Home – Home – Jornals – Atmospheric and Oceanic Optics 2017 number 11

The structure of the interference field resulted from the combination of the wave fields of subbeams with apertures located on sides of a regular hexagon is studied. The field on each subapertures is a truncated Gaussian beam with the constant phase shift between neighbor subapertures so as the total phase incursion becomes equal to 2p when walking around the hexagon. It is ascertained that the total angular momentum of the beam synthesized in such a way is zero. There is a region in the central part of the beam where the integral of the density of orbital angular momentum gives the unit orbital angular momentum, and the circulation of the phase gradient at the boundary of this region gives unit topological charge.

The results of experimental studies of the formation of a transverse structure of a laser beam after multiple filamentation are presented. Ring structures of radiation are formed around individual filaments in the transverse beam cross section inside the region of multiple filamentation, and at a dozen meters from it a common ring structure begins to form 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 wave length and is mainly concentrated in the short wavelength region. The PFC spectrum broadens more and more symmetrically and covers the range 600-1100 nm.

Issues about improving the performance of Monte Carlo numerical simulation of light transport in the Earth’s atmosphere by moving from consecutive calculations to parallel ones are discussed. A new parallel algorithm oriented to a computing system with a graphics processor that supports the NVIDIA CUDA technology is suggested. The efficiency of parallelization is analyzed on the basis of calculating the fluxes of downward and upward solar radiation in both vertically homogeneous and heterogeneous models of the atmosphere. The results of approbation of the new code under various atmospheric conditions including continuous single-layered and multilayered clouds and selective molecular absorption are presented. The results of testing the code using video cards with different compute capability are analyzed. It is shown that the changeover of computing from conventional PCs to the architecture of graphics processors gives more than a hundredfold gain in performance and fully reveals the capabilities of the technology used.

The problem of taking into account the influence of polarization is considered for correction of satellite images of the Earth surface in the visible wavelength range for the distorting effect of the atmosphere. A program complex for calculation of the radiation components forming the satellite images has been developed with and without allowance for radiation polarization in the approximation of the homogeneous surface. Conditions are established under which the neglect of the radiation polarization can lead to significant errors in reconstruction of the reflection coefficients of weakly reflecting surfaces.

An atom-atom interaction potential for H₂O-A system is proposed in the form which depends on the normal coordinates q of H₂O molecule. The vibrational and rotational contributions in this potential are calculated for H₂O-He and H₂O-Ar systems. It is shown that the excitation of the stretching modes of the vibrations in H₂O molecule leads to an increase in the calculated broadening coefficients γ. In the case of broadening by He, γ increases by 15% for the lines with the rotational quantum number Ka = 9 of the lower state in the transition. In the case of broadening by Ar, this increase is 4%.

In continuation of works on the determination of cyclic tree stem CO₂ efflux, vacuum-extracted gas samples of large woody roots of Siberian stone pine and Scots pine are studied. Spectral and cross- spectral analyses reveal the cyclic character of variations in the chronologies. This behavior of total pressure and CO₂ in large roots testifies to possible cyclic diffusion of CO₂ from large roots into soil and then into the atmosphere, which can be considered as a new feature of autotroph respiration. An attempt is made to revise previously obtained results in some related works on the basis of cyclic large root CO₂ efflux.

We discuss the results of spectral measurements of aerosol optical depth (AOD) of the atmosphere, carried out in warm periods of 2011-2016 in the Arctic settlement Barentsburg (Spitsbergen Archipelago). The statistical characteristics of seasonal and interannual variations in atmospheric AOD in the wavelength range 0.34-2.14 μm are presented. The average AOD (0.5 μm) for the six-year period of observations had been 0.086, including the fine-mode AOD component 0.062 and coarse-mode AOD component 0.024. It is shown that the seasonal variations were best manifested in the decrease in modal (most probable) values of fine-mode AOD component from 0.055 in spring to 0.025 in autumn. As compared to the preceding (pre-2011) period, we noted a closer correspondence in the average AOD values between spring and summer, primarily due to a decreasen the content of fine-mode aerosol in spring and its increase in summer. The summertime AOD growth is most likely due to episodic outflows of smoke aerosol from boreal zones of Eurasia and North America.

Aerosol samples PM_2.5 (44 pieces) collected in 2013-2014 on the White Sea coast were analyzed on trace-element concentrations. The sampling period was divided in conventional seasons: a snow-cover season with minimal influence of terrestrial dust and two snowless seasons with distinct influences of both anthropogenic and terrigenic sources. The snowless seasons are featured by the highest dispersion of element concentrations. The snow-cover season differs from snowless ones by prevalence of the western direction of transport. The direction analysis of atmospheric transport of pollutants allows distinguishing few groups of elements of natural (La, Nd, Sr, Ga) and mainly anthropogenic origin (V, Ni, Cu and Pb, Bi, Cd).

Unique large-scale smoke haze over European part of Russia (EPR) and adjacent territories in July 2017 was caused by long-range smoke transport from the forest fires in Siberia, which is supported by 10-day back trajectories of air mass transfer in cities at EPR, from Archangelsk to Rostov-on-Don. The territory with AOD > 0.3 (average value is 0.43 and extreme is 2.5) bounded by the coordinates 45-70N and 20-60E reached about 5 million km² 25.07.2016, and the total smoke mass over EPR comprised  1.2 million tonns. It is shown that the daily average mass concentration of aerosol with particles smaller then 2.5 m exceeded the maximum permissible concentration at the majority of ecological monitoring stations in Moscow during 24.07-27.07.2016. The influence of local sources of carbon monoxide, nitrogen oxides, and aerosol on the air pollution was estimated. Carbon monoxide deficiency in smoke haze 2016 as compared with smoke haze 2010 was ascertained. It is shown that temperature and wind stratification may markedly influence the pollution level in the smoky urban atmosphere. Smoke aerosol radiative impact was evaluated. On July 25, 2016, the average aerosol radiative forcings over EPR at the top and the botton of the atmosphere were equal to -29 and -53 W/m² and extreme forcings reached -112 and -215 W/m², respectively.

The temperature dependence of the atmospheric ozone generation rate on the air temperature is studied on the basis of measurement data in a background area. The type of this dependence is ascertained by the method based on the comparison of variations in the ozone concentration when waves of heat and cold pass through the measurement site. This approach allowed us to derive the quantitative, but not qualitative, dependence for the first time. The coefficients of the expression depend on both the air temperature and initial ozone concentration. Thus, at a long-term minimum of surface ozone concentration (1999) at a temperature of 30 °C, its change by 1 °C corresponds to the increase in the ozone concentration of 5 μg/m³. At a maximum of concentration (2001) at the same temperature, the increase can make nearly 25 mg/m³ per 1 °C. In the intermediate periods (1997 and 2010), it is about 14 μg/m³ per 1 °C. The analysis shows that this dependence is quadratic due to a nonlinear increase in the constants of reactions and quadratic increase in the hydrocarbon emissions by vegetation with the air temperature.

The effects of penetrating short-wave radiation on the Arctic Ocean water temperature and sea ice state have been studied with an ocean-ice general circulation model. Numerical experiments show that during summer period, while the ice thickness is reduced to 2 m, the absorption of penetrating radiation results in the formation of the subsurface temperature maximum. This temperature maximum gradually decays during the fall season due to strong vertical mixing and heat flux to the ice and underlying waters.

We examine variations in airglow in the 555.7 nm atomic oxygen line and the ONI index of the El Niño Southern Oscillation (ENSO) phenomenon in 1997-2017. Correlation between these parameters is revealed. During the prolonged La Niña episode of 1991-2001, the 557.7 nm emission depression was observed, where as in the extreme El Niño episode of 2015-2016, the 557.7 nm emission increased. We discuss possible mechanisms of the ENSO phenomenon effect on the airglow. A tentative conclusion has been made that long-term and interannual intensity variations in the 557.7 nm emission can result from the joint effect of solar activity and changes in the global atmospheric circulation.

Wavefront aberrations at the input aperture of the Large Solar Vacuum Telescope were measured by a wavefront sensor of the adaptive optics system by a sunspot. To calculate the image displacement, a correlation algorithm with quadratic interpolation of the correlation function maximum position was used. The quality of astronomical vision, characterized by the Fried radius, was estimated from the same experimental data as the statistical characteristics of the fluctuations of the coefficients of the wavefront aberrations’ expansion in Zernike polynomials. The results were obtained at a Fried radius 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 were calculated. The analysis of the given spectra implies that the wavefront aberrations should be compensated in the frequency band 0-20 Hz for the effective correction of the images formed.