Vol 59, No 5 (2023)

More than 90% of oceanic heat enters the Arctic Ocean with the Norwegian Current. In this paper we examine the mechanisms of variability of the oceanic heat flux in the Norwegian Current (across the Svinoy section in the southern Norwegian Sea) in 1993–2019. GLORYS oceanic reanalysis with a spatial resolution of 1/12° is used. It is found that the variability of oceanic heat flux is associated with that of water transport, which, in turn, is associated with variability of the sea level gradient across the Norwegian Current. It is shown that an increase in water transport of the Norwegian Current is a result of a decrease of the atmospheric pressure over the central part of the Norwegian Sea. The latter intensifies the southwesterly winds along the Scandinavian Peninsula. The sea level gradients across the Norwegian Current, formed by the winds, are primarily associated with Ekman pumping towards the coast, as well as with the wind stress curl. Both have a significant impact on the variability of water transport through the section. Another factor is variability of the steric sea level gradient, which significantly affects the water transport during the period of a rapid temperature rise of in the Norwegian Current (1995–2005).

In the framework of a two-level quasi-geostrophic model, the stability of flow with a constant vertical shear is investigated. Analytical expressions for the increment of perturbation growth in linear stability theory were obtained. The Galerkin method with three basic Fourier harmonics was used to describe the nonlinear dynamics of perturbations. A nonlinear system of ordinary differential equations is formulated for amplitudes of Fourier harmonics. It is shown that in the absence of bottom friction all solutions of the system describe periodic mode of nonlinear oscillations or vascillations. The situation changes fundamentally in the model with bottom friction. In this case, for a wide range of parameter values, the system solutions exhibit complex chaotic behavior. Thus, chaos or turbulence emerges for large-scale motions.

Analysis of variations of stratospheric ozone content at 13–18, 18–23 and 23–30 km layers is presented from data of lidar and satellite measurements in 2014–2022 over Obninsk city (55.1° N, 36.6° E). Modeling of deviations from seasonal run for separate quarters of year are fulfilled by using of linear regression method. Impact factors under consideration are quasi-biennial oscillation of zonal wind in tropical stratosphere (QBO), Arctic oscillation (AO), El-Nino – Southern oscillation (ENSO), solar activity (SA), volcanic aerosol (VA) and polar stratospheric clouds (PSC). Enhancement of ozone content is observed in eastern QBO phase at 18–30 km layer (I–II quarter) and in western QBO phase at 13–23 km layer (IV quarter). At separate layers it is revealed significant impacts of AO (II–III quarters), SA (I–II quarters) and VA (III–IV). During a year influence of PSC is originally showed in II quarter at 13–18 layer and then in IV quarter at 13–18 layer. Possible physical mechanisms are discussed which are the basis of the correlation relations observed.

Data from field experiments on the dynamics of SO₂ oxidation in cloud droplets are presented. The rapid oxidation of SO₂ by molecular oxygen observed in experiments is attributed here to the catalytic action of a pair of manganese and iron ions in droplets. Their inhomogeneous effect by the drop-size distribution, attributed in experiments only to the leaching of ions of these metals from coarse particles of mineral dust is also due to the transition of the oxidation reaction into a branched mode. The results obtained indicate that the branched regime of catalytic oxidation of SO₂ detected in cloud droplets should be considered as a new and significant source of sulfates in the atmosphere. This process must be taken into account when considering both the budget of sulfates in the global atmosphere and their impact on the climate.

The analysis of the dynamic and energy characteristics of water circulation in the northern part of the Black Sea was performed on the basis of the assimilation in the numerical model of the data of three hydrological surveys in 2016, carried out on expeditions of 87, 89 and 91 cruises of the R/V Professor Vodyanitsky (summer, autumn and autumn-winter seasons). Numerical experiments were implemented on a horizontal grid (~1.6 km × ~1.6 km) with 27 vertical horizons and an atmospheric effect close to the real one was used. A procedure of assimilation of the observational data was based on the Kalman filter, taking into account the heterogeneity and nonisotropy of the errors of the estimates of the temperature and salinity fields. The integral energy terms in the kinetic and potential energy budget equations for three seasons were estimated. In the summer season, there was a slight weakening of the RC and the main mechanism for the formation of anticyclonic eddies near Sevastopol and near the southeastern shores of Crimea was baroclinic instability of the current (as evidenced by the increase in the slope of isopycnical surfaces and negative values of the work of the buoyancy force). An anticyclonic eddy near Yalta with a radius of about 25 km was generated due to the development of shear instability of the current. In the autumn season, the RC jet was pressed to the shore and there was a decrease in the number of eddies in comparison to the summer season. The formation of anticyclonic eddies with a radius of about 35–40 km in the western part of the region was caused by barotropic instability of the current, the formation of eddies along the Crimean coast – by baroclinic instability. In the autumn-winter season, the RC had a pronounced jet character and there was an increase in the processes of baroclinic instability with the generation of eddies of different scales between the coast and the RC, as well as in the area, located between 31.5 and 33° E, with the weakening of the wind effect. During all seasons, small-scale anticyclonic and cyclonic eddies could be generated along the western and eastern coast of Crimea in the upper layer when current flowed around the coastline and inhomogeneities of the bottom topography under the action of weak winds.

Processes of the wind waves formation remain poorly understood, despite the numerous studies. One of the main reasons, in our opinion, is that simplified theoretical analysis does not take into account the weak film of natural contaminants. In the present work waves generation in two channels is experimentally studied and compared for ethanol, water and water with addition of soluble surfactant SDS (sodium dodecyl sulphate) in various concentrations. The employed concentrations hardly affect the surface tension coefficient, but lead to significant modification of the subsurface flow structure. In ethanol the surface film is not formed, so it can be considered as reference case. In water and water with added surfactant the film gets broken and the surface becomes clean at certain critical wind speed, which grows for increasing surfactant concentration. For the surface to remain clean, the contaminant adsorption to the surface must be compensated by its removal by the tangential stress. Three experimental techniques are used to study the influence of cool skin on formation of the wind waves. The surface relief is measured with modified color schlieren technique and the liquid velocity fields are determined with Particle Image Velocimetry (PIV). The surface temperature fields, which allow identification of the regions of the cool skin rupture, are obtained with IR thermography. IR thermography is also used to study the surface velocity field (IR PIV). The film is shown to have significant influence on both the waves amplitude and the structure of subsurface flow.