Mooring Observations of Near-Inertial Waves in the Southern South China Sea

Tropical cyclones (TCs) “RAI” (C5) in December 2021, significantly enhance near-inertial waves (NIWs) in the southern South China Sea (SCS). Observations near Taiping Island from 2020–2022 show that RAI increased wave heights to 6 m, wind speeds to 20 m/s, and generated strong currents <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(&gt; 0.5\mathrm{m}/\mathrm{s})$</tex> in the upper 300 m. Wavelet analysis reveals intensified near-inertial frequencies (~66.6 hours) post-RAI, with near-inertial kinetic energy reaching 10–20 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{J}/\mathrm{m}^{3}$</tex> in open waters and 5–10 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{J}/\mathrm{m}^{3}$</tex> in shallow areas. The ADCP data highlights downward NIW propagation and strong current shear in the upper 100 m.