Vol 29, No 6 (2016)

The reconstruction of the spatial intensity distribution of structurally stable axially symmetrical beams in free space optical data transmitting channels has been studied experimentally. The structure transformation invariants of а beam as а space code bearer are discussed. The correlation and dispersion parameters of a random process of optical density modulation are estimated; a possibility of their multiple differences in different directions perpendicular to the beam axis is shown.

A series of experiments aimed at studying the effect of combustion regimes of typical Siberian biomasses on the optical, microphysical, and physical-chemical properties of smoke aerosols was performed in the Large Aerosol Chambe, Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences. A comprehensive data analysis showed that temperature regime of Siberian pine and coniferous tree burning has a key effect on the formation and time dynamics of all smoke characteristics. The polarization spectronephelometer measurements of light scattering are used to determine the size distributions and absorption indices of particles. Particles in the smoldering phase are weakly absorbing, but the mixed phase contains a strongly absorbing fine component produced in open flame phases. We studied microstructure characteristics of aerosols by the analysis of morphology and elemental composition. Groups of soot and organic particles were determined as micromarkers of emissions in open flaming and smoldering phases, respectively. The organic and elemental carbon contents, origin and concentration of chemical compounds in the water-soluble ion fraction exhibit a strong dependence on the combustion phase. Sugar anhydride (levoglucosan) was determined in the smoldering phase as a stable molecular marker of Siberian pine burning. A number of specific markers of coniferous wood burning were identified among the chemical compounds. Smoke aging is accompanied by condensation of organic and inorganic compounds, transformation of aerosol surface chemistry, and the formation of the group of potassium-rich particles, all demonstrating the complexity and variability of the chemical composition and microstructure of atmospheric aerosol pollution during Siberian forest fires.

Continuous sampling of aerosols is carried out on the north-western (NW) coast of the Kandalaksha Bay of the White Sea. Aerosol matter from 30 filters collected in summer and autumn, 2013, and spring, 2014, was studied by scanning electron microscopy. The elemental composition of aerosol matter was determined by the inductively-coupled plasma mass-spectrometry (ICP-MS). The major portion of aerosol particles collected in summer is of biogenic origin. Heavy metal concentrations in aerosols are at the Arctic background level. The distribution of trace element concentrations is characterized by simultaneous peaks of different elements. The backward trajectory analysis shows an increase in Ni and Cu concentrations corresponding to the arrival of air masses from the western part of the Kola Peninsula. That suggests the influence of smelters.

A method is proposed for solving the inverse problem in multifrequency lidar sensing of the atmospheric aerosol. The method allows retrieving the spatial distribution of volume concentrations of aerosol components, the aerosol particle size distribution integral over the sensing path, and the complex refractive index of the particles, without any additional data for the lidar calibration and supplement of the inverse problem definition. The method is based on the assumption that the average sizes, their variances, and the complex refractive indices for the particles of each aerosol component do not change along the sensing path, and the number of the lidar spectral channels is greater than the number of aerosol components. In this case, the system of equations for the spectral-spatial readings of the lidar signal becomes overdetermined, and its numerical solution allows deriving not only the microphysical parameters of the aerosol, but also the lidar calibration constants at operational wavelengths. Examples of processing the elastic and Raman scattering lidar signals in a model aerodispersive medium at the wavelengths λ₀ = 0.355, 0.532, and 1.064 μm and λ_R = 0.387 and 0.607 μm, respectively, are presented. It is shown that microphysical parameters of the fine aerosol component (with particle sizes less than 1–2 μm) can be retrieved from the signals with an error less than 10%, and the error in retrieving the microphysical parameters of coarse particles depends strongly on their contribution to the total medium transmission. The aerosol extinction and backscattering coefficients calculated on the basis of the aerosol microphysical parameters retrieved differ from their actual values by a few percent.

Three algorithms of the Monte Carlo method for the calculation of the pulse reaction in channels of laser sensing and communication are considered: the local estimation algorithm, double local estimation algorithm, and proposed modified double local estimation algorithm. Results of testing the algorithms and their comparison are shown. For the case of a homogeneous medium, the performances of the algorithms are compared. The comparison shows conditions for which the proposed algorithm has the advantage over the double local estimation algorithm. The contribution of double, triple, and higher multiplicity scattering is estimated. The high contribution of multiple scattering justifies the applicability of the Monte Carlo method for solving such problems.

We discuss the results from the analysis of the hydrological input data for a model of Siberian river runoff for the 21st century. The INM, CRNM, GFDL, MIROC5, and HadGEM model calculations according to the RCP 8.5 scenario of the IPCC CMIP5 Project were used for the analysis. The calculations show a positive centennial trend for all the models. These data were used for the calculations of Siberian river discharge to the Arctic Ocean. The river runoff calculations in accordance with the data also indicate a positive trend, though with a different runoff magnitude.

Ozone sources and factors responsible for anomalous surface ozone concentrations are discussed. Foreign observations and measurements of surface ozone in Moscow, nearby suburbs, and on the territory far removed from the megalopolis, as well as on the coast of the Black Sea, are used as an example to illustrate the interrelations between elevated surface ozone concentrations, air temperature, and transport speed in the planetary boundary layer, and to show the dependence on advection of ozone and its precursors. Studies of factors responsible for ozone episodes and causes of decreased ozone concentrations under meteorological conditions favorable for photochemical ozone production are the basis for interpretation and correction of model ozone predictions.

Using a numerical mesoscale model of the atmospheric boundary layer, the dynamics of air streams in the Norilsk valley is studied for typical weather conditions. It is shown that the orographic features of the region form a wind field, horizontally inhomogeneous and highly variable in altitude. The fields of local and regional dust and heavy metal precipitations are numerically reconstructed on the basis of expedition data on snow cover pollution in the environs of the Norilsk copper plant.

Results of experimental studies of the gas mixture (laser active medium) effect on the lasing energy and overall efficiency of excimer discharge ArF (193 nm), KrCl (222 nm) KrF (248 nm), and XeCl (308 nm) lasers operating in buffer-free gas mixtures are presented. The optimal (in terms of maximum radiation energy) ratios of the gas components of the excimer laser active media are found, at which efficient operation is achieved with a sufficiently high power of the laser radiation. It is confirmed experimentally that for the rare gas halide discharge pumped excimer lasers the presence of a buffer gas in the active medium is not required for efficient laser operation. For example, in two-component excimer laser gas mixtures, containing working rare and halogen-containing gases, laser pulse energy of up to 170 mJ and high pulsed power of laser radiation of up to 24 MW have been attained for the first time for pulsed gas-discharge excimer lasers operating on electronic transitions at excimer ArF*, KrCl*, KrF*, and XeCl* molecules pumped by a transverse electric volume discharge of a low-pressure buffer-free gas mixture. A overall efficiency maximum of up to 0.8% was experimentally attained for binary gas mixture of KrF and XeCl lasers.