Simulation Of Thermocline In The Yellow Sea And East China Sea By Using Internal Wave Mixing Scheme

Many observations show that there exists strong thermocline in the Yellow Seaand East China Sea during summer. Investigations have been taken to study themechanism of the formation of the strong thermocline. It shows that physicalprocesses such as wind, tide, current, and solar radiation are important in thethermocline’s formation. Internal waves often occur in the place where strongthermocline exists. Strong internal tide and internal solitary waves are frequentlyobserved in the Yellow Sea and East China Sea in summer. However, few studies havefocused on this inner ocean movement and its effects on the thermocline formationdue to its movement and breaking process. Internal wave often occurs in the stablystratified thermocline and its propagate and breaking process induces strong mixingwhich enhances the vertical eddy diffusion. Thus it is important to consider themixing effect caused by internal wave when studies the formation of thermocline.Based on the distribution of vertical turbulent mixing parameter by internal tidalwave and internal solitary wave in the south Yellow Sea by Si et al, a parameterizationscheme of vertical mixing induced by internal wave is applied to a circulation modelin the continental shelf region. Using Princeton Ocean Model, two numericalexperiments with wind forcing and without wind forcing are designed respectively. Inboth cases, Mellor-Yamada’s second moment turbulence closure mixing scheme andinternal wave mixing scheme are applied to simulate the thermocline in the YellowSea and East China Sea in august respectively. Analysis of typical longitudinaltransects along31°N and35°N is given. The results show that when wind stress is notconsidered, the simulation of temperature which is using internal wave mixingscheme is better than that of Mellor-Yamada second moment turbulence closuremixing scheme, and when wind stress is considered, the results of Mellor-Yamadasecond moment turbulence closure mixing scheme and internal wave mixing schemeare coincide with the observation. The platform-shaped temperature and cold water mass can be simulated but the temperature gradient is weak along the transaction of35°N in summer. Mellor-Yamada second moment turbulence closure mixing schememainly reflects the influence of wind mixing in the upper ocean of continental shelf,but lacks in the reflection of internal wave mixing. Internal wave mixing schememainly considers internal tides and internal solitary waves, and partly considers windand bottom friction mixing. The simulation result is in good agreement of theobservation by using the internal wave mixing scheme.