VENM: An Algorithm to Accurately Calculate Neutral Slopes and Gradients

Area of Science:

• Oceanography
• Fluid Dynamics
• Numerical Modeling

Background:

• Neutral diffusion is key for subgrid-scale tracer transport in ocean models.
• Traditional neutral slope calculation is problematic in weakly stratified waters, leading to nonphysical results.
• Existing regularization methods introduce arbitrary dependencies into tracer gradient calculations.

Purpose of the Study:

• Introduce and validate the VErtical Non-local Method (VENM) for calculating neutral slopes and diffusion.
• Improve the numerical accuracy and physical realism of neutral tracer gradient computations.
• Provide a robust alternative to traditional methods for oceanographic modeling.

Main Methods:

• Implemented VENM, a search algorithm that bypasses the need for ad hoc regularization.
• Calculated neutral slopes, tracer gradients, and diffusive fluxes using VENM.
• Compared VENM against a traditional method using objective neutrality conditions and transport rates.

Main Results:

• VENM significantly improves the numerical accuracy of neutral slope and tracer gradient calculations.
• The method avoids nonphysical dependencies often seen with traditional approaches.
• VENM demonstrates superior physical and numerical accuracy compared to conventional techniques.

Conclusions:

• VENM offers a more accurate and physically sound approach to calculating neutral diffusion.
• This method eliminates the need for problematic ad hoc regularization.
• VENM is recommended for future oceanographic studies involving neutral diffusion from observations and model simulations.