| Автор | Eriksen, Charles Curtis |
| Дата выпуска | 1978 |
| dc.description | Measurements of horizontal and vertical current by propeller cluster current meters and temperature by thermistors mounted on a rigid array 8 m high and 20 m long moored in the oceanic main thermocline near Bermuda are interpreted in terms of thermocline‐trapped internal wave modes in the presence of temperature and velocity fine structure. The array was deployed roughly 250 m off the sloping bottom in water roughly 900 m deep on three occasions. Two‐turning‐point uniformly valid asymptotic solutions to the internal wave equation are developed to describe the wave functions. Mode decay beyond the turning point in depth or frequency produces a sharp cutoff in vertical current spectra above the local buoyancy frequency N(z). An internal wave wave number‐frequency spectral model E( α,ω) = E(ω/N<sub>0</sub>)<sup>−2</sup>(α/α<sub>0</sub>)<sup>−2</sup> describes vertical current spectra and ratios of potential energy to horizontal kinetic energy. The red wave number shape suppresses peaks in both these quantities at frequencies near N(z). A dip in the vertical current spectra at 0.5 cph not predicted by the model appears related to the bottom slope. Temperature fine structure is modeled as a passive vertical field advected by internal waves. Quasi‐permanent fine‐scale features of the stratification and vertically short internal waves are indistinguishable in this study. The model of McKean [1974] is generalized to include fine structure fields specified by their vertical wave number spectra. In addition to the trapped internal wave model, moored temperature spectra, temperature vertical difference spectra, and coherence over vertical separations are described by using a fine structure vertical wave number spectrum P<sub>T</sub>(k) A<sub>T</sub>k<sup>−5/2;</sup> which agrees with other spectra made by using vertical profiling instruments in the range 0.1–1.0 cpm. Horizontal current fine structure is also modeled as a passive field advected by vertically long internal waves. The model describes moored horizontal current spectra (least successfully at frequencies near N(z)) and finite difference vertical shear spectra. Contours of temperature in depth versus time indicate possible mixing events. These events appear concurrently with high shear and Richardson numbers 0.25 ≲ Ri ≲ 1.0. Over a 7‐m vertical separation a cutoff in Ri at 0.25 is observed, indicating possible saturation of the internal wave spectrum. Spectra of finite difference approximations to shear and buoyancy frequency are dominated by fine structure contributions over nearly the entire internal wave range, suggesting that breaking is enhanced by fine structure/Breaking appears equally likely at all frequencies in the internal wave range. |
| Формат | application.pdf |
| Копирайт | Copyright 1978 by the American Geophysical Union. |
| Тема | "Symposium on Oceanic Microstructures |
| Тема | OCEANOGRAPHY: GENERAL |
| Тема | Oceanography: Internal waves |
| Название | Measurements and models of fine structure, internal gravity waves, and wave breaking in the deep Ocean |
| Тип | article |
| DOI | 10.1029/JC083iC06p02989 |
| Electronic ISSN | 2156-2202 |
| Print ISSN | 0148-0227 |
| Журнал | Journal of Geophysical Research: Oceans |
| Том | 83 |
| Первая страница | 2989 |
| Последняя страница | 3009 |
| Выпуск | C6 |
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