Submesoscale eddies in eastern Guangdong identified using high-frequency radar observations

The statistical characteristics and mechanism underlying the generation of submesoscale eddies in eastern Guangdong were examined using high-frequency radar (HFR) observations of surface currents during 2019_2021. By applying the vector geometry-based (VG) eddy detection algorithm to HFR datasets, 313 submesoscale eddies with 229 cyclonic and 84 anticyclonic eddies were identified. Cyclonic eddies were significantly more common than the anticyclonic eddies, but they had similar distributions in terms of eddy lifespan and radius. The trajectories showed that the submesoscale eddies within the study area tended to move northward and westward. Submesoscale eddies revealed annual variations with decreasing cyclonic eddies and increasing anticyclonic eddies during the observation period. Submesoscale eddies displayed a remarkable spatial distribution. Most of cyclonic (anticyclonic) eddies occurred at the eastern and southeastern regions of the Huilai Headland (south of the Nanao Island). Eddy evolution was linked to the production of vorticity in a narrow layer along the headland, the injection of vorticity into the interior at the point of flow separation, and vorticity damping by bottom friction.