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| Titel |
Convex and concave types of second baroclinic mode internal solitary waves |
| VerfasserIn |
Y. J. Yang, Y. C. Fang, T. Y. Tang, S. R. Ramp |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 17, no. 6 ; Nr. 17, no. 6 (2010-11-02), S.605-614 |
| Datensatznummer |
250013752
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| Publikation (Nr.) |
 copernicus.org/npg-17-605-2010.pdf |
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| Zusammenfassung |
| Two types of second baroclinic mode (mode-2) internal solitary waves
(ISWs) were found on the continental slope of the northern South China Sea.
The convex waveform displaced the thermal structure upward in the upper layer
and downward in the lower layer, causing a bulge in the thermocline. The
concave waveform did the opposite, causing a constriction. A few concave
waves were observed in the South China Sea, marking the first documentation
of such waves. On the basis of the Korteweg-de Vries (K-dV) equation,
an analytical three-layer ocean model was used to study the characteristics
of the two mode-2 ISW types. The analytical solution was primarily a
function of the thickness of each layer and the density difference between
the layers. Middle-layer thickness plays a key role in the resulting
mode-2 ISW. A convex wave was generated when the middle-layer
thickness was relatively thinner than the upper and lower layers, whereas
only a concave wave could be produced when the middle-layer thickness was
greater than half the water depth. In accordance with the K-dV
equation, a positive and negative quadratic nonlinearity coefficient,
α2, which is primarily dominated by the middle-layer thickness,
resulted in convex and concave waves, respectively. The analytical solution
showed that the wave propagation of a convex (concave) wave has the same
direction as the current velocity in the middle (upper or lower) layer.
Analysis of the three-layer ocean model properly reproduced the
characteristics of the observed mode-2 ISWs in the South China Sea and
provided a criterion for the existence of convex or concave waves. Concave
waves were seldom seen because of the rarity of a stratified ocean with a
thick middle layer. This analytical result agreed well with the observations. |
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