Spatial-temporal variability of inertial currents in the eastern part of the Black Sea in a storm period

N. A. Diansky, V. V. Fomin, A. V. Grigoriev, A. V. Chaplygin, A. G. Zatsepin
2019 Physical Oceanography  
Introduction. Analysis of numerical simulation of the inertial oscillations evolution in a storm period in the northeastern Black Sea is represented in comparison with the observations and the analytical solutions. The simulations confirm significant contribution of the inertial motions to formation of the velocity fields. It is shown that inertial oscillations do not affect the sea level changes and their character depends on vertical structure of the sea upper mixed layer. Data and methods.
more » ... Data and methods. Comparison the simulation results to the drift observations in the Black Sea were represented. It is noted that intensity of inertial oscillations in the deep-sea areas significantly exceeds the one in the shallow areas. At that, contribution of the inertial currents to the Black Sea general circulation in the deep-sea zone is comparable to that of the mesoscale motions. Analytical solution of the inertial oscillations' equation system (taking into account wind and its absence) was studied. Results. Inertial oscillations are excited in the velocity module due to an abrupt change of the wind speed. Moreover, harmonic oscillations are disturbed with depth. After the wind affect is over, the current velocity is barotropized due to fast transition from a quasi-stationary state to another one. It is shown that inertial oscillations are of two time scales conditioned by vertical viscosity. Discussion and conclusion. The first, short time scale is responsible for rapid formation of a new quasi-stationary state. It does not depend on the viscosity coefficient and is approximately equal to two inertial periods. The other, longer scale of the inertial oscillations attenuation, is associated with the energy drain of quasi-stationary oscillations from the upper layers of the sea to the deeper ones. This slow process of attenuation is proportional to the root of time.
doi:10.22449/1573-160x-2019-2-135-146 fatcat:wk5rwaajgzh55gw6yemftuzc6i