Home – Home – Jornals – Atmospheric and Oceanic Optics 2021 number 10

At present, the most complete theoretical list of H₂O monomer absorption lines is the POKAZATEL data bank, which contains H₂O lines up to energy dissociation ~ 40000 cm^-1 (0.25 mm). The atmospheric transmission of ultraviolet (UV) radiation is simulated with use of H₂O lines from the POKAZATEL. The broadening parameters of the absorption lines are defined more accurately with use of different approximations in the UV region. It is shown that the H₂O absorption lines contribution to the atmospheric transmission can reach 0.03 near 25000 cm^-1 at a spectral resolution of 0.01 cm^-1.

Information about an angular distribution of emission from the filamentation region is required to select an effective scheme for remote sensing of the aerosol atmosphere by femtosecond laser-induced breakdown spectroscopy. We present the results of a series of experiments on identification of an impurity with the use of femtosecond LIBS. The angular distribution of the emission from the femtosecond radiation filamentation region in the atmosphere for an impurity in water aerosol is estimated in the range from 0 to 180° based on the experimental data. A model of the angular distribution of the emission is suggested, where absorption in the filament plasma is taken into account. The variation in the intensity of the emission line with the impurity concentration is analyzed. It is shown that emission from the filamentation region occurs due to spontaneous emission.

The quantitative and physico-geochemical characteristics of particulate matter in the winter atmosphere of Yakutsk, accumulating in the solid phase of the snow cover, are examined. Snow survey was carried out on the territory of the city in 2020. Based on modern methods of analysis the features of the transformation of the chemical composition of particulate matter in the winter atmosphere of an urbanized territory are analyzed. The main source of pollution of the winter atmosphere of the city is motor transport; energy facilities and industrial enterprises contribute less. The features of the macro- and microelement composition of the solid phase of snow on the territory of the city have been ascertained. The intensity of the intake of chemical elements with winter dust varies within 6-7 mathematical orders: from a maximum of 103-104 mg/(m² × day) for Ca, Fe, and Al, to a minimum of £ 10-3 mg/(m² × day) for Pt, Au, and Hg. The most unfavorable from a sanitary point of view is the fallout of Fe, Zn, and As from the winter atmosphere. Heavy metal pollution of the snow cover on the territory of Yakutsk is noticeably lower than in a number of cities in Eastern Siberia.

A method has been developed for determining the turbulent energy dissipation rate, the dispersion of the radial velocity and the integral scale of turbulence from the spectral density of the vertical wind velocity measured by a pulsed coherent Doppler lidar. To obtain unbiased estimates of these wind turbulence parameters, the averaging of the radial velocity over the probed volume is taken into account. The method has been tested in a numerical experiment. An algorithm is proposed for calculating the error of the lidar estimates of the dissipation rate obtained by this method.

In order to test a new method for determining the parameters of wind turbulence from the spectra of the vertical component of the wind speed vector measured by a pulsed coherent Doppler lidar (PCDL), in the summer of 2020 we conducted an experiment on the territory of the Basic Experimental Observatory (BEO) of the IAO SB RAS. A comparative analysis of the estimates of the turbulent energy dissipation rate obtained by two methods: 1) from the spectrum of the vertical component of the wind velocity vector (new method) and 2) from the azimuth structure function of the radial velocity measured by a conically scanning PCDL (previously used method) showed that the new method also gives an unbiased estimate. The results of lidar measurements of wind turbulence parameters in the presence of a low-level jet stream and an internal gravity wave in the atmospheric boundary layer are presented.

The results of statistical simulation of the albedo and diffuse transmission of the atmosphere in the visible region in the presence of overcast and broken cirrus clouds are presented. The main numerical experiments were performed using the third version of the model proposed by a group of authors consisting of B.A. Baum, P. Yang, A.J. Heymsfield et al. (a mixture of particles of different shapes and sizes with a rough surface). To assess the effect of random geometry of clouds on the solar radiation transfer in the atmosphere, G.A. Titov method of closed equations, developed within the framework of a model based on Poisson fluxes of points on straight lines, was used. Analysis of the influence of the microstructure of cirrus clouds on the mean albedo and diffuse transmission at average cloud fraction showed that the average value of the uncertainty due to the lack of information on the particle shape and size is within ~ ± 2%. This value is comparable to the effect of random geometry effects in optically thin clouds, while in optically dense clouds the range of errors caused by ignoring the horizontal heterogeneity increases and is ~ ± 5% in albedo calculations with an underestimation of the diffuse transmission by ~ 10-20%.

This influence of assimilation of date from lightning detection networks on the quality of the weather forecast using the numerical model is analysed. For 10 dates of 2020 over the Krasnodar Territory, estimates of the quality of forecasts for some meteorological parameters were calculated: without lightning assimilating; with assimilation of data from global and regional networks separately; with assimilation of data from all networks. WRF-LTNGDA was used as the assimilation procedure, and WRF-ARW model ver. 3.9.1 was used as a predictive model. We have studied the influence of information from: WWLLN, GGO, and VGI networks, as well as the new global lightning network TLN.

The application of a method based on artificial neural networks for assessing the total water vapor content in the atmospheric column from data of the MSU-GS satellite instrument of Electro-L No. 3 geostationary spacecraft is considered. The results of comparing the estimates of the total water vapor content from the MSU-GS data with MODIS satellite instrument data and AERONET measurements showed high agreement. The root mean square error when compared with the MODIS data was 0.311 cm, with the AERONET data, 0.409 cm, and the correlation was 98.2% and 84.7%, respectively. The results indicate the effectiveness of the method for determining the total content of water vapor for solving problems of atmospheric physics.

A review of methods for calibrating optical raingauges is carried out. The disadvantages of the existing calibration methods of the optoelectronic raingauge OPTIOS are analyzed and the ways to eliminate them are proposed. The original patented method for calibrating the optical raingauge is described in detail, which makes it possible to increase the accuracy of determining the dimensions of hydrometeors by taking into account the effective size of each photosensitive element of the linear sensor. A conclusion is made about the reliability of the proposed calibration method, which makes it possible to use the method to improve the accuracy of any optical meters of linear dimensions of various objects using a linear array of photosensitive elements as a measuring transducer.

The joint influence on the systematic error of sonic temperature measurements of the unaccounted time delay of signal transmission between sound transmitter-receiver pairs and temperature changes in the distances between them is considered. Analytical relations for estimating the considered error and the results of its calculations are given. The method of calibration of such devices in a climate chamber with the use of reference measuring instruments is described, which allows one to reduce this influence by more than an order of magnitude in the range of measured temperatures from -70 to + 50 °C.

The process of second harmonic generation (SHG) of laser radiation in a BBO crystal is theoretically studied with the aim of determining optimal values of focusing and wave detuning parameters providing maximal SHG efficiency. This optimization problem is solved under an additional condition, that is, the maximal radiation power density should not exceed an a priori specified value. No restrictions are posed on the radiation power. The study consists of two parts. In the first part (this work), the influence of this additional condition on the process and results of solution of the optimization problem is studied with the use of the preset field approximation. Due to the additional condition, optimal focusing and wave detuning parameters become dependent on the radiation power, but the algorithm of solution of the problem becomes noticeably simpler, which allows the computation time to be significantly reduced, by about an order of magnitude.