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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.

A time-varying flow velocity method for a conceptual model of river flow generation is implemented with the aim of improving flow routing in the Lena river basin. In contrast to constant velocity models, this approach uses a time-varying velocity which depends on the amount of flow generated in a land grid cell. The Manning equation is used to estimate flow velocity in the rectangular cross-sectional approximation for the river channel. Numerical experiments with constant and variable flow velocities made it possible to compare the model flow with the observed daily hydrographs at the runoff stations of Kyusyur, Tabaga, and Verkhoyanskiy Perevoz. The work provides an estimate of the heat flow from the Lena river basin to Kyusyur gauging station for 2002-2011.

An approach which combines remote and ground-based methods for monitoring oil-contaminated soil and vegetation cover is suggested. A map is presented that reflects the natural and anthropogenic structure of the territory of the Nefteyugansk region of the Khanty-Mansiysk Autonomous Okrug in the conditions of oil and gas production. The legend of the map shows 10 natural and 3 anthropogenic types of vegetation cover and the open surface of the Earth in the area located in the Salym-Ob flat terraced swamp-taiga landscape province. It was revealed that after oil spills, the soil and vegetation cover experiences a long-term negative impact. The NDVI values in the oil-contaminated areas are 0.1-0.3 lower than in the background ones. In satellite imagery in days close to those of ground-based surveys, the NDVI of oil-contaminated areas of sedge-sphagnum bogs is 0.45 (8.08.2020) and 0.42 (23.08.2021), respectively. In small-leaved and light-coniferous forests on sites with a negative impact of fresh oil spills, NDVI = 0.32 (25.09.2020) and 0.42 (23.08.2021), respectively. The concentration of oil products in contaminated soil samples lies in the range 280-580 g/kg, exceeding the approximately permissible concentrations by 70-145 times.