wave boundary strictly remains under arbitrary distortions. The findings of a numerical simulation with the use of anisotropic transfer matrix and Berreman transfer matrix are coherent and confirmed by analytical derivation.

The study of the absorption of water vapor, the most powerful greenhouse gas, is important for the development of climate models of our planet. The broadening of spectral lines become of special importance for variations in temperature and pressure in the atmosphere. The paper presents the measured broadening and shift coefficients of H₂O lines by N₂O and air pressure at room temperature for 11 vibrational-rotational transitions in the 2ν₁ + ν₂ + ν₃ band, the rotational quantum number J varies from 0 to 6. The measurements were carried out on a CRDS spectrometer of high sensitivity (6.5 × 10^-11 cm^-1), the apparatus function of which is orders of magnitude narrower than the width of the lines under study. Line broadening and shift coefficients were also calculated using the semi-classical approach modification, where a correction factor is included in the calculation scheme. The obtained parameters were compared with published data. The results can be used for refining spectroscopic information in HITRAN database.

Molecular oxygen is an important gas both in the Earth's atmosphere and in the atmospheres of Mars and Venus. To determine its content the highly accurate absorption line parameter values are required. For this purpose, O₂ absorption spectra were recorded in the 7800-7990 cm^-1 range using a Bruker IFS 125HR Fourier spectrometer. The spectra were recorded at a spectral resolution of 0.01 cm^-1, a room temperature, and an optical path length of 2880 cm for five values of oxygen pressure. The intensities, broadening and shift coefficients, and parameters characterizing the dependence of broadening on the velocity of colliding molecules were determined for 55 O₂ absorption lines broadened by self pressure. A good agreement between our intensity values and high-precision measurements by other authors is shown. The self-shift coefficients are obtained for the first time.

According to the conclusion of the UN Intergovernmental Panel on Climate Change (IPCC), in order to determine the main causes of global warming caused by the increase in greenhouse gas content, an accurate assessment of their emissions and sinks is required, since there is still significant uncertainty in assessing their balance. To clarify this, the present work studies the heterogeneity in the distribution of their flows and sinks at the mesoscale level. Considering that soil plays a significant role in gas exchange processes, which significantly differ in properties on both scales, this approach seems very promising. The work uses hourly measurement data from three posts of integrated air composition monitoring: TOR station, the “Fonovaya” observatory, and the Basic Experimental Complex (BEC). It is shown that the differences in long-term (2013-2017) average concentrations between stations are within the ranges 116-195 mg/m³ for CO, 3.3-8.3 ppm for CO₂, 0.4-0.8 mg/m³ for NO, 4.6-15.5 mg/m³ for NO₂, 8.1-14.3 mg/m³ for O₃, and 2.3-6.9 mg/m³ for SO₂. Annual and daily variations in the concentration differences have been revealed for the first time. The results expand our knowledge of the dynamics of greenhouse and oxidizing gases in the atmosphere and can be useful in developing requirements for their measurement accuracy.

Turbulent processes in the atmospheric boundary layer have not been fully studied yet. The most effective tool for studying these processes is a pulsed coherent Doppler lidar (PCDL). In the work, the second version of the electro-optical unit of a PCDL LVR-2 created at the Laboratory of Wave Propagation of V.E. Zuev Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, is tested. The correctness of wind radial velocity (RV) estimates by LVR-2 during its operation in the “short” pulse mode is verified in an experiment with a Stream Line lidar. The errors in RV estimates by LRV-2 are analyzed. A possibility of using RV estimates by LRV-2 made in the vertical sounding mode to estimate the kinetic energy dissipation rate of wind turbulence by the vertical velocity spectral density method is shown. The results can be used to create techniques for testing PCDLs and determining the efficiency of such lidars in estimating atmospheric turbulence parameters.

Human activity is currently causing global warming of the planet, primarily due to the emission of greenhouse gases into the Earth's atmosphere (CO₂, CH₄, etc.). Despite international agreements and commitments made by various countries, the concentration of key greenhouse gases - CO₂ and CH₄ - in the atmosphere continues to rise. The increase in greenhouse gas levels leads to changes in the Earth’s radiation balance, which is the cause of modern climate changes affecting many extreme weather and climate events across the globe. One of the most important components of the atmospheric radiation balance is the molecular absorption of solar radiation by greenhouse gases. In this study, using the SCIATRAN model and calculations of solar radiation fluxes in the spectral range of 1-4 μm, the molecular absorption of solar radiation by key anthropogenic greenhouse gases, CO₂ and CH₄, is analyzed for their past, present, and future concentrations. The calculations were performed for three latitude zones (tropics, mid-latitudes, and subarctic) and two seasons (winter and summer). According to the calculations, the maximal molecular absorption of incoming solar radiation in the 1-4 μm range by the greenhouse gases occurs in the tropics and reaches 153-168 W/m² throughout the year. Over the period from 1750 to 2100, the molecular absorption of solar radiation by CO₂ and CH₄ is expected to increase to 0.8-1.2 W/m². The projected increase in molecular absorption of solar radiation by the end of the 21st century is close to current estimates of changes in Earth’s radiation balance, which range from 0.5 to 1.0 W/m². At the same time, the global average increase in the molecular absorption of outgoing Earth’s thermal radiation is approximately 3-4 times greater than the increase in solar radiation absorption. Both of these changes, driven by rising greenhouse gas concentrations, intensify the Earth energy imbalance and contribute to changes in the planet average temperature.

The long-term monitoring of atmospheric parameters in the surface air layer is conducted at the Fonovaya observatory. To study biophysical processes in the active soil layer, a soil temperature measurement complex was put into operation. Four-year series of soil temperatures in the 0-320 cm layer at the measuring site with natural cover are analyzed. It has been established that positive temperatures are observed from May to October to depths of 320 cm. The maximal depth of seasonal freezing did not exceed 60 cm. The standard deviation of soil temperature at all depths in winter is 2-4 times smaller than the standard deviation in summer. The daily variation in soil temperature from April to October is clearly expressed to a depth of 10 cm, below which the amplitude of the daily variation fades. From November to March, the amplitude of the daily variation is minimal (0.02 °C). The results can be used to study biophysical processes in the active soil layer and gas exchange at the soil - air boundary.

Retrieval of atmospheric aerosol optical properties from limited data volume is a crucial task for assessing radiative forcing and simulating climate in high latitudes. This work presents, for the first time, an approach to simulation of aerosol optical characteristics based on a limited set of measured input parameters using a representative ensemble of solutions. The numerical experiment involves comparison of aerosol optical properties for a typical summer background haze calculated from averaged measured parameters assumed as “reference”. In each ensemble realization, a random deviation within the range of instrumental uncertainty was introduced for each input parameter, followed by calculation of optical properties. It is shown that, for the chosen model scenario, 200 ensemble members are sufficient to achieve retrieval accuracy of 2%. The results are applicable for evaluating radiatively significant atmospheric properties based on airborne and shipborne measurements, and for validation of satellite retrievals and climate models. The proposed technique can also be used in regional aerosol pollution monitoring applications.

In the context of accelerated warming in the Arctic, the study of changes in permafrost zone characteristics is a question of high interest. The paper analyzes current and future changes in climate variables (surface air temperature, soil temperature at depth, precipitation, and snow cover depth) in the Arctic part of Western Siberia based on the ERA5 reanalysis and CMIP6 modeling data. The contribution of climate variables to the variability of the soil temperature at depth is estimated in three climate scenarios (Historical, SSP2-4.5, SSP5-8.5). The surface air temperature, soil temperature at depth, and precipitation are predicted to increase in all seasons by the end of the 21st century, while the snow cover depth will decrease. This will result in an increase in the area and depth of seasonal thawing layer and a northward shift of the southern boundary of permafrost zone. According to the SSP5-8.5 scenario, the annual average soil temperature zero isotherm will be located at a depth of ~ 6 m at latitude of 70° N (the territory between the Gulf of Ob and the Lower Yenisei Upland). Currently, the influence of the climate variables on changes in the soil temperature at depth is maximal in summer (due to air temperature) and autumn (due to snow cover) with their maximum contribution in October (up to 60% at a depth of 1 m). According to the SSP5-8.5 scenario, a decrease in the contribution of climate variables in summer and its increase in November are expected. By the end of the 21st century, the predominant contribution to the variability of the permafrost zone characteristics will belong to summer precipitation. The results can be used in studies and simulation of changes in the permafrost zone characteristics.

For efficient operation of lidar systems, highly coherent radiation with a capability of smooth wavelength tuning in a given spectral range is required. This paper presents the results of experimental studies of an alexandrite laser on the generation of coherent radiation in a compound dispersion cavity with various spectral and spatial selectors located in the external and main cavities, respectively. The mode structure of the output radiation is studied depending on the selective properties of the cavity used. The operating conditions of the compound cavity necessary for the generation of narrow-band tunable radiation in the self-injection mode are considered.

Requirements for the elements of adaptive optics systems are largely related to atmospheric conditions at their locations. The primary task is to ensure a photon flux from a sodium laser guide star (LGS) sufficient for the operation of wavefront sensors. One of ways of increasing the photon flux is the use of circularly polarized laser radiation, due to the influence of the Earth's magnetic field on the energy levels of the sodium atom. The geomagnetic field strength at Siberian observatories is 56-58 nT, which is significantly higher than that of any known observatory. Another feature is the low (about 2 × 10¹³ atoms/m²) density of sodium atoms in the mesosphere in summer. The article presents the results of numerical simulation of the return photon flux from a sodium LGS for atmospheric conditions in Siberia. Approaches to increasing the LGS brightness are considered.

The present work develops a technique for measuring the intensity of atmospheric optical turbulence in crossed optical beams. A new calibration function is suggested which allows estimating vertical profiles of the structure characteristic of the air refractive index turbulent fluctuations using covariance functions of differential jitters of solar subimage fragments detected by Shack-Hartmann sensor. Using observational data obtained at the Large Solar Vacuum Telescope (LSVT) of the Baikal Astrophysical Observatory (BAO), a characteristic vertical profile of the structure characteristic of the air refractive index turbulent fluctuations was measured. For comparison, the vertical profile of the structure characteristic of the air refractive index turbulent fluctuations was calculated based on the mean meteorological atmospheric characteristics. Both modeling and measurement data indicate the existence of turbulent layers at certain altitudes above the LSVT. The suggested approaches can be used in the optimization of adaptive optics systems, as well as in the development of optical turbulence profilers.