Solitons Northeast of Tung-Sha Island During the ASIAEX Pilot Studies

Yang, Ying-Jang; Tang, Tie-Qiao; Chang, Ming‐Huei; Liu, A.K.; Hsu, Meng−Kai; Ramp, S.R.

doi:10.1109/joe.2004.841424

Cited by 128 publications

(90 citation statements)

References 38 publications

(66 reference statements)

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“…In a pilot program Yang et al (2004) observed a single mode-two wave in 426 m deep water. Yang et al (2009Yang et al ( , 2010 analysed mooring data obtained during the VANS/WISE program which was conducted in 2005 and 2006 in the vicinity of the ASIAEX field program.…”

Section: Discussionmentioning

confidence: 99%

“…Mode-two solitary-like waves were observed during the ASIAEX experiment (Orr and Mignerey, 2003) but not reported on in detail. Observations of a mode-two ISW made during a pilot study for the ASIAEX experiment were reported by Yang et al (2004). Many mode-two solitary-like waves were observed at 350 m depth in a nearby region during the joint VANS/WISE experiments (Yang et al, 2009.…”

Section: K G Lamb and A Warn-varnas: Shoaling Internal Solitary Wavesmentioning

confidence: 95%

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Two-dimensional numerical simulations of shoaling internal solitary waves at the ASIAEX site in the South China Sea

Lamb

Warn-Varnas

2015

Nonlin. Processes Geophys.

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Abstract. The interaction of barotropic tides with LuzonStrait topography generates some of the world's largest internal solitary waves which eventually shoal and dissipate on the western side of the northern South China Sea. Twodimensional numerical simulations of the shoaling of a single internal solitary wave at the site of the Asian Seas International Acoustic Experiment (ASIAEX) have been undertaken in order to investigate the sensitivity of the shoaling process to the stratification and the underlying bathymetry and to explore the influence of rotation. The bulk of the simulations are inviscid; however, exploratory simulations using a vertical eddy-viscosity confined to a near bottom layer, along with a no-slip boundary condition, suggest that viscous effects may become important in water shallower than about 200 m. A shoaling solitary wave fissions into several waves. At depths of 200-300 m the front of the leading waves become nearly parallel to the bottom and develop a very steep back as has been observed. The leading waves are followed by waves of elevation (pedestals) that are conjugate to the waves of depression ahead and behind them. Horizontal resolutions of at least 50 m are required to simulate these well. Wave breaking was found to occur behind the second or third of the leading solitary waves, never at the back of the leading wave. Comparisons of the shoaling of waves started at depths of 1000 and 3000 m show significant differences and the shoaling waves can be significantly non-adiabatic even at depths greater than 2000 m. When waves reach a depth of 200 m, their amplitudes can be more than 50 % larger than the largest possible solitary wave at that depth. The shoaling behaviour is sensitive to the presence of small-scale features in the bathymetry: a 200 m high bump at 700 m depth can result in the generation of many mode-two waves and of higher mode waves. Sensitivity to the stratification is considered by using three stratifications based on summer observations. They primarily differ in the depth of the thermocline. The generation of mode-two waves and the behaviour of the waves in shallow water is sensitive to this depth. Rotation affects the shoaling waves by reducing the amplitude of the leading waves via the radiation of long trailing inertiagravity waves. The nonlinear-dispersive evolution of these inertia-gravity waves results in the formation of secondary mode-one wave packets.

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Section: Discussionmentioning

confidence: 99%

Section: K G Lamb and A Warn-varnas: Shoaling Internal Solitary Wavesmentioning

confidence: 95%

Two-dimensional numerical simulations of shoaling internal solitary waves at the ASIAEX site in the South China Sea

Lamb

Warn-Varnas

2015

Nonlin. Processes Geophys.

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“…During April 2000, there was a much larger Kuroshio intrusion than during April 2001 [3]. The solitons observed at IW1 during 2000 were also larger than the solitons observed nearby at S7 during 2001 [49]. So, there is some incidental evidence to support the idea that more energetic Kuroshio intrusions that loop around the Luzon Ridge favor the generation of larger amplitude internal waves.…”

Section: B Wave Amplitudes In Cluster 1 Versus Clustermentioning

confidence: 91%

Internal Solitons in the Northeastern South China Sea Part I: Sources and Deep Water Propagation

Ramp

Tang²,

Duda³

et al. 2004

IEEE J. Oceanic Eng.

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340

321

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Abstract-A moored array of current, temperature, conductivity, and pressure sensors was deployed across the Chinese continental shelf and slope in support of the Asian Seas International Acoustics Experiment. The goal of the observations was to quantify the water column variability in order to understand the along-and across-shore low-frequency acoustic propagation in shallow water. The moorings were deployed from April 21-May 19, 2001 and sampled at 1-5 min intervals to capture the full range of temporal variability without aliasing the internal wave field. The dominant oceanographic signal by far was in fact the highly nonlinear internal waves (or solitons) which were generated near the Batan Islands in the Luzon Strait and propagated 485 km across deep water to the observation region. Dubbed trans-basin waves, to distinguish them from other, smaller nonlinear waves generated locally near the shelf break, these waves had amplitudes ranging from 29 to greater than 140 m and were among the largest such waves ever observed in the world's oceans. The waves arrived at the most offshore mooring in two clusters lasting 7-8 days each separated by five days when no waves were observed. Within each cluster, two types of waves arrived which have been named type-a and type-b. The type-a waves had greater amplitude than the type-b waves and arrived with remarkable regularity at the same time each day, 24 h apart. The type-b waves were weaker than the type-a waves, arrived an hour later each day, and generally consisted of a single soliton growing out of the center of the wave packet. Comparison with modeled barotropic tides from the generation region revealed that: 1) The two clusters were generated around the time of the spring tides in the Luzon strait; and 2) The type-a waves were generated on the strong side of the diurnal inequality while the type-b waves were generated on the weaker beat. The position of the Kuroshio intrusion into the Luzon Strait may modulate the strength of the waves being produced. As the waves shoaled, the huge lead solitons first split into two solitons then merged together into a broad region of thermocline depression at depths less than 120 m. Elevation waves sprang up behind them as they continued to propagate onshore. The elevation waves also grew out of regions where the locally-generated internal tide forced the main thermocline down near the bottom. The "critical T. Y. Tang is with the Institute of Oceanography, National Taiwan University, Taipei, ROC.H. point" where the upper and lower layers were equal was a good indicator of when the depression or elevation waves would form, however this was not a static point, but rather varied in both space and time according to the presence or absence of the internal tides and the incoming trans-basin waves themselves.

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“…The terrain of the strait makes it an active ground for the generation of internal waves. Recently, dramatic internal tides, solitary waves and bores were observed at locations from LS to the northern South China Shelf (NSCS) both in satellite images and field observations Hsu & Liu, 2000;Liu et al, 2006Liu et al, , 2008Yang et al, 2004;Zhao, Klemas, Zheng, & Yan, 2004).…”

Section: Introductionmentioning

confidence: 99%

Current Observations of Internal Tides and Parametric Subharmonic Instability in Luzon Strait

et al. 2012

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Acoustic Doppler Current Profiler (ADCP) measurements of the velocity structure in the thermocline in Luzon Strait are presented. The statistics for current, vertical variation of the inertia-gravity waveband, parametric subharmonic instability (PSI), and current shear are analyzed. It was found that 1) barotropic flow primarily consists of a nearly circular mixed tide. Diurnal tides are strongest and show smooth variance with a fortnightly spring-neap cycle, indicative of the astronomical tide-generating force. However, the semi-diurnal band power exhibits a high-frequency oscillation as a result of non-linear interactions. The high-frequency band power with high values during the spring tide oscillates with the tidal cycle. Near-inertial wave motions showing random variance may be caused by changes in the wind forcing at the sea surface or by random forcing. 2) Baroclinic velocities exhibit strong shear structure. The observed large changes in the amplitude of the baroclinic velocity and the limited vertical extent of the high-velocity cores may be interpreted as internal wave beams that pass through the observed water column. Semi-diurnal tides are dominant in the baroclinic velocity. Kinetic energy spectra also revealed that additional peaks were centred at sum-tidal-inertial interaction frequencies (such as M 2 + f) and difference-interaction frequencies (such as M 2 − f). The spectral exponent of the baroclinic velocity is ω −α (1 < α < 3). 3) Strong non-linear interactions among internal waves exist, and the semi-diurnal (M 2 ) component plays a key role in these interactions. Bicoherence analysis showed that M 2 /2 waves were non-linearly coupled with the dominant M 2 internal tide. 4) The polarization relations were used to diagnose observational internal tidal motions. Diurnal waves propagate to the east-northeast, and the semi-diurnal-diurnal waves propagate westward. In the case of diurnal tides, the minor to major axis ratio is different from the expected value of f/ω K1 because of the deviation of inclinations, whereas, for semi-diurnal tides, it is close to the expected value of f/ω M2 at depths from 30 to 150 m.RÉSUMÉ [Traduit par la rédaction] Nous présentons les mesures de la structure des vitesses dans la thermocline faites par profileur de courant à effet Doppler (ADCP) dans le détroit de Luçon. Nous analysons les statistiques sur le courant, la variation verticale de la gamme d'ondes d'inertie-gravité, l'instabilité subharmonique paramétrique (PSI) et le cisaillement du courant. Il ressort que 1) l'écoulement barotrope consiste principalement en une marée mixte presque circulaire. Les marées diurnes sont les plus fortes et présentent une variance régulière dans un cycle vives-eaux mortes-eaux de deux semaines qui révèle la nature astronomique de la force qui produit les marées. Cependant, la puissance de bande semi-diurne affiche une oscillation de haute fréquence causée par des interactions non linéaires. La puissance de bande de haute fréquence avec des valeurs élevées durant les ...

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Solitons Northeast of Tung-Sha Island During the ASIAEX Pilot Studies

Cited by 128 publications

References 38 publications

Two-dimensional numerical simulations of shoaling internal solitary waves at the ASIAEX site in the South China Sea

Two-dimensional numerical simulations of shoaling internal solitary waves at the ASIAEX site in the South China Sea

Internal Solitons in the Northeastern South China Sea Part I: Sources and Deep Water Propagation

Current Observations of Internal Tides and Parametric Subharmonic Instability in Luzon Strait

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