The simulation of the South China Sea by the variable resolution version of the global ocean general circulation model LICOM3.

We develop a variable-resolution method based on the tripolar grid to achieve fine-resolution regional simulations with limited computational resources. Based on the global ocean general circulation model LICOM3.0, we select the South China Sea (SCS) as the refined area and design five experiments to assess the impact of the variable-resolution grid on oceanic simulation. The results show that the method can retain the model capacity for global ocean simulation and obtain results in the refined region comparable to the reference global high-resolution model. Improving the resolution in the SCS from 0.1◦ to 0.02◦ significantly enhances the model performance in simulating submesoscale phenomena. The model can effectively reproduce submesoscale processes generated by frontogenesis, topographic wakes, and their seasonal variation. We uncover the effect of the submesoscale vortex train near the Luzon Strait. In summer, the vortex train tends to carry positive vorticity westward into the SCS and constrain the negative vorticity along the Kuroshio Current. In winter, the vortex train is more intrusive into the SCS with enhanced filament activities.