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Atmospheric and Oceanic Optics

2020 year, number 8

1.
Universal analytical function for calculations of broadening of H2S absorption lines by noble gases

V.I. Starikov
Tomsk State University of Control Systems and Radioelectronics, Tomsk, Russia
Keywords: сероводород, уширение линий, столкновения, аналитическая модель, hudrogen sulphide, noble gas broadening, analytical model

Abstract >>
A universal function is suggested for calculation of the A-broadening coefficients γ of H2S absorption lines (A = He, Ne, Ar, Kr, and Xe). Only one parameter of this function depends on the broadening gas atom, while other parameters are common for all atoms. This parameter determines the ratio γ(А)/γ(А') for A and A' atoms. Parameters of the function are determined in the fitting procedure from the coefficients g measured and calculated for ν1, ν2, and ν3 vibrational bands of H2S molecules. The coefficients γ calculated are statistically compared with measurements. With the exception of some data for the ν1 and ν3 bands, the calculated and measured γ are in a good agreement for all collisional partners A.
																								



2.
The analysis of intensity correlation in laser transceiving systems for keying

V.P. Aksenov1, V.V. Dudorov1, V.V. Kolosov1,2, Ch.E. Pogutsa1, M.E. Levitskii3
1V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
2Tomskiy Nauchnyy Tsentr SO RAN, Tomsk, Russia
3Innovation Research Association "TOPAS", Tomsk, Russia
Keywords: лазерное излучение, конфиденциальная оптическая связь, криптография, атмосферная турбулентность, флуктуации интенсивности, теорема взаимности, laser radiation, confidential optical communication, cryptography, atmospheric turbulence, intensity fluctuations, reciprocity theorem

Abstract >>
The potentials for and limitations to the use of intensity fluctuations of laser beams propagating through a turbulent atmosphere for generating random data when keying in confidential optical communication systems are analyzed. The technique is based on the reciprocity theorem for optical fields. Light propagation in a system of two transceivers directed at each other, the signals from which are distorted by an atmospheric channel, is numerically simulated. An experimental setup is created; the generation of random correlated signals in such a system is experimentally studied. A need for low-pass filtering of signals received is experimentally ascertained. The efficiency of this filtration is estimated. The dependences of the correlation coefficient on the geometrical parameters of the system and turbulent conditions along the propagation path are derived from the numerical simulation in a wide range of distances, aperture radii, and values of turbulence intensity. Theoretical results are shown to be in a good agreement with the results of laboratory experiments.
																								



3.
Comparison of post-detection correction of shortand long-exposure images formed by commonly used and multi-aperture observation systems in a turbulent atmosphere

V.V. Dudorov, A.S. Nasonova
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: многоапертурные системы, турбулентная атмосфера, некогерентное изображение, multiaperture system, turbulent atmosphere, incoherent image

Abstract >>
The retrieval efficiency is analyzed for atmospheric turbulence distorted images formed by single- and multi-aperture systems. Based on numerical simulation it is shown that the use of multi-aperture observation systems for computer correction of atmospheric distortions under anisoplanatism can significantly reduce the exposure time. In this case, the main distortions are well corrected when imaging for a short exposure time, which corresponds to the case of a “frozen” turbulent medium. Correction of residual small-scale distortions requires an-order-of-magnitude shorter time than in the case of long-exposure imaging with the use of common single-aperture observation systems.
																								



4.
Short-term stability of temperature retrieval functions in the traditional pure rotational Raman lidar technique

V.V. Gerasimov1,2
1V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
2National Research Tomsk State University, Tomsk, Russia
Keywords: комбинационное рассеяние, лидар, уширение спектральных линий, калибровочная функция, температура тропосферы, Raman scattering, lidar, spectral line broadening, calibration function, tropospheric temperature

Abstract >>
In the traditional pure rotational Raman (PRR) technique, air temperature is retrieved from lidar signals with a temperature retrieval function (TRF). The TRF coefficients are determined using a reference temperature profile from a model of the atmosphere or radiosonde data. In this work, we study the stability of several TRFs in time, i.e., we investigate to what extent the TRF coefficients determined on one of the measurement campaign days can be used to retrieve temperature on other days. We also analyze the situation when the reference data are absent on one of the measurement days (for example, due to a radiosonde fall) and the TRF coefficients are determined from the reference data over the remaining days. The stability of five TRFs is studied on the example of nighttime temperature profiles that were obtained using the IMCES PRR lidar (Tomsk) on April 6, 7, and 8, 2015. The function which retrieves the temperature in the troposphere (3-9 km) with the least errors for the considered three-day period has been determined.
																								



5.
Application of a regression algorithm to the problem of studying horizontal inhomogeneity of the cloud liquid water path on the basis of the ground-based microwave observations in the angular scanning mode

E.Yu. Biryukov, V.S. Kostsov
Saint Petersburg State University, Petrodvorets, St. Petersburg, Russia
Keywords: водозапас облаков, тропосфера, горизонтальные неоднородности параметров атмосферы, дистанционное зондирование, микроволновый радиометр, обратные задачи, регрессионный алгоритм, cloud liquid water path, troposphere, horizontal inhomogeneity of atmosphere parameters, remote sensing, microwave radiometer, inverse problems, regression algorithm

Abstract >>
The results of the cloud liquid water path (LWP) “land-sea” gradient retrieval from ground-based measurements of downwelling microwave radiation near the coastline of the Gulf of Finland in Saint-Petersburg region are presented. The measurements were carried out with the RPG-HATPRO radiometer operating at the Faculty of Physics of Saint-Petersburg State University in the angular scanning mode. The inverse problem was solved by the linear regression method. Different statistical models of cloud cover were used for training the algorithm. The LWP gradient mean values were derived over the winter and summer periods of seven years of observations. The results have shown positive “land-sea” LWP gradient (higher values over land and lower over sea) during both summer and winter seasons. This fact is qualitatively consistent with available satellite data.
																								



6.
Wind temperature probing in the atmospheric boundary layer in the coastal area of Lake Baikal. I. The Richardson number

V.A. Banakh, I.N. Smalikho, A.V. Falits
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: пограничный слой атмосферы, скорость ветра, температура, зондирование, число Ричардсона, устойчивая стратификация, atmospheric boundary layer, wind velocity, temperature, remote sensing, Richardson number, stable stratification

Abstract >>
The results of experimental studies of the atmospheric boundary layer in the coastal zone of Lake Baikal using a coherent Doppler wind lidar and a temperature profiler are presented. Temporal-altitude distributions of the wind speed, temperature, and the Richardson number are derived. It is found that in the measurement site during all the experiment from August 6 to 23, 2018, day and night the thermal stratification was stable with formation of low-level jets. The temporal-altitude distributions of the Richardson number have layered structure. Layers with Richardson numbers higher than the critical value alternate with layers with the Richardson number lower than the critical value.
																								



7.
Wind temperature probing in the atmospheric boundary layer in the coastal area of Lake Baikal. II. Atmospheric waves and wind turbulence

V.A. Banakh, I.N. Smalikho, A.V. Falits
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: пограничный слой атмосферы, устойчивая стратификация, ветровая турбулентность, атмосферные волны, струйные течения, atmospheric boundary layer, stable stratification, wind velocity turbulence, atmospheric waves, jets

Abstract >>
The results of experimental studies of the atmospheric boundary layer in the coastal zone of Lake Baikal using a coherent Doppler wind lidar and a temperature profiler are presented. Temporal-altitude distributions of the wind speed, temperature, and the Richardson number are derived. The parameters of atmospheric waves in a stably stratified boundary layer are determined. Variations in the dissipation rate of the kinetic energy of turbulence, the variance of the fluctuations of the radial velocity, and the outer turbulence scale during the low level jets and internal atmospheric waves in the stable boundary layer and their relation to variations in the Richardson number are analyzed.
																								



8.
Peculiarities of atmospheric boundary layer sounding with a turbulent lidar

I.A. Razenkov
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: турбулентность, лидар, пограничный слой атмосферы, turbulence, lidar, atmospheric boundary layer

Abstract >>
Recommendations for the use of aerosol turbulent lidar for research in the atmospheric boundary layer are presented. The peculiarity of the turbulent lidar is that the sounding path angle should not exceed 10°. It is found that the optimal angle is 4°, at which it is possible to determine the structural constant of the refractive index in the range of altitudes from 100 m to 1 km. This range can be extended by 2 times if sounding at two or three angles to the horizon.
																								



9.
Investigating the relationship between ultraviolet radiation and the factors affecting it. Part I. The role of the total ozone content, cloudiness and aerosol optical depth

B.D. Belan, G.A. Ivlev, T.K. Sklyadneva
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: атмосфера, ультрафиолетовая радиация, общее содержание озона, облачность, вариации, atmosphere, ultraviolet radiation, total ozone content, cloudiness, variations

Abstract >>
The relationship of the daily UV-B radiation with factors influencing it (total ozone content, cloudiness, and aerosol optical depth) is analyzed. For this purpose, a homogeneous series of UV-B radiation data obtained at the TOR-station of the IAO SB RAS from 2003 to 2016, as well as satellite data on TOC, AOT data from AERONET network, and the data on total cloud cover from the meteorological site of IMCES SB RAS were used. The regression equations of the daily UV-B radiation variations depending on the changes in total ozone content under different cloudiness and air transparency conditions have been derived.
																								



10.
Generation of high-contrast "Talbot carpets" with the use of a mesoscale amplitude-phase mask

Yu.E. Geints1, A.A. Zemlyanov1, E.K. Panina1, I.V. Minin2,3, O.V. Minin2,3
1V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
2Research Tomsk Polytechnic University, Tomsk, Russia
3Siberian State University of Geosystems and Technologies, Novosibirsk, Russia
Keywords: эффект Талбота, фотолитография, дифракционные маски, Talbot effect, photolithography, diffraction mask

Abstract >>
The spatial near-field structure of optical wave scattered by a composite amplitude-phase diffraction mask with a ruling period on a wavelength scale is studied in numerical simulations by the finite element method. As applied to the displacement Talbot-nanolithography, such a combined binary mask is shown to provide multiple enhancement of the optical contrast of an integral "Talbot carpet" as compared to pure amplitude and phase masks. The physical causes of this effect are analyzed and the key role of Mie resonances excited inside the dielectric bars of the phase mask is ascertained. Meanwhile, the combined mask suggested ensures a high spatial resolution (up to a quarter of optical wavelength) and maximal optical contrast (up to 24 dB) of integral Talbot's self-images.