Home – Home – Jornals – Atmospheric and Oceanic Optics 2016 number 5

A model of single filamentation of a high-power ultrashort light pulse has been developed on the basis of evolutionary dependences of phase and amplitude parameters of the light field derived from numerical solution of the nonlinear Schrödinger equation for air. A key role of aberrations and diffraction effects during formation of stable dynamic light structures near the propagation axis is shown. It is found that the angular divergence of post-filamentation light channel decreases with increasing radius of the laser beam at a fixed pulse peak power and reaches saturation at the radius greater than 1 mm.

Based on the numerical solution of the parabolic wave equation for the complex spectral amplitude of the wave field by using the splitting into physical factors method the fluctuations of energy density of the broadband pulsed optical radiation for various modes of Laguerre-Gaussian beam under different turbulent conditions on the propagation path were studied. It has been shown that with the increase of optical turbulence the relative variance of energy density fluctuations of pulsed radiation of femtosecond duration becomes much lower than that of continuous-wave radiation and, in contrast, may become smaller than unity. Provided the pulse duration is short the energy density fluctuations tend to decrease as the order of Laguerre-Gaussian beam mode rises. The level of residual spatial correlation of strong energy density fluctuations of pulsed radiation exceeds the level of continuous-wave intensity correlation in all examined Laguerre-Gaussian beam modes and the typical two-scale structure of spatial correlation for strong fluctuations of continuous-wave radiation in the case of pulsed radiation is less expressed.

Normalized temporal autocorrelation function of fluctuations of the scattered radiation of a focused laser beam (0.63 μm) in the surface atmosphere in precipitation (rain, drizzle), fog, and haze on a path with a length of 130 m is measured. It is found that the time correlation of the fluctuations of the scattered radiation of a focused laser beam in the rain, drizzle, fog, and haze decreases with increasing wind speed component noramal to the path at close atmospheric conditions (at close values of optical depth and particle size). The correlation time in drizzle is more than in the rain. The correlation time in haze is more than in the rain and drizzle. The correlation time in the fog is an order of magnitude or even more longer than in the rain.

Transformation of C₂H₄, CO₂ and C₂H₆ absorption spectra under condition of nanoconfinement in SiO₂/Al₂O₃ aerogel is presented for the first time. It is shown that integral intensity of confined C₂H₄ within 5700-6250 cm^-1, CO₂ within 4760-5160 cm^-1 and C₂H₆ within 2830-3030 cm^-1 are respectively by 13.3, 15, and 18 times higher than in free gas.

The description of published data on properties of spectral line parameters for deutero-substituted isotopologues of hydrogen sulfide molecule (HDS, HD³⁴S, D₂S и D₂³⁴S) is given. The majority of the properties characterize the results of vacuum wavenumber quality analysis. Two applications used for data quality analysis in information system W@DIS are described. The results of computed data quality analysis of vacuum wavenumbers are completed by the expert assessment of quality of the same set of data. The data sources containing parameters of vibration-rotational transitions and energy levels deutero-substituted isotopologues of hydrogen sulphide molecule acquired from publications are stored in databases of information system W@DIS and provided the formal description of their properties. The properties and their values are represented in ontological knowledge base and accessed in W@DIS (http://wadis.saga.iao.ru/) via Internet.

Three algorithms of the Monte Carlo method for calculation of impulse transfer function in channels of laser sensing and communication are considered: the local estimation algorithm, the double local estimation algorithm, and the suggested modified double local estimation algorithm. Results of testing of the algorithms and their comparison are considered. For a homogeneous medium, the complexities of the algorithms are compared, demonstrating under what conditions the suggested algorithm is advantageous as compared to the double local estimation algorithm. The contributions of double, triple, and higher-order scattering are numerically estimated. High contribution of multiple scattering proves the expediency of application of the Monte Carlo method for solving problems of this type.

We have proposed a method for solving the inverse problem of multifrequency lidar sensing of the atmospheric aerosol, which enables to retrieve the spatial distribution of volume concentrations of aerosol components, aerosol particle size distribution integrated along the sensing path, and the complex refractive index of the particles, without any additional data for calibration of the lidar and for supplementary definition of the inverse problem. The method is based on the assumption that the average sizes, the variance of sizes and the complex refractive index of the particles of each aerosol components do not change along the sensing path, and the number of lidar spectral channels is greater than the number of aerosol components. In this case the system of equations for the spectral-temporal readings of lidar signal becomes overdetermined, and its numerical solution allows determining not only the microphysical parameters of aerosol but also lidar calibration constants at operating wavelengths. Examples of processing of elastic and Raman scattering lidar signals of model aerodispersive medium at wavelengths λ₀ = 0.355, 0.532, 1.064 μm and λ_R = 0.387, 0.607 μm, respectively, were presented. It is shown that microphysical parameters of fine components (with particles size less than 1-2 μm) are retrieved from the signals with an error less than 10%. The error of microphysical parameters of coarse particles retrieval is strongly dependent on the significance of their contribution to the total transmission of the medium. The difference between aerosol extinction and backscatter coefficients calculated on the base of retrieved microphysical aerosol parameters and their actual values are within a few percents.

Monitoring of the state of vegetation of oil producing areas of Western Siberia for the period 2010-2015 using thematic products MODIS are carried out. The approach is suggested to assessment of the impact of various factors on the environment areas of oil and gas on the base of remote sensing data by NDVI. Testing of the approach undertaken for the technologically-disturbed areas of four oil fields in Tomsk region - Krapivinsky, Ladyzhensky, Luginetskoye, and Urmanskoye. Additionally, as the background area, the area of ​​the State nature reserve of regional importance “Oglatsky” is studied.

Twelve air temperature and humidity measurement series were carried out with the use of AKV-2 mobile station in Tomsk and its suburbs in different seasons and under different weather conditions. The urban heat island effect is shown to be observed in Tomsk in all seasons; the mean temperature increment is 2 °C in winter and 1 °C in summer. The fields of absolute humidity differ significantly for warm and cold seasons in Tomsk. It is shown that the humidity in Tomsk is mainly of anthropogenic origin in winter and of natural origin in summer.

The relative contribution of different factors into formation of the urban heat island in Tomsk is estimated. It is shown that the key factors are anthropogenic heat emissions (80-90% in winter and 40-50% in summer) and absorption of short-wavelength radiation by the urban underlying surface (5-15% in winter and 40-50% in summer), while the absorption of long-wavelength radiation by the underlying surface, absorption by moisture and admixtures, and heat loss on the evaporation contribute insignificantly. It is shown that the turbulent heat flow prevents a linear increase in the intensity of the urban heat island with an increase in the sum of radiation fluxes that ensure the energy income into the heat island region. Due to an increase in the turbulent heat flow in Tomsk, 40-50% of the absorbed energy is carried over in summer and 20-30% in winter. An equation is suggested that allows calculation of the heat island intensity in different seasons, time, and under different atmospheric conditions from weather parameters measured at a stationary site.

A narrowband VUV radiation (near a wavelength of 147 nm) corresponding to optical transitions of the heteronuclear dimer ArXe from plasma formed during the excitation of the Ar-Xe mixture at a pressure of 400 mbar with high-voltage nanosecond discharge initiated by runaway electrons was registered. Amplifying properties of the discharge plasma with respect to this radiation were found.

Particular properties of formation of the optical field in the composite spherical microcapsules of different size consisting of a polymer absorbing shell and a non-absorbing liquid core are presented. The numerical simulation shows that changes in the thickness of the shell, grown on the core fixed radius, and the coefficient of its own radiation absorption determine the nature of spatial distribution and amplitude characteristics of the absorbed power. Variations in these parameters allow changing position and peak values of the areas of the effective absorption volume of the particle and, consequently, create conditions favourable for opening the shells in the appropriate spatial areas. This is important for the solution of practical tasks associated with the problem of release of the contents of the microcapsules.

The calculations results of LED light intensity necessary for reliable visual detection of runway lights in field conditions are presented. The following groups of LED lights are considered: approach threshold lights, lights of the last 600 m of a runway, and runway end lights. Detection threshold were chosen. The effectiveness of LED lights is analyzed in different weather conditions during the night, at twilight, and in the day time, and questions of speed adjustment of LED radiation intensities in accordance with ICAO standards are considered.