Effects of a two-equation turbulence model on the simulation of the internal lee waves

In order to understand the wave-turbulence interaction under non-hydrostatic conditions to prepare future advanced very-high-resolution ocean reanalysis data, an sigma-coordinate ocean model-namely, the Marine Environment Research and Forecasting (MERF) model-with an idealized supercritical slope topography is applied to conduct a series of high-resolution numerical experiments with and without the non-hydrostatic approximation. The popular Mellor-Yamada two-equation turbulence model (MY2.5) is enclosed in MERF to validate its effect on small-scale internal lee waves. Instantaneous results show that the internal lee-wave processes are relaxed through employment of the MY2.5 scheme, whether or not in the non-hydrostatic model. Time averaged results suggest the influences of the vertical mixing parameterization scheme on the numerical results are more dominant than the non-hydrostatic/hydrostatic selection for the large-scale dynamic process. Besides, diagnostic analyses of the energy budget show that the spread of internal lee waves at the slope is dramatically suppressed by the vertical turbulent mixing, indicating more tidal energy is able to be converted into the irreversible mixing when the two-equation turbulence model is employed.