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Asymmetric tidal mixing due to the horizontal density gradient

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dc.contributor.author Li, Ming
dc.contributor.author Trowbridge, John H.
dc.contributor.author Geyer, W. Rockwell
dc.date.accessioned 2010-11-02T12:51:06Z
dc.date.available 2010-11-02T12:51:06Z
dc.date.issued 2008-02
dc.identifier.citation Journal of Physical Oceanography 38 (2008): 418-434 en_US
dc.identifier.uri http://hdl.handle.net/1912/4032
dc.description Author Posting. © American Meteorological Society, 2008. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 38 (2008): 418-434, doi:10.1175/2007JPO3372.1. en_US
dc.description.abstract Stratification and turbulent mixing exhibit a flood–ebb tidal asymmetry in estuaries and continental shelf regions affected by horizontal density gradients. The authors use a large-eddy simulation (LES) model to investigate the penetration of a tidally driven bottom boundary layer into stratified water in the presence of a horizontal density gradient. Turbulence in the bottom boundary layer is driven by bottom stress during flood tides, with low-gradient (Ri) and flux (Rf) Richardson numbers, but by localized shear during ebb tides, with Ri = ¼ and Rf = 0.2 in the upper half of the boundary layer. If the water column is unstratified initially, the LES model reproduces periodic stratification associated with tidal straining. The model results show that the energetics criterion based on the competition between tidal straining and tidal stirring provides a good prediction for the onset of periodic stratification, but the tidally averaged horizontal Richardson number Rix has a threshold value of about 0.2, which is lower than the 3 suggested in a recent study. Although the tidal straining leads to negative buoyancy flux on flood tides, the authors find that for typical values of the horizontal density gradient and tidal currents in estuaries and shelf regions, buoyancy production is much smaller than shear production in generating turbulent kinetic energy. en_US
dc.description.sponsorship This work is supported by Grants OCE-0451699 and OCE-0451740 from the National Science Foundation. en_US
dc.format.mimetype application/pdf
dc.language.iso en_US en_US
dc.publisher American Meteorological Society en_US
dc.relation.uri http://dx.doi.org/10.1175/2007JPO3372.1
dc.subject Tides en_US
dc.subject Mixing en_US
dc.subject Large eddy simulations en_US
dc.title Asymmetric tidal mixing due to the horizontal density gradient en_US
dc.type Article en_US
dc.identifier.doi 10.1175/2007JPO3372.1


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