Observations of the shape and group dynamics of rogue waves

Gemmrich, Johannes; Thomson, Jim

doi:10.1002/2016gl072398

Cited by 32 publications

(16 citation statements)

References 31 publications

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“…Similar results were obtained by [140] in a study of 2 million wave groups where they identified 300 rogue waves. Although nonlinear modulation instability is discussed as a possible effect that can increase wave envelope steepness, the conclusion (based on the symmetric shape of the wave groups) was that random superposition of the Stokes waves was sufficient to explain the observations of individual rogue waves.…”

Section: B Rogue Waves In the Natural Environmentsupporting

confidence: 84%

Rogue waves and analogies in optics and oceanography

et al. 2019

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We review the study of rogue waves and related instabilities in optical and oceanic environments, with particular focus on recent experimental developments. In optics, we emphasize results arising from the use of real-time measurement techniques, whilst in oceanography we consider insights obtained from analysis of real-world ocean wave data and controlled experiments in wave tanks. Although significant progress in understanding rogue waves has been made based on an analogy between wave dynamics in optics and hydrodynamics, these comparisons have predominantly focused on one-dimensional nonlinear propagation scenarios. As a result, there remains significant debate about the dominant physical mechanisms driving the generation of ocean rogue waves in the complex environment of the open sea. Here, we review stateof-the-art of rogue wave studies in optics and hydrodynamics, aiming to clearly identify similarities and differences between the results obtained in the two fields. In hydrodynamics, we take care to review results that support both nonlinear and linear interpretations of ocean rogue wave formation, and in optics, we also summarise results from an emerging area of research applying the measurement techniques developed for the study of rogue waves to dissipative soliton systems. We conclude with a discussion of important future research directions. the underlying carrier wave is considered sinusoidal at frequency ω whereas in hydrodynamics, the NLSE envelope modulates the Stokes wave which (to second-order) contains contributions at both ω and the second harmonic 2ω [31]. In addition, even though the terminology "optical wave breaking" is used in an NLSE context to describe the steepening of an optical envelope from nonlinear focussing [32], optical carrier waves themselves do not "break" or plunge as they do in hydrodynamics [33,34]. There are also important differences concerning measurements. Specifically, experiments in optical fibres generally measure only the time-domain envelope intensity, and information about carrier oscillations is not recorded. In contrast, measurements in hydrodynamics directly record the individual carrier wave amplitudes (although envelope information can be reconstructed straightforwardly [35]). Particular care must therefore be taken when comparing statistics between optics and hydrodynamics, because statistics in fibre optics experiments are determined

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Section: B Rogue Waves In the Natural Environmentsupporting

confidence: 84%

Rogue waves and analogies in optics and oceanography

et al. 2019

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“…As a matter of fact, analyzing a long series of single-point field measurements, Christou and Ewans 2 established that only one every 145 20-min sea states contained one rogue wave, implying that these waves occur rarely, on average once every about ∼33000 waves (a recent study by Gemmrich and Thomson 15 revealed similar statistics analyzing time records at Station P ), consistent with the Tayfun model 8 prediction of the probability that nonlinear crest heights exceed 1.25 H s . In this respect, a key finding of our study is that at least one wave whose crest height exceeds 1.25 H s was observed within the ST records, which contain on average less than 12000 individual 3D waves (Table 1 ), the minimum ( N 3D ~ 400–600) being for the two records collected near Station P .…”

Section: Resultsmentioning

confidence: 99%

“…There is increasing consensus 1 – 3 that a likely physical mechanism explaining the formation of oceanic rogue waves in stormy conditions is the spatio-temporal focusing due to the dispersive nature of water waves in intermediate-deep waters 4 – 6 , further enhanced by second-order non-resonant nonlinearities 7 – 9 . The role of the modulation instability due to third-order nonlinearities on the statistics of ocean waves 10 – 12 was shown to have a minor effect during directionally spread sea states 13 – 15 . The same conclusion holds for the extreme wave temporal profile 1 .…”

Section: Introductionmentioning

confidence: 99%

On the shape and likelihood of oceanic rogue waves

Benetazzo

Ardhuin

Bergamasco

et al. 2017

Sci Rep

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We consider the observation and analysis of oceanic rogue waves collected within spatio-temporal (ST) records of 3D wave fields. This class of records, allowing a sea surface region to be retrieved, is appropriate for the observation of rogue waves, which come up as a random phenomenon that can occur at any time and location of the sea surface. To verify this aspect, we used three stereo wave imaging systems to gather ST records of the sea surface elevation, which were collected in different sea conditions. The wave with the ST maximum elevation (happening to be larger than the rogue threshold 1.25H s) was then isolated within each record, along with its temporal profile. The rogue waves show similar profiles, in agreement with the theory of extreme wave groups. We analyze the rogue wave probability of occurrence, also in the context of ST extreme value distributions, and we conclude that rogue waves are more likely than previously reported; the key point is coming across them, in space as well as in time. The dependence of the rogue wave profile and likelihood on the sea state conditions is also investigated. Results may prove useful in predicting extreme wave occurrence probability and strength during oceanic storms.

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“…This was later shown to be related to the slowing of crests and thus the local accumulation of wave energy in groups Banner et al (). Gemmrich and Thomson () found that rogue waves were tied closely to wave groups. van den Bremer and Taylor () showed that wave groups are related to Lagrangian transport.…”

Section: Introductionmentioning

confidence: 99%

Wave Groups Observed in Pancake Sea Ice

et al. 2019

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Ocean surface waves propagating through sea ice are scattered and dissipated. The net attenuation occurs preferentially at the higher frequencies, and thus the spectral bandwidth of a given wave field is reduced, relative to open water. The reduction in bandwidth is associated with an increase in the groupiness of the wave field. Using Surface Wave Instrument Float with Tracking buoy data from the 2015 Arctic Sea State experiment, bandwidth is compared between pancake ice and open water conditions, and the linkage to group envelopes is explored. The enhancement of wave groups in ice is consistent with the simple linear mechanism of superposition of waves with narrowing spectral bandwidth. This is confirmed using synthetic data. Nonlinear mechanisms, which have been shown as significant in other ice types, are not found to be important in this data set. Key Points:• Ocean surface waves are attenuated by sea ice, particularly at high frequencies • The preferential loss of high-frequency energy causes a narrowing of the scalar wave spectrum in sea ice • The narrow-banded waves have more prominent group structures, which can be explained by linear mechanisms Supporting Information:• Supporting Information S1

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Observations of the shape and group dynamics of rogue waves

Cited by 32 publications

References 31 publications

Rogue waves and analogies in optics and oceanography

Rogue waves and analogies in optics and oceanography

On the shape and likelihood of oceanic rogue waves

Wave Groups Observed in Pancake Sea Ice

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