Home – Home – Jornals – Atmospheric and Oceanic Optics 2023 number 3

Three-dimensional ab initio potential energy surfaces of the interacting triplet states ³ A ₂ and ³ B ₁ of the О₃ molecule are constructed within the diabatization approach implemented in the MOLPRO package. These two states are responsible for the strongest singlet-triplet transitions in the Wulf band of O₃. The molecular orbitals are optimized by the state-averaged CASSCF with the active space CAS(18, 12) involving three electronic states ( X ¹ A ₁, ³ A ₂, and ³ B ₁). The correlation energy is computed by icMRCI(Q). The impact of the basis set size on the accuracy of both the adiabatic excitation energy and origins of the vibronic transitions is analyzed.

From the known experimental data, the parameters of the non-polynomial analytical model γ(sur) for the broadening coefficients γ of the ammonia molecule absorption lines by the pressure of helium, argon, nitrogen, oxygen, air, hydrogen, carbon dioxide, and its own pressure are determined. The accuracy of the experimental data recovery by the model γ(sur) varies from 3.3 (nitrogen broadening) to 8.5% (carbon dioxide broadening). The comparison with the polynomial representation and with the results of calculations of these coefficients by the semi-classical method is made.

The criterion for stopping the intensity collapse is established in the approximation of the nonlinear Schrödinger equation for the problem of self-focusing of high-power femtosecond laser radiation in an optical medium. Using propagation of a femtosecond laser pulse in air as an example, it is shown that the collapse stops when the role of diffraction increases due to a decrease in the radius of the laser beam, and occurs not at a point, but at an interval in front of the nonlinear focus, where the self-phase modulation of the radiation due to the plasma nonlinearity prevails over the Kerr effect. The result (collapse stop criterion) makes it possible to take into account the features of the nonlinear activity of various optical media during the propagation of high-power femtosecond laser pulses; in particular, the role of nonlinear absorption is determined under the conditions considered.

We present the results of the assessment of multiyear variability for the parameters of single-layer cloud fields over the territory of Western Siberia in summer in 2001 to 2019 based on MODIS data. The seasonal average proportion of coverage by single-layer clouds of different types and values of their features are determined based on the results of cloud classification from summer (June, July, August) daily satellite images of the target region. Parameters of single-layer clouds are considered for three latitudinal zones of Western Siberia: southern (< 60° N), transitional (60-65° N), and northern (> 65° N). We found linear trends of the proportion of coverage by different single-layer cloud types and of their parameters: optical thickness, effective particle radius, waterpath, and cloud top height. A discussion of the results is given. The greatest variability of the physical parameters considered in this work is characteristic of the vertical development and low-level clouds in the northern and transition zone of the target region. The effect of anomalous blocking anticyclones on some features of different cloud types in the considered latitudinal zones of Western Siberia is shown.

Quantitative estimates of changes in wind energy resources in the high latitudes of the Northern Hemisphere are obtained using ERA5 reanalysis data for 1979-2021. The wind energy potential (WEP) was estimated during the analysis. According to the ERA5 reanalysis data, a marked increase in the WEP over the Greenland, Norwegian, Barents, Kara, and Chukchi Seas, as well as over the European territory of Russia in winter, over the Kara and Norwegian Seas in spring, and a general increase in WEP along the Arctic coast, in particular over its Russian sector in summer and autumn, are noted under the current climate regime. The noted changes in WEP quite well correlate with the retreat of sea ice in the Arctic, as well as with the leaf area index, which characterizes the roughness of the underlying surface in the high latitudes of the Northern Hemisphere. The increase in the proportion of the year when wind generators are capable to operate over the Russian Arctic makes the region quite promising for the use and development of wind power in the context of the climate change.

This paper is devoted to assessing the long-term variability of the parameters of sudden stratospheric warmings (SSW) from 1979 to 2021. The values of the mean zonal air temperature at a latitude of 80°N and zonal average wind speed at 60°N at altitudes of 10 hPa are used as a criterion for estimating the SSW. Major SSWs are classified according to their types - with split of the polar vortex (PW) and with PW displacement. Estimates are made of the variability of such SSW parameters as the number of events per winter, SSW type, SSW duration, start date and maximal temperature during SSW over the past 42 years. No trend changes are found, but oscillatory behavior of the parameters is observed in the high-latitude stratosphere.

The results of experiments carried out in the Large Aerosol Chamber of IAO SB RAS during 2021-2022 to study the optical characteristics of smoke aerosol with a long aging time (up to 2-3 days) are presented. The influence of the evolution of optical characteristics of pyrolysis and mixed smokes on the radiative forcing of smoke aerosol (RFA) at the top of atmosphere in the Arctic region in summer is estimated. It is shown that for pyrolysis smokes, the main factor that determines the time dependence of RFA is the evolution of the aerosol optical thickness, while for mixed smokes, it is also necessary to take into account the temporal variability of the single scattering albedo of aerosol particles. The dependence of RFA on underlying surface types and illumination conditions typical for the Arctic region is considered for different modes of biomass combustion.

An original statistical model of laser pulse propagation in a scattering medium is considered, which makes it possible to calculate the power of a lidar signal taking into account scattering effects of any multiplicity. A comparative analysis of the temporal structure of the signal obtained using the model suggested and alternative methods is carried out. The features of the propagation of a laser pulse from a ground-based lidar in continuous cirrus clouds are studied taking into account the effects of multiple scattering. The dependence of the multiple scattering background on the cloud optical and microphysical characteristics (extinction coefficient, degree of roughness, size and shape of ice particles) and parameters of the lidar receiving system is studied. The simulation results indicate a high sensitivity of the part of the echo signal due to multiple scattered light to variable parameters, which should be taken into account when setting and solving inverse problems.

The applicability of semiconductor methane sensors, designed to detect explosive concentrations of gas in rooms, to the study of background concentrations of methane in the atmosphere and its emissions from the water body surface is studied. An experimental prototype of the methane sensor is designed, for which, in order to increase the accuracy of determining the methane content in air, a calibration plan is suggested, which takes into account the humidity, temperature, and pressure of the environment. Laboratory and field experiments show that the TGS series sensors are capable of detecting methane concentration changes from 0.1 ppm and higher and can be mounted in floating chambers used to determine methane emissions from the water surface. An experimental setup is described. The results of calibration and selection of the best parametric model are presented. Recommendations for further development of the device are given.

The paper presents the results of the development of an active optical system (a laser monitor) to form enhanced images simultaneously in the visible and near-IR spectral regions. Imagining is carried out in the active medium of a manganese atom brightness amplifier. Images are formed for a time corresponding to the amplification (generation) pulse, which is about 25 ns for the visible region and 35 ns for the IR. Image recording is carried out using digital cameras, including those based on a Russian-made InGaAs sensor. Images of processes accompanied by background radiation formed by a single pulse of a brightness amplifier based on manganese chloride vapors are shown for the first time.

Methods for measuring the salinity of seawater are considered. The results of an experimental study of samples of common and sea salt solutions with different salinity, poured into a hollow trihedral optical glass prism are presented. To measure the angles of refraction of light, a goniometric system was used, the minimum deviation method was implemented, which has a high accuracy of determining the refractive index. With dispersion analysis of experimental results, it is proved that the refractive index of water does not depend on its salt composition. An equation is suggested which describes the dependence of the refractive index on salinity and temperature for a fixed wavelength.