A Study On Turbulent Mixing Induced By Wave-breaking And Langmuir Circulation Under Typhoon Kalmaegi

It's very important to simulate temperature, salinity and turbulent mixing of the upper ocean accurately under typhoon conditions for predicting typhoon paths and intensities. Wave-breaking and Langmuir turbulence are two significant processes for the turbulence mixing of the upper ocean. The nonlinear interaction of wind-driven current and surface wave generates Langmuir circulation, which brings the surface material, momentum and heat to deep and enhances the ocean mixing and affects the air-sea energy exchange. Wave-breaking is the main way to transfer momentum of wind to upper ocean turbulence and current. This paper considers both wave-breaking and Langmuir turbulence effect.Firstly, one-dimensional general ocean turbulence model is used to simulate temperature, salinity under typhoon Kalmeagi on Sep. 15th, 2014, and results are consistent with observation. The mean of the deviation between the modeled temperature, salinity and observation are 0.3703??0. 0215 psu, respectively. Then,the existing model is improved by introducing wave-breaking and Langmuir turbulence effect, which decreases the mean of the deviation of temperature.In addition, the influence of the above two wave effects on the turbulent mixing of the upper ocean under typhoon Kalmeagi is studied. Langmuir turbulence mainly increases the shear production, dissipation rate and turbulence length scale of the upper ocean and makes the whole mixed layer more uniform. Its' influence decreases exponential with depth. Wave-breaking adjusts turbulent kinetic energy (TKE) by increasing the energy and momentum and it deepens the mixing layer. Wave-breaking increases the turbulence length scale, dissipation rate near surface, eddy diffusion rate and turbulent diffusivity of heat, momentum and salinity. And Wave-breaking enhances the Langmuir turbulence below the surface, the two wave effects make the above-mentioned additions more pronounced together. This paper has some innovation in introducing the wave-breaking and Langmuir turbulence effect in typhoon simulation.