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Preliminary results from the trimoored internal wave experiment (IWEX)

1975; American Geophysical Union; Volume: 80; Issue: 27 Linguagem: Inglês

10.1029/jc080i027p03872

2156-2202

Melbourne G. Briscoe,

Reservoir Engineering and Simulation Methods

Journal of Geophysical Research (1896-1977)Volume 80, Issue 27 p. 3872-3884 Preliminary results from the trimoored internal wave experiment (IWEX) Melbourne G. Briscoe, Melbourne G. BriscoeSearch for more papers by this author Melbourne G. Briscoe, Melbourne G. BriscoeSearch for more papers by this author First published: 20 September 1975 https://doi.org/10.1029/JC080i027p03872Citations: 77AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Abstract A three-dimensional array of 20 current meters, temperature sensors, and vertical temperature gradient sensors was successfully deployed for 40 days in late 1973 in the main thermocline over the Hatteras Abyssal Plain southeast of Bermuda. Sensor spacings in the main array were 1.4–1600 m in the horizontal, 2.1–1447 m in the vertical. The minimum sampling interval was 225 s. The ultimate purpose of the experiment was to estimate a vector wave number-frequency spectrum of internal waves without the usual assumptions of simple modal structure, horizontal isotropy, and linearity. The purpose of this paper is to describe some of the early results. Autospectra from the array normalize quite well in depth according to the WKBJ 'high-mode' solutions. Spectra of vertical displacements show a significant contribution from the internal semidiurnal tide. Samples of 1760 cross spectra calculated (based on a 40-day averaging interval) suggest horizontal isotropy, vertical homogeneity, and a possible degradation of current coherences because of fine structure in the velocity profile. Coherence of vertical displacements (i.e., temperature fluctuations) for measurements separated horizontally decays with increasing separation according to ƒ1/2X = 330 m·cph, where ƒ1/2 (cph) is the frequency at which the coherence falls to one half and X (m) is the horizontal separation. This empirical rule is based on 1600 m > X > 140 m; for smaller X, ƒ1/2 exceeds the local buoyancy frequency. Autospectra and cross spectra of vertical displacements sometimes show peaks at frequencies just less than the local buoyancy frequency; current spectra do not show such peaks. Inverse modeling of the internal wave field is in progress; expected results are a vector wave number-frequency spectrum and a description in parameter space that hopefully will permit future experiments to be less elaborate. References Amos, D. E., L. H. Koopmans, Tables of the distribution of the coefficient of coherence for stationary bivariant Gaussian processesSCR-483Sandia Corp., Albuquerque, N. Mex., 1963. Bell, T. H., Numerical calculation of dispersion relations for internal gravity wavesRep. 7294Nav. Res. Lab., Washington, D.C., 1971. Bendat, J. S., A. G. Piersol, Random Data, 388, Interscience, New York, 1971. Briscoe, M. G., A note on internal gravity wave spectra, J. Geophys. Res., 77, 3278–3280, 1972. Briscoe, M. G., Near-surface experiment at Mode site, Mode Hot Line News47, 3, 1974. Briscoe, M. G., Internal waves in the ocean, Rev. Geophys. Space Phys., 1975. Brown, N. L., A precision CTD microprofiler, Ocean 74, 2, 270–278, 1974. Cairns, J. 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Wunsch, C., J. Dahlen, A moored temperature and pressure recorder, Deep Sea Res., 21, 145–154, 1974. Zenk, W., Temperature variability below the mixed layer in the Model area, Mode Hot Line News61, 5, 1974. Citing Literature Volume80, Issue27Oceans20 September 1975Pages 3872-3884 ReferencesRelatedInformation