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Some Expectations for Submesoscale Sea Surface Height Variance Spectra

Callies, Jörn and Wu, Weiguang (2019) Some Expectations for Submesoscale Sea Surface Height Variance Spectra. Journal of Physical Oceanography, 49 (9). pp. 2271-2289. ISSN 0022-3670. doi:10.1175/JPO-D-18-0272.1.

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In anticipation of the Surface Water and Ocean Topography (SWOT) wide-swath altimetry mission, this study reviews expectations for sea surface height (SSH) variance spectra at wavelengths of 10–100 km. Kinetic energy spectra from in situ observations and numerical simulations indicate that SSH variance spectra associated with balanced flow drop off steeply with wavenumber, with at least the negative fourth power of the wavenumber. Such a steep drop-off implies that even drastic reductions in altimetry noise yield only a modest improvement in the resolution of balanced flow. This general expectation is made concrete by extrapolating SSH variance spectra from existing altimetry to submesoscales, the results of which suggest that in the extratropics (poleward of 20° latitude) SWOT will improve the resolution from currently about 100 km to a median of 51 or 74 km, depending on whether or not submesoscale balanced flows are energetic. Internal waves, in contrast to balanced flow, give rise to SSH variance spectra that drop off relatively gently with wavenumber, so SSH variance should become strongly dominated by internal waves in the submesoscale range. In situ observations of the internal-wave field suggest that the internal-wave signal accessible by SWOT will be largely dominated by internal tides. The internal-wave continuum is estimated to have a spectral level close to but somewhat lower than SWOT’s expected noise level.

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Callies, Jörn0000-0002-6815-1230
Additional Information:© 2019 American Meteorological Society. Manuscript received 9 January 2019, in final form 4 June 2019. Published online: 22 August 2019. We thank Bob Weller and Tom Farrar for providing us with the Stratus data. We had useful discussions about this work with Tom Farrar, Roger Samelson, Patrice Klein, Jinbo Wang, and Carl Wunsch.
Subject Keywords:Internal waves; Ocean dynamics; Turbulence; Tides
Issue or Number:9
Record Number:CaltechAUTHORS:20190911-150907009
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:98586
Deposited By: Tony Diaz
Deposited On:11 Sep 2019 23:11
Last Modified:16 Nov 2021 17:40

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