Том 31, № 2 (2018)

The results of experimental studies of the transverse structure of a laser beam after multiple filamentation are presented. A ring structure of radiation is formed around individual filaments in a beam cross section inside the multiple filamentation domain, and at a dozen meters from it a common ring structure starts forming surrounding postfilamentation light channels (PFC). It is shown that the spectra of the PFC, rings, and beam are significantly different. The ring spectrum broadens asymmetrically relative to the carrier wavelength and is mainly concentrated in the short wavelength region. The PFC spectrum has a significant and more symmetrical broadening and covers the range 630–1000 nm.

Problems of improving the efficiency of the Monte Carlo numerical simulation of solar radiation propagation in the Earth’s atmosphere by transition from sequential to parallel computations are discussed. A new parallel algorithm oriented to a computational system with the NVIDIA CUDA enabled graphics processor is presented. The efficiency of parallelization is analyzed by an example of calculating the upward and downward fluxes of solar radiation both in a vertically homogeneous and in an inhomogeneous model of the atmosphere. The results of testing the new algorithm under various atmospheric conditions including continuous single-layered and multilayered cloudiness are presented, with allowance for selective molecular absorption and without regard to it. The results of testing the code using video cards with different computational capabilities are analyzed. It is shown that the changeover of computing from conventional PCs to the architecture of graphics processors gives more than a hundredfold increase in performance and fully reveals the capabilities of the technology used.

An atom-atom interaction potential for the H₂O–A system is proposed in a form that depends on the normal coordinates q of an H₂O molecule. Vibrational and rotational corrections to the effective potential for H₂O–He and H₂O–Ar systems are calculated and their impact on the calculated broadening coefficients γ is analysed for the absorption lines of different vibrational H₂O bands in the case of broadening by helium and argon. It is shown that excitation of the stretching modes of vibrations in the H₂O molecule leads to an increase in the calculated broadening coefficients γ. Accounting for rotational corrections, γ increases by 15% for the lines with rotational quantum number K_a = 9 for the lower transition state in the case of broadening by He and by 4% when broadening by Ar.

Absorption spectra of methane in the 11000–11400 cm^–1 spectral region were recorded with an IFS-125M Fourier spectrometer at pressures from 11 to 100 mbar, a room temperature, and a spectral resolution of 0.03 cm^–1. A multipass cell 60 cm long with 44 passes provided a total path length of 2640 cm and threshold sensitivity to absorption of about 10^–8 cm^–1. Line centers, intensities, self-broadening, and selfshift coefficients of methane lines were determined by fitting Voigt profile parameters.

The glory formation (optical phenomenon observed in clouds) is considered in the context of new experimental data acquired during the cloud microphysics investigations with the Roshydromet YAK-42D aircraft-laboratory in polar and central regions of Russia. Data on the cloud particle-size distribution are presented and conditions for occurrence of the glory on these clouds are discussed.

We have characterized the large-scale smoke pollution of the European territory of Russia (ETR) and adjoining areas in July 2017, caused by long-range transport from forest-fire areas in Siberia, confirmed by calculations of ten-day back trajectories of air mass motion to the ETR urban area, spanning Archangelsk to Rostov-on-Don. The smoke-laden ETR area with an AOD > 0.3 (average value being 0.43 and maximal value being 2.5) on July 25, 2016, covered 5 million km², and the total smoke mass was ~1.2 million tons. It is shown that the daily average mass concentration of aerosol with particle sizes less than 2.5 μm exceeded the corresponding maximum permissible concentration in the Moscow region during the period from July 24 to 27, 2016. The influence of local sources on aerosol and gas pollution of atmospheric air was estimated. The smoke haze in 2016 was found to be deficient in carbon monoxide as compared to smoke pollution in 2010. It is shown that the thermal and wind stratification in the atmospheric boundary layer markedly influenced the pollution level in the smoke-laden urban atmosphere. Smoke aerosol radiative effect was estimated. The average aerosol radiative forcings at the top and bottom of the atmosphere over ETR on July 25, 2016, were–29 and–53 W/m², and extreme forcings reached–112 and–215 W/m², respectively.

The temperature dependence of the atmospheric ozone generation rate was studied based on measurements in a reference area. The type of this dependence is determined by the method based on the comparison of variations in the ozone concentration when a hot or cold wave passes above the measurement post. This approach allowed us to derive for the first time the quantitative, but not qualitative, dependence type. The coefficients of the expression used depend on both the air temperature and initial ozone concentration. Thus, at the long-term minimum of the surface ozone concentration (1999) at a temperature of 30°C, its increase of 5 μg/m³ corresponded to a temperature change of 1°C. At a maximal concentration (2001) and the same temperature, the increase is almost 25 μg/m³ per 1°C. In the intermediate periods (1997 and 2010), it was about 14 μg/m³ per 1°C. The analysis shows that the quadratic character of the given dependence is conditioned by the nonlinear increase in reaction constants and the quadratic increase in hydrocarbon emissions by vegetation with increasing air temperature.

Spectral line profiles are used to process experimental spectra when solving the inverse problem of computing the collisional parameters of the profiles [1]. The difference in their shapes is due to different physical conditions (hard/soft collisions, high/low pressures, etc.). Numerous different profiles are used in the study of the spectral line parameters of carbon dioxide, methane, methyl halides, and other molecules. The diversity of the line profiles used in the systematization of spectral line parameters adds complexity to the structures of data available in information systems and to the structures of individuals involved in ontological descriptions of the spectral line properties, which characterize the line profiles. A brief classification of spectral line profiles and their parameters is given, and the results of the systematization of spectral data relating to different line profiles used in processing carbon dioxide spectra are presented. The line profiles available in the library are described, and a system is built for importing spectral line parameters derived from the solution of the direct and inverse problems. Computer software for an automatic description of the properties of the solutions imported has been developed. The basic properties of the spectral data compiled in the W@DIS information system provide a description of the outcome of the imported data quality assessment.

Wavefront aberrations at the entrance aperture of the Large Solar Vacuum Telescope were measured with a wavefront sensor of the adaptive optics system by a sunspot. To calculate the image shifts, a correlation algorithm with quadratic interpolation of the correlation function maximum position is used. The quality of astronomical vision, characterized by the Fried length, was estimated from the same experimental data as the statistical characteristics of the fluctuations of the coefficients of expansion of wavefront aberrations in Zernicke polynomials. The results were obtained at a Fried length of 51.6 mm in a sample 43 s long with a sampling frequency of 70 Hz. The means and standard deviations of the expansion coefficients are calculated. The analysis of the given spectra shows that the wavefront aberrations should be compensated in the frequency band 0–20 Hz for the effective correction of the images formed.