Biases in Thorpe-scale estimates of turbulence dissipation. Part I : Assessments from large-scale overturns in oceanographic data Mater, Benjamin D. Venayagamoorthy, Subhas K. St. Laurent, Louis C. Moum, James N. 2015-11-09T19:10:56Z 2016-04-01T08:01:18Z 2015-10
dc.description Author Posting. © American Meteorological Society, 2015. 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 45 (2015): 2497–2521, doi:10.1175/JPO-D-14-0128.1. en_US
dc.description.abstract Oceanic density overturns are commonly used to parameterize the dissipation rate of turbulent kinetic energy. This method assumes a linear scaling between the Thorpe length scale LT and the Ozmidov length scale LO. Historic evidence supporting LT ~ LO has been shown for relatively weak shear-driven turbulence of the thermocline; however, little support for the method exists in regions of turbulence driven by the convective collapse of topographically influenced overturns that are large by open-ocean standards. This study presents a direct comparison of LT and LO, using vertical profiles of temperature and microstructure shear collected in the Luzon Strait—a site characterized by topographically influenced overturns up to O(100) m in scale. The comparison is also done for open-ocean sites in the Brazil basin and North Atlantic where overturns are generally smaller and due to different processes. A key result is that LT/LO increases with overturn size in a fashion similar to that observed in numerical studies of Kelvin–Helmholtz (K–H) instabilities for all sites but is most clear in data from the Luzon Strait. Resultant bias in parameterized dissipation is mitigated by ensemble averaging; however, a positive bias appears when instantaneous observations are depth and time integrated. For a series of profiles taken during a spring tidal period in the Luzon Strait, the integrated value is nearly an order of magnitude larger than that based on the microstructure observations. Physical arguments supporting LT ~ LO are revisited, and conceptual regimes explaining the relationship between LT/LO and a nondimensional overturn size are proposed. In a companion paper, Scotti obtains similar conclusions from energetics arguments and simulations. en_US
dc.description.embargo 2016-04-01 en_US
dc.description.sponsorship B.D.M. and S.K.V. gratefully acknowledge the support of the Office of Naval Research under Grants N00014-12-1-0279, N00014-12-1-0282, and N00014-12-1-0938 (Program Manager: Dr. Terri Paluszkiewicz). S.K.V. also acknowledges support of the National Science Foundation under Grant OCE-1151838. L.S.L. acknowledges support for BBTRE by the National Science Foundation by Contract OCE94-15589 and NATRE and IWISE by the Office of Naval Research by Contracts N00014-92-1323 and N00014-10-10315. J.N.M. was supported through Grant 1256620 from the National Science Foundation and the Office of Naval Research (IWISE Project). en_US
dc.format.mimetype application/pdf
dc.identifier.citation Journal of Physical Oceanography 45 (2015): 2497–2521 en_US
dc.identifier.doi 10.1175/JPO-D-14-0128.1
dc.language.iso en_US en_US
dc.publisher American Meteorological Society en_US
dc.subject Circulation/ Dynamics en_US
dc.subject Diapycnal mixing en_US
dc.subject Small scale processes en_US
dc.subject Turbulence en_US
dc.subject Atm/Ocean Structure/ Phenomena en_US
dc.subject Mixing en_US
dc.subject Observational techniques and algorithms en_US
dc.subject Profilers, oceanic en_US
dc.subject Models and modeling en_US
dc.subject Parameterization en_US
dc.title Biases in Thorpe-scale estimates of turbulence dissipation. Part I : Assessments from large-scale overturns in oceanographic data en_US
dc.type Article en_US
dspace.entity.type Publication
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