Processes influencing the non‐linear interaction between inertial oscillations, near inertial internal waves and internal tides

Xing, Jiuxing; Davies, Alan M.

doi:10.1029/2001gl014199

Cited by 43 publications

(59 citation statements)

References 6 publications

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“…This interaction can involve both horizontal and vertical current gradients. In particular, vertical gradients in the u current due to shear across the thermocline have been shown [ Xing and Davies , 2002b] to be responsible for nonlinear interaction between inertial and internal tidal currents. A detailed discussion of this interaction is given in the work of Davies and Xing [2003b].…”

Section: Numerical Calculationsmentioning

confidence: 99%

On the influence of a surface coastal front on near‐inertial wind‐induced internal wave generation

Xing

Davies

2004

J. Geophys. Res.

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[1] A numerical model is used to examine the wind-induced near-inertial internal waves in the coastal region in the presence of a surface front. Initial calculations with the front separating a well-mixed coastal region from a stratified offshore area in an infinite sea domain showed that away from the front, surface inertial oscillations are dominant. Near the front on the positive vorticity side, superinertial internal waves are generated and propagate offshore in an analogous manner to that found when stratification intersected a coastal boundary. However, in the case of a coastal boundary, the no-flow condition at the coast produced inertial oscillations at depth phase shifted by 180°from those at the surface. On the negative vorticity side of the front, internal waves at the subinertial frequency are trapped between the well-mixed region and the front. Some inertial energy is found at depth in the frontal region. Although the large-scale features of the distribution of inertial energy are independent of vertical eddy viscosity parameterization, its magnitude depends upon it. In the case of a stratified nearshore region and an offshore front, near-inertial waves generated at the coast were trapped between the coastal boundary and the front, which results in a surface region of enhanced inertial energy. This gradually decreased with time as inertial energy diffused to depth. This timescale depended upon vertical eddy viscosity magnitude.

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Section: Numerical Calculationsmentioning

confidence: 99%

On the influence of a surface coastal front on near‐inertial wind‐induced internal wave generation

Xing

Davies

2004

J. Geophys. Res.

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“…The nonlinear interaction between inertial motions (frequency f) and internal tides (frequencyω) can produce energy at the superposition f+ω frequency (Xing and Davies, 2002). Similarly, the frequency of inertial motions can be shifted by the background vorticity to create an effective frequency, leading to the region of wave trapping or propagation (Kunze, 1985).…”

Section: Introductionmentioning

confidence: 99%

Features of near-inertial motions observed on the northern South China Sea shelf during the passage of two typhoons

Chen

Polton

2015

Acta Oceanol. Sin.

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Abstract:Features of near-inertial motions on the shelf (60 m deep) of northern South China Sea were observed under the passage of two typhoons during the summer of 2009. There are two peaks in spectra at both sub-inertial and super-inertial frequencies.The super-inertial energy maximizes near the surface, while the sub-inertial energy maximizes at a deeper layer of 15 m. The sub-inertial shift of frequency is induced by the negative background vorticity. The super-inertial shift is probably attributed to the near-inertial wave propagating from higher latitudes. The near-inertial currents exhibit a two-layer pattern being separated at mid-depth (25~30 m), with the phase in the upper layer being nearly opposite to that in the lower layer. The vertical propagation of phase implies the near-inertial energy is not dominantly downward. The upward flux of near-inertial energy is more evident at the surface layer (<17 m). There exist two boundaries at 17 m and 40 m, where the near-inertial energy is reflected upward and downward. The near-inertial motion is intermittent and can reach a peak of as much as 30 cm/s. The passage of Typhoon Nangka generates an intensive near-inertial event, but Typhoon Linfa does not. This difference is attributed to the relative mooring locations, which is on the right hand side of Nangka's path (leading to a wind pattern rotating clockwise with time) and is on the left hand side of Linfa's path (leading to a wind pattern rotating anti-clockwise with time).

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“…The coastal upwelling/downwelling gives rise to internal waves that subsequently propagate away from the coastal region [e.g., Millot and Crepon , 1981; Rippeth et al , 2002; Davies and Xing , 2003a]. In the case of forcing at subinertial frequencies, the internal wave is trapped in the coastal region, although at superinertial frequencies, offshore propagation with a significant influence upon current profiles and mixing [ Davies and Xing , 2003a; Xing and Davies , 2002, 2003] can occur. This generation process for internal waves at a coastline is comparable to although different than that examined by Greatbatch [1983], Gill [1984], and others (see references in these papers) in connection with a moving storm.…”

Section: Introductionmentioning

confidence: 99%

Wind‐induced motion in the vicinity of a bottom density front: Response to forcing frequency

Davies

Xing

2004

J. Geophys. Res.

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A numerical model is used to examine the influence of nonlinear processes in the vicinity of a shallow sea bottom density front upon the depth of penetration of the wind's momentum at both superinertial and subinertial frequencies. Calculations show that nonlinear effects associated with differences in vorticity across the frontal jet significantly influence the depth of penetration of the wind's momentum and internal wave propagation. Differences in wind‐induced current amplitude and phase at depth due to nonlinear effects give rise to substantial vertical velocity in the frontal region, which drives near‐bed currents and forces internal waves. At superinertial frequencies, internal waves propagate away from the positive vorticity side of the front. However, at depth, internal waves are generated and current amplitude increases in the region of sloping density surfaces associated with the front. On the negative vorticity side, due to an effective inertial frequency below inertial, the wind's energy can propagate deeper into the water column. Wind forcing at subinertial frequencies does not lead to internal wave propagation. On the positive vorticity side of the front the wind's momentum cannot diffuse to depth due to turbulence suppression by stable stratification. The ability of the wind's momentum to penetrate to a greater depth in a frontal region through nonlinear effects suggests that these may be important processes influencing wind mixing in frontal regions.

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Processes influencing the non‐linear interaction between inertial oscillations, near inertial internal waves and internal tides

Cited by 43 publications

References 6 publications

On the influence of a surface coastal front on near‐inertial wind‐induced internal wave generation

On the influence of a surface coastal front on near‐inertial wind‐induced internal wave generation

Features of near-inertial motions observed on the northern South China Sea shelf during the passage of two typhoons

Wind‐induced motion in the vicinity of a bottom density front: Response to forcing frequency

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