Characteristics And Numerical Modelling Of The Internal Tides And Solitary Waves In The Northern South China Sea

Northern South China Sea (SCS) is one of the most active areas for internal tides and solitary waves because of the rugged submarine topography and the complicated dynamic processes. The data used in the article is from the ADCP on submarine mooring system, the thermistor-chain hanged on the ship and the CTD, assisted with the tidal constituents of TPXO derived from the TOPEX/Poseidon and Jason altimeter data. The tidal system of northern SCS is figured out with the constituents of TPXO7.1. The characteristics of the internal tide are depicted with the long-term mooring measurements and a large nonlinear internal solitary wave and some weakly nonlinear internal waves.Based on the in situ currents data from the ACDP on submarine mooring system, the characteristics of the barotropic and baroclinic tides are analyzed, especially the constituents of the internal tides varied with the depth. The residual currents are discussed in different seasons in the prototype layers. Abnormal residual currents from February to March in 2009 are studied, which are in response to a mesoscale eddy. The EOF deposition method is used to study the vertical structure and variation of the internal waves. The EOFs of them are related to the mode structure of internal waves.The characteristics of internal solitary waves are analyzed based on a chain of instruments including temperature sensors, pressure sensors and temperature-pressure meters. The large amplitude and the period of a nonlinear internal solitary wave are obtained. The abrupt strong currents induced by the large solitary wave which are observed by ship-mounted Acoustic Doppler Current Profile.It is founded that the large solitary wave occurs roughly 2～3 days after spring tides.The propagation of internal waves is simulated with MITgcm ocean model. The transformations of the wave shape and the variations of and the energy in the propagation over a slope and a sill are studied.These results and knowledge of the internal tides and solitary waves partly reveal the rules of temporal and spatial evolution. The characteristics of them have important scientific values and may contribute to the understanding of the generation mechanism.