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

ABSTRACT

This 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.

Acknowledgements

This work is supported by the National Natural Science Foundation of China: [Grant Numbers 41476009, U1495233, and 41676008]; the National Program on Global Change and Air-Sea Interaction: [Grant Numbers GASI-02-SCS-YGST2-02, GASI-IPOVAI-01-02, and GASI-IPOVAI-04]; the Foundation of Guangdong Province for Outstanding Yong Teachers in University: [Grant Number YQ2015088]; and the Project of Enhancing School with Innovation of Guangdong Ocean University: [Grant Number GDOU2016050240].

The satellite altimeter data are downloaded from Archiving Validation and Interpretation of Satellite Data in Oceanography (AVISO) and the Centre National d’Etudes Spatiales (CNES) of France (http://www.aviso.altimetry.fr/en/data/products/sea-surface-height-products/global.html). The ETOPO2 data are downloaded from https://www.ngdc.noaa.gov/mgg/global/global.html. The Nino 3.4 index data are downloaded from http://www.esrl.noaa.gov/psd/gcos_wgsp/Timeseries/Nino34/.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Foundation of Guangdong Province for Outstanding Yong Teachers in University: [Grant Number YQ2015088]; National Natural Science Foundation of China: [Grant Numbers 41476009, U1495233, and 41676008]; National Program on Global Change and Air-Sea interaction: [Grant Numbers GASI-02-SCS-YGST2-02, GASI-IPOVAI-01-02, and GASI-IPOV-04]; the Project of Enhancing School with Innovation of Guangdong Ocean University [Grant Number GDOU2016050240].