Home – Home – Jornals – Atmospheric and Oceanic Optics 2017 number 5

Quasistationary approximation is formulated for the problem of stimulated Brillouin scattering (SBS) in air, which is considered as a multimode acoustic medium. In the approach suggested, the equation for the envelope of the complex amplitude of the light field is solved numerically. On the basis of numerical experiments, it is ascertained that when powerful laser radiation λ = 1.315 μm is propagating in air, the SBS effect can lead, at a sufficient power, to a significant increase in the angular divergence of laser beams.

Results of simulation of the impulse response of an atmospheric optical communication channel on scattered radiation at wavelengths of 0.3, 0.5, and 0.9 mm are considered. Our analysis shows that the maximal power of the received information-bearing signal is attained at λ = 0.3 mm for base distances between the source and the receiving system of 2-3 km and shorter. For larger base distances and low atmospheric turbidity, the maximum is attained at λ = 0.5 μm. When the atmospheric turbidity is high and the base distances are 3-10 km, the maximal power is observed at λ = 0.5 μm. However, when the base distances exceed 10 km, the maximal power of information-bearing signal is attained at λ = 0.9 μm. For a particular example of laser source and receiver system, the limiting base distance between the source and the receiver and the limiting pulse repetition frequency which is not filtered out by the communication channel are estimated using the results of calculations of the impulse response of the atmospheric communication channel at λ = 0.5 μm.

Possibilities of retrieving the asymmetry factor of the atmospheric aerosol phase function from spectral measurements of light extinction and scattering are analyzed. An empirical formula for parameterization of the relation between the asymmetry factor and Ångström exponent and complex refractive index has been suggested. Several approaches to the determination of the asymmetry factor from data of integrating nephelometers are considered. An empirical relation connecting the asymmetry factor with the ratio of the scattered radiation into forward and backward hemispheres has been derived. Using the data of field measurements in Saint Petersburg suburbs in 2015, the asymmetry factor has been calculated at three wavelengths.

Specific features of scattering and absorption of laser radiation by an ensemble of two identical microcapsules are theoretically investigated. Each capsule is modelled by a two-layered spherical micron-sized particle consisting of water core and light absorbing polymer shell. By virtue of the numerical electrodynamics technique it is shown that the internal particles structure, as well as their mutual arrangement affect the character of the spatial distribution and amplitude characteristics of the power absorbed. The highest values of the absorbed power density in the microcapsule dimer could be achieved if the particles are displaced relative to each other by a distance of about diameter (strongly absorbing particles) or if the particles are in the geometric shadow of each other (weak absorption).

The first estimates of a contribution of midges into extinction of optical radiation for background conditions of summer in Western Siberia are received. Values of the midges extinction coefficient received on the basis of experimental data on a wavelength of 1.06 mm change from 0 to 0.14 km^-1. The estimate of the mean value of midges extinction coefficient in visible and infrared regions makes 0.07 km^-1. It is shown that the relative contribution of midges into extinction coefficient of optical radiation in the 0.5-16 mm is essential and changes on average from 26 to 63%.

We estimated a change in the methane concentration during the periods of atmospheric blocking observed in summer time. Methane concentrations have been derived from continuous measurements carried from 2005 to 2013 in Siberia at Japan-Russia Siberian Tall Tower Inland Observation Network (JR-STATION). The blocking events were identified in accordance with Tibaldi and Molteni criteria and surface temperature anomalies with the use of the Era-interim reanalysis data. The events lasting more than five days have been included in the blocking event list (13 in total). All found events are separated into two groups by spatial coverage (bordering and sector) and three groups by duration (5-6, 7-9, >10 days). We analyzed these events for natural fires and precipitation anomalies before them. It was found that almost all blocking events selected caused an increase in the methane concentration independently of the duration and spatial coverage. The degree of impact differs depending on the blocking characteristics and concomitants. On the basis of these differences, four main groups are distinguished, characterizing the “blocking-methane concentration” connection: “large-long blocking / extensive fires” (maximum impact), “large-long blocking / abnormal rainfall before blocking / local fires” (next in degree of impact), “short blocking / without additional conditions” (the third), and “bordering-long blocking / local fires” (minimum impact).

A substantial temperature rise regarding long-term rates is observed in the stratosphere due to intense tropical eruptions. The detected temperature anomalies account for volcanogenic aerosol absorption of short-wave solar radiation and outgoing longwave radiation. An intermediate complexity spectral model of general circulation was used to analyze the atmospheric circulation response to variations in transmission coefficients of short-wave radiation in the stratosphere after volcanic emissions of carbon aerosols which absorb the radiation. The results show considerable differences in the Northern and Southern hemisphere responses. Surface temperature anomalies in the southern polar region may be observed for 10 years following tropical volcanic eruptions.

Correlations of latitudinal dynamics of the atmospheric moisture content (W) with quasi-biennial oscillations (QBO) of zonal wind in the equatorial stratosphere and solar activity over the north-east of Eurasia during 1979-2015 are analyzed with the use of data of AERONET sun-sky photometers (st. Yakutsk, st. Tomsk, st. Irkutsk, and st. Dalanzadgad) and ERA-Interim reanalysis, based on the regular meteorological observations, aerological and satellite information. Reliably significant correlation is found between the mean annual values of W and QBO during its eastern phase. At the same time, variations in W, depending on latitude, reveal the fundamental cycles of solar activity (Schwabe, Hale, and Bruckner).

A semi-empirical model for the description of spectral contribution of main components of natural water, including pure water, chlorophyll, yellow substance, and organo-mineral suspension into spectral light attenuation at three wavelengths of 430, 550, and 670 nm is developed based on the data from field studies conducted at Altai Krai waterbodies, i.e., Lapa, Krasilovskoye, and Bolshoye Ostrovnoye lakes, in 2014-2016. The predictive capabilities of the developed model of integral spectral light attenuation in the multicomponent aqueous medium for solving problems of complex water and environmental monitoring and rational water management are estimated.

Laser technologies used in order to provide the development of ROV sensor elements are presented, as well as the latest results in underwater robotics, where laser spectroscopy methods are applied to underwater environment monitoring. A designed submersible laser spectrometer is presented, intended for research of Raman and laser induced fluorescence (LIF) spectra. The spectrometer was developed and designed as an element of ROV sensor system for detection and measurements of organic matter concentrations in sea water. LIF spectrometer’s in situ tests in different marine areas including Arctic region are described.

We examine the main sources of uncertainties in measuring the near-infrared water vapor continuum absorption using the Fourier spectrometric complex of Institute of Atmospheric Optics SB RAS. The instrumental and methodical errors are considered, including the error in determining baseline, as well as the possible impact of nanoscale complexes of water molecules.

The description of the improvement of the experimental setup based on Fourier spectrometer Bruker IFS-125 and 30-meter multipath optical cell is given in the paper. The improvement includes the cell equipment with a system of automatic adjustment of the number of beam passes without its depressurization and ensures the cell work at high temperatures.

The system of collection and preparation of patient’s exhalation samples for medical laser photoacoustic gas analyzer is developed and tested. A comparative study of different types of exhaled air dryers is carried out. It is proposed to produce the dehumidification of expiratory sample directly in the sampling bag by freezing the moisture in the freezer, then transferring the drained sample to the analyzer via syringe. It is experimentally shown that when exposing an expiratory sampling probe packet for 10 min at -18 ^oC the water vapor content in the sample decreased by ~20 times. A gas circuit diagram of a medical laser gas analyzer is developed, which allows sterilization of the inner surfaces of the gas system using ozone.

On the basis of a common understanding of the calculation of the response R of photoelectric counters to aerosol particles, a formula for R is derived for commercially available counters with a specific geometry and the spectral characteristics of the source and the radiation detector. To correct size ranges of the counters tables are obtained using the Mie theory. The tables call attention to the difference between the complex refractive index of calibration and test particles. Ignorance of the difference can lead to large errors in the determination of particle size. The attention is drawn to the need to consider the dependence of the complex refractive index of particles in different size ranges on the relative air humidity.