The Structure of Near-Inertial Waves during Ocean Storms

Qi, Hongbo; Szoeke, Roland A. de; Paulson, Clayton A.; Eriksen, Charles C.

doi:10.1175/1520-0485(1995)025<2853:tsoniw>2.0.co;2

Cited by 47 publications

(55 citation statements)

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“…The 100-m lower core could be explained by the appearance of a second wave group from west of the moorings, as investigated by Qi et al (1995). This is not ruled out in our observations.…”

Section: Internal Wave Activitymentioning

confidence: 56%

“…The Ocean Storms Experiment (see Oceans Storms collection of papers: D 'Asaro 1995a,b,c;Niiler and Paduan 1995;Large and Crawford 1995;Qi et al 1995;Zervakis and Levine 1995;Levine and Zervakis 1995;Large et al 1995) was an effort to examine more closely the processes of air-sea interaction using a collection of moored and drifting instruments, and our interest here is the response of the mixed layer to surface forcing and the mechanisms responsible for the momentum transfer below the mixed layer. We approach this through analysis of previously unreported moored observations taken during Ocean Storms for two distinct autumn storms with clear but dramatically different upper-ocean responses.…”

Section: Introductionmentioning

confidence: 99%

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Mixing in the Transition Layer during Two Storm Events

Dohan

Davis

2011

Journal of Physical Oceanography

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Upper-ocean dynamics analyzed from mooring-array observations are contrasted between two storms of comparable magnitude. Particular emphasis is put on the role of the transition layer, the strongly stratified layer between the well-mixed upper layer, and the deeper more weakly stratified region. The midlatitude autumn storms occurred within 20 days of each other and were measured at five moorings. In the first storm, the mixed layer follows a classical slab-layer response, with a steady deepening during the course of the storm and little mixing of the thermocline beneath. In the second storm, rather than deepening, the mixed layer shoals while intense near-inertial waves are resonantly excited within the mixed layer. These create a large shear throughout the transition layer, generating turbulence that broadens the transition layer.Details of the space-time structure of the frequencies in both short waves and near-inertial waves are presented. Small-scale waves are excited within the transition layer. Their frequencies change with time and there are no clear peaks at harmonics of inertial or tidal frequencies. Wavelet transforms of the inertial oscillations show the evolution as a spreading in frequency, a deepening of the core into the transition layer, and a shift off the inertial frequency. A second near-inertial energy core appears below the transition layer at all moorings coincident with a rapid decay of mixed layer currents.An overall result is that direct wind-generated motions extend to the depth of the transition layer. The transition layer is a location of enhanced wave activity and enhanced shear-driven mixing.

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“…The 100-m lower core could be explained by the appearance of a second wave group from west of the moorings, as investigated by Qi et al (1995). This is not ruled out in our observations.…”

Section: Internal Wave Activitymentioning

confidence: 56%

Section: Introductionmentioning

confidence: 99%

Mixing in the Transition Layer during Two Storm Events

Dohan

Davis

2011

Journal of Physical Oceanography

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“…4c and 5c). According to the method utilized in Qi et al (1995), the downward group velocity (c gz ) can be estimated via the ratio of the vertical migration of the near-inertial groups and the corresponding time period (Fig. 5c).…”

Section: Summary Of the Observed Internal Wavesmentioning

confidence: 99%

“…Besides, the correlation between the near-inertial waves and strong surface forcing is lagged in time. It is found that the gradual propagation of storm induced inertial waves into the thermocline that lasted many days after the initiation of the storm based on the Ocean Storm Experiment in the northeast Pacific Ocean (Qi et al 1995). Three cycles of a single, energetic, downward-propagating near-inertial wave associated with enhanced mixing were observed in the Banda Sea (Alford and Gregg 2001).…”

Section: Introductionmentioning

confidence: 99%

Enhanced turbulent mixing induced by strong wind on the South China Sea shelf

Zhang

Tian

2014

Ocean Dynamics

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Integrated observations were made on the South China Sea shelf at 19°37' N, 112°04' E, under strong wind and heavy raining weather conditions in August 2005. Current data were obtained using a moored 150-kHz Acoustic Doppler Current Profiler, turbulent kinetic energy dissipation rate were measured with TurboMapII, and temperature was recorded by thermistor chains. Both the mixed layer thickness and the corresponding mean dissipation rate increased after the strong wind bursts. Average surface mixed layer thickness was 13.4 m pre-wind and 22.4 m post-wind, and the average turbulent dissipation rate in the mixed layer pre-wind and post-wind were 4.26 × 10 −7 and 1.09 × 10 −6 Wkg −1 , respectively. The post-wind dissipation rate was 2.5 times larger than the pre-wind dissipation rate in the interior layer and four times larger in the intermediate water column. Spectra and vertical mode analysis revealed that near-inertial motion post-wind, especially with high modes, was strengthened and propagated downward toward the intermediate layer. The ratio of post-wind high-mode energy to total horizontal kinetic energy increased below the surface mixed layer, which would have caused instabilities and result in turbulent mixing. Based on these data, we discuss a previous parameterization that relates dissipation rate, stratification, and shear variance calculated from baroclinic currents with high modes (higher than mode 1) which concentrate a large fraction of energy.

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“…In order to estimate quantitatively the downward energy propagation of these events we computed the correlation coefficient of the complex near‐inertial velocity, D , within the time interval [10–40] days, with a reference depth at the upper level z 1 = 240 m. This coefficient is computed using the following expression [see also Qi et al , 1995, equation (8)]: …”

Section: Focus On Events Of High‐amplitude Inertia‐gravity Wavesmentioning

confidence: 99%

Evidence of strong inertia‐gravity wave activity during the POMME experiment

et al. 2005

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[1] The purpose of this paper is to characterize inertia-gravity waves (IGW) activity and to investigate the variability of these waves in relationship to atmospheric forcing and larger-scale motions. To this aim, we analyzed Eulerian measurements of horizontal currents and temperature collected over 1 year during the Programme Océan Multidisciplinaire Méso Echelle (POMME). We focused on the main frequency components of the IGW spectrum, namely the inertial frequency f and the semidiurnal frequency M2. Time evolution of the relative energy of these two components gave evidence of isolated events of high intensity. We performed a detailed analysis of these events and identified mechanisms of generation of these waves. Localized spots of intense, near-inertial IGW were observed in winter. During the mixed layer deepening, one event was correlated with plume-like structures resulting from peaks of intense surface cooling. This suggests a local generation process driven by strong downward vertical motions. Instead, other events of strong IGW could be related to submesoscale features, characteristic of a frontal region, in particular, wave trapping within anticyclonic eddies. In contrast, a downward energy propagation down to about 500 m below the mixed layer was isolated after a stormy period. Eventually, internal tidal beams, possibly generated at a nearby seamount, intermittently crossed the mooring, though less energetically than the previous events. Last, we estimated the eddy diffusivity from the velocity vertical shear. Large variations were obtained, from 10 À6 m 2 /s up to 10 À3 m 2 /s, consistent with the intense events previously isolated.Citation: Bouruet-Aubertot, P., H. Mercier, F. Gaillard, and P. Lherminier (2005), Evidence of strong inertia-gravity wave activity during the POMME experiment,

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The Structure of Near-Inertial Waves during Ocean Storms

Cited by 47 publications

References 0 publications

Mixing in the Transition Layer during Two Storm Events

Mixing in the Transition Layer during Two Storm Events

Enhanced turbulent mixing induced by strong wind on the South China Sea shelf

Evidence of strong inertia‐gravity wave activity during the POMME experiment

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