Two-layer Eddy-resolving Model of Wind Currents in the Black Sea

Abstract

Processes of formation and variability of the Black Sea circulation are investigated using a two-layer eddy-resolving model. The wind effect only is considered as an exciting force; energy sink takes place due to horizontal turbulent viscosity, friction between the layers and the bottom friction. The rivers’ flowing to the sea and the water exchange through the straits are not taken into account. Numerical approximation requires application of the finite-difference scheme based on the box-method with the grid B (according to the Arakawa terminology), the two-layer scheme of time integrating, the friction implicit approximation nearby the interface and bottom, and the Coriolis force. Being nonlinear, the model, alongside with large-scale circulation, permits to describe vortex structures, formation of which is related to hydrodynamic instability of currents, coastline features, bottom topography and other factors. Discussed are the results of numerical experiments in which, for better understanding of mass transfer and vortex formation processes in the sea, the motion excited by stationary cyclonic winds is considered, whereas bottom topography, friction between the layers, and the β-effect are not taken into account. Relative role of horizontal viscosity and bottom friction is studied. The most interesting results are obtained at mall values of the bottom friction when the motions in the lower layer become significant. It is shown that the model reproduces the major features of the Black Sea circulation, and the most important particular is that it permits to simulate formation and transformation of vortices.

Keywords

the Black Sea, eddy-resolving model, hydrodynamic instability, horizontal and bottom friction.

DOI: 10.22449/1573-160X-2015-5-3-21

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