The Rossby normal modes in the South China Sea deep basin evidenced by satellite altimetry

Abstract

ABSTRACTThis study investigates the mechanism of mesoscale eddies observed in the South China Sea (SCS) deep basin, which are characterized by high-frequency occurrence, long life, and regular distribution patterns. Geophysical fluid dynamics predicts that for an enclosed ocean basin, there exist the Rossby normal modes if considering the Earth rotation effect. We use a rectangular ocean basin with a uniform depth to simulate the SCS deep basin and obtain 2D (x − y) sea level distribution patterns of the Rossby normal modes, consisting of alternating cyclonic and anticyclonic eddies, as well as their dynamic parameters. The periods of the modes are evidenced by the Fourier period power density spectra of satellite altimeter sea level anomaly (SLA) data from 1993 to 2015. The 2D normal mode patterns are evidenced by SLA images. The phase speeds are evidenced by that derived from the westward movement of the wave/eddy patterns on SLA time-series images.