Atmospheric and Oceanic Optics最新文献

Natural and anthropogenic increase in the greenhouse gas concentrations in the atmosphere is currently considered a determining factor in climate change and global warming. In this regard, there is an urgent need for the development of new techniques for remote monitoring of greenhouse gases with high spatiotemporal resolution and accuracy. Remote laser (lidar) systems enable more accurate and of higher information content measurements of atmospheric concentrations of greenhouse gases in comparison with standard contact gas analysis methods. The characteristics and description of differential lidars for monitoring methane, carbon dioxide, water vapor, ozone, and other gas components are given. The results of the development of ground-based stationary differential absorption lidar systems for remote monitoring of key greenhouse gases in the atmosphere in the past 25 years are systematized and analyzed. This review can be useful for specialists who design systems for remote gas analysis of the atmosphere.

Algorithms for stochastic simulation of a polarized signal arriving at a photodetector of an aircraft laser navigation system are developed. The angular distributions of Stokes parameters of radiation recorded by the detector are estimated by a Monte Carlo method; the effect of different-order scattering on the total recorded signal and polarization degree is analyzed. The signal intensity is calculated with the use of linear polarization filters. The suggested algorithms enable estimating the efficiency of the laser navigation system taking into account radiation polarization under different weather conditions and a possibility of enhancing signal contrast by using the polarization filters.

The spatial distribution of the relative concentration of chlorophyll-a in surface waters was estimated at three sites in the southwestern region of the Kara Sea based on laser-induced fluorescence measurements with an aircraft lidar. The fluorescence intensity was normalized to the simultaneously recorded intensity of Raman scattering signals from water. For two sites in the shelf zone near the western coast of the Yamal Peninsula, the spatial distribution of the normalized fluorescence intensity Cl is quite homogeneous, with variation coefficients of 9 and 15%. The third site in the northern tip of the Yamal Peninsula is strongly affected by river runoff, which is manifested in the presence of sharp frontal zones 5–10 km long. At this site, the Cl variation coefficient attains 40%, and the variations are mainly due to the strong variability of the Raman signals and, to a much lesser extent, to variations in the fluorescence intensity. Factors influencing the variability of Raman signals are considered. Synchronous shipboard in-situ measurements and remote aircraft measurements enabled us to find the calibration coefficient k_Cl = 1.03 ± 0.09 μg/L for the first two sites.

Contactless laser transillumination method is promising for studying the flow structure in turbulent supersonic jets. However, interpretation of the experimental results is a nontrivial task, especially in terms of turbulence, due to the spatial inhomogeneity of the fields of gas-dynamic characteristics. In this work, the spectral composition of turbulence in axially symmetric jets in the root region (before closing mixing layers) is analyzed based on laser sensing results. Intensity fluctuations of a laser beam propagating through a submerged supersonic jet are experimentally studied. The spectral density of the power of the fluctuations fully corresponds to the known experimental and calculated spectra for a moving turbulent medium, with the exception of the high-frequency range, where the spectrum is a superposition of two exponential components: the first is close to the known value −14/3 and the second is lower. This is shown to be due to the difference in motion speeds and the structure of vortex flows in the external and internal regions of the mixing layers. The results can be used in calculations of gas-dynamic characteristics and the acoustic emission of jet engines.

Parameters of the spectral model of small-scale turbulence are the most important characteristics used to describe the propagation of light and sound in the atmosphere. One of the factors determining the spectral composition of turbulence is the stratification regime. The effect of surface air layer stratification on the deviations of a turbulence spectrum from the Kolmogorov–Obukhov model is studied based on the processing of time series of fluctuations in meteorological parameters recorded by acoustic weather stations. A significant correlation between the stability characteristic (Monin–Obukhov number) and the exponent of the power-law model of the spectrum of temperature fluctuations is found from the comparison of their dynamics. An empirical model of the dependence of the spectrum exponent on the stability characteristic is suggested. The model makes it possible to estimate changes in the parameters of the spectral structure of small-scale turbulence based on estimates of the magnitude and direction of turbulent heat and momentum fluxes. The dependence reflects the features of generation of temperature turbulence under different stratification of the surface air layer. Information on turbulent spectral parameters derived from stratification estimates can be further used to solve problems of optical and acoustic wave propagation and atmospheric sounding.

The relationship between sulfur dioxide (SO₂) concentration and small-scale turbulence within Southern Baikal is understudied. The work studies jet streams and atmospheric turbulence affecting the surface SO₂ content over Listvyanka station. The cases are considered where the surface SO₂ concentration tends to increase at negative vertical turbulent specific heat fluxes. This occurs against the background of jet streams within the lower air layer and large vertical wind speed shear below the altitude of the jet stream generation. A vertical turbulent specific heat flux in the surface air layer can serve a key indicator of possible positive relationship between the surface SO₂ concentration and the total kinetic energy of turbulence. The analysis has shown that SO₂ concentration tends to increase at negative vertical turbulent temperature fluxes against the development of low-level jet streams. In similar situations, but with positive or near-zero temperature fluxes, SO₂ concentrations usually remain at a background level.

We present the results of comparative characterization of fractional composition of surface aerosols in the period of summer vegetation and winter dormancy of woody plants in the boreal zone of Western Siberia. The article presents statistics on the size distribution of aerosol particles at the Fonovaya Observatory of IAO SB RAS (Tomsk Region) from July 1, 2022, to June 30, 2023. The analysis of the ratios of aerosol fractions revealed a paradoxical situation, where the number concentration of aerosol particles 0.3–2.0 μm diameter turned out to be significantly higher in winter than in summer. A phenomenological model is suggested which describes this effect as a manifestation of the action of radiometric forces.

Parameters of the SO₂–CO₂ line profile are important to study the carbon dioxide atmospheres of terrestrial planets (Venus and Mars) and exoplanets. The carbon-dioxide shift coefficients of sulfur dioxide lines in ν₁ + ν₃ band are calculated at room temperature; the rotational quantum numbers J varies from 0 to 100 and K_a varies from 0 to 20. Calculations were made using a semi-empirical method, which includes a correction factor with adjustable parameters depending on the rotational quantum numbers. The calculated shift coefficients are in good agreement with few published data.

The study of internal gravity waves (IGWs) generated in the atmospheric boundary layer (ABL) under stable temperature stratification and the mechanisms of interaction between IGWs and wind turbulence is important for understanding dynamic processes in the atmosphere and improving algorithms for ABL numerical modeling and weather forecasts. This work is devoted to the study of wave structures and turbulence in a stable ABL with the use of the data of our experiments conducted in 2023. In these experiments, two pulsed coherent Doppler lidars (PCDLs) horizontally spaced 3250 m apart were simultaneously involved. The analysis of the experimental results has shown that from the measurements of two PCDLs it is possible to determine the time shift of the moments at which the leading edge of an atmospheric wave passes through the lidar locations; using this shift, one can determine the propagation velocity of the atmospheric wave. For the first time in our lidar experiments, the case of atmospheric wave propagation in the layer at heights from 200 m to 1 km with a maximum amplitude of quasi-harmonic oscillations of the vertical component of the wind velocity vector of about 4 m/s (at a height of 400 m) has been revealed. It has been found that due to the transfer of energy from an atmospheric wave to small-scale wind fluctuations, it is possible to increase the turbulent energy dissipation rate by four orders of magnitude in just a few tens of minutes.