Volume 50, Nº 5 (2023)

With the help of numerical modeling and reanalysis data, interactions between the components of the climate system in the Arctic under the conditions of climate warming have been studied. When analyzing the data and results of numerical experiments, the method of expanding fields of state characteristics in terms of empirical orthogonal functions was used. Trends in the atmospheric impact on the ocean–ice system during the warming period and their relationship with trends in future warming projections under the most severe RCP 8.5 scenario in the CMIP-5 project are identified. In addition, numerical modeling revealed a 44-year periodicity in the interaction between the Arctic Ocean circulation and the heat content of the Atlantic water layer: this can be associated with the Atlantic meridional overturning circulation.

Model estimates were made for changes in the actual evaporation of boreal forests in the taiga zone of European Russia caused by climate evolution in the XXI century. Climate changes were forecasted using the results of calculations by an MGO regional climate model. The space and time specification of the forecast data was made with the use of a model of the atmospheric boundary layer. Variations of the forecasted changes due to the use of different methods to calculate evaporation were studied. Calculations based on an additional (complementary) relationship, determining the actual evaporation with the use of standard meteorological characteristics were compared with observations and calculations based on a detail model of energy transport in a forest massif. The model values of the actual evaporation in the XXI century increase all over the European Russia. The effect of the intensity of dry periods on the evolution of actual evaporation is analyzed. It is shown that, despite the arid climate, the effect of dry periods on taiga forests will be moderately negative.

The article presents a revue of the estimates of soil surface moisture, soil water content, and evapotranspiration as elements of water and heat regimes of land surface areas at various spatial scales, made with the use of remote sensing data for Earth in various spectral ranges. In most cases considered in the study, such estimates were obtained with the use of land surface models. A special section is focused on the results of estimating soil surface moisture and water content using satellite data from microwave range, including radar data. Estimates of soil surface moisture content obtained with the use of neural networks are presented. A brief description is given to international hydrological–atmosphere experiments carried out under world research projects aimed to obtain data on the processes of moisture and heat exchange between the land surface and the surface atmosphere layer. Land surface, satellite, and model databases that have been formed using the results of studies in the field under consideration since the mid-1980s are reviewed. Prospects of further studies based on the development of new multispectral instrumentation, the creation of new databases, and the use of a new generation of satellites—global-coverage microsatellites with high-resolution sensors are presented.

The results of measurements of atmospheric turbulence characteristics were used to obtain parameterizations for calculating the dynamic roughness parameter and the roughness parameters for temperature and humidity for a shallow closed water body. At medium wind speeds, the results of calculations by Charnock formula are in agreement with observation data; in this case, the c parameter is three times as large as that in the case of an open ocean, and the passage from the viscous to wave mechanism occurs at high wind speeds, while the dynamic roughness parameter at the same wind speeds is greater. The roughness parameters for temperature and humidity at wind speed from 0.5 to 3 m/s are not equal. The empirical coefficients in the equations describing the ratio of the dynamic roughness to the roughness parameter for temperature (humidity) on Reynolds number are close to those obtained before for other closed water bodies, thus suggesting a common formation mechanism of transport processes in a viscous sublayer. The obtained parameterizations can be used in Earth system models and lake models for calculating turbulent flows over continental water bodies.

The article presents the results of application of Implicit Large Eddy Simulation method to numerical simulation of under-ice radiatively driven convection, developing in ice-covered water bodies in the moderate zone at the end of freeze-up period. Studies of the radiatively driven convection are of importance because of the role it plays in the temperature regime of lakes and the functioning of lake ecosystems at the end of freeze-up period. The simulation was carried out with the use of the finite-volume software code SINF/Flag-S, developed in SPbPU. The SIMPLEC algorithm with second-order accuracy was used for ad­vancing in time. The discretization of the convective terms was made with the use of QUICK scheme. The results of calculations were used to study variations in the temperature and pulsation velocity components with periodically varying intensity of external energy pumping during the daily cycle. The dissipation of the kinetic energy, background potential energy, and buoyancy flux were evaluated, and changes in these variables during a daily cycle of radiation impact were calculated. The efficiency mixing of water column was evaluated for the period of development of radiatively driven convection in a model domain simulating a small lake covered by ice.