Three-dimensional Numerical Simulations Of Internal Solitary Waves In The North South China Sea

Most of former studies on internal solitary waves (ISWs) in north South China Sea(SCS) are limited by idealized topography and2-D model. But recent studies showstrong3-D features in the generation and propagation processes of ISWs from theLuzon Strait (LS). To get a better understanding of the3-D features in the processesabove, a high resolution, nonhydrostatic model based on real topography and tidal forcehas been applied in the north SCS, including the whole LS.The model results have been compared with widely used tidal database, in-situobservation and SAR images to prove their reliability. The evolution of sea surfacegradient shows that the a-wave in north SCS comes from wave-wave interactionbetween internal waves from southwest of Sabtang Island and middle of Hengchun sill.And the evolution of baroclinic energy flux distribution shows that the b-wave comefrom the south of Taiwan Island and north-central of Hengchun sill.Eight areas location on both eastern and western ridges in the LS are identified asgeneration sites of ISWs through analysis of baroclinic energy flux and some non-dimensional parameters in the LS. Three-dimensional features during the generationprocesses are also referred. The internal waves generated in these areas are eithergenerated by mixing lee-wave mechanism or internal tide mechanism. And the largeamplitude ISWs with long crestlines come from wave-wave interaction between someof these eight generation sites.Sensitivity experiments show that the b-wave is dominated by semi-diurnal tide(M2) with little connection to diurnal tides, while a-wave are dominated by both diurnaland semidiurnal tides. Similarly, the mode-2ISWs are dominated by semi-diurnal tide (M2), while the mode-1ISWs are dominated by both diurnal and semidiurnal tides.Besides, K1tide itself cannot generate any significant ISWs. Another sensitivityexperiment show that the zonal asymmetry distribution of temperature and salt aroundthe LS can significant enhance the ISWs in the north SCS, but this cannot change thegeneration processes or generation sources of the ISWs. And the zonal asymmetrydistribution of temperature and salt should be considered in future works on this area,especially for prediction of ISWs.