Home – Home – Jornals – Atmospheric and Oceanic Optics 2018 number 5

The software was created that allows automatic retrieval of water vapor continuum absorption from experimental data. The program includes baseline correction (if necessary), automatic correction of the experimental spectrum by frequency, automatic “spectroscopic” correction of the measured pressure value, subtraction of the spectral line local contributions, automatic selection of microwindows of transparency with the most reliable results of continuum retrieval and smoothing of the values obtained. Currently the software is intended to be used for processing Fourier measurement data, but it can be adjusted for other experimental methods.

Spectral line contour found on the basis of the asymptotic line wing theory with parameters obtained from fitting to experiment in the 8-12 mm region and describing the spectral and temperature behavior of the water vapor absorption coefficient in this region is used to calculate absorption in the long-wave wing of the H₂O rotational band. The absorption coefficient calculated within the asymptotic line wing theory takes into account the absorption by any colliding molecular pairs except the absorption due to stable dimers. The application of this contour in calculation of the absorption coefficient in the range of 14-200 cm^-1 allows us to extract the absorption part due to stable dimers from the absorption measured with the special resonator spectrometer. The dimer absorption spectrum derived shows a consistency with the spectra from quantum-mechanical calculations and measured in other experiments.

Numerical experiment is used to study the distribution laws of intensity fluctuations of laser beams propagating in the atmosphere. The probability density functions of intensity of fundamental Gaussian beam and beam having an orbital angular momentum (vortex beam) are compared for different positions of the observation point in a cross plane. An analytical model is suggested for the probability density function of intensity fluctuations, which works well for the conditions of strong (when the variance of intensity fluctuations takes the highest values) and saturated intensity fluctuations.

The results of the statistical analysis of experimental data obtained during the polygon tests of a passive optical wind speed meter are presented. During the tests, a possibility of using the device for aiming correcting to compensate the wind shift of bullets was evaluated. During the experiments, the arrays of the coordinates of the impact points and the values of the component of the wind speed averaged over the line of sight were recorded; the one-to-one correspondence of the elements of the arrays was not established. A method for determining the coefficient of linear interrelation for such arrays is proposed. It is shown that taking into account the corrections formed on the basis of wind measurements by a passive optical meter decreases the spread of the impact points to values corresponding to shooting standards for the best snipers in the absence of wind.

The concept of non-stationary diffraction-beam optics of powerful femtosecond laser pulses is presented. According to the concept the power of a beam propagates along specific light structures--diffraction-beam tubes. These tubes do not intersect, do not exchange energy, but changes in their shape and cross sections during propagation reflect the effect of physical processes that occur with radiation in the medium. The non-stationary theory is supplemented with evolutionary equations for time averaged diffraction beams and effective squared radii of diffraction tubes.

The process of near-ground propagation of monochromatic acoustic radiation at frequencies of 300, 1000, 2000, and 3150 Hz along atmospheric paths up to 100 m long is investigated experimentally and theoretically depending on altitudes of acoustic source and receiver. Experiments were performed at the experimental site of the IMCES SB RAS using a specially developed setup. The dependence of the recorded sound pressure level on the propagation path length and the initial signal power is studied. The theoretical analysis is performed by the Monte Carlo method that allows contributions of multiple scattering of acoustic radiation, refraction, and reflection by the underlying surface to the acoustic signal recorded with the detector to be taken into account for realistic models of the atmosphere. The local estimation algorithm of the Monte Carlo method developed by the authors was used for calculations. The comparison of the experimental and theoretical results shows their satisfactory agreement, which testifies to the efficiency of the suggested Monte Carlo algorithm and its applicabilty to the prediction of near-ground acoustic radiation propagation.

A new hardware-software ultrasonic complex AMK-03-4 is created for measurements of the characteristics of turbulent weather fields. In contrast to similar measuring instruments, the complex consists of four identical ultrasonic anemometers. The design of the complex allows one to record not only turbulent, but also statistical characteristics of spatial derivatives of turbulent pulsations of temperature and orthogonal wind speed components along the Cartesian axes. This allows investigating the spatial-temporal structure of turbulent meteorological fields of a surface air layer for subsequent applications in the similarity theory. Besides, the standard algorithm for calculation of structural characteristics of fluctuations of temperature and wind speed used in the ultrasonic anemometers is improved, which provides for considerably lower errors of their measurements.

This research is a part of the series of works devoted to the study of different factors that influence the phase function of cloudless atmosphere’s brightness: the elongation of aerosol scattering phase function, solar zenith angle, optical thickness, and albedo of underlying surface. The near-infrared region is under the analysis. While calculating the brightness of the cloudless day sky in the solar almucantar, we use the radiation transfer equation. The form of the aerosol phase function is determined by including three types of particles into the atmospheric model: submicroscopic, submicron, and coarse, as well as their mixtures in different proportions. We have received the data for a wavelength of 1.02 μm. The data may be used in atmospheric optics as an additional assessment of asymmetry of the aerosol scattering phase function and in approximate calculations of the flow of scattered solar radiation incoming to Earth’s surface.

Results of measurements of a complex of aerosol microphysical, chemical, and optical characteristics in two cruises of the research vessel «Akademik Mstislav Keldysh» in 2016 are analyzed. The work was carried out in the Kara Sea from July 10 till August 20 and in the Barents Sea from August 25 till October 10, 2016. The mean values of the following aerosol characteristics are presented: AOD of the atmosphere, fine and coarse components of AOD, number concentration of particles in the near-water layer of the atmosphere, mass concentrations of the absorbing matter («soot»), water-soluble ions (Na⁺, Mg²⁺, Cl^-, K⁺, Ca²⁺, NH₄⁺, NO₃^-, SO₄^2-), and gaseous admixtures (SO₂, HCl, HNO₃, NH₃). The characteristic particle size distribution functions are presented for different regions of the Kara and Barents Seas. It is shown that the levels of both aerosol turbidity of the atmospheric column (AOD) and the concentrations of aerosol and soot in the near-water atmospheric layer were close to the long-term mean values in Arctic latitudes. The atmospheric turbidity during the period of measurements was noticeably affected by emissions of forest fire smokes from the continent. The contribution of smoke aerosol into the mean values of AOD at λ = 0.5 µm obtained from shipborne measurements is about 44%.

Atmospheric air quality is determined by the concentrations of some gaseous pollutants and mass concentrations of aerosol particles in different size ranges. A wide range of atmospheric pollutants in both gaseous and aerosol phases was studied in the vicinity of Gelendzhik simultaneously in several sites of the region and at altitudes of up to 2200 m in July 2009. No such complex experiment was conducted there before. The following characteristics of the atmospheric aerosol were studied in the partical size range 3 nm - 32 μm: elemental composition of particles (23 chemical elements) and concentrations of polyaromatic hydrocarbons (14 compounds), unsaturated hydrocarbons, total protein, biotoxins, and culturable microorganisms. The concentration fields of different air pollutants and the integrated air pollution index were constructed using mathematical models of pollutant propagation and data on the hydrometeorological conditions during the period of measurements. The sources of aerosols in the region were revealed by studying the chemical composition of the airborne particles. The data obtained allowed us to estimate air pollutants and to calculate air quality indexes for the Gelendzhik area. The daily average concentrations of all the pollutants were compared to the daily average maximum permissible concentrations. All these concentrations were less than appropriate values of daily average maximum permissible concentrations.The integrated air pollution index did not exceed 1. Consequently, the atmosphere in the vicinity of Gelendzhik did not contain any significant pollutants in that period.

Experimental data on variability of light absorption by yellow substance in the surface layer of Lake Teletskoye (Gorny Altai) received during field hydrophysical studies carried out in the summer of 2017 are presented. The indices of light absorption by yellow substance calculated in the spectral range 400-800 nm (at natural logarithmic base) are within 0.1-2.1 m^-1. The yellow substance concentration in Lake Teletskoye determined by the optical method from the measured light absorption by yellow substance varies from 2.9 to 5.1 g/m³. To assess the effect of light absorption by yellow substance on the total attenuation, the relative spectral contribution of major optically active components of the lake water (yellow substance, suspended matter, chlorophyll, and pure water) to the spectral attenuation index for the water area under study is calculated. It is found that just the yellow substance makes the maximum contribution at all sampling points (21) of the lake.