Numerical Simulation of Vertical Heat Flux Induced by Near‐Inertial Waves With the Modulation of Mesoscale Eddy

Abstract

Recent in situ observations reveal that typhoon‐induced near‐inertial motions provide an efficient pathway for heat flux from the upper ocean into the interior, which is significantly modulated by mesoscale eddies. However, the dynamics driving the process is not well understood due to the limited observational data. In this study, a high‐resolution Regional Ocean Modeling System (ROMS) simulation is used to explicitly resolve vertical velocity and to decompose the full heat budget, enabling a quantitative separation of advective and diffusive contributions. The scenario that the near‐inertial waves (NIWs) triggered by Typhoon Kalmaegi (2014) in the South China Sea with the presence of two specific eddies along the typhoon track, one cyclonic eddy (CE) and one anticyclonic eddy (ACE) is presented by the numerical model. Following the typhoon passage, banded near‐inertial currents develop in both eddies and are accompanied by reduced Richardson numbers, indicating enhanced shear‐driven instability. Spectral analyses reveal a pronounced energy peak near the local inertial frequency with near‐inertial kinetic energy penetrating deeper and persisting longer in the ACE. Heat budget diagnostics further show intensified post‐typhoon vertical mixing, with the ACE characterized by a stronger and deeper‐reaching response. Consistently, the vertical heat flux in the inertial band is enhanced and extends deeper in the ACE than in the CE, implying more efficient downward heat redistribution under anticyclonic conditions. These results highlight the critical role of mesoscale eddies in regulating the penetration depth and efficiency of typhoon‐induced near‐inertial heat transport.