Nonhydrostatic simulation of internal lee wave-induced turbulence mixing: A comparative study of second-moment closure mixing schemes for an idealized marginal sea sill topography. (April 2023) - Wang, Shifan
Abstract: To further understand the processes of wave-turbulence interactions under nonhydrostatic conditions and to gain insight into the selection of second-moment closure models in subsequent nonhydrostatic ocean models, a newly developed nonhydrostatic ocean model is coupled with the General Ocean Turbulence Model (GOTM) to form a robust version of the Marine Environment Research and Forecasting Model (MERF). On this basis, internal lee wave simulation with various turbulent mixing schemes is investigated for an idealized two-dimensional supercritical sea slope topography with high-resolution (100 m). First, the LES-type simulation based on a 3D Smagorinsky diffusivity scheme can reproduce well the characteristics of lee waves, serving as a benchmark for comparison. Second, the Mellor and Yamada (MY) scheme and the quasi-equilibrium scheme are able to effectively simulate the effects of internal waves on large-scale structures, while small-scale dynamic processes are partially suppressed by turbulent mixing. However, the K-ε model and the one-equation model further suppress the small-scale dynamic processes and weaken the propagation of internal lee waves due to overly strong turbulence mixing. Finally, the generation of a lee wave changes the instantaneous temperature field, and the use of the second-moment closure models converts more energy into irreversible mixing. Enhancing the model resolution can slightly improve the accuracy of the simulation in exchange for paying considerable computation. Highlights: A newly non-hydrostatic model is coupled with GOTM to simulate internal Lee waves. Four second-moment closure mixing schemes were employed to explore their sensitivities. The characteristics of various schemes are discussed by wave-turbulence interaction.