Mesoscale eddies in the northern South China Sea

A fine-grid resolution model with realistic bathymetry and forcing has been developed to study the characteristics of the mesoscale eddies for the northern South China Sea (SCS). The SCS model derives its open-boundary conditions from a larger-scale model, which minimizes errors related to the uncertainty of the Kuroshio intrusion at the open boundaries. The model results are consistent with previous observations. Model sea-surface height anomaly demonstrates that the hydrography and circulation in the northern SCS are modulated by westward-propagating mesoscale eddies originating in the vicinity of the Luzon Strait. This explains the observed intra-seasonal fluctuations at the SouthEast Asian Time-series Study (SEATS) station. The mesoscale eddies have the same propagation speed as baroclinic Rossby waves (∼0.1 ms−1). The periods of eddy shedding estimated from Strouhal number are around 40–50 days in December and 80–120 days in August, respectively. The seasonal variability of the Kuroshio intrusion results in more eddies in winter than in summer.