东海陆架参量次谐频不稳定和风生近惯性波研究OA

This study aims to enhance our understanding of the physical characteristics of the East China Sea,in-cluding the generation mechanisms and modal structures of near-inertial internal waves over the shelf.The study analyzes the bimodal characteristics observed within the near-inertial frequency band as well as the modal structure and vertical shear of these waves based on mooring observations from the region.The power spectrum reveals the presence of a subharmonic M1 peak and blue-shifted f peak in the near-inertial frequency band north of the semidi-urnal critical latitude.The kinetic energy enhancement in the M1 frequency band corresponds to a negative back-ground vorticity field.Bicoherence spectrum analysis confirms that the M1 motions are generated by parametric subharmonic instability(PSI).In addition,the slab model indicates that wind forces primarily drives the increase in blue-shifted near-inertial kinetic energy.In general,near-inertial waves in shallow waters exhibit vertical structures of the first mode,constrained by two-layer stratification.However,the wind-induced near-inertial velocities ob-served in this study are predominantly influenced by the second mode.This phenomenon may be associated with the proximity of the observation location to the Yangtze River estuary,where a larger salinity gradient leads to the disappearance of the two-layer stratification and promotes the formation of higher modes.Both wind forcing and PSI can induce energetic near-inertial vertical shear,which may be beneficial in studying the mixing characteristics near the critical latitude.