Impacts of tidal-mixing parameterization on the simulation of the South China Sea circulations

A parameterization of three-dimensional climatologically vertical diffusivity driven by internal tides is implemented in a regional ocean model to simulate the circulations of the SCS. This new tidal-mixing parameterization scheme takes into account the local and non-local energy dissipation of internal tides in the South China Sea (SCS) and Luzon Strait (LS) and thus enhances vertical mixing in the SCS basin significantly compared to the scheme of St. Laurent et al. (LSJ02) that only takes into account the local energy dissipation of internal tides. Results from experiments with different vertical diffusivity parameterization schemes show that the simulated stratification of the deep SCS and water transport of the LS by the new tidal mixing scheme are more stable and much closer to the previous observation reports, which suggests that the non-local dissipation of internal tides is a non-negligible energy source for the vertical mixing in the SCS and thus is important for the maintenance of the deep water transport in the LS and the circulations in the SCS. Moreover, obvious differences between the new scheme and the LSJ02 scheme are seen in the deep currents and meridional overturning circulation in the SCS, which needs further verification against observations in the future.