Parameterizing the breaking and scattering of a mode-1 internal tide on abrupt step topography
Date
2014-04-30
Authors
Murowinski, Emma Christina
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Abstract
A parameterization is presented for turbulence dissipation due to baroclinic tide impacting on abrupt shelf topography that is supercritical with respect to the tide. The parameterization requires knowledge of the topography, stratification, and the remote forcing velocity. Upon impact, the tide cascades to higher vertical modes. Vertical internal modes that are arrested at the crest of the topography in the form of lee waves are assumed to dissipate, while faster modes are assumed to propagate away. The energy flux in each mode is predicted with topography that allows linear numer- ical solutions. The parameterization is tested using high-resolution two-dimensional numerical models of baroclinic tides impinging on an isolated shelf of various heights approximated as a step-function. The recipe is seen to work well compared to numeri- cal simulations of isolated shelves, although it consistently underestimates model flux divergence. Despite low forcing velocities having a more accurate numerical linear solution, the recipe does poorly because it does not accurately predict the modes that become trapped and dissipate. Maximum dissipation occurs when flow is on-shelf and lee waves form, indicating lee waves are the mechanism by which dissipation occurs.
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Keywords
internal tides, ocean physics, physical oceanography