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Three-dimensional ab initio potential energy surfaces of the interacting triplet states ³ A ₂ and ³ B ₁ of the О₃ molecule are constructed within the diabatization approach implemented in the MOLPRO package. These two states are responsible for the strongest singlet-triplet transitions in the Wulf band of O₃. The molecular orbitals are optimized by the state-averaged CASSCF with the active space CAS(18, 12) involving three electronic states ( X ¹ A ₁, ³ A ₂, and ³ B ₁). The correlation energy is computed by icMRCI(Q). The impact of the basis set size on the accuracy of both the adiabatic excitation energy and origins of the vibronic transitions is analyzed.

From the known experimental data, the parameters of the non-polynomial analytical model γ(sur) for the broadening coefficients γ of the ammonia molecule absorption lines by the pressure of helium, argon, nitrogen, oxygen, air, hydrogen, carbon dioxide, and its own pressure are determined. The accuracy of the experimental data recovery by the model γ(sur) varies from 3.3 (nitrogen broadening) to 8.5% (carbon dioxide broadening). The comparison with the polynomial representation and with the results of calculations of these coefficients by the semi-classical method is made.

The criterion for stopping the intensity collapse is established in the approximation of the nonlinear Schrödinger equation for the problem of self-focusing of high-power femtosecond laser radiation in an optical medium. Using propagation of a femtosecond laser pulse in air as an example, it is shown that the collapse stops when the role of diffraction increases due to a decrease in the radius of the laser beam, and occurs not at a point, but at an interval in front of the nonlinear focus, where the self-phase modulation of the radiation due to the plasma nonlinearity prevails over the Kerr effect. The result (collapse stop criterion) makes it possible to take into account the features of the nonlinear activity of various optical media during the propagation of high-power femtosecond laser pulses; in particular, the role of nonlinear absorption is determined under the conditions considered.

We present the results of the assessment of multiyear variability for the parameters of single-layer cloud fields over the territory of Western Siberia in summer in 2001 to 2019 based on MODIS data. The seasonal average proportion of coverage by single-layer clouds of different types and values of their features are determined based on the results of cloud classification from summer (June, July, August) daily satellite images of the target region. Parameters of single-layer clouds are considered for three latitudinal zones of Western Siberia: southern (< 60° N), transitional (60-65° N), and northern (> 65° N). We found linear trends of the proportion of coverage by different single-layer cloud types and of their parameters: optical thickness, effective particle radius, waterpath, and cloud top height. A discussion of the results is given. The greatest variability of the physical parameters considered in this work is characteristic of the vertical development and low-level clouds in the northern and transition zone of the target region. The effect of anomalous blocking anticyclones on some features of different cloud types in the considered latitudinal zones of Western Siberia is shown.

Quantitative estimates of changes in wind energy resources in the high latitudes of the Northern Hemisphere are obtained using ERA5 reanalysis data for 1979-2021. The wind energy potential (WEP) was estimated during the analysis. According to the ERA5 reanalysis data, a marked increase in the WEP over the Greenland, Norwegian, Barents, Kara, and Chukchi Seas, as well as over the European territory of Russia in winter, over the Kara and Norwegian Seas in spring, and a general increase in WEP along the Arctic coast, in particular over its Russian sector in summer and autumn, are noted under the current climate regime. The noted changes in WEP quite well correlate with the retreat of sea ice in the Arctic, as well as with the leaf area index, which characterizes the roughness of the underlying surface in the high latitudes of the Northern Hemisphere. The increase in the proportion of the year when wind generators are capable to operate over the Russian Arctic makes the region quite promising for the use and development of wind power in the context of the climate change.

The snow cover pollution in Kyzyl in 2013-2021 is analyzed based on remote sensing data. Software scripts are created in the GEE software environment; NDSI, S3, and SCI indices are calculated. Maps of the annual average value of NDSI are constructed; the degree of contamination of the territory is determined. It is found that the areas with NDSI < 0.3 weakly changed in 2013-2021: it was minimal in 2015 and 2017 and maximal (0.68%) in 2018. The NDSI values from 0.3 to 0.45 (more than 64% of the total territory under study) prevailed from 2014 to 2017.

Quantitative estimates of regional features of the frequency distribution of extreme temperature, precipitation, and wind anomalies in the winter months in the extratropical zone of the Northern Hemisphere associated with atmospheric circulation regimes in the Euro-Atlantic sector are obtained. Using the k-means cluster analysis for the daily geopotential height fields from the ERA5 reanalysis for 1979-2021 four winter atmospheric circulation regimes are identified in the Euro-Atlantic sector corresponding to the North Atlantic Oscillation (NAO) in the positive (NAO+) and negative (NAO-) phases, Scandinavian blocking (SCAND), and regime with anomalously high pressure over the North Atlantic and low pressure over Europe (ATL). Characteristic fields and frequencies of occurrence of the regimes are analyzed. The NAO+ and NAO- regimes turned out to be asymmetric in the spatial structure with significantly different frequencies of occurrence (33% and 19%, respectively). Spatial distributions of the frequencies of occurrence of extreme weather anomalies associated with the regimes are also asymmetric. For all regimes, an asymmetric frequency of occurrence of positive and negative temperature anomalies is noted. During the period under study, no statistically significant trends in the seasonal frequency of the regimes and no large areas with statistically significant trends in the average seasonal fields of the regimes near the areas of geopotential height anomalies maxima are found, which can indicate the stability of these regimes under recent climate changes.

A method is suggested for classifying weather forecast ensemble members and identifying the set of the ensemble members which most likely reflects the future state of the atmosphere. The first forecast month of the ensemble is used for the comparison between every selected class and observation data in order to identify the most realistic scenario of the development of atmospheric processes. The best class is used for prediction of the sea level pressure and surface temperature anomaly fields for the next month. The method suggested allows improving the quality of forecasts for north-west of the Russian Federation and the Arctic.

The mechanisms of the formation of ozone mini-holes (OMHs) and their influence on the levels of UV radiation (UVR) over May 22-24, 2021, in the middle and southern parts of the Volga region and the south of the Urals and Western Siberia and over March 16-18, 2022, in the northwest of the European of Russia are studied using data from the AIRS satellite infrared spectrometer and NCEP reanalysis. It is shown that the formation of these OMHs is due to the increase in the tropopause level associated with the anticyclone and the transfer of low-ozone air masses from the subtropics. In the first period of the OMH, negative total ozone (TO) anomalies were up to ~ 20% of the average values from 2003 to 2021, and positive UVR anomalies attained 40-60%, the UV index increased from ~ 6 to ~ 8. In the second period, in the region of the OMH with negative TO anomalies up to ~ -40%, positive UVR anomalies attained 40-60%, and the UV index increased from ~ 1 to ~ 2. Calculations with an original spectral model, which allows solving the transport equation at a single point, confirmed the increase in UVR revealed in satellite observations in the OMH regions.

The efficiency of monostatic and bistatic schemes of the formation of a laser guide staris is analyzed on the basis of the correlation theory of Gaussian random processes. In the focal plane of a ground-based optical telescope, the position of a natural star relative to the measured instantaneous position of a laser guide star is calculated based on Pearson's linear regression. An expression is derived for the correlation coefficient of random angular displacements of images of a natural star and a laser guide star. Based on this expression, the normalized dispersion of uncompensated (residual) angular errors is determined. The results of calculations for monostatic and bistatic schemes of the formation of a laser guide star are presented, which make it possible to estimate and compare their efficiency.