Kaifeng Fan^a; Jiahao Huang^a; Bicheng Chen^a,b
a. State Key Laboratory of Marine Environmental Science, Department of Physical Oceanography, College of Ocean and Earth Sciences, Xiamen University, Xiamen, 361102, Fujian, China
b. Fujian Ocean Innovation Center, Xiamen 361102, Fujian, China

          The Taiwan Strait, constrained by a narrow channel with two lateral lands and shallow bathymetry, accelerates monsoon winds and tidal currents passing through it. Therefore, oceanic turbulence in this region is subject to the coupling of multiscale forcing from wind, waves, tides, and seafloor topography. Two critical questions remain unclear: which forcing dominates the turbulent mixing state under different combinations of forcings and locations, and what mixing structures these combinations produce? In response to these questions, the study uses a dimensional analysis approach to construct the forcing parameter space that represents the spatiotemporal pattern of the relative strength of wind, wave, and tidal forcing across the strait. Four dimensionless parameters are used: the turbulent Langmuir number, the dimensionless e-folding depth of the Stokes drift velocity, the surface-to-bottom friction velocity ratio, and the Obukhov length normalized by the water depth. These parameters are computed using ERA5 wind and wave spectral reanalysis data, TPXO tide data, and CMEMS ocean reanalysis data. Representative parameter combinations from the analysis are then used as forcing conditions to drive high-resolution Large-Eddy Simulations (LES) of oceanic boundary-layer turbulence. The results present the responses of turbulent kinetic energy to these parameter combinations and establish functional relationships between these statistics and the dimensionless parameters, providing a physical basis for parameterizing boundary-layer turbulent mixing under complex dynamical conditions in the Taiwan Strait.
Key words: dynamical regime; boundary layer; turbulence; Taiwan Strait