Abstract. We used a well-validated three-dimensional ocean model to investigate the
process of energetic response of near-inertial oscillations (NIOs) to a
tropical cyclone (TC) and strong background jet in the South China Sea
(SCS). We found that the NIO and near-inertial kinetic energy (KEni) varied
distinctly during different stages of the TC forcing, and the horizontal and
vertical transport of KEni was largely modulated by the velocity and
vorticity of the jet. The KEni reached its peak value within ∼1/2 the inertial period after the initial TC forcing stage in the upper
layer, decayed quickly by 1∕2 in the next 2 d, and further
decreased at a slower rate during the relaxation stage of the TC forcing.
Analyses of the KEni balance indicate that the weakened KEni in the upper
layer during the forcing stage was mainly attributed to the downward KEni
transport due to pressure work through the vertical displacement of
isopycnal surfaces, while upward KEni advection from depths also contributed
to the weakening in the TC-induced upwelling region. In contrast, during the
relaxation stage as the TC moved away, the effect of vertical advection on KEni
reduction was negligible and the KEni was chiefly removed by the outward
propagation of inertial-gravity waves, horizontal advection, and viscous
dissipation. Both the outward wave propagation and horizontal advection by
the jet provided the KEni source in the far field. During both stages, the
negative geostrophic vorticity south of the jet facilitated the vertical
propagation of inertial-gravity waves.
Eddy Heat Transport in the South China Sea as Estimated from In Situ Data and an Assimilated Ocean Model
