Home – Home – Jornals – Atmospheric and Oceanic Optics 2024 number 8

An analytical model δ(sur) is suggested for nitrogen and oxygen shift coefficients of water vapor in the visible region. The model δ(sur) linearly depends on the broadening coefficient of a given line and fitted parameters. The analysis of the available experimental data on d coefficients for the near infrared and visible regions is performed. The model δ(sur) retrieves 486 nitrogen shift coefficients for lines from the range 13550-22590 cm^-1 with a mean square deviation of 6.0 × 10^-3 cm^-1/atm and oxygen shift coefficient for lines from the range 13550-14000 cm^-1 with a mean square deviation of 2.5 × 10^-3 cm^-1/atm.

Methane is one of key greenhouse gases, whose concentration has been increasing in recent decades. This leads to an increase in the temperature of the Earth's surface. To monitor the methane content in the atmosphere the accurate knowledge of the absorption spectrum of CH₄ molecule is required. In this work, the parameters of methane absorption lines broadened by atmospheric air pressure are presented in the spectral region 4345-4360 cm^-1. Data were obtained from spectra recorded at a Bruker IFS 125HR Fourier spectrometer with a spectral resolution of 0.005-0.01 cm^-1 at room temperature and five values of buffer gas pressure. Atmospheric transmission was simulated using the obtained results and the line parameters from HITRAN and GEISA spectroscopic databases. The comparison with measured atmospheric solar spectra shows that the use of the CH₄ absorption line parameters obtained in this work gives the best result in terms of root-mean-square deviation.

The article studies the influence of deviations from the Kolmogorov-Obukhov model in the spectra of refractive index fluctuations in a supersonic air flow on transmitted optical radiation. Analytical estimates of the statistical moments of the field and the results of numerical simulation of laser radiation propagation through a high-speed air flow generated during flowing around an aircraft are presented. The estimates of the coherence length and the relative dispersion of optical wave intensity fluctuations are compared. Consideration of deviations from the model of developed turbulence is shown to cause significant (several times) changes in the estimates of laser beam characteristics at a distance of several hundred meters. The results can be used to estimate radiation distortions under the turbulence effect in the optically active layer near the surface of supersonic aircraft on location and communication routes.

Experimental results and the analysis of the reasons for the transformation of spectral parameters of a femtosecond laser pulse propagating in atmosphere and in pure molecular nitrogen are presented. The experiment was carried out under aberration focusing conditions. It is shown that the main contribution to the anti-Stokes spectrum broadening is made by cascade parametric four-wave mixing initiated in the filamentation domain by stimulated Raman Stokes scattering on rotational transitions of nitrogen.

St. Petersburg is the second most populous city in the Russian Federation and the fourth in Europe. According to official statistics, ~ 5.6 million people live in the city permanently. In order to experimentally estimate greenhouse gas emissions from the territory of the St. Petersburg agglomeration, an original combined approach was developed and implemented during EMME-2019 and ЕММЕ-2020 observational campaign. The paper summarizes the results of mobile experiments in 2019 and 2020. It is shown that the period “March - early May”, chosen for the EMME campaigns, is optimal for estimating CO₂ emissions. It was found that the average values of anthropogenic additives caused by emissions from the territory of St. Petersburg are ~ 1.07 ppmv and ~ 6.61 ppbv for CO₂ and CH₄, respectively. Experimental estimates of specific greenhouse gas fluxes for the territory of the St. Petersburg agglomeration amounted to 72 kt × km^-2 × year^-1 CO₂ and 198 t × km^-2 × year^-1 CH₄ for six days of 2020 campaign; 80 kt × km^-2 × year^-1 CO₂ and 161 t × km^-2 × year^-1 CH₄ for 15 days of campaigns 2019 and 2020. The CH₄/CO₂ and CO/CO₂ emission ratios for St. Petersburg in March - early May 2020 averaged 6.4 and 5.7 ppbv/ppmv, respectively. Quarantine restrictions (COVID-19) affected the emission structure of St. Petersburg: a sharp decrease in transport activity led to a significant decrease in CO emissions from motor vehicles.

Laser remote sensing of cirrus clouds is accompanied by the problem of taking into account the multiple scattering of radiation, which influences the reliability of measurement interpretation. The contribution of multiple scattering of radiation to echo signals of a space-borne lidar is estimated. The non-stationary problem of laser pulse propagation in continuous cirrus clouds with separation by scattering multiplicities is solved by the Monte Carlo method at different values of the optical-microstructural characteristics of clouds (optical thickness and shape and size of ice particles) and lidar parameters (distance from the sensing object, radiation divergence, and field of view angle of the receiver). Numerical experiments were carried out taking into account the permissible range of the parameter for operational or promising space-borne lidar systems. The features of the formation of the return signal when aerosol and Rayleigh particles, as well as the underlying cloud layer, are introduced into an atmospheric model are discussed. The simulation results indicate the high sensitivity of the part of an echo signal caused by multiply scattered radiation to the parameters under study, which should be taken into account when formulating and solving inverse problems.

The study of the field of total ozone column (TOC) is one of the important problems of atmospheric optics. In this paper, the spatial distribution of TOC over the Russian territory is analyzed based on Aura/OMI (Ozone Monitoring Instrument) data. The observation results for individual areas (points) are presented in the form of TOC time series, which cover the observation period from January 2005 to December 2022. Integral (excluding seasonal variations) latitude-longitude features of TOC distribution over the territory under study are revealed; correlation coefficients between the TOC series for different points are calculated; their relationship is studied depending on the distance between the points; the spatial autocorrelation function is derived and the sizes of spatial inhomogeneities of the TOC field are estimated. The spatial mismatch of the data is analyzed using a parameter which is a measure of the standard deviation from the average mismatch. The results of the work provide an idea of the scale of the spatial correlations in the TOC field and can be used for clarifying the optically active component of the atmosphere when developing weather and climate change prognostic models.

The electric field of the atmosphere, along with electrical conductivity and ionization of air, is the main characteristic of atmospheric electricity, which is a set of electrical phenomena occurring in the atmosphere, including in clouds and precipitation. There is a close connection between the intensity (potential gradient) of the atmospheric electric field and the topography and landscape of an area and meteorological parameters. A disruption of the normal electric field, characteristic of fair-weather conditions, occurs during the formation and development of clouds, precipitation, thunderstorm, etc. In general, the variability of the electric field is determined by a number of individual or combined factors, both of global and regional (or local) character. Therefore, studying and understanding the functioning of the Global Electric Circuit and its local variability seems to be a relevant scientific problem, especially in the context of the modern climate change. The variability of the electric field potential gradient and meteorological parameters is analyzed in this work based on long-term observations in a large urban settlement. The analysis shows a pronounced dependence of the potential gradient on the wind direction in fair-weather conditions, especially in winter, associated, we believe, with aerosol transfer. We also found that the variability of the surface electric field, including seasonal and daily variations, under all meteorological conditions significantly differs from the variability under exceptionally fair-weather conditions. The results are in good agreement with similar studies at other observation sites located near large populated areas, and are of interest for simulating the state and variability of the Global Electric Circuit depending on various physiographic and meteorological conditions.

The relevance of studying the dynamics of ozone concentration is due to the fact that at high concentrations it is a potent poison and a powerful oxidizer that extremely negatively impacts both biological objects and the environment. Based on the monitoring data, the paper examines the distribution of tropospheric ozone in Russia in 2023 in the surface air layer, as well as its vertical distribution based on the results of aircraft sounding. It is shown that the maximum allowable daily average concentrations established by the domestic hygienic standard, maximum single, daily average, and annual average, were exceeded at all measurement points. The current situation necessitates widespread public awareness of the results of monitoring and the development of environmental measures to reduce the concentration of ozone and its precursors in the surface air layer.

Expansion of the functional capabilities of lasers in general and metal vapor lasers in particular is a relevant problem. Its solution is associated with both the study of the kinetics of processes in laser media and the development of new excitation systems. In this work, a system for exciting metal vapor active medium is suggested. It consists of three pumping sources, a synchronization system, and software. High voltage pulses are generated by three independent inverters; thyratrons are used as switches. The main capabilities of the system and the prospects for its use for implementing non-typical lasing modes are considered.

The technique of laser reference stars is an integral part of modern adaptive optical systems of ground-based telescopes. The requirements for the energy, spectral, and spatiotemporal characteristics of a laser beam for creating sodium laser guide star, as well as for the adaptive optical system as a whole, are largely related to the atmospheric parameters of telescope site. One aspect of optimizing the brightness of a sodium laser guide star is the choice of linewidth of the laser. In this work, based on numerical simulation of the interaction of laser radiation with mesospheric sodium atoms under the conditions of midlatitude atmosphere in the Russian Federation, the effect of laser bandwidth on the magnitude of the return photon flux from a sodium laser guide star is estimated to determine the requirements for the parameters of the laser. Results are presented for laser radiation with circular polarizations and linewidths from 10 MHz to 3.5 GHz.

The paper presents the results of studying the influence of the morphology and composition of thin films that form the structure of dielectric mirrors of optical resonators of coherent sources for LIDARs. The Optilayer software simulated dielectric mirrors based on two pairs of materials: TiO₂/SiO₂ and ZnS/YbF₃. Using electron and atomic force microscopy, their morphological features were determined. The calculated structure of the interference coating was deposited onto a substrate using the ion-beam sputtering method. The threshold of laser-induced breakdown of dielectric mirrors by Nd:YAG laser radiation at a wavelength of 1064 nm was found to be 4 J/cm² for a TiO₂/SiO₂ mirror and 4 J/cm² for a ZnS/YbF₃ mirror.