Observation of interactions between internal tides and near-inertial waves after typhoon passage in the northern South China Sea

During the observational period of our study, Typhoon Hagupit passed over the mooring site and induced strong near-inertial waves (NIWs), which provided an opportunity to investigate the interactions between internal tides (ITs) and NIWs. Based on the mooring data, we compared the current spectra during the typhoon period and non-typhoon period in the northern South China Sea, and found that the high-frequency waves (fD₁ and fD₂) were evident during the former. Moreover, the observations of the current revealed that fD₁ and fD₂ occurred near the depth of strong vertical shear in the NIWs. In order to confirm the generation mechanism of fD₁ and fD₂, we compared the positions of strong vertical shear in the NIWs and strong vertical velocity in the ITs. It was established that the vertical shear of the horizontal current of the NIWs and the vertical current of the ITs contributed to the generation of fD₁ and fD₂.