Home – Home – Jornals – Atmospheric and Oceanic Optics 2022 number 1

The nature of the water vapor self-continuum absorption is investigated within fundamental bending and stretching bands at 279-351 K. The integral contribution of the water dimer absorption to the experimental water vapor continuum is preliminary estimated based on the available spectroscopic information as 70-40% in the 1600 cm^-1 band and 90-60% in the 3600 cm^-1 band; the inverse temperature dependence is shown. The analysis of the temperature dependences of the continuum absorption and its components indicates the probable contribution of the water monomer line wings to the continuum along with the absorption by water dimers.

The correlation between the radon influx into the atmosphere and the formation of ions has been studied based on observations at the Fonovaya Observatory of Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences. This correlation is shown to be stable in the period from October to January. In the other months, the correlation is disturbed. However, if the events of nucleation and lightning discharges are removed from the data set, then the correlation is kept throughout the year.

The results of microscopic analysis of 114 samples of solid atmospheric precipitation (snow) taken during two cold periods (2015/2016 and 2016/2017) in the south of Western Siberia for the presence of bioaerosols are presented. With the use of trajectory, synoptic and cartographic analyses, the main regions were identified from which pollen grains and algae arrived with air masses and precipitated with atmospheric precipitation.

The comparison of data on the moisture content of the troposphere obtained from GPS satellite monitoring, radiosondes, and water vapor radiometer measurements at permanent observation points IRKM (Irkutsk, 52°13¢ N, 104°19¢ E, h = 511 m) and BADG (Badary, 51°46¢ N, 102°14¢ E, h = 838 m) is presented. Values of the total zenith tropospheric delay for the BADG observation point derived from processing of the primary GPS data with the GAMIT and Bernese software packages are compared. Time series of tropospheric moisture content for the IRKM station derived from GPS observations and radio soundings and for the BADG station found from GPS observations and water vapor radiometer measurements during 2020 are analyzed and compared. The use of the GPS method for monitoring the moisture content of the troposphere at the network being created in the Baikal region has been substantiated.

The measurements of aerosol backscattering ration in the lower mesosphere by means of sounding at two wavelengths of 355 and 532 nm at lidar stations of Roshydromet from 2012 to 2021 are presented. Appreciable increase in the backscattering ratio R has been observed in the altitude range 50-70 km since 2018. In 2019-2020, the average R attained 1.25 at an altitude of 70 km. The temperature measurements by the Rayleigh method at 532 nm in this period show a positive bias of the temperature of up to +20 K. The two-wavelength temperature measurement method allows one to eliminate this error.

The calculation of the light backscattering matrices of atmospheric hexagonal ice particles distorted with different methods within the physical optics approximation for the case of arbitrary spatial orientation and single scattering was carried out. The hexagonal prism with height of 31.62 mm and external diameter of 22.14 mm, which is typical for “column” shape that is occurs in cirrus clouds, was chosen as the base geometrical shape for distortion. The calculation was carried out for particles generated with three methods of distortion of base facets: tilt, pike, and cavity. The angle of distortion varied from 0 to 50° for every type of particles. The wavelength of incident radiation was equal to 1.064 mm.

Trends in long-term changes in the annual average and seasonal average temperatures within the atmospheric boundary layer in Siberia over 1981-2020, estimated based on observations at 24 aerological stations in winter, spring, summer, autumn, and for the year as a whole, are analyzed. It has been established that during the 40-year period under study, statistically significant positive trends in the annual average air temperature are observed throughout the atmospheric boundary layer over the Siberian territory; the trend value decreases from north to south and with altitude. The main contribution to the regional warming of the atmospheric boundary layer climate over Siberia is made by the spring, summer, and autumn periods. The warming of the boundary layer has intensified in the past decade, from 2011 to 2020.

The annual variability of aerosol microstructure of the near-surface aerosol has been studied based on solving the inverse problem for spectral measurements of aerosol extinction coefficient. The numerical algorithm based on the method of integral distributions was used to solve the inverse problem. The geometrical section, volume concentration, and mean radius of aerosol particles are considered. Aerosol microstructure parameters were estimated for the fine and coarse fractions and the total ensemble of particles. Estimates of the statistical characteristics of the distributions of aerosol microstructure parameters on monthly intervals are obtained. It has been shown that the fine particles make the main contribution to the total geometrical cross section of the near-surface aerosol, which varies within 73-88%. The coarse fraction predominates in the volume content of the near-surface aerosol, averaging about 75% over the entire observation period. During the observation period, the dependences of the monthly mean values of the geometrical cross section and the volume concentration of the fine aerosol had a monotonically increasing character. The volume concentration of fine particles has increased more than four times. The monthly average values of the volume concentration of coarse particles have changed twice.

Results of field and laboratory experiments on non-line-of-sight communication under water and in a model air medium are considered. For the first time, the experiments have been performed for non-coplanar communication schemes of the first (when single scattered radiation was present in the information-bearing signal) and second type (when this radiation was absent). The feasibility of communication through an ice interface with an underwater source was confirmed. It was shown that transition from the coplanar to non-coplanar communication scheme, accompanied by changes in the angles defining mutual orientation of the optical transmitter and receiver axes, can cause nonlinear changes in communication errors. The explanation of this dependence is suggested.

The results of studies of the precipitable water vapor (PWV) at Terskol, Kislovodsk, Nauchny, Sheki, and Hunzakh sites are presented. The comparative analysis of changes in GNSS-derived PWV and PWV estimated from the ERA-5 reanalysis database has been performed. The ERA-5 data make it possible to reveal new sites suitable for millimeter/submillimeter telescopes. In view of the comparatively low total cloud cover, Rutulsky and Agulsky regions are the most promising for building millimeter/submillimeter telescopes in the North Caucasus (Dagestan, mt. Horai (3521 m), Kаtаlnats (3780 m), mt. Karah (2876 m), and mt. Sindaky (2849 m)).

The modified method for retrieving the altitude profiles of the optical turbulence parameters is described. The altitude profiles of the dimensionless turbulent parameter and the structural constant of the air refractive index fluctuations are retrieved from the analysis of the Large Solar Vacuum Telescope data. The optical turbulence profiles are analyzed. It is found that the effective turbulence altitude is close to 2000 m at the site of the Large Solar Vacuum Telescope.

We consider the features of the weakening of the stratospheric polar vortex that precede its breakdown. To analyze the abnormal dynamics of the polar vortices, we used the method of estimating the main parameters of the vortex by delineating its edges using the geopotential values determined from the maximum temperature gradient and maximum wind speed according to the ERA5 reanalysis data. As a result, we showed that the criteria for the abnormal weakening of the polar vortex preceding its breakdown is a decrease in the vortex area to less than 10 million km² and a subsequent decrease in the average wind speed along the vortex edge below 30 and 45 m/s in the lower and middle stratosphere, respectively. In this case, the polar vortex becomes a small cyclone (characterized by high temperatures and the absence of a dynamic barrier) and collapses within three weeks.