Abstract: Near-inertial motion represents a significant dynamic process in the ocean, profoundly influencing vital physical phenomena such as energy transfer, circulation evolution, and vertical mixing. This study employs the FVCOM (Finite Volume Community Ocean Model) regional ocean model to construct a three-dimensional dynamic model covering the northern South China Sea. The model was thoroughly validated using High-Frequency radar observations. This study employs the model to simulate the near-inertial motion stimulated by Typhoon Talim (No. 4, 2023) in the northern South China Sea. It focuses on investigating the triggering mechanism, duration, and decay process of near-inertial kinetic energy during the typhoon, providing scientific basis for understanding the characteristics of near-inertial motion in this region. The results indicate that the energy driving the quasi-inertial motion triggered by Typhoon Talim primarily originates from wind energy input. In offshore regions, the quasi-inertial motion dissipates mainly through vertical turbulent dissipation; while in coastal areas, near-inertial motion primarily dissipates through bottom friction. The vertical convective term plays a dominant role in energy dissipation. Regions with strong buoyancy frequencies exhibit significant density stratification, suppressing vertical mixing and turbulence development, resulting in slower near-inertial energy dissipation that can persist for about one week. Conversely, regions with weak buoyancy frequencies show weaker density stratification and enhanced vertical mixing, leading to faster near-inertial energy dissipation that can last for three days.

Key words: near-inertial motion, typhoon, FVCOM model, northern South China Sea