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Both internal solitary waves (ISWs) and mesoscale eddies are ubiquitous in the northern South China Sea (SCS). In this study, the authors examine the impacts of mesoscale eddies on the ISWs transiting the northern SCS deep basin that evolve from the steepening internal tide generated in the Luzon Strait, using in situ data collected from a specifically designed mooring array. From November 2013 to January 2014, an energetic mesoscale eddy pair consisting of one anticyclonic eddy (AE) and one cyclonic eddy (CE) propagated across the mooring array. Observations revealed that the amplitude, propagation direction, and speed of the transbasin ISWs were significantly modulated by the eddy pair. When the moorings were covered by the southern portion of the AE, the ISW amplitudes decreased by as much as 67% because of the thermocline deepening along the wave direction and the energy divergence along the wave front. When the moorings were covered by the northern portions of both eddies, the amplitude of ISWs also decreased but to a relatively smaller degree. ISWs propagated the fastest inside the southern portion of the AE, where both the thermocline deepening and eddy currents enhanced the propagation speed of ISWs. Under the influence of the AE (CE) core, ISWs propagated more northward (southward) than usual. The observational results reported here highlight the importance of resolving mesoscale eddies in circulation-internal wave coupled models to accurately predict kinematic characteristics of ISWs. [ABSTRACT FROM AUTHOR]

The activities of internal solitary waves (ISWs) over the continental shelf of the northern South China Sea (SCS) are of high complexity. In this study, we investigated the spatial-temporal characteristics of the shoaling ISWs over the northern SCS continental shelf using the satellite images and the results of numerical simulation. The examination of the ISW signals in the satellite optical images revealed the existence of three types of ISWs in the region north to the Dongsha Island, namely, mode-1 depression ISW, mode-1 elevation ISW, and mode-2 convex ISW. The geographical distributions of these ISWs were derived from the satellite images. Numerical results exhibited the process of polarity conversion of ISWs, by which mode-1 elevation waves were transformed from the shoaling mode-1 depression waves. The mode-2 convex ISWs generally followed the mode-1 depression ISWs. The numerical results suggested that the interaction of the mode-1 depression ISWs with the up-slope topography locally generated mode-2 ISWs, and such waves of high vertical mode dissipated rapidly during the inshore propagation. [ABSTRACT FROM AUTHOR]

Based on the z-coordinate ocean model HAMSOM, we introduced the internal-tide viscosity term and applied the model to numerically investigate the M2 internal tide generation and propagation in the Luzon Strait (LS). The results show that (1) in the upper 250 m depth, at the thermocline, the maximum amplitude of the generated internal tides in the LS can reach 40 m; (2) the major internal tides are generated to the northwest of Itbayat Island, the southwest of Batan Island and the northwest of the Babuyan Islands; (3) during the propagation the baroclinic energy scattering and reflection is obvious, which exists under the effect of the specific topography in the South China Sea (SCS); (4) the westward-propagating internal tides are divided into two branches entering the SCS. While passing through 118°E, the major branch is divided into two branches again. The strongest internal tides in the LS are generated to the northwest of Itbayat Island and propagate northeastward to the Pacific. However, to the east of 122°E, most of the internal tides propagate southeastward to the Pacific as a beam. [ABSTRACT FROM AUTHOR]

A numerical study of sea waves generated by tropical cyclone Jelawat is carried out using the cycle 4 version of the WAM. The model domain currently covers the latitudes 20°-45°N and longitudes 115°-135°E, and the model spatial resolution reaches 0.25°×0.25°. Comparison of the model results with buoy observations reveals that the model can fairly reproduce the temporal variation of observed waves. Two-dimensional comparison is also made against the satellite altimeter significant wave heights derived from TOPEX/POSEIDON and ERS-2 data, showing high quality of the model performance. [ABSTRACT FROM AUTHOR]

A 30-d current numerical simulation is running for the Yangshan Port, the Changjiang Estuary, the Hangzhou Bay and their adjacent seas using a finite volume coastal ocean model (FVCOM), with Changjiang River runoff and wind effect being considered. At the open boundary, this model is driven by the water level obtained from prediction including eight main partial tides. After the harmonic analysis, the cotidal chart and the iso-amplitude line as well as the current ellipse distribution map are displayed to illustrate the propagation property of a tidal wave. Horizontal velocity of both the U and V components coincides with the actual measurement, which shows that the model result is credible to describe the hydrodynamic pattern in this sea area. On this basis, real-time current data from high-frequency radar is assimilated with the implementation of quick ensemble Kalman filter, which takes the variation tendency of the state vector to compute the analysis field, instead of integrating the field for N (the number of ensemble) times as it used to in the standard EnKF, aiming at raising the efficiency of computation, reducing the error of prediction and at the same time, improving the forecast effect. [ABSTRACT FROM AUTHOR]