How slippery are piecewise-constant coastlines in numerical ocean models?
- Publisher: Co-Action Publishing
(issn: 1600-0870, eissn: 0280-6495)
arxiv: Physics::Geophysics | Physics::Atmospheric and Oceanic Physics
Coastlines in numerical ocean models are oriented at various finite angles to the model grid.The true coastline is usually replaced by a piecewise-constant approximation in which the modelcoastline is everywhere aligned with the model grid. Here we study the consequences of thepiecewise-constant approximation in an idealised shallow-water ocean model. By rotating thenumerical grid at various finite angles to the physical coastlines, we are able to isolate theimpact of piecewise-linear boundaries on the model circulation. We demonstrate that piecewiseconstantcoastlines exert a spurious form stress on model boundary currents, dependent onboth the implementation of the slip boundary condition and the form of the viscous stresstensor. In particular, when free-slip boundary conditions are applied, the character of thecirculation can be reduced to no-slip in the presence of a piecewise-constant boundary. Thespurious form stress can be avoided in a free-slip limit if the viscous stress tensor is written interms of vorticity and divergence.DOI: 10.1034/j.1600-0870.1998.00007.x