Physical Oceanography (Apr 2023)
Anomalous Variations of the Typhoon Lionrock Induced Inertial Oscillations of Shelf Waters in the Peter the Great Bay in August – September, 2016
Abstract
Purpose. The purpose of the study is to analyze the characteristics of inertial oscillations induced by extreme atmospheric effects against the background of the shear current, using the example of inertial oscillations caused by the typhoon Lionrock in the shelf waters of the southwestern Peter the Great Bay against the background of the near-slope Primorskoe current. Methods and Results. The frequency-temporal spectral analysis of the typhoon Lionrock induced mesoscale variability of the rotational components’ realizations of the current velocity vector was applied. The current velocity realizations were obtained using the Seawatch oceanographic system moored on the southwestern shelf of the Peter the Great Bay. The specified analysis made it possible to establish that at the latitude at which the Seawatch system had been installed and at the initial stage of the typhoon impact, the spectral density of currents kinetic energy grew significantly at clockwise rotation at frequency ωi close to the Coriolis parameter f ≈ 2π/18 (rad/h). A similar growth of the kinetic energy spectral density was recorded at the same frequency ωi, but at the counterclockwise rotation and at the final stage of typhoon impact. The recorded inertial oscillations of velocity vector at opposite directions of its rotation at frequency ωi demonstrate a significant difference of their travel time curves from the canonical one at a circular clockwise rotation. Conclusions. Against the background of the near-slope Primorskoe current significantly amplified (up to 0.9 m/s) by the typhoon Lionrock, the velocity inertial variations of this current induced by the typhoon on the shelf of the Peter the Great Bay, show anomalous variability. The model of these oscillations in the presence of a shear current proposed by G. K. Korotaev and K. D. Sabinin (2017) provides a qualitative interpretation of the inertial oscillations’ variability in the bay shelf waters resulted from the typhoon Lionrock impact in August – September, 2016.
