Parameterization of Shear-To-Strain Ratio Used in Finescale Parameterization

The Gregg-Henyey-Polzin (GHP) finescale parameterization is widely employed to infer turbulent mixing when microstructure measurements are unavailable. However, the strain-only GHP scaling is the only option when shear information is lacking, in which case the shear-to-strain ratio (R_ω) is commonly treated as a constant. Since R_ω has been reported to vary spatiotemporally, using a fixed value of R_ω might result in a significant bias in inferring turbulent mixing. In this study, we present a global map of R_ω, based on the microstructure database contributed by the Climate Process Team on internal wave-driven ocean mixing, which covers the Indian, Pacific, and Atlantic oceans across both high and low latitudes. Then, we propose a parameterization of R_ω by considering buoyancy frequency, Coriolis frequency, and topographic features. Compared to the GHP scaling with constant R_ω, the turbulent dissipation rate values inferred from the GHP scaling with parameterized R_ω are more accurate. In this manner, this study provides a reference for choosing optimal R_ω when using the strain-only GHP scaling to explore turbulent mixing in the open ocean.