Home – Home – Jornals – Atmospheric and Oceanic Optics 2021 number 9

Theoretical aspects of nonlinear propagation in air under filamentation of high-power ultrashort laser radiation with coronalike transverse intensity distribution are theoretically considered. A coronal intensity profile is assumed to be formed by incoherent superposition of several emitting sub-apertures arranged into a ring. Using the numerical solution to the time-averaged nonlinear Schrödinger equation, the transformations along an optical path of the intensity profile of the synthesized beams by varying the number and power of the partial emitters composing them are investigated. We show that the synthesized beams of coronal profile have a number of advantages from the point of view of control over the filamentation region. Particularly, by changing the number and geometric size of the individual subapertures it is possible to significantly delay the beginning of filamentation of the whole beam and increase the distance of its existence in comparison with beams of traditional unimodal profile (Gaussian, plateau-shaped).

The nitrogen-, oxygen and air-broadening coefficients of CH₃I lines in the n₆ band (^RP-, ^PP-, ^RQ-, ^PQ-, ^RR-, and ^PR-sub-branches) are calculated at room temperature with the rotational quantum numbers 0 ≤ J ≤ 70, 0 ≤ K ≤ 20. Calculations are performed by two methods: the semi-classical method with exact trajectories, adapted for the case of an absorbing molecule such as a symmetric top, colliding with a diatomic homonuclear partner, and the semi-empirical method based on the impact semi-classical theory and using an empirically adjusted factor for the efficiency functions. When comparing with recently published experimental data, a good agreement was obtained for the semi-empirical approach, so that the half-widths can be calculated by this method for reliable use in atmospheric applications.

In this work, based on experimental ground-based observations of the intensity and spectrum of solar radiation in the UVB range in the city of Tomsk (56°29' N, 84°56.89' E) from 26.03.2020 to 26.03.2021 and analysis of works on the structure and chemical molecular composition of SARS-CoV-2, primary photoacceptors and spectra of photobiological inactivation of the SARS-CoV-2 molecular structures (genome and S-thorn) by UVB radiation were determined for the first time.

The events of the dust aerosol transport to the water and coastal areas of the Caspian Sea during 2008-2010 are analyzed. This aerosol type is shown to be an additional source of biogenic elements in the surface layer of the sea. The comparative analysis of the optical characteristics of the northern, middle, and southern parts of the Caspian Sea, which significantly differ in hydrometeorological conditions and, hence, in the contribution of various factors which determine a possibility of anomalous cyanobacteria blooming, has been carried out. The effect of dust aerosol on the bloom of cyanobacteria is maximal in the southern part of the region under study. The results of the study of algae bloom anomalies in the Caspian Sea region are presented.

Remote passive optical measurements of the state of waters from a ship, air carrier, or satellite are the most informative due to the coverage of a large area and high frequency of measurements. At the same time, for a correct assessment of the data obtained it is usually necessary to carry out in situ measurements of the water state, which means the analysis of water samples taken at a limited number of points. Using the studies carried out in coastal regions of the Middle Caspian, the conditions for the suitability of such point measurements for calibrating the results of remote hydro-optical measurements by the EMMA complex (Ecological Monitoring of Marine Waters) from board of a moving vessel have been identified. The explanation for the identified limitations was given by analysis of the structure of coastal waters obtained by water vertical sounding at the stations and operation of a flow-through system for determination of surface water temperature and salinity. An algorithm is proposed for selecting water samples suitable for calibration of remote sensing data by correlating them with the Secchi disk depth. The efficiency of this method is demonstrated. It is shown what kind of hydrophysical conditions should be taken into account for the preliminary selection of water sampling sites for calibration of optical remote measurements.

The trends in variation in the monthly mean temperature of the atmospheric boundary layer (ABL) are analyzed for January and July on the basis of data of radiosonde observations at 10 aerological stations in the Siberian region for the period from 1981 to 2020. Positive temperature trends are observed in the ABL at all the stations in January and July, except for the temperate zone (50-60°N) of Western Siberia, where negative trends are noted in January. The values of the trends in temperature anomalies for the periods (1981-2010) and (1981-2020) are also compared. The comparison shows that warming has increased in polar latitudes in Western Siberia over the past 40 years, both in January and July, and the cooling is weakening in the subpolar and temperate zones in January. In Eastern Siberia, on the contrary, the warming has slowed down throughout the ABL at polar latitudes and increased in temperate latitudes, especially near the earth's surface, in January as compared to the period (1981-2010); the cooling has intensified in subpolar latitudes. In July, a decrease in warming is observed throughout Eastern Siberia at all ABL altitudes, except for polar latitudes, but only near the earth's surface, where warming has increased.

The analysis of the atmospheric model, presented in the form of one and two homogeneous layers up to a height of 5 km, was carried out. The parameters of the layers are determined for the standard atmosphere, provided that the contribution to the outgoing radiation of the atmosphere in the spectral ranges of the methane absorption line 1235.95-1236 cm^-1 and 1277.5-1277.55 cm^-1 is equal to the contributions to the outgoing radiation of the Earth by all inhomogeneous layers which make them up. Possible correction of the air and underlying surface temperature in determination of methane content in the Earth's atmosphere is considered.

A technique is developed for extracting an information currying signal from a beam with optical vortices in the wavefront due to distortions. Specific feature of this communication system is that information is also transferred by an optical vortex. The analysis has been carried out with the use of numerical simulation techniques. In the model developed, all singular points were introduced into the wavefront in the plane of the source emitting aperture, after which the radiation propagates under diffraction-free conditions. This schematic of numerical experiment roughly corresponds to an optical communication line, where a beam passes through a thin medium layer near the laser source, and beam distortions are so strong in this layer that additional vortices appear in the wavefront. Two techniques for extracting an information carrying signal from the distorted beam are considered. A possibility of solving the problem stated with the use of the technique developed is shown.

This overview is devoted to the intermittency of atmospheric turbulence of different types (of Kolmogorov and coherent) in the mountain boundary layer. A brief overview of the world scientific literature on the types of turbulence intermittency is made for a better understanding of the place of intermittency of different types among them. Due to available in literature various interpretations of the coherent turbulence concept, our earlier overviews of the world scientific literature on coherent turbulence and coherent structures are supplemented; these overviews describe the mechanisms of the origination (formation) of coherent turbulence and the key properties of coherent turbulence, as well as indicate the differences and relationships between the Kolmogorov and coherent turbulence. Discussion of the contemporary scientific understanding of turbulence structure can be attributed to the overviews results. Thus, the authors previously (2008-2019) independently showed that atmospheric turbulence can be considered as an incoherent mixture of various coherent structures. At the same time, there is a conjecture by E. Hopf (1948) about the finite dimensionality of attractors in the phase space of solutions of the Navier-Stokes equations. Physical interpretation of this conjecture, as pointed out by A.S. Monin and A.M. Yaglom (1991, 1992), is the representation of turbulence structure as a spatio-temporal chaos of a finite number of interacting coherent structures. From comparison of these representations, it can be seen that the authors’ results are in fact a proof of E. Hopf's conjecture in interpretation, formulated by A.S. Monin and A.M. Yaglom, and that the “chaos" of a turbulence is to a large extent determinate. The overview results of the study of the turbulence intermittency of different types are the consequent of many years experimental studies of turbulence by acoustic and optical methods performed by the authors at mountain astronomical observatories. Lifetimes of the turbulence different types: Kolmogorov and coherent, recorded in optical and meteorological measurements are given. It is shown that the effect of the intermittency of turbulence types characterizes the turbulence local structure over the observatory location region and allows to develop practical recommendations for the most favorable observation regime at astronomical observatories.