Home – Home – Jornals – Atmospheric and Oceanic Optics 2026 number 8

The development of precise light scattering models for lidar sensing of the Earth's atmosphere requires reliable data on the polarization characteristics of molecules. However, for several key atmospheric constituents, such information is either incomplete or entirely absent. In this work, spontaneous Raman spectroscopy is used to experimentally determine the depolarization ratios of the Q-branches of vibrational bands for N₂, O₂, H₂O, CO₂, and CH₄, which are the main components of atmospheric air. The measurements were performed using a high-sensitivity Raman spectrometer with laser excitation at 532 nm. For the first time, the depolarization ratios were estimated for the CO₂ Fermi-triad bands, as well as 2ν₂ and 2ν₄ overtones of CH₄. Based on the obtained data, the ratios of the derivatives of the polarizability tensor invariants for these molecules were determined. The results complement the existing knowledge on the polarization characteristics of atmospheric gas molecules, which is essential for modeling light scattering processes in the Earth's atmosphere.

The work studies the origin and evolution of water aerosol in the so-called plasmoid, which is generated by a high-voltage discharge above a water surface in the form of a luminous spherical object and considered a laboratory analogue of natural ball lightning. The laboratory ball lightning was investigated not only in situ using non-contact probing techniques, but also by sampling with the use of specially designed devices. Water vapor condensation occurs during the glowing stage of the plasmoid, implying that the internal temperature drops to at least 100 °C. The experimental data indicate that the water droplets inside the plasmoid are not luminous. After the glow ceases, a phantom resembling the spherical structure of the plasmoid persists for about 1 s; inside this phantom, water aerosol can still be observed. The existence of a “shell” confining the spherical object is plausible not only during the glow, but also for a certain time thereafter. The aerosol particles produced by erosion of the central electrode during the discharge were measured with a diffusion spectrometer. Their sizes lie in the submicron range and are substantially smaller than those of the water droplets inside the plasmoid. The principal conclusion is that the long-lasting glow results from chemical processes occurring in the gas phase of the plasmoid rather than from high-temperature heating of the gas or from emission by aerosol particles.

Carbon dioxide is one of the main greenhouse gases; it significantly contributes to the atmosphere through natural processes and anthropogenic impacts. Therefore, the development and modernization of CO₂ sensing devices and technologies is an urgent applied problem. This paper presents the results of developing a mobile atmospheric CO₂ sensor based on tunable diode laser absorption spectroscopy in the 1567-1573 nm absorption band of the target gas. The mobile sensor was tested on a horizontal sensing path using a topographic target under mid-latitude summer conditions. The average CO₂ content in the atmosphere retrieved from experimentally recorded back reflected signals was 451,03 ppm with a deviation from the readings of a local gas analyzer of 6.16% for a single measurement and 428,02 ppm after averaging over 120 s. The results can be useful in studying the dynamics of atmospheric CO₂ content under background conditions, as well as in monitoring anthropogenic emissions from the industrial sector.

February 2024 was globally the record warmest; however, temperatures in southern Siberia were abnormally low, reaching -40 °C. That coincided with the anomalous “Warm Arctic - Cold Eurasia" (WACE) pattern. This study focuses on identifying the causes of this anomaly. Analysis of stratosphere-troposphere interactions revealed that the emergence of the WACE anomaly occurred simultaneously with the weakening of a stratospheric polar vortex (SPV) and a sudden stratospheric warming (SSW) in the second half of February 2024. Our findings confirm that the influence of SPV weakening on tropospheric anomalies occurs not only after SSW events but also during them. Anomalously strong stratosphere-troposphere exchange can induce localized and prolonged cold spells in the troposphere over Siberia. These conclusions are supported by wave activity flux calculations based on reanalysis data and instrumental observations during aircraft-based sounding. Our research highlights the crucial role of complex interactions between the troposphere and stratosphere in shaping and amplifying climate anomalies, such as WACE, in winter.

The ongoing global warming requires increased attention to the dynamics of greenhouse gas concentrations in the atmosphere, which is not sufficiently studied. In this paper, the variability of CO₂ and CH₄ concentrations on the meso-α-scale (200-2000 km) was analyzed based on hourly observation from 2013 to 2017 at six stations of the JR-STATION network for greenhouse gas monitoring, established within the Russian-Japanese scientific cooperation. The absolute differences in hourly concentrations between adjacent observation sites are discussed. It is shown that the long-term average | ΔСО₂ | can vary from 3.8 to 4.5 ppm, and | ΔСН₄ |, from 47 to 105 ppb. The gradients of CO₂ concentrations in Western Siberia on the meso-α-scale were in the range 0.006-0.007 ppm/km, and of CH₄, in the range 0.077-0.179 ppb/km, which were significantly less than those on the meso-β (20-200 km) and meso-γ (2-20 km) scales. Aannual cycle of the average long-term absolute differences in CO₂ concentrations between all stations is charactarized by a minimum in March-April, and a maximum in June-August. Their minima were ≈ 2 ppm, while their maxima ranged from 6 to 9 ppm. In the daily cycle, the maxima of the long-term average absolute differences in CO₂ and CH₄ concentrations were observed in darkness, while the minima were observed during the daylight and varied throughout the year. They remained nearly constant during the day from October to April. Nighttime differences become to be distinguishable in May, reaching maxima in July and August. A decrease is then observed in September. The results of this study expand our knowledge of greenhouse gas dynamics in the atmosphere on the meso-α-scale and can be useful in developing requirements for both measurement accuracy and the scaling of atmospheric budget calculations.

This paper presents a comprehensive analysis of long-term thunderstorm activity dynamics in the Irkutsk Region and examines its relationship with solar activity. Data from the Irkutsk Hydrometeorological Center's network of meteorological stations was obtained and systematized. The number of thunderstorm days per year, historically studied for this region, was used as the primary thunderstorm activity parameter. The long-term dynamics of the number of thunderstorm days per year in the Irkutsk Region across the entire study region show no statistically significant trend, demonstrating stability in the face of climate change. The spatial distribution of thunderstorm days is consistent with physical and geographical conditions: maximum values are observed in mountainous regions and minimum values are found in the north of the region. The proposed modification of the F 10.7 index (the centered variation module) shows a statistically significant positive correlation with the long-term dynamics of the number of thunderstorm days for meteorological stations located in the Verkhnelensky districts and on Olkhon island in the Irkutsk Region.

Observed growth of the atmospheric concentration of gases, such as CO₂ and CH₄, strengthens the greenhouse effect in the atmosphere and impacts on climate. One of the characteristics of the greenhouse effect is the radiative forcing of the atmospheric gases which is defined as the difference between the longwave radiative fluxes at different concentrations of gases other parameters of the atmosphere being constant. From 1990 to 2023, the radiative forcing of long-lived greenhouse gases due to their concentration grow from the pre-industrial period (1750 year) has increased by more than 50%. In the work, the impact of atmospheric water vapor content variability on the CO₂ and CH₄ radiative forcing for summer and winter conditions of south Western Siberia is investigated. The longwave IR radiative fluxes are calculated on the basis of upper-air sounding data of meteorological station in Novosibirsk for 10 years. The maximum of absolute value of the CO₂ radiative forcing was observed at the top of troposphere, at that, in summer, it was higher by 50% than in winter conditions, and relation of CH₄ radiative forcing to CO₂ forcing at this altitude was about 12%. The sign of the forcing is negative, which means heating of the troposphere. At the top and bottom of the atmosphere, a decrease in CO₂ and CH₄ radiative forcing is observed with an increase in atmospheric water vapor content, which is caused by overlapping of H₂O bands and continuum absorption with CO₂ and CH₄ absorption bands. The contribution of H₂O continuum absorption to the CO₂ radiative forcing increases from 30 to 70% when the water vapor atmospheric total column increases from 1 to 4 g/cm². For winter cases with low water vapor content, the average CO₂ radiative forcing at the bottom of the atmosphere increases by 1.5 times in comparison with summer conditions, which leads to additional warming of the surface.

One of the most important problems of a modern city is the provision of clean air. A lot of very expensive activities are being carried out in connection with this problem. The paper presents the results of numerical simulation of nitrogen dioxide dispersion in the atmosphere of the cities of Kemerovo and Astrakhan before and after transport infrastructure modernization. Data on gross nitrogen dioxide emissions from vehicles over sections of city roads were obtained through field surveys conducted as part of the Federal Project "Clean Air". The study used a modeling complex consisting of the WRF-ARW atmospheric circulation model and the CHIMERE chemical transport model. Model calculations confirmed a reduction in nitrogen dioxide concentrations in the cities under study. The maximal reduction was recorded in Astrakhan (by 55.3%). It is shown that the impact of reducing gross nitrogen dioxide emissions on near-surface air quality within the city depends on local geographical and meteorological conditions affecting transport, dispersion, and chemical reaction processes. For cities in basins, local emission reduction measures are effective, while coastal cities require measures to regulate transit traffic flows. The use of chemical transport models at the planning stage of transport infrastructure modernization enables assessing the contribution of each specific emission reduction measure.

Measurement of heavy precipitation intensity remains an unresolved problem, particularly by common radar methods. The application of dual-polarization radars provides a solution to this issue. This paper presents a comparative analysis of heavy precipitation measurements by traditional radar method and a new approach based on specific differential phase measurements. Precipitation measurements with a DMRL-C radar and Pluvio² 200 weighing precipitation gauges were performed in St. Petersburg and the Leningrad Region on July 1, 2023. To calculate precipitation intensity ( R ) from radar data, Z _h- R relationships ( Z _h is the reflectivity at horizontally polarization) based on the Marshall-Palmer equations and measurements of the specific differential phase ( K _dp) were used. These data were compared with measurements from the precipitation gauge network. The comparison showed a high correlation between precipitation intensity measured by gauges and R ( K _dp) and no correlation with R ( Z _h). According to precipitation gauge network, the average precipitation intensity was 52 mm/h and the maximal intensity was 186 mm/h on July 1, 2023. The results of this study can be used to improve heavy precipitation measurement methodologies and to estimate fluxes of extreme rainfall in northwest of the Russian Federation.

One of the complex problems in monitoring various natural and technological objects is smoke contamination of an optical path and appearance of flames on it. This paper analyzes experimental studies of flame optical characteristics and their impact on the detection of flame-shielded objects. Based on experimental data received by different methods (IR thermography and emission spectral measurements) and the analysis of atmospheric transparency characteristics, including molecular absorption and scattering, and the effects of aerosols (smoke and fog) on radiation propagation, the spectral range 3.7-3.9 μm is shown to optimal for monitoring objects shielded from an observer by flame, smoke, or fog. This spectral range minimizes the impact of flame and atmosphere on IR radiation propagation and ensures optimal diffraction resolution, which determines the distance and minimal size of detected objects.

Cirrus clouds cover a significant part of the Earth's surface and have a significant impact on the radiation balance and climate. To calculate the solar radiation transmittance of clouds, it is necessary to control the optical thickness of clouds. Lidar sensing is an optimal method for this. The paper compares two lidar methods for determining the optical thickness τ of cirrus clouds, using elastic or Raman scattering signals. Both techniques are based on recording signals from the clear atmosphere down to and above a сloud, but the use of elastic scattering is associated with errors caused by the possible presence of sub-cloud or above-cloud aerosol layers. Different methods for processing experimental data were compared, and the error in determining the optical thickness was assessed. It is shown that deviations in retrieving the thickness from elastic scattering signals can attain ~ 0.5 for clouds with the optical thickness τ > 2. At t ≤ 1, the correlation coefficient between the data of the two methods is 0.94, which enables the use of elastic scattering signal measurements, available even during daytime, to estimate the optical thickness of cirrus clouds. The results of the work can be used in the development of lidar systems for sensing upper-level clouds.