Home – Home – Jornals – Atmospheric and Oceanic Optics 2026 number 7

The absorption bands of bulk water are characterized by a mode structure determined by the presence of a network of hydrogen bonds between water molecules with different degrees of OH bonding. Determining the parameters characterizing water structure is important for studying external effects on water. The temperature dependence of the absorption band of bulk water corresponding to ν + δ combination band (4500-5600 cm^-1) was studied by Fourier-transform infrared spectroscopy in the temperature range from +10 to +90 °C. A technique for determining the sample temperature from its absorption spectrum in the 2 mm region was developed based on a regression analysis of the spectral data. The technique enables temperature estimation with an error of no more than 1-2 °C. Decomposition of the spectral contour revealed that the observed changes are due to a redistribution of intensity between constituent sub-bands (modes). These modes are interpreted as contributions from water molecules engaged in hydrogen bonds of different strengths. To characterize the structural state of water, a quantitative spectroscopic parameter C(T) is suggested, which is defined as the ratio of the intensity of the low-frequency mode (~ 4900 cm^-1), which characterizes the number of strongly bound water molecules, to the intensity of the high-frequency mode (~ 5200 cm^-1), which describes the number of weakly bound molecules. The value of C(T) systematically decreases with an increase in the water temperature, reflecting a reduction in the proportion of molecules with strong hydrogen bonds. The coefficient C(T) can be determined from a water absorption spectrum with a precision of ±4%. This approach provides a tool for investigating the effect of weak external perturbations on water structure.

Highly sensitive analysis of neutral gas components, including H₂O vapor, in high-vacuum electrical installations designed to generate low-temperature plasma is a pressing analytical and metrological challenge. This article presents a spectrophotometer based on tunable diode lasers designed for the spectral analysis of H₂O traces in the vacuum chambers of low-temperature plasma generators using RF- and MW-discharges. The spectral range 7338-7370 cm^-1 where vibration-rotational absorption lines of H₂O of various symmetry and intensity are located was used for the analysis. Both the detection of the transmission spectra and their derivatives were used for highly sensitive analysis of traces of H₂O at low pressures. The sensitivity to resonance absorption and concentration sensitivity in detecting traces of H₂O in a rarefied gaseous medium were estimated.

The paper considers the possible structure of the water vapor continuum absorption. The continuum absorption within the v₂ H₂O band and in its high-frequency wing was calculated based on the asymptotic line wing theory (ALWT) taking into account the violation of the long-wave approximation for the centers of mass of molecules. To explain the spectral and temperature behavior of the continuum absorption coefficient, the same line profile was used throughout the entire frequency range under study. The results are important for problems of spectroscopy and radiation propagation in different media.

The absorption of pico- and subpicosecond laser pulses in water vapor is described using the total absorption coefficient (TAC) in the spectral range 7000-7450 cm^-1. The dependences of TAC on the carrier frequency, pulse duration, and absorbing layer thickness are calculated. The characteristic features of the process under study, caused by the specific nature of ultrafast electromagnetic interaction, are established. The suggested approach can simplify calculation and analysis of absorption of laser pulses in water vapor in the near-infrared range.

The second part of the article continues numerical studies of convective and dynamic turbulence fields in the vicinity of a group of extended inclined linear optical sources. This paper studies convective air motions in the vertical configuration of an open-side room of optical systems under external wind effect. The initial and boundary conditions of the boundary value problem being solved are similar to those for the horizontal configuration; the geometric and energy characteristics of the optical sources are analogous; the composition and scope of the study are the same as in the first part. The similarities and differences between the results for both configurations are shown.

This article presents the results of an experimental study of the dynamics of background aerosol filling of the stratosphere over Western Siberia in 2017-2025. The time period under study was characterized by the absence of large global-scale volcanic eruptions, which made it possible to identify natural variations in the background aerosol component. The observations were conducted using the lidar complex of Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences (Tomsk) by the elastic scattering method at a wavelength of 532 nm. To improve the reliability of the estimates, comprehensive statistical time series analysis technique was applied, including seasonal decomposition and iterative Z-score outlier removal. This enabled minimizing the impact of short-term local disturbances, including forest fire traces and instrumental anomalies. The analysis shows that, the overall background stratospheric aerosol level is statistically stable over the long term and does not exhibit a significant trend. At the same time, a clear seasonal asymmetry was revealed: the summer period is characterized by a statistically significant upward trend in aerosol loading, while a steady downward trend is observed in spring. The annual dynamics has a pronounced cyclical nature. The aerosol loading is maximal in winter and minimal in summer, which corresponds to a threefold difference in the integral aerosol backscatter coefficient. The results are valuable for the verification of climate models, as well as for the formation of a regional database of the background state of the stratosphere under conditions of minimal volcanic activity.

The main problem in studying atmospheric ice particles is the lack of information on their morphology and size. Traditional active and passive monitoring methods do not applicable to determination of these parameters due to physical limitations of the wavelengths and spatial resolution. There is a need in alternative methods, such as near-infrared lidars, where the absorption effect of ice particles is sufficient. This effect causes differences in lidar signals, thus opening a possibility of retrieving particle sizes from the spectral ratio. In this paper, the color ratio of atmospheric ice particles with sizes from 5 to 1000 mm, typical of high-altitude clouds, is studied. The dependence of the color ratio on particle size is derived. The study uses the ScIce-2023 light scattering matrix database for random spatial orientation of particles and single scattering approximation. Several particle shapes typical for ice clouds are studied at incident wavelengths from 0.355 to 2.150 mm. The results can be used for interpreting data of ground-based and satellite laser sensing of crystal clouds.

Variations in solar radiation caused by perturbations of the Earth's orbital motion by the Moon and some other planets of the solar system are studied. Short-period variations in the Earth's insolation in the range of periods 3 months to 30 years over the period from 1300 to 3000 are considered. The amplitudes, periods, and phases of the main short-period oscillations for 12 astronomical months in the latitude range 90° S to 90° N are 0. Calculations of seasonal and latitude dependences of periods and amplitudes of solar radiation arriving to the top of the atmosphere have shown that the periods of oscillations from 3 to 30 years are near constant and independent of latitude and time. Near the equinoxes, amplitudes in these oscillations caused by perturbations of the Earth's orbit by Venus, Mars, Jupiter, and Saturn are approximately symmetrical relative to the equator; near the solstices, the region of maximal amplitudes shifts towards the high latitudes of the summer hemisphere. Two closely spaced oscillations with periods of 2.6702 ± 0.0001 and 2.7154 ± 0.0001 years with different latitudinal and seasonal dependences are shown to exist in all latitudinal zones probably for the first time. The spatiotemporal variations in the 2.71-year oscillation are similar to the variations in the 18.6-year oscillation associated with the Moon, with a minimum at the equator and a maximum at high latitudes, and the 2.67-year variations are caused by perturbations of the Earth's orbit by Venus. The results of calculations of seasonal and latitudinal variations in solar radiation can be useful in climate modeling and analysis of the influence of short-period insolation variations on different geophysical and other processes.

Radiation balance of the underlying surface ( B ) is one of climate-forming factors, which influences the current climate change. The work discussed the measurements of the components of B (the counter-radiation of the atmosphere E _a and the radiation of the Earth's surface E _z) in a background region of Western Siberia in 2021-2024. The ranges of variability (hourly, daily, and monthly), extreme hourly and daily totals, and hourly average values of E _a and E _z are estimated; their daily cycles are analyzed. The maximal average amplitudes of E _z daily cycle are observed in summer (50-70 W/m²); in winter they are significantly smaller (7-11 W/m²). The daily cycle of E _a is weaker pronounced, its amplitude is 2.5-3.5 times lower than that of E _z throughout the year. Overcast sky conditions increase the atmospheric counter-radiation by 40-80 W/m² compared to clear sky conditions. The measurements are shown to meet the criteria for monitoring long-wave components of the radiation balance specified for the Roshydromet network stations. The results are of interest for the climate change analysis and verification of radiation patterns.

Ensuring security against threats associated with the use of explosive devices requires the development of effective methods for remote detection of explosive traces on different surfaces. This work discusses the way of improving the efficiency of the laser fragmentation/laser-induced fluorescence (LF/LIF) method for remote detection of surface traces of nitrocompounds. Using trinitrotoluene (TNT) as an example, it experimentally shows that time separation of fragmenting and probing pulses can significantly increase the efficiency of LF/LIF compared to single-pulse and simultaneous two-pulse irradiation. The relative intensity of fluorescence of NO fragments of TNT traces is assessed versus the fluence of fragmenting Nd:YAG laser (266.038 nm) and probing KrF laser (247.866 nm) at an optimal interpulse delay of 200 ns. The results can be used to improve the sensitivity and/or range of detection of nitrocompound traces by the LF/LIF method.

The development of domestic greenhouse gas monitoring solutions is crucial for Russia, addressing needs in both import substitution and assessment of the carbon balance of its vast wetland ecosystems. This paper presents the Russian automated chamber system KASM-8 for long-term high-frequency measurement of carbon dioxide (CO₂) and methane (CH₄) fluxes. The design features of the system are described, as well as measurement and data processing technique, which includes automated outlier filtering and error estimation. Field testing was conducted in 2023-2024 at the “Mukhrino" carbon supersite (Khanty-Mansi Autonomous Okrug-Yugra) and the “Vasyuganye" research station (Tomsk Oblast) in ridge-hollow complexes of ombrotrophic bogs. The resulted data series (192 measurements per day) revealed fundamental differences in carbon exchange between microlandscape elements: in KhMAO-Yugra, hollows acted as a net CO₂ sink (mean NEE ranged from -0.19 to -0.28 mmol × m^-2 × s^-1), whereas ridges were a net source (mean NEE was 0.17 mmol × m^-2 × s^-1). At the “Vasyuganye" station, hollows demonstrated lower CO₂ uptake capacity, and ridges exhibited higher emission fluxes. The data also revealed pronounced daily and seasonal dynamics and interannual variability. The results confirm the operational reliability of the KASM-8 complex and can be used for assessing the carbon balance with allowance for spatial heterogeneity of bog microlandscapes in climate projects and for creating long-term monitoring systems.