Evolution of oceanic near-inertial waves induced by typhoon Sarika (2016) in the South China Sea

Abstract

Oceanic near-inertial waves (NIWs) are typically generated by wind. Utilizing moored observations and hybrid coordinate ocean model (HYCOM) analysis, we investigated the NIWs induced by typhoon Sarika (2016) in the South China Sea. Sarika-induced NIWs exhibited an approximately 10% blue-shift to the local Coriolis frequency, which was largely due to a cyclonic eddy (CE) formed around the mooring. The development, decay and modal content of Sarika-induced NIWs displayed spatial differences. High near-inertial kinetic energy (NIKE) was concentrated to a small region on the right side of Sarika's track and exhibited slow damping. In contrast, the NIKE in the CE damped quickly, because the downward propagation of NIKE was prevented by the strong stratification in the CE. Additionally, modal decomposition revealed that the mode-2 and mode-3 NIKE induced by Sarika was significant but exhibited different evolution characteristics.