Home – Home – Jornals – Atmospheric and Oceanic Optics 2021 number 12

Two spectra of the ¹⁸O-enriched ozone were recorded at the Fourier spectrometer of Reims in the range 3400-5600 cm^-1. The experimental centers of 12 vibrational-rotational bands of the ¹⁶O¹⁶O¹⁸O isotopologue were determined from the analysis of the spectra. They were compared with theoretical calculations based on the potential energy surface of the molecule.

Water vapor continuum absorption in the H₂O-N₂ mixture is examined on the basis of the CKD model and using the line shape with parameters found from fitting the calculated absorption coefficients to the CRDS data in the 4000-5100 cm^-1 window. Differences of these two definitions are analyzed as applied to the IR region. It is shown that the CKD continuum includes the absorption due to excess of the line contour over the Lorentzian one at distances less than 10 cm^-1 from the line centers. The possibility is examined of extracting the absorption by additional objects (like water dimers) when calculating the Н₂О-N₂ continuum absorption on the basis of the ATLW approach.

A combined experiment aimed at the study of the air composition over all the seas of the Russian Arctic was carried out in September 2020 with the Optik Tu-134 flying laboratory. The experiment included sampling the atmospheric aerosol in a layer of 200 to 9000 m above the sea level and determining the concentration of saturated hydrocarbons ( n -alkanes) in aerosol particles. Saturated hydrocarbon compounds С₉Н₂₀-С₂₇Н₅₆ were detected. The main mass of this class of organic compounds is concentrated in the narrower range С₁₀Н₂₂-С₂₀Н₄₂. The concentrations of n -alkanes in aerosol over all the seas were low (9.3-12.6 ng/m³). The only exception was the Chukchi Sea, over which the concentrations reached 37.7 ng/m³.

According to monitoring data at AERONET stations in Beijing region in the 21th century, the aerosol optical depth can attain 4.0-4.5 during a dust haze. The optical and microphysical characteristic of the tropospheric aerosol are determined by the coarse mode, with a modal radius of particles of ~ 2-4 mm and a mass content of dust aerosol of 11-12 g/m². In accordance with monitoring data at the Beijing and Xinglong stations in April 2006 and at the Beijing-CAMS station in March 2021, the imaginary part of the refractive index of dust aerosol in an optically dense dust haze was comparatively small, from 0.0005 to 0.003, with the detection probability 54 and 77% at the Beijing and Xinglong stations, respectively. The spatial distribution of the aerosol optical depth and the wind field reanalysis data are analyzed. The analysis has shown the long-range dust aerosol transport from Takla-Makan desert to Northern China Plain in April 2006. The aerosol radiative forcing at the top and bottom of the atmosphere are calculated for the period of dust haze propagation in China. Its efficiency is shown to be 85 W/m² at the top of the atmosphere and attains 135-140 W/m² at the bottom in the Beijing region. Using the wind field reanalysis data, aerosol optical depth monitoring data, and retrievals of the optical and microphysical characteristics of the tropospheric aerosol, the dust aerosol mass flux from Takla-Makan desert to Northern China Plain and the daily total dust aerosol mass transport are estimated to be ~ 1.5 ton/s and 1.5 million tons, respectively.

The results of experimental study of the condensation activity of particles of different size carried out in October 2020 till June 2021 with use of an AZ-10 optical counter, equipped with a system for artificial humidification of atmospheric aerosol collected, are considered. Hygrograms of the total aerosol scattering coefficient were simultaneously measured with a M903 integral nephelometer. The atmospheric conditions and aerosol characteristics during the measurement period were typical, which was confirmed from the comparison with long-term series of the condensation activity parameter for the scattering coefficient at an angle of 45°.

In a Large aerosol chamber of the IAO SB RAS, experiments were carried out to simulate the smoke aerosol formed as a result of burning pine wood, with different ratios of smoldering and flame combustion modes. The variability of the chemical composition of mixed smokes at the stage of their formation and during 2-day aging under UV irradiation and dark aging was revealed. The dependence of the mass concentrations of light-absorbing carbon-containing particles on the mixing parameter of smoldering and flame combustion modes is considered.

Multiple scattering in cirrus clouds occurring in lidar sensing of the atmosphere is studied in Monte-Carlo simulation with the use of model phase functions appropriate to crystal cloud particles of 20-100 mm in size. Critical analysis of some common methods for multiple scattering correction in cirrus clouds is presented. Sensing of cirrus clouds and stratosphere aerosol from the Earth surface with signal calibration at 30 km is numerically simulated. A significant deformation of the altitude profile of the backscattering coefficient at cirrus clouds and above without multiple scattering correction is shown, meanwhile the error in the optical depth of clouds is small. An iteration multiple scattering correction procedure is suggested and verified in numerical simulations. The comparison between the simulation and experimental data is performed.

The results are presented of atmospheric experiments on compensation for the artificially introduced initial aberrations of the wavefront of a focused laser beam using the aperture sounding method based on an atmospheric backscatter signal from an additional source at a different wavelength. It is shown that adaptive compensation can reduce the amount of wavefront distortions, increase the backscatter signal, and restore the focusing of the main laser beam

The sequence of appearance of various atmospheric discharges (lightning, elve, and blue jet) shown on video from the International Space Station is analyzed. For comparison, experimental data on the formation of diffuse, corona, and apokampic discharges with participation of cylindrical and spherical streamers are used. It is assumed that the formation of the elve filmed from the space is initiated by extensive discharges in clouds with subsequent formation of lightning closed to the Earth in this area. In this case, the lightning reaches the positively charged upper cloud layer. The dense plasma of the upper part of the lightning initiates the development of a blue jet, consisting of cylindrical streamers of the ionization wave.

The operation of an anti-jamming modem for wireless remote communication with deep-sea vehicles using ELF radio signals with quadrature intrapulse phase modulation (QIPPM) is described. In QIPPM, the signals quadrature are manipulated by mutually orthogonal binary sequences, which allows a radio anti-jamming pulse to transmit various code combinations, which are control and communication commands. It is shown that the technique for transmitting control commands by QIPPM gives an energy gain of about 3 dB over the method of transmitting information using phase shift signals. Therefore, the maximum transmission depth of control commands to underwater objects increases by up to 2 times.

The dynamic (temporal) characteristics of adaptive optics systems operating through a turbulent atmosphere are analyzed. An analytical calculation of the Strehl parameter is used based on the results of the theory of optical wave propagation in randomly inhomogeneous media. The analysis uses a model of the active correcting mirror. A traditional adaptive optics system with a finite response time is described as a dynamic constant lag system. In such a system, the admissible time delay turns out to be comparable with the time of transport of turbulent inhomogeneities through the radius of coherence by the average wind speed. An expression is derived which connects all the most important parameters of the system: the accuracy and frequency of the wavefront sensor, the size of the aperture of the optical system, the parameters of the atmosphere: the Fried parameter and the wind speed with an achievable level by the Strehl parameter. Differences between open and closed loops in AO systems are analyzed. The possibilities of the "predictive" algorithm for adaptive correction are shown.