статья в журнале

En

Physical Oceanography

ISSN:1573160
eSSN:1573-160X

2022

10.22449/1573-160X-2022-6-587-601

Purpose. The work is aimed at investigating the influence of seasonal variability of tangential wind stress vorticity on the features of formation and intensity of the large-scale circulation in the Black Sea using the numerical simulation method. Methods and Results. Numerical experiments within the framework of the two-layer eddy-resolving model of the Black Sea were carried with the sea surface subjected to a periodical seasonally changing field of tangential wind stress, the average annual intensity of which was constant during one individual experiment, but was various in different experiments. Numerical integration over time was performed for a long time period, which was sufficient for the model solution to be considered statistically equilibrium. The large-scale circulation intensity was determined from the integral values of the model energy characteristics, namely the kinetic and available potential energies. The calculations have resulted in the long-term series of instantaneous current fields in the two-layer sea at different wind forcing intensity, which were subjected to further analysis. Conclusions. It has been established that in the Black Sea at certain parameters of wind forcing, the fluctuations can be induced in the large-scale circulation intensity with a period 6–8 years; at that the interannual variabil-ity of the average annual value of the tangential wind stress vorticity is not a reason of this phenomena. Taking into account the fact that the exciting wind forcing in the performed experiments was only of seasonal variability and repeated from year to year, the model-obtained longterm fluctuations in the large-scale currents intensity could be classified as the self-oscillations. The latter are the non-damped oscillations supported by an external energy source, the supply of which is regulated by the oscillatory system itself. In the case under consideration, the feedback mechanism required for the existence of self-oscillations, is provided by the dependence of the wind energy flow entering the sea upon the spatial distribution of surface currents, which can change in consequence of hydrodynamic instability of the currents and generation of the Rossby waves. © А. A. Pavlushin, 2022.

baroclinic Rossby waves, Black Sea, interannual variability, large-scale circulation intensity, self-oscillations

2023-01-26 12:21:39