Climate warming changes in heat fluxes within the atmosphere–surface cover–soil system and affects the thermal state of permafrost. A comparison of heat fluxes from the atmosphere to the soil during the period with positive air temperatures and from the soil to the atmosphere during the cold period makes it possible to assess the permafrost stability. Snow and moss cover are important factors influencing heat fluxes. The influence of surface fluxes on heat fluxes is estimated based on mathematical modeling and numerical experiments on the model. The processing of data from field measurements of soil temperature made it possible to determine the heat fluxes for the cold and partially warm periods of the year. A comparison of the data from model calculations and measurements of heat fluxes showed a satisfactory agreement. The difference between them from December to February did not exceed 4%; in November and March, 9 and 8%, respectively. In 2023/24, during the period with negative air temperatures lasting 255 days with an average air temperature of −7°C, soil heat losses amounted to 76.5 and 92.3 MJ/m2 with snow thickness of 1.14 and 0.63 m, respectively; the average values of heat fluxes from October to March were 4.9 and 5.9 W/m2. According to model calculations, with an average daily positive air temperature of 6.8°C, the loss by the soil in winter is 10 MJ/m2 less than the heat flux into the soil in summer, which leads to permafrost degradation. At snow cover depth of 0.5 m, the heat input into the soil in summer coincides with the heat loss in winter. With a higher snow cover depth, the heat flux from the soil to the atmosphere decreases, soil cooling decreases, and permafrost degradation will occur. The same processes will occur when the snow cover is 1-m-deep and the moss cover is less than 3-cm-thick. For a moss cover of greater thickness, the thermal stability of permafrost rocks is preserved. Numerical experiments on the model estimated the heat fluxes and the thickness of the active layer for different snow and moss cover thicknesses and atmospheric air temperatures.

The results of verification of the aerodynamic method for calculating turbulent heat fluxes between the glacier and the atmosphere using the eddy covariance method are presented. The experiment was conducted on Aldegondabreen, Svalbard, in August 2022. Comparison of the methods showed a high agreement between the fluxes estimated by the two methods (R2 = 0.7), but the aerodynamic method underestimated the flux (with a mean error of 14%). The eddy covariance method allowed us to estimate the aerodynamic roughness length parameter for Aldegondabreen z0m = 0.8 mm, and the thermal roughness length z0h = 0.08 mm. The uncertainty analysis of the aerodynamic method revealed systematic errors related to the wind flow direction. The coefficient of proportionality was 0.67–0.70 for the wind direction along the glacier slope and 0.98 for the wind direction perpendicular to the glacier slope. Mean values of heat fluxes during the ablation season for the period 1991–2020 were calculated for Aldegondabreen: the shortwave balance is 72.6–113.8 W m–2; the longwave balance is 14.5 W m–2; the turbulent fluxes of sensible and latent heat determined by the aerodynamic method are 20.5 and about 1 W m–2, respectively. Thus, even allowing for a systematic method error of 14% (~3 W m–2), the total turbulent heat exchange of 24.5 W m–2 was lower than the mean estimates for the shortwave balance.

Ice cover is one of the main parameters describing the state of various water areas. The simplicity of calculation determines the frequency of using the indicator in research both for reading the seasonal course and interannual changes in the state of the ice cover and for verifying model data or reanalysis data. In this paper, ice cover is calculated based on five data sources. The comparison is based on satellite data from the NSIDC DAAC archives (October 26, 1978, to March 31, 2023; spatial resolution is 25 × 25 km, temporal resolution is 1 day; the data were collected by SMMR, SSM/I, and SSMI/S sensors on the DMSP program satellites, as well as the Nimbus-7 satellite and OSISAF (product code OSI-401-d; March 1, 2005, to present; spatial resolution is 10 × 10 km and temporal resolution is 1 day; the data were collected by the SSMI/S sensor on the DMSP program satellites). Model data from the international CMIP (Coupled Model Intercomparison Project) project are used for comparison and verification. Of the more than 40 models of the sixth phase of the project, two were selected that provided the necessary data and were suitable in terms of spatial and temporal resolution: MPI-ESM1-2-HR and AWI-CM-1-1-MR of the Max Planck Institute and the Alfred Wegener Institute, respectively. For all obtained coverage series, the mean, standard deviation, range, correlation intervals, trend coefficients, and standard error were estimated relative to the NSIDC series for the data intersection period of September 19, 2016 to June 31, 2023, in each of the Russian Arctic seas, as well as for the water area as a whole. Using the statistical characteristics, satellite data on ice cover were compared with the results of modeling in accordance with different socioeconomic trajectories (Shared Socioeconomic Pathways (SSPs)) for both models, the quality of ice cover modeling was assessed, and scenarios were selected that most closely matched the satellite data for both the entire Russian Arctic water area and for individual seas. Based on the optimal scenarios, possible changes in ice content were predicted.

This paper considers a forecast of avalanche danger in the Caucasus at the end of the 21st century based on the climatic avalanche indicator criterion developed at Moscow State Universityusing the results of the CMIP6 Earth System Models (ESM). The quality of model estimates of modern winter climate in the Caucasus has been evaluated. The best models are selected, for which the average temperature error is –0.6°C and precipitation error is 10%. According to the data of these models, by the end of the 21st century, the average winter air temperature in the Caucasus will be 4–6°C higher than the present one, and the precipitation sum will exceed the modern value by 25%. The frequency of seasons with extreme moisture will increase 2–3 times (monthly precipitation more than 100 mm). The seasonal maximum precipitation at the end of the 21st century will shift to March, while extremely dangerous avalanche winters are usually accompanied by a January maximum precipitation with a significant negative temperature anomaly. Experiments were also conducted with the numerical model SNOWPACK, which showed that, despite the positive precipitation anomaly and the possible occurrence of cold winters, the most typical situation by the end of the 21st century will be the formation of a homogeneous snow column with low density, or heavily watered snow cover. Both situations are not avalanche-prone. Therefore, the background forecast of avalanche danger for the years 2071–2100 can be formulated as follows: a significant decrease in the frequency of the most destructive large avalanches from dry snow in high-mountain areas and their disappearance in midmountain areas, as well as an increase in the number of less dangerous avalanches from loose and wet snow.

The results of experimental studies of the propagation of a nonlinear acoustic wave (NAW) in the surface layer of the atmosphere are analyzed. The influence of the underlying surface and vegetation on the waveform, as well as on its amplitude and width of the frontal region, is considered. A large-scale effect of the interaction of a NAW with vegetation is revealed. It is shown that the expansion of the front region of the wave obeys the law of energy similarity. The necessity of searching for a mechanism that causes such a character of wave development is noted.

The boundary conditions at the Earth’s surface have a significant influence on the planetary and synoptic scale flows that form in the atmosphere. In the Earth’s real atmosphere, it is difficult to isolate and study the influence of boundary conditions, because the spatial structure of large-scale flows and their temporal variations are strongly influenced by the distribution of land and ocean, surface relief, the hydrological cycle, and other factors. It is possible to study the role of the underlying surface using idealized models of Earth-like planets. This paper presents a comparative analysis of the structure and dynamics of the atmospheric general circulation and baroclinic waves for idealized, zonally homogeneous planets. Numerical experiments are performed using the WRF-ARW software package for the built-in characteristics of the Earth’s atmosphere and the terrestrial parameters of planetary motion and insolation. Three model configurations are considered: a desert planet (DP), a desert planet with an equatorial ocean (EOP), and an aquaplanet (AP) with a fixed meridional temperature distribution. It is shown that the DP is characterized by strong seasonal variations, leading to remarkable features both in the structure of the mean general circulation and in the distribution of velocity and temperature pulsations. On an EOP, the meridional velocity and temperature pulsations are similar to those observed in the Earth’s atmosphere. They are concentrated at midlatitudes and separated by height, with the maximum of temperature pulsations in the lower part of the troposphere and the maximum of velocity in its upper part. On the AP, the temperature pulsations are significantly smaller in amplitude and shifted into the middle layers of the troposphere. Simulations have shown that, despite zonally homogeneous boundary conditions and the absence of relief, the intensity, lifetime, phase, and group velocity of the baroclinic waves vary significantly on all the model planets. On a DP and an EOP, there is a pronounced season of maximum wave activity. On the AP, there are no strong seasonal variations, but long intervals of westward blocking are observed. The spectral composition of the baroclinic waves and their seasonal variability have been analyzed.

Space methods for remote sensing of the Earth began to develop almost immediately after the first launches of artificial Earth satellites. As early as in 1962, the first Soviet satellites of the Kosmos series were developed, which played an important role in the study of physical processes in the Earth’s atmosphere and the World Ocean, as well as in the treatment of many scientific, economic, and defense problems. In subsequent years, these studies were continued on satellites of the Okean, Meteor–Priroda, and Interkosmos series, as well as on the Salyut-6 and Salyut-7 space stations and the Priroda module of the Mir station.

Long-term average values and anomalies of the duration of the period of positive temperatures and the total water-temperature value have been calculated using satellite data sets on the average daily temperature of the surface water layer for 2010–2020 in sites of traditional fishing for Pacific oyster Crassostrea gigas (Salmon Bay and Busse Lagoon). The dependence of the shell size and total weight of Crassostrea gigas on temperature has been revealed. On the whole, the average values of its height and weight are much lower than the normal value in abnormally warm years and higher than the normal value in abnormally cold years. This may indicate that the oyster, as a temperate-latitude species, is tolerant to cold and moderate temperatures; however, it can hardly develop under conditions of long-term elevated temperatures. The exception is the weight of the mollusk in the Salmon Bay, where its weight is directly correlated with the total water-temperature value.

A fundamentally new mechanism of tsunami generation as a result of water discharge into rapidly opening seismic fractures of the bottom is proposed. A mathematical model of the phenomenon developed within the framework of the linear potential theory is presented. The main parameters of the problem that affect the characteristics of the formed wave are revealed.