Influence of Seasonal Variability of the Wind Stress Vorticity on the Structure of the Black Sea Circulation

• Main Authors: A.А. Pavlushin, N.B. Shapiro, E.N. Mikhailova
• Format: Article
• Language: English
• Published: Federal State Budget Scientific Institution «Marine Hydrophysical Institute of RAS» 2018-10-01
• Series: Physical Oceanography
• Subjects: the black sea; eddy-resolving model; large-scale circulation; wind stress vorticity; seasonal variability; "knipovich glasses"
• Online Access: http://physical-oceanography.ru/repository/2018/5/en_201805_01.pdf

The present paper represents the results of two experiments on numerical modeling (within the framework of the two-layer eddy-resolving model) of the Black Sea large-scale circulation under the influence of the seasonally-variable wind. The actual bottom topography is taken into account in the model. The motion is excited only by the tangential wind stress with a non-zero vorticity. The energy loss is due to the bottom friction, the friction at the layers’ interface and the horizontal turbulent viscosity. In one of the experiments under consideration, the wind stress vorticity changes its sign depending on the season (in winter it is cyclonic, in summer – anticyclonic), but remains constant in space. In the other experiment, the field of the tangential wind stress is preset (according to the modern notions on its spatial variability) in such a way that over the sea western half there is the zone of anticyclonic vorticity, the area and intensity of which vary throughout the year. In both cases, the circulation in the Black Sea is periodically divided into two large cyclones – the “Knipovich glasses”. However, due to the western intensification of currents caused by the β-effect, the wind stress with spatially uniform vorticity results in formation of a cyclonic cycle of extremely high intensity in the southwestern part of the basin. In the other experiment that takes into account spatial variability of the wind stress vorticity above the sea, namely, anticyclonic vorticity of the wind tangential stress over the basin western part, the obtained circulation quite corresponds to the observational data.