Surface gravity wave and double diffusion effects to the upper ocean dynamics:an improved MY2.5 turbulence closure model and it's verification

Turbulence mixing of upper ocean not just affect the air-sea momentum, heat and vapor exchange, but also affect the large scale wind driven current. The surface gravity waves and double diffusion are two very important influence factors to the mixing. Based on the original MY2.5 turbulence closure model, considered the Langmuir turbulence and double diffusion effects on the pressure covariances to get new dimensionless efficiency of the vertical eddy viscosity and diffusivity. On the other hand, the pressure transport term expressed as wave energy dissipation rate add to the turbulence kinetic energy equation. The results from the modified turbulence model show that under the same external forcing condition, the Langmuir turbulence effects and wave breaking made the mixing intensify and deepen the mixing layer depth. The double diffusion effect lead an unstable convective structure and enhance the mixing intensity and effect depth, as the same time modulate the wind driven current variation, its effect can not neglect in deep water condition. Compare with the original MY2.5 model, the results from the modified model agreed well with the observational data.