The asymptotic behavior of Rossby waves in the ocean interacting with a shear stationary flow is considered. It is shown that there is a qualitative difference between the problems for the zonal and non-zonal background flow. Whereas only one critical layer arises for a zonal flow, then several critical layers can exist for a non-zonal flow. It is established that the integrated ray equations of Hamilton are equivalent to the asymptotic behavior of the Cauchy problem solution. Explicit analytical solutions are obtained for the tracks of Rossby waves as a function of time and initial parameters of the wave disturbance, as well as the magnitude of the shear and angle of inclination of the flow to the zonal direction. The ray equations of Hamilton are analytically integrated for Rossby waves on a shear flow. The obtained explicit expressions make it possible to calculate in real-time the Rossby wave tracks for any initial wave direction and any shear current inclination angle. It is shown qualitatively that these tracks for a non-zonal flow are strongly anisotropic.

The climate change is becoming more and more obvious, which leads to an increase in the number of intense atmospheric vortices (tropical and quasi-tropical cyclones, polar hurricanes, tornadoes) and an expansion of the geographical and seasonal limits of their occurrence. A recent example was the quasi-tropical cyclone in the Black Sea on August 11–16, 2021. Under these conditions, the accurate diagnosis of cyclogenesis is extremely important and, based on it, the forecast of further evolution and the trajectory of the forming vortex. The main source of energy for tropical, quasi-tropical and polar hurricanes is thermal convection caused by significant temperature differences between the atmospheric layer and the underlying water surface. This allows us to propose a unified approach for the diagnosis of cyclogenesis in all three cases.

For the first time, an original approach is proposed for determining the exact time of the onset of tropical cyclogenesis. This approach includes a combined analysis of satellite images of cloudiness and the corresponding data of cloud-resolving numerical modeling for the region of developing vortex disturbance. The theoretical basis is the fundamental hypothesis of a turbulent vortex dynamo. The theory provides quantitative criteria that determine the excitation of large-scale vortex instability in the atmosphere. Atmospheric numerical modeling makes it possible to accurately determine the moment of time at which the necessary conditions for the onset of instability are realized. This moment is interpreted as the beginning of cyclogenesis. The specific configurations of vortical cloud convection found in the work, which correspond to the initial stage of cyclogenesis, can be used in operational meteorological diagnostics when analyzing satellite images of cloudiness. The approach is illustrated by the example of diagnostics of tropical cyclogenesis.

This study analyses climatic changes in the Chukchi Sea and the Beaufort Sea based on numerical modeling using a regional ice-ocean model. Numerical experiments were carried out for the period 2000–2019. NCEP/NCAR reanalysis data were used to determine the ocean and sea ice surface fluxes. The temperature, salinity, and transport of Pacific waters entering the Arctic Ocean were specified as boundary conditions in the Bering Strait. Three types of boundary values were used for the experiments: a) monthly average climate data averaged over the period 1990–2003; b) monthly average climate data averaged over the period 2003–2015; c) average monthly measurement data since 2016 to 2019. The sensitivity of the model to the variability of the transport and temperature of the incoming Pacific waters was studied, and the effect on the ocean heat content, the volume and sea ice extent was analyzed.

Numerical experiments simulate the transport of warm Pacific water across the Chukchi shelf in the north direction and onto the Beaufort Sea shelf, the process of warm water sinking on the continental slope in the autumn-winter period. In recent years, at the points on the boundary of the shelf and deep-water areas, the amplitude of seasonal temperature fluctuations in the surface

layer increases and the temperature rises significantly at a depth of 100 m.

The simulation results demonstrate an increase in the ocean heat content and decrease in the ice volume in the Beaufort and Chukchi Seas, caused by an increase in atmospheric temperature. We also showed that the increase in temperature and transport of the Pacific water, which began after 2003, contributed to an additional increase in the ocean heat content of both seas, a reduction in the ice cover area, and a delay in the ice formation in the Chukchi Sea.

Despite a wide-ranging research, there is almost no information regarding the major biogeochemical fluxes that could characterize the past and present state of the European Lake Onego ecosystem and be used for reliable prognostic estimates of its future. To enable such capacity, we adapted and implemented a three-dimensional coupled hydrodynamical biogeochemical model of the nutrient cycles in Lake Onego. The model was used to reconstruct three decades of Lake Onego ecosystem dynamics with daily resolution on a 2 × 2 km grid. A comparison with available information from Lake Onego and other large boreal lakes proves that this hindcast is plausible enough to be used as a form of reanalysis. This model will be used as a form of studies of Lake Onego ecosystem, including long-term projections of ecosystem evolution under different scenarios of climate change and socio-economic development.

A three-dimensional coupled hydrodynamical biogeochemical model of the nitrogen and phosphorus cycles has been used for a long-term reanalysis of the Lake Onego ecosystem. The comparison between simulation and sparse irregular observations, presented in the first part of this paper, demonstrated plausibility of the reconstructed temporal and spatial features of biogeochemical dynamics at a long-term scale, while seasonal dynamics of variables and fluxes are presented here. As new regional phonological knowledge, the reanalysis quantifies that the spring phytoplankton bloom, previously overlooked, reaches a maximum of 500 ± ± 128 mg C m^–2 d^–1 in May, contributes to approximately half of the lake’s annual primary production of 17.0–20.6 g C m^–2 yr^–1, and is triggered by increasing light availability rather than by an insignificant rise in water temperature. Coherent nutrient budgets provide reliable estimates of phosphorus and nitrogen residence times of 47 and 17 years, respectively. The shorter nitrogen residence time is explained by sediment denitrification, which in Lake Onego removes over 90 % of the bioavailable nitrogen input, but is often ignored in studies of other large lakes. An overall assessment of the model performance allows us considering the model a necessary and reliable tool for scenario simulations of possible changes in the Lake Onego ecosystem at the requested spatial and temporal scales.

The numerical experiments were carried out to assess the hydrodynamic regime of the eastern part of the Sevastopol Bay, subject to the Chernaya River runoff (high- and low-water periods) and the Yuzhnaya Bay, subject to the technogenic load using the hydrothermodynamic block of the numerical three-dimensional unsteady model MECCA (Model for Estuarine and Coastal Circulation Assessment).

The simulated hydrodynamic parameters of the selected parts of the Sevastopol Bay were used to analyze the self-purification capacity of their water bodies by calculating the assimilation capacity for inorganic phosphorus. Phosphates suggested as a priority pollutant in municipal and storm runoffs in the water area of the bay and a determining factor of its in the bay eutrophication. At the same time, to neutralize the differences in the water volumes of the studied water areas when calculating the self-purification ability, estimates of the specific assimilation capacity of their ecosystems were obtained.

According to the simulations for the eastern apex part of the bay during high-water period, the water circulation in the surface layer contributes to the spread of pollutants throughout the entire water area of the bay. During the low-water period in the eastern part of the bay, currents prevail, directed towards the Chernaya River mouth in the surface and in the bottom water layer both in the northwestern and western wind directions. It contributes to pollutant accumulation in this part of the bay, thus reducing ability to self-purification.

Possible reasons for the low self-purification capacity of the ecosystem of the eastern part of the Sevastopol Bay with respect to inorganic phosphorus are analyzed, which are associated both with the volumes of incoming Chernaya River waters during winter high- and summer low-water periods, as well as with the features of the morphometric structure of the water area bottom.

For the Yuzhnaya Bay water area, the hydrodynamic regime is defined by a difficult water exchange with the main water area. Ventilation of the waters of the Yuzhnaya Bay is mainly determined by the wind regime, as a result of which the waters are either trapped in the bay or carried out of it, which undoubtedly affects the self-purification capacity of its ecosystem.

Here we describe the features of the horizontal and vertical distribution of total suspended matter in the northern part of the Black Sea and their relationships with the water temperature, salinity, and density fields measured at the identical grid during hydro-optical surveys from 2016 to 2020. The results show that the primary sources of increased total suspended matter concen trations in the northern part of the Black Sea are low-salinity and turbid waters of the Kerch Strait; runoffs of the Rioni, Enguri, and other rivers in the east of the survey area; together with freshened waters of the Dnieper, Dniester, and Danube runoff from the northwestern shelf. Higher turbidity was observed in the deep-water part of the sea, associated with the cyclonic gyres and meanders of the Rim Current effects. The total suspended matter vertical structure features an upper mixed layer, which usually coincides in thickness with the upper thermohaline upper mixed layer. Significant negative correlations were found for this layer comparing total suspended matter concentration versus temperature and salinity, while the correlation appears positive with density values. Below, a total suspended matter subsurface maximum was observed in the seasonal thermocline and pycnocline layer. The high turbidity layer appeared almost an order of magnitude thinner in the regions of maximum temperature gradients versus the areas where the temperature gradient was weak. A local total suspended matter minimum occurred below the cold intermediate core, corresponding to the main thermocline, halocline, and pycnocline layer. Beneath this minimum, there was a local increase of total suspended matter coinciding with the upper boundary of the hydrogen sulfide zone.

The paper presents the results of the interrelated calculation of the unsteady uneven movement of the river flow and the re-formation of the bottom of the largest flowing Kuibyshev reservoir in Eurasia in different phases of water content. These calculations are based on the hydrodynamic model “Wave” and algorithms for calculating solid runoff (analytical formula for sediment flow rate), changes in the transport potential of the flow and, as a result of the latter, changes in the bottom marks. In this case, the dynamics of the bottom marks is taken into account in subsequent calculations and is one of the arguments of the model. Based on the model calculations, the spatial distribution of bottom sediments in the water area of the reservoir was investigated and maps of accumulation and erosion of the bed in different phases of water content were constructed. It is shown that for the entire calculation period, an uneven redistribution of sediments in the reservoir is observed: erosion occurs in the upper part, and accumulation occurs in the middle and lower parts. In general, for the Kuibyshev reservoir, the contribution to siltation only by river sediment is insignificant. On average, over the 150-day modeling period for the entire reservoir water area, sediment accumulation is 0.5 mm/period. The weak dynamics of currents in the vast water area of the reservoir reaches does not contribute to active channel transformations. The most intensive processes of bottom transformation occur in places of narrowing of the water area, where the contribution of the non-stationary regime to the formation of the bottom relief during the rise and fall of the flood is best expressed. More full-flowing years will also lead to a more intensive redistribution of solid runoff and bottom sediments coming from the upper strata.

The current paper considers the possibility of physical modeling of ice cover deformation under the action of a moving load at low speed. Using an equation for elastic plate oscillations on the foundation of a hydraulic type, it is shown that similarity of a stress and strain state (SSS) of model ice can be achieved but within the scope of the approaches based on a classical theory of Nogid-Shimansky modeling of ice cover. Taking into account certain complications connected with practical implementation of the above method, the applicability of a reduced-thickness ice model developed at NNSTU is investigated. This model uses the ice thickness that intentionally does not comply with the similarity requirements, all other requirements being satisfied, thus providing incomplete similarity of the model. Some disagreements with a Nogid-Shimansky model connected with that are revealed and their influence on the end result is evaluated. The applicability of a thin ice model is investigated in natural cooled model tanks of classical shape used for modeling of load movement at low speed. The results of the experimental investigation of ice cover deformation under the action of a moving load using a model for the natural thin ice are given. The modification of a wave shape and maximum ice deflection depending on change of a movement speed and loading are investigated. The connection of decrease of a ratio of the deflection basin profile area to the outward ice bending profile in front of a moving load with increase of speed at the start of the movement is demonstrated, which can be an evidence of a sharp growth of energy expenses for ice cover deformation when the interaction between the technical facility and ice cannot be considered as quasistatic. An exact evaluation of such expenditures is crucial when designing the ice-breaking facilities clearing a path through floe ice.

The paper concentrates on the influence of grid parameters, the time step size, and the order of temporal and spatial approximation on the solution accuracy of the floating body problem. Damped free oscillations of the cylinder on the water surface is under consideration. The numerical simulation method of the floating bodies is based on the solution of a system of Navier-Stokes equations together with a VOF (Volume of Fluid) method. The Navier-Stokes equations are discretized using finite volume method (FVM), and solved by SIMPLE method. The motion of the body is ensured by the deformation of the computational grid. A CSF (Continuum Surface Force) model is used to account for the surface tension forces. The method is implemented in LOGOS software package. The research has shown that implementation of the second-order scheme for temporal and spatial discretization leads to a more accurate result. The relaxation factor of body surface force has no affects on the solution accuracy.

The professional tool’s investigations of climate in the world began relatively recently. Since the second half of the XIX century Russia was one of the meteorological investigation’s leaders. Study of the history of meteorology in the Russian Far East and in China, systematization, and analysis of research results would be a great contribution to a better understanding of the importance of Russian research in the development of meteorology. The article discusses about the background of the creation of the observatory in Vladivostok. The author analyzed the chain of political and scientific decisions about the transfer of the magnetic and meteorological observatory of the Academy of Sciences from Beijing, through the plans of the creation an observatory in Port Arthur to the construction of an observatory in Vladivostok. In addition, the observatory’s budget and plans for its equipment are considered. Such materials are usually not the subject of close attention of researchers. In the historiography lacks an investigation about the role of the Russian Academy of Sciences to the development of a network of magnetic meteorological stations and observatories in the Russian Far East and in adjacent territories (Korea, China). The author introduced into scientific circulation new archival data from the Russian State Archive of the Navy and the St. Petersburg branch of the Archive of the Academy of Sciences.