Numerical Simulation Of The Influence Of Wave-current Interaction On Storm Surge In The Northern South China Sea

The northern South China Sea(SCS) is one of the areas, that frequently affected by typhoon,and each year local household and economy are often in risk for suffering from great damages by storm surge-induced disasters. Under extreme weather conditions, the typhoon-induced waves can lead to considerable wave set-up and current. And therefore, the effect of surface gravity on oceanic current and turbulence have been considered to play an important role in forecasting tropical storm surge. However, it is still controversial in both research of physical mechanisms and applications on numerical simulating of wave-current interaction and need further study.The effects of waves on current(hereafter called WEC) comprise additional momentum and mass flux to mean flow, and the effect of mean currents on waves, which are represented both as radiations stress(hereafter called RS) and vortex force(hereafter called VF). Beside this, non-conservative WEC include several kinds of wave forces as the following:(1) mixing enhancement and turbulent kinetic energy injection(TKE) induced by wave breaking, implemented by using Generic Length Scale turbulence closure scheme in the form of surface boundary condition.(2) Bottom stress(bottom streaming; WBST), caused by the friction between the wave and the sea bed within the wave boundary layer and surface stress(surface streaming; WSST), similar to bottom streaming at the surface of the water column. In order to study WEC, we used coupled ocean-atmosphere-wave-sediment transport(COAWST) modeling system, which contained both RS(Mellor,2008) and VF(McWilliams et al., 2004), and conducted multi groups of experiments, with and without the WEC to simulate two typical tropic storms of invading SCS process, typhoon Nuri(0812) and typhoon Hagupit(0814). The result shows that:(1) Both set-up and set-down induced by WEC were strengthened on the right and left side of typhoon center, along with wave-induced current, especially in VF experiments, which is more sensitive in nearshore area;(2) Non-conservative WEC caused weeker set-up/set-down. However, the adjustment of it to water elevation and current could not be neglected;(3) the simulation of inundation in COAWST also improved the accuracy;(4) To different paths and speed of typhoon and in different depth of bathymetry, the coupling simulation could inflected the WEC, and in shallower area or under faster speed of typhoon, the WEC are stronger and caused more obvious wave-induced set-up/set-down.