A Modified Finescale Parameterization for Turbulent Mixing in the Western Equatorial Pacific

Finescale parameterizations are of great importance to explore the turbulent mixing in the open ocean due to the difficulty of microstructure measurements. Studies based on finescale parameterizations have greatly aided our knowledge of the turbulent mixing in the open ocean. In this study, we introduce a modified finescale parameterization (MMG) based on shear/strain variance ratio R-omega and compare it with three existing parameterizations, namely, the MacKinnon-Gregg (MG) parameterization, the Gregg-Henyey-Polzin (GHP) parameterization based on shear and strain variances, and the GHP parameterization based on strain variance. The result indicates that the prediction of MG parameterization is the best, followed by the MMG parameterization, then the shear-and-strain-based GHP parameterization, and finally the strain-based GHP parameterization. The strain-based GHP parameterization is less effective than the shear-and-strain-based GHP parameterization, which is mainly due to its excessive dependence on stratification. The predictions of the strain-based MMG parameterization can be comparable to that of the MG parameterization and better than that of the shear-and-strain-based GHP parameterization. Most importantly, MMG parameterization is even effective over rough topography where the GHP parameterization fails. This modified MMG parameterization with prescribed R-omega can be applied to extensive CTD data. It would be a useful tool for researchers to explore the turbulent mixing in the open ocean.

Automated summary

This study introduces a modified finescale parameterization (MMG) based on shear/strain variance ratio R-omega and compares it with three existing parameterizations. The result shows that the MG parameterization has the best prediction, followed by the MMG parameterization, the shear-and-strain-based GHP parameterization, and the strain-based GHP parameterization. The study suggests that the modified MMG parameterization can be a useful tool for researchers to explore turbulent mixing in the open ocean, especially over rough topography where other parameterizations fail.