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The spectrum of the ¹⁵N¹⁶O molecule in the region 5200-5500 сm^-1 is recorded and analyzed. As a result of the analysis, 150 Λ-doublets of vibration-rotational lines are found in the 3-0 band of the main transitions between the ²Π_1/2 and ²Π_3/2 electronic states. For 108 of them, when the splitting value was greater than 4.5 × 10^-13 сm^-1, it was possible to obtain the positions and relative intensities of each component of the doublet, while the self-expansion parameter was fixed to the value from HITRAN2020, and the intensities of the components e and f were considered equal. The maximum of the rotational quantum number J was 30.5. The frequencies of the transitions recorded, weighted in accordance with the experimental uncertainties, were processed by the program code using the non-linear least squares method. As a result of processing, the spectroscopic constants for the v = 3 vibrational state of the ¹⁵N¹⁶O isotopologue are found. The Λ-doubling constants for this state are determined for the first time. The results are compared with the well-known database of spectroscopic information HITRAN2020.

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.