A study of internal waves in the China Seas and Yellow Sea using SAR

Hsu, Meng−Kai; Liu, Antony K.; Liu, Cheng

doi:10.1016/s0278-4343(99)00078-3

Cited by 183 publications

(104 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The SAR imagery from the Yellow and East China Sea indicates that internal solitons are prevalent there also [52] but there is little in the way of in situ observations. Some moorings and thermistor chains were deployed in the ECS recently during the ASIAEX ECS program during 2000 and 2001.…”

Section: Comparison With Other Locationsmentioning

confidence: 99%

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.

330

321

View full text Add to dashboard Cite

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.

show abstract

Section: Comparison With Other Locationsmentioning

confidence: 99%

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.

330

321

View full text Add to dashboard Cite

show abstract

“…SAR satellite imagery may be used to gain information about dynamic processes in the upper ocean. Large amplitude internal waves are a well-documented example (Alpers, 1985;Hsu et al, 2000;Alpers et al, 2008, and others). Furthermore, under certain conditions, currents and winds can also be inferred from the new generation of SAR satellites (Horstmann et al, 2000;Romeiser et al, 2001Romeiser et al, , 2010Brusch et al, 2008).…”

Section: Introductionmentioning

confidence: 93%

Fine-scale features on the sea surface in SAR satellite imagery – Part 2: Numerical modeling

et al. 2014

View full text Add to dashboard Cite

Abstract. With the advent of the new generation of synthetic aperture radar (SAR) satellites, it has become possible to resolve fine-scale features on the sea surface on the scale of meters. The proper identification of sea surface signatures in SAR imagery can be challenging, since some features may be due to atmospheric distortions (gravity waves, squall lines) or anthropogenic influences (slicks), and may not be related to dynamic processes in the upper ocean. In order to improve our understanding of the nature of fine-scale features on the sea surface and their signature in SAR, we have conducted high-resolution numerical simulations combining a three-dimensional non-hydrostatic computational fluid dynamics model with a radar imaging model. The surface velocity field from the hydrodynamic model is used as input to the radar imaging model. The combined approach reproduces the sea surface signatures in SAR of ship wakes, low-density plumes, and internal waves in a stratified environment. The numerical results are consistent with observations reported in a companion paper on in situ measurements during SAR satellite overpasses. Ocean surface and internal waves are also known to produce a measurable signal in the ocean magnetic field. This paper explores the use of computational fluid dynamics to investigate the magnetic signatures of oceanic processes. This potentially provides a link between SAR signatures of transient ocean dynamics and magnetic field fluctuations in the ocean. We suggest that combining SAR imagery with data from ocean magnetometers may be useful as an additional maritime sensing method. The new approach presented in this work can be extended to other dynamic processes in the upper ocean, including fronts and eddies, and can be a valuable tool for the interpretation of SAR images of the ocean surface.

show abstract

“…The largest elevation soliton on 10 September with the amplitude of 35 m was very strong in related to the total depth of 117 m. The high energy of this type of elevation ISW must be important for sediment resuspension (Bogucki et al, 1997;Klymak et al, 2003) and in the energy budget. Hsu et al (2000) have demonstrated using KdV-type numerical model that both depression and elevation waves can be generated in the upwelling area dependent on the stratification and the initial tidal mixing condition near the generation area. In the next section, we will also use the KdV equations to investigate the nonlinear effects, and then demonstrate the significant role of the ISWs in affecting the platform and biological system in the ocean interior.…”

Section: Elevation Internal Solitary Wavesmentioning

confidence: 99%