Vol 32, No 2 (2019)

The results of experimental and theoretical studies of femtosecond laser pulse filamentation with use of a bimorph deformable mirror are presented. The mirror allows controlling the position of the filamentation domain throughout a model path due to phase distortions of different parts of a laser beam, determining localization of filaments and high-intensity channels in a beam cross section, and forming long (>100 m) high-intensity (10¹¹–10¹² W/cm²) weakly diverging plasma-free channels.

A high-resolution vibrational-rotational absorption spectrum of НD¹⁶О molecule has been studied in the visible region from 16 600 to 17 400 cm^–1 using LED-based Fourier-transform spectroscopy. The spectrum was recorded using a IFS-125M Fourier-transform spectrometer with a resolution of 0.09 cm⁻¹. A high-brightness 3HP LED was used as a source of radiation. For the measurements, we used a White-type multipass cell with an optical path length of 2880 cm. The spectral line parameters (line centers and intensities) were derived from the spectral analysis. The linelist contains more than 300 transitions to (005) and (104) vibrational states. The results obtained have been compared with the calculated and experimental data of other authors.

Results on retrieving parameters of the near-surface aerosol microstructure from spectral measurements of the coefficient of aerosol extinction of light in summer are presented. The experimental data have been obtained using an atmospheric transmittance meter at 11 wavelengths in the range 0.45–3.91 μm on a horizontal path near Tomsk. The inverse problem was solved using a numerical algorithm based on the integral distribution method. In the first part of the work, the variability of the geometrical cross section of particles from the fine fraction, coarse fraction, and total ensemble is analyzed. The effect of the smoke pollution of the atmosphere on variations in microstructure parameters has been considered. It has been shown that the main contribution (73–77%) to the total cross section of near-surface aerosol is made by particles of the fine fraction. Coefficients of variation in the cross sections of particles on monthly intervals without regard to the influence of smokes are high within 53–61% for the fine fraction and 53–69% for the coarse fraction of aerosol. The correlations between the aerosol extinction coefficients at different wavelengths and retrieved parameters of the aerosol microstructure have been studied.

The optical depths of summertime clouds are statistically analyzed in the region of Ob Bay in three bounded zones over “dry” areas and areas comprising large water basins. We used experimental data, obtained onboard the European satellite ENVISAT (MERIS instrument) in 2008–2011. The shape of the probability distribution functions of the optical depths in each of the zones is determined. These functions have 3–4 modes in logarithmic coordinates. The functions were fit using a set of normal logarithmic distributions with adjusted parameters, found to be well repetitive from one year to another. The water-poor western zone is characterized by three modes; and for eastern zones, with northward-flowing rivers full of relatively warm waters, the number of modes increases to four. Very likely, the additional mode at small optical depths is explained by water evaporation, followed by condensation of water vapor. It is hypothesized that a certain role in the latter case may be played by anthropogenic emissions, owing to which the number of condensation nuclei in the atmosphere is larger in the eastern than the western zone. We present the plots of the distribution functions and tables of fit parameters that define these functions. These data may be useful in calculation of radiation budget for small territories in the region of the Yamal Peninsula.

We present a method and algorithm for inverse problem solution in satellite sounding of the atmosphere for retrieval of vertical profiles of optically active gases by joint use of high-resolution thermal and near-infrared atmospheric spectra. To show the capabilities of the method, a computational experiment was performed on retrieving the vertical profile of the main methane isotopologue with simultaneous use of the simulated thermal and near-infrared spectra. The spectra simulated are similar to those measured by TANSO-FTS/GOSAT IR spectrometer. The signal-to-noise ratio in the simulated spectra was set to 350. The model experiments show higher accuracy of retrieval of the methane vertical profile and its total column in the case when both spectral bands (thermal and near-IR) are used in comparison with the case when each band is used separately.

The possibility of retrieving, using a neural network, the columnar carbon dioxide concentration profile when sounding from a space orbit of 450 km and from a balloon at altitudes of 23 and 10 km are analyzed. The use of a priori data on temperature, pressure, and reflected and scattered signals is considered. The errors of retrieval of the columnar CO₂ are 0.15% and 0.5% at altitudes lower than 2 km for lidar with a telescope diameter of 1 m and laser pulse energy of 50 μJ at a resolution of 60 km.

Synoptic processes that occurred in the Tomsk region between 1993 and 2016 are analyzed. A significant decrease in the difference between the frequency of cyclones and anticyclones over the past decade is revealed. There are tendencies to a decrease in the frequency of Arctic air mass invasion, and to an increase, of subtropical and tropical air masses.

We describe the current state and technical characteristics of Tropospheric Ozone Research (TOR) station, created 25 years ago to monitor atmospheric composition, basic meteorological variables, and other parameters. The multiyear observations showed that the air quality on the territory of Akademgorodok in Tomsk has been substantially degraded since the creation and development of the Special Economic Zone on its territory.

The work is aimed at the improvement of the model of a turbulent atmosphere at the Large Solar Vacuum Telescope site using the analysis of the energy turbulence spectrum in a wide range of frequencies and deformations of the vertical profile of the structure parameter of the refractive index of air in the atmospheric boundary layer (up to 1 km), depending on the energy of the surface turbulence.

A software-controlled photoacoustic spectrometer designed on the basis of a TEC-520 diode laser (output power 30 mW, coarse tuning range 6060–6600 cm⁻¹, bandwidth ∼5 × 10^–5 cm⁻¹, fine tuning range is 0–2.5 cm⁻¹), WS-UIR laser wavelength meter (relative error Δλ/λ ∼ 10^–8), and resonance photoacoustic detector with a threshold sensitivity of ∼3 × 10^–10 W cm⁻¹ Hz^−1/2 is described, as well as techniques and software developed for measurements and spectra processing. The water vapor spectra are analyzed.

The results of remote detection of objects containing explosives with a lidar detector of traces of explosives in combination with a portable express gas chromatograph are presented. It is shown that the lidar detector of traces of explosives confidently detects the simulators of TNT, hexogen, and PETN from a distance of 5 m when sounding the surface of a sample. Laser action on the sample surface causes desorption of vapors, which are reliably detected by the gas chromatograph. It is shown that the joint use of the laser sounding and gas chromatography techniques makes it possible to increase the reliability of detection of explosives. The prospects of using the gas chromatography in the development of laser sounding techniques are determined.