Home – Home – Jornals – Atmospheric and Oceanic Optics 2024 number 10

The photoacoustic (PA) method is widely used in studies of the absorption of optical radiation by various media. As a rule, it is assumed that the PA signal is formed due to the relaxation of vibrationally excited molecules with a common characteristic time τ_VT. The kinetics of heat release in a PA cell at absorption of a laser radiation pulse in a mixture of two molecular gases with two independent channels of vibrational-translational relaxation with very different times is considered. An example of calculations of the kinetics of heat release for a mixture of H₂O and CO₂ at absorption of a CO₂ laser radiation pulse and variations in gas concentrations is presented. It is shown that it is necessary to take into account the relationship between the laser pulse duration and the characteristic times of vibrational-translational relaxation in the gas mixture under study.

In the Arctic, climate warming is occurring several times faster than in other regions of the globe. This сan be the result of strengthening feedbacks between climate and atmospheric composition. However, there are very few data on changes in the concentration of climatically active substances in this region. Therefore, to fill the gap in data on the vertical distribution of gas and aerosol composition of the air over the Russian Arctic, an airborne survey of the atmosphere and water surface over the all Russian seas of the Arctic Ocean was performed with use of the Tu-134 Optik aircraft laboratory in September 2020. This paper analyzes the spatial distribution of gas and aerosol composition in the Arctic troposphere. It is shown that during the experiment, the CO₂ mixing ratio changed from west to east in the opposite direction in the near-water and boundary layers compared to the free troposphere (FT), namely, it was increasing in the planetary boudary layer (PBL) and was decreasing in the FT. The methane content in the near-water layer decreased in the same direction. Concentrations of CO, NO _X , and SO₂ in the Russian Arctic were very low, which is typical for remote background areas. All aerosol fractions also showed a decrease in their content from west to east.

The results of experiments on determining the turbulence parameters of a stratified atmospheric boundary layer using remote sensing are presented. The height-time distributions and vertical profiles of the dissipation rate of kinetic energy of turbulence and the structural constant of turbulent fluctuations of temperature obtained from measurements of radial velocity with a coherent wind lidar and temperature with a microwave radiometer are compared with altitude variations in the parameters characterizing atmospheric stability. It is shown that the dissipation rate, which determines the intensity of wind turbulence, decreases in the boundary layer with altitude for all types of thermal stratification. The intensity of turbulent fluctuations of temperature depends to a greater extent on altitude variations in thermodynamic conditions in the atmosphere. If the thermal instability of the atmosphere at higher altitudes exceeds that in lower layers, then the structural constant of temperature fluctuations can not decrease but increase with altitude. In accordance with the altitude variation in the structural constant of temperature, the values of the structural constant of turbulent pulsations of the refractive index can also increase with altitude and differ from those predicted on the basis of known models.

Ozone is one of the important trace gases of the Earth's atmosphere. This study anal yses ground-based synergetic MW + IR method for remote measurements of ozone using ground-based instruments at Peterhof (SPbSU) - MW ozonometer and Bruker IFS-125HR Fourier transform infrared spectrometer. Numerical estimates of the errors and vertical resolution of remote measurements showed that uncertainties of remote ozone measurements at different altitudes vary from 5 to 20% or more. The vertical resolution of the MW + IR method varies from ~ 10 to ~ 12 km. These estimates demonstrate the potential for determining ozone in Peterhof using ground-based combined MW and IR measurements.

The operation of thermal power plants (TPP) is accompanied by the emission of various pollutants into the atmosphere, including nitrogen oxides. This paper presents the results of spectrometric measurements of the atmospheric NO₂ content carried out on circular routes around large urban TPPs of St. Petersburg. The spatial variability of tropospheric NO₂ content in the vicinity of a TPP, determined from experimental data using the DOAS (Differential Optical Absorption Spectroscopy) method, demonstrates increased values in the downwind side of smokestacks. The spatial distributions observed in the mobile DOAS measurements are confirmed by the results of numerical calculations of the NO₂ content field using the HYSPLIT (HYbrid Single-Particle Lagrangian Integrated Trajectories) model, taking into account a priori information on the volume of NO_x emissions from the main urban TPPs. Approximate estimates of NO_x emissions from the two largest TPPs in St. Petersburg, obtained on the basis of calculations of the total flow of NO₂ molecules through a closed loop of DOAS measurement routes, amounted to ~ 2 ÷ 3 thousand tons per year. These experimental data are important for determining the contribution of thermal power plants to anthropogenic atmospheric pollution.

The spatiotemporal distribution of the intensity of bioluminescence formed by hydrobionts in the Black Sea based on the data of expeditionary research conducted in June 2013 and September 2014 during the voyages of NIS “Professor Vodyanitskiy" (IBSS) was investigated. Comparison of this characteristic in the N-W and N-E parts of the Black Sea has been done. Satellite data on near-surface wind and geostrophic currents are used to explain the causes of spatiotemporal variations in the intensity of hydrobiont bioluminescence. It has been shown that in the vertical distribution of bioluminescence intensity, most stations had one maximum at the top part of the seasonal thermocline. At deep-sea stations in the north-western part of the sea located in the zone of weak vertical movements, two maxima were observed due to the development of heat-loving hydrobiont species in the upper maximum and cold-loving species in the lower one. The maximum values of the integral intensity of hydrobiont glow were observed in the divergence zone in the deep-water north-eastern part of the sea, which is explained by more active enrichment of waters with biogenic substances due to more intense upward movements. Obtained results can be utilized for more accurate assessment of the upper layer water bioproductivity in the Black Sea from satellite data.

Two methods of delineation of the stratospheric polar vortex were compared by the main characteristics of the vortex they provide - vortex area, average wind speed at the edge, mean temperature inside the vortex. Both methods use the ERA5 reanalysis data for isobaric and isentropic surfaces, one of them is based on the geopotential and another one - on the potential vorticity (PV). Geopotential method gives higher vortex area than the PV method: 1.3 times higher for Arctic and 1.14 for Antarctic. The estimates of the average wind speed at the edge are very similar: the wind speed by PV method is 5% higher than by geopotential for the Arctic, and 3% higher in the Antarctic. Mean temperature inside the vortex by PV method is 1% lower in both the Arctic and Antarctic. The largest difference in the estimates of vortex area in the Arctic was 25.52 million km², which was reached on November 23, 2022 at the 600 K isentropic surface; and in the Antarctic it reached a value of 23.78 million km² on December 14.2. The significant difference in area demonstrates the need for careful selection of the delineation method when studying polar vortices. The significant difference in area demonstrates the need for careful selection of the delineation method when studying polar vortices.022 at the 475 K surface. The differences of vortex area are increasing with height: from 4.23 million km² at the 475 K surface to 10.24 million km² at the 600 K surface in the Arctic, from 4.91 million km² at the 475 K surface to 6.17 million km² at the 600 K surface in the Antarctic. The significant difference in areas demonstrates the necessity for careful selection of the delineation method when studying polar vortices.

The intensity and frequency of events associated with severe weather phenomena are currently increasing in Western Siberia. The Weather Research and Forecasting (WRF) atmospheric model makes it possible to study such phenomena, in particular, for warning about their occurrence. This article defines a set of WRF parameterization schemes that provide a full-fledged analysis of the causes of occurrence and monitor the further development of severe weather events. This set of schemes ensures correct operation of the WRF model under conditions corresponding to severe weather events. The paper details two weather events with such severe phenomena as very strong wind, very heavy rainfall, prolonged heavy rain, and abnormally cold wave, which occurred in Western Siberia on April 29-30, 2019, and December 25-26, 2020.

Solving of the light scattering problem of atmospheric ice crystals is necessary for the interpretation of laser sensing data of atmosphere. This article presents the results of calculating light backscattering matrices for ice atmospheric crystals of arbitrary shape. The number of faces for these particles is 15, 20, and 40 and the size range is from 10 to 300 mm. Calculations were carried out within the physical optics approximation for the case of arbitrary spatial orientation of particles and single light scattering. The wavelengths of the incident light are 0.532 and 1.064 mm. According to the statistical analysis of crystals, their optical properties slightly differ. It is shown that the optical properties of an etalon particle taken from the IAO SB RAS data bank is satisfied the above distribution. Thus, the results confirm the validity of using the database for the case of a large set of particles with the number of faces from 15 to 40. The results are necessary for constructing algorithms for the interpretation of data of lidar sounding of cirrus clouds.

The history of the creation of a turbulent lidar at IAO SB RAS began 11 years ago, when, with the help of a bulky laboratory installation, it was first experimentally possible to register the backscatter enhancement (BSE) effect in a turbulent atmosphere. Subsequently, a number of design solutions were proposed to improve the lidar, which made it possible to reduce dimensions and increase reliability. The main features of the lidar design are: the coincidence of the optical axes of the transmitter and receiver; the presence of an additional receiving channel; operation in the photon counting mode with the accumulation of echo signals. The experimental technique using a turbulent lidar, which is a new type of laser locator, is described. An algorithm is given for determining the profile of the structural characteristic of turbulent fluctuations of the refractive index of air from the ratio of echo signals. The experimental verification of the technique was performed and the lidar data were compared with the readings of a solar radiometer and a scintillometer. In the future, the development of turbulent lidar technology will allow remote monitoring of the turbulence intensity in the atmospheric boundary layer from the ground, for example, on the glide path at airports; detecting clear air turbulence (CAT) in advance from aircraft, etc.

Trace atmospheric gases (TAGs) are optically active elements of the atmosphere. TAGs have a great influence on atmospheric processes: transformation of solar radiation, weather formation, air pollution by industrial emissions, and propagation of optical waves. Ozone occupies a special place among TAGs. The ozone layer plays the role of natural protection of the planet from short-wave solar radiation. Therefore, monitoring of the ozonosphere by ground-based and satellite instruments allows us to obtain the most reliable data on the state of the atmosphere and, in particular, the ozone layer. The solution of this urgent problem is possible only with permanent improvement of the hardware base and perfection of methodological approaches to scientific research of the atmosphere. In this work, a number of measurements were carried out using a mobile ozone lidar at wavelengths of 299/341 nm in the altitude range 0.1-12 km at the Siberian lidar station (SLS). Vertical ozone profiles retrieved from lidar and meteorological satellite data of the European Space Agency (MetOp) obtained in 2023 were compared. The comparisons showed that the average relative difference between the profiles varies from -65.6% to 15.3% at altitudes from 0.1 km to 12 km. The comparison results confirm good prospects for using these ozone sensing wavelengths in the altitude range 0.1-5 km, previously uncovered by the SLS. The results will be used in modeling the vertical distribution of ozone concentration and in assessing the ecological state of the atmosphere in the Tomsk region.

In adaptive optics systems (AOS) applied in astrophysics, normalized cross correlation (NCC) algorithm is widely used, usually in tracking and stabilization blocks, as well as for measuring the optical parameters of AOS, for example, local tilts in wavefront sensors (WFS). Due to the tendency to increase the apertures of modern telescopes and the improvement of the resolution of digital video cameras, the problem of increasing the speed of the NCC algorithm for real-time control calculations is relevant. The article proposes a modification of the NCC algorithm for measuring the displacement of images of extended objects of a static scene in adaptive atmospheric optics applications. This type of algorithm can be used in tracking systems to eliminate jitter of the entire image, as well as for measuring the wavefront phase in WFS. Due to the simplification of the reference frame normalization procedure, the algorithm wins in speed and can be used in AOS of large-aperture solar telescopes.