Simulation of Nonlinear Internal Wave Generation in the Northeastern South China Sea

Large-amplitude nonlinear internal waves (NLIW) in the South China Sea (SCS) are hypothesized to be generated by the interaction of barotropic ocean tides with irregular topography on the eastern end of the sea, but because of a lack of detailed in-situ measurements, the exact location and mechanism remain unclear. To improve our understanding of NLIW generation, a high-resolution numerical simulation is employed with a three-dimensional nonhydrostatic unstructured grid Navier-Stokes simulator (SUNTANS). Both the Luzon Strait and Dongsha Islands are contained in our simulation domain to investigate the entire life cycle of NLIW, including tide-topography interaction (generation and dissipation), tide conversion and propagation. By imposing currents associated with nine tidal components obtained with the OSU Tidal Inversion Software (OTIS) over a 10-day spring tidal period in June 2005 and initializing the 950 km by 550 km domain with a representative summer stratification, we analyze results of east-west (u component) velocity profiles and temperature contours along several transects that cross the Batan Islands in the Luzon Strait, the Dongsha atoll, and mooring sites of recent field observations. These are analyzed in order to identify locations of NLIW generation, to examine the propagation characteristics of NLIW, and to determine how the properties of NLIW change as they propagate from their generation site at the Luzon Strait to the Dongsha atoll. Time series of model results are compared with and verified by data obtained in a 2005 SCS field campaign.