Home – Home – Jornals – Atmospheric and Oceanic Optics 2023 number 5

The perturbation theory is applied to calculation of the vibrational energy levels of isotopically substituted molecules. Within the Born-Oppenheimer approximation, the isotopic shifts of energy levels are represented in the form of power series of small parameters, i.e., the relative change in the masses of substituted atoms. The coefficients of the series are functions of the molecular constants of only one modification of the isotopic family of a molecule. This makes it possible, having determined these coefficients either from calculation or on the basis of a semi-empirical approach from experimental data, to calculate isotopic shifts for any isotopologues, including short-lived ones. As an example, the isotopic shifts of the levels of unstable water isotopologues Н₂^ХО, Х = 13-15 and 19-24, with a half-life of more than 1 ms are calculated. The levels calculated are compared with the results of variational calculations with a high-precision function of the intramolecular potential energy.

Absorption spectrum of water vapor highly enriched with ¹⁷O (more than 80%) was recorded using a Bruker IFS 125M Fourier spectrometer in the 7900-9500 cm^-1 range at room temperature. The spectrum was recorded at a pressure of about 24 mbar with a spectral resolution of 0.02 cm^-1. About 6300 lines with a minimal intensity value of 5.0 × 10^-27 cm/molecule are found in the recorded spectrum. 4835 recorded lines are assigned to 5185 transitions of five water isotopologues (H₂¹⁶O, H₂¹⁷O, H₂¹⁸O, HD¹⁶O, and HD¹⁷O). H₂¹⁷O lines are assigned to 14 vibration bands. Most of them are the lines of the ν₂ + 2ν₃, 3ν₂ + ν₃, ν₁ + ν₂ + ν₃, ν₁ + 3ν₂, and 2ν₁ + ν₂ bands. The lines of the ν₁ + 2ν₂ + ν₃ - ν₂, 2ν₁ + ν₃ - ν₂, and 2ν₁ + 2ν₂ - ν₂ hot bands are assigned for the first time. The assigned lines allow us to determine 153 new vibration-rotation energies of nine vibrational states of the H₂¹⁷O molecule and 22 energies of two states of the HD¹⁷O molecule. The data obtained are compared with the results of previous studies, the HITRAN2020 spectroscopic database, and W2020 list.

Using numerical finite-difference time-domain (FDTD) calculations, we simulate and examine the absorption dynamics of the near-infrared optical radiation in a spherical microcapsule surrounded by solid nanoparticles of different optical properties (metal, biocompatible dielectric). A model microcapsule resembles a microcontainer used in modern bio- and medical technologies for targeted delivery of therapeutic nanodoses of drugs to the desired region of the biological tissues. We show that due to light scattering on nanoparticles, the optical field superlocalization in the "hot regions" on the microcapsule surface take place. The three-fold light absorption enhancement can be achieved due to the addition of buffer nanoparticles.

Ground-based MW spectrometers play an important role in the O₃ regional monitoring. They measure the downward thermal radiation in various ozone absorption lines. Using numerical simulation, the information content of typical ground-based measurements of downward MW thermal radiation in the ozone absorption line at 110.836 GHz, the errors in the ozone vertical profiles at altitudes of 20-60 km, and the influence on them of a priori information about the solution and type of the inverse operator used in the regression method for solution of the inverse problem are studied.

The observations of stratospheric aerosol layers at the lidar stations of Roshydromet in Sankt-Peterburg (59.9° N), Obninsk (55.1° N), and Znamensk (48.6° N) some months after the explosive eruption of the submarine Hunga Tonga (21° S, 175° W) volcano in January 2022 are presented. Aerosol layers at 20-24 km altitudes are observed in April, May, and October with a backscattering ratio of 1.2-1.4. The degree of depolarization at 532 nm and the ratio of the backscattering coefficients at 355 and 532 nm wavelengths show that aerosol consists of submicron spherical particles. The observation results are compared with known data on Hunga Tonga aerosol propagation.

The results of measurements of atmospheric parameters (level of turbulence and average wind speed) along an extended path are discussed. These measurements were carried out to determine the effective average values of atmospheric turbulence parameters along the path of optical radiation propagation. The measurements were carried out in August 2022 using an AMK-03 acoustic weather station. It is shown that the AMK-03 weather station, with a certified measurement technique, provides reliable information on the level of turbulence and on the wind speed. The measurement data of the turbulence level at different points along the atmospheric path are correctly recalculated into the values of the coherence length (the Fried parameter) for an optical wave of an arbitrary length and different divergence by the formulas of the wave propagation theory. This makes it possible to compare local acoustic and optical path measurements of the turbulence level.

We quantified the seasonal/regional patterns and changes in cyclone activity in the atmosphere of the Northern Hemisphere and determined the contribution of extratropical cyclones to the formation of corresponding patterns and precipitation changes. It is established that the contribution of extratropical cyclones to the total amount of precipitation exceeds 60% on the whole; for regions with a high cyclone occurrence, it attains 75% in winter and 65% in summer. The strongest contribution is related to intense cyclones: 60% in winter and 35% in summer.

The combined effect of wind and lake topographic characteristics on the temperature distribution and autumnal thermal bar evolution on an example of Lake Baikal was studied by numerical modeling. It was determined that under meteorological conditions in November 1-30, 2015, the thermal bar behavior at an initial stage of its development on the Boldakov River - Maloye More Strait cross-section was more sensitive to the wind action than that on the Srednyaya arm (Selenga River Delta) - the Buguldeika River cross-section. However, faster water cooling and thermal front propagation take place in the Selenga shallow water basin.

An impact of uncertainties of the atmospheric gases absorption line parameters in the modern spectroscopic databases on the longwave fluxes simulation in the atmosphere is estimated. The mass calculations of downward and upward IR fluxes are carried out for meteorological conditions observed in summer months in the Lower Volga Region and winter months in Novosibirsk and for average zonal meteorological models. The radiative fluxes and cooling rates at different levels of the atmosphere calculated with use of new versions of HITRAN and GEISA spectroscopic databases and its previous versions are compared. It is shown that the difference in absorption line parameters in the spectroscopic databases leads to an error less than 0.7 W/m² (0.3%) in the simulated integral fluxes in the 0-3000 cm^-1 region, at that the relative differences in the spectral fluxes calculated with moderate spectral resolution (20 cm^-1) are up to 10%. The atmospheric gases and spectral intervals contributing more to the errors in the IR fluxes simulations due to uncertainties of initial spectroscopic information are revealed.

The seasonal and daily variations in the radiation extinction coefficient due to midges (RECM) in Western Siberia are calculated for June, July, August, and September 2018. The average RECM values in the visible and infrared spectral regions were ~ 0.06 km^-1 in June, ~ 0.05 km^-1 in July, ~ 0.04 km^-1 in August, and ~ 0.02 km^-1 in September. There are two maxima in the daily variations in June, July, August, and September. The first maximum falls at 9 a.m. The second maximum is more pronounced and is observed at 17 p.m. The RECM is minimal in nighttime and at noon. In addition, a different daily behavior is characteristic for certain days of September, with a maximum in daytime and a minimum in nighttime.

We present a mathematical model of the process of laser-induced fluorescence of phosphorus oxide (PO) molecules. Based on the model, the dependences of the fluorescence intensity of PO molecules on the energy and time parameters of the exciting laser radiation are derived. It has been established that the dependence of the PO fluorescence signal on the energy density of the exciting radiation has the form of a saturation curve, and the dependence on the pulse duration under real atmospheric conditions has a local maximum. It is shown that the optimal pulse duration decreases with the energy density of the exciting radiation.

A mobile ozone lidar for sounding at wavelengths of 299 and 341 nm was designed and put into operation. The lidar is capable of covering the altitude range from 0.1 to 12 km with a spatial resolution of lidar signals from 1.5 to 150 m. The specification of the mobile lidar is given; the results of a field experiment on laser sounding of the atmosphere in Tomsk are presented. Echo signals received and the ozone profiles retrieved confirm the information content of lidar measurements in the troposphere. The results of lidar and satellite (MetOp) measurements are compared.

We compare the main characteristics of the Arctic polar vortex obtained from the NASA GSFC data (zonal mean wind at 60° N, mean temperature in the region 60-90° N) and by the vortex delineation method using geopotential (mean wind speed along the vortex edge, mean temperature inside the vortex) on the example of three largest Arctic ozone depletion events and on average over 1979-2021. The mean wind speed along the vortex edge according to the delineation method is on average two times higher than the zonal mean wind at 60° N and is 37.3 ± 5.6 and 58.9 ± 13.1 m/s in January at the 50 and 10 hPa levels, respectively. The mean temperature inside the vortex according to the delineation method is on average 5 °C lower than the mean temperature in the region 60-90° N in the lower stratosphere. The quantitative characteristics obtained expand the understanding of the Arctic polar vortex dynamics in the lower stratosphere.