Motions and Wave-Turbulence Interactions in the Upper Ocean Mixed Layer

ZHU Donglin; GAO Jingsong; GUAN Changlong

Abstract：Ocean models are always blamed for the overestimation of sea surface temperature and underestimation of mixed layer depth due to insufficient mixing.For further understanding of the wave effects on turbulence of the upper ocean mixed layer,parameterizations of turbulence induced by wave orbital motion and wave-turbulence interaction are implemented in a 1-D vertical turbulence model GOTM.The influences of wave breaking(WB),wave orbital motion(NWB) and wave-turbulence interactions(WT) on the k-ω scheme and the upper ocean thermal structure are examined and compared with each other using the modified model.Model results show that while the effect of wave breaking is always limited in the very near-surface layer and is quite insufficient for enhancing mixing,the adding of production terms due to NWB and WT can greatly improve the simulated thermal structure,leading to a deepened mixed layer depth,enhanced shear production term,turbulent kinetic energy,dissipation rate and vertical mixing,as well as temperature distributions that are more consistent with the observations.In winter the inclusion of NWB and WT does not produce as idealized results as in summer,and the possible reason may be some other mechanics (e.g.lateral advection) dominates the turbulent mixing process.