Vol 60, No 3 (2024)

Analysis of the wind waves dispersion relation becomes complicated if drift current is present. In general, this relation is derived from the Rayleigh equation, which does not have an analytical solution for an arbitrary velocity profile. In the limiting case, when the gravity-capillary wavelength is small compared to the typical flow depth, the simple Doppler approximation can be used. But in general, this approximation is not valid, and it necessary to take into account the vertical profile of horizontal velocity up to the depth, which corresponds to the considered wavelength. The velocity profile of the drift current is determined using Particle Image Velocimetry. High-resolution spatiotemporal spectra of the waves are obtained with color schlieren technique. Small addition of sodium dodecyl sulfate enabled us to estimate the influence of soluble impurities on the structure of the drift current and modification of the ratio between the drift current depth and the gravity-capillary wavelength. In the present work, an algorithm for numerical calculation of the dispersion relation for a given velocity profile is proposed. It is shown that the dispersion relation for a wind channel is adequately described by Rayleigh equation and the angle between the wave propagation direction and the wind, which is introduced in geophysics for correction of the dispersion relation, may be actually related to different values of the ratio between the wavelength and the drift current depth.

Current Earth climate changes are caused by the violation of the planet’s radiation balance (RB). In this study the changes of the one of RB’s components – yearly and monthly averaged global and regional outgoing thermal radiation of Earth or the Earth own radiation (EOR) in a spectral range 660–1300 cm^-1 for 2015–2022 by IR Fourier-spectrometer IKFS-2 onboard the “Meteor-M” No2 satellite – is analyzed.

It is shown that EOR on a global scale in a range 660–1300 cm^-1 on average decreased during the period of 2015–2022. Mean integral radiation in the same wave-lenght range decreased by ~0.5 W m^-2 during 2015–2022. The most pronounced decrease of EOR was found in tropics, when the least pronounced – on polar latitudes. Besides, a negative trend of the integral EOR was found in tropics (up to 0.95–1.3 ± 0.1 W m^-2 for the 8 years) with relatively high coefficient of determination (0.46–0.57). At the same time, there is no pronounced trend of EOR on the polar and middle latitudes.

In this paper, we discuss parameterizations of turbulent mixing processes in models of inland water bodies (lakes and reservoirs) that allow turbulent fluctuations to develop in the presence of small velocity shear even in the case of highly stable stratification. A parameterization of the turbulent Prandtl number is proposed, which takes into account the non-gradient correction for the mass flux and depends on two parameters: the anisotropy parameter, which describes the differences in the vertical and horizontal scales of the density field correlations, and the maximum flux Richardson number. It is shown that the value of the maximum flux Richardson number and, as a consequence, the asymptotical increase in the turbulent Prandtl number under strong stability are associated with differences in the integral time scales determined by the dissipation rate of the kinetic or potential energy and the fluctuation intensities of the corresponding fields. This is consistent with the direct numerical simulation of shear-driven stably stratified turbulence. The anisotropy parameter sets the transitional regime from neutral stratification to strong stability. Using the proposed parameterization, numerical experiments were carried out to reproduce the thermal and biochemical regime of a inland water bodies (Lake Kuivajärvi and Rybinsk Reservoir). The results show that the distribution of biochemical concentrations, gas exchange processes are more sensitive to the value of maximum Richardson flux number.

The paper provides an overview of a series of articles aimed at creating a regional model based on the WAVEWATCH III spectral wave model adapted to the conditions of an inland water body using the WRF atmospheric model. Adaptation and verification of the models was carried out on the basis of the results of a series of field experiments to study the wind-wave regime of the Gorky reservoir performed in 2012–2019 using an autonomous buoy station based on the Froude oceanographic buoy. Within the framework of the WAVEWATCH III model, an analysis was made of the influence on the simulation result and subsequent adjustment of the parameters of the WAM 3 wind input parameterization, as well as the scheme for the approximate calculation of the Boltzmann integral Discrete Interaction Approximation (DIA). Within the framework of the WRF model, calculations were carried out using various parameterizations of the planetary boundary layer and the near-surface layer of the atmosphere, and the advantage of using the Large Eddy Simulation method was shown. In addition to the review, the paper presents preliminary results of coupling the wave and atmospheric models, which makes it possible to adjust the interchange of parameters between the models at each time step.

The paper presents a technique for measuring the temperature of an inhomogeneous underlying surface using unmanned aerial vehicles (UAVs). To test the proposed technique, measurements over various landscapes are presented: dunes in an arid zone, a temperate swamp, a subarctic city, and a combination of natural and anthropogenic landscapes in the Arctic. A measuring complex based on a DJI Mavic 2 Zoom quadrocopter with an installed Flir TAU2R thermal camera was used. Methods for correcting emerging hardware errors have been developed. To obtain detailed data on the spatial distribution of the surface brightness temperature, the orthomosaic construction method was used. Thermal maps of surfaces with relief inhomogeneities (dunes), moisture inhomogeneity (swamps), urban areas in polar and subpolar conditions were obtained at different times of the day. It is shown that thermal contrasts can reach the first ten degrees within an area of = 10–20 ha, both against the background of daytime heating and nighttime cooling of the surface, and could have a significant effect on the spatial distribution of the heat transfer characteristics of the atmosphere and the underlying surface. The developed methods are recommended for constructing surface thermal maps using thermal imaging technology.