Infragravity Wave Generation by Wind Gusts

Vrecica, Teodor; Soffer, Rotem; Toledo, Yaron

doi:10.1029/2019gl084241

Cited by 8 publications

(2 citation statements)

References 29 publications

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“…The majority of this increase is related to free IG waves that are preceding the peak of the storm. Based on the observations, it is not clear whether these IG forerunners are related to the earlier release of bound IG waves due to bathymetric variability (see Figure 1), the generation by other mechanisms like wind gusts [17] or the arrival of reflected IG waves from nearby up-wave coasts [11,12]. The predominance of free IG waves trailing the peak of the storm is consistent with the reflection and trapping of IG waves in the down-wave sea-swell direction.…”

Section: Discussionmentioning

confidence: 95%

North Sea Infragravity Wave Observations

Reniers

Naporowski

Tissier

et al. 2021

JMSE

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Coastal safety assessments with wave-resolving storm impact models require a proper offshore description for the incoming infragravity (IG) waves. This boundary condition is generally obtained by assuming a local equilibrium between the directionally-spread incident sea-swell wave forcing and the bound IG waves. The contribution of the free incident IG waves is thus ignored. Here, in-situ observations of IG waves with wave periods between 100 s and 200 s at three measurement stations in the North Sea in water depths of O(30) m are analyzed to explore the potential contribution of the free and bound IG waves to the total IG wave height for the period from 2010 to 2018. The bound IG wave height is computed with the equilibrium theory of Hasselmann using the measured frequency-directional sea-swell spectra as input. The largest IG waves are observed in the open sea with a maximum significant IG wave height of O(0.3) m at 32 m water depth during storm Xaver (December 2013) with a concurrent significant sea-swell wave height in excess of 9 m. Along the northern part of the Dutch coast, this maximum has reduced to O(0.2) m at a water depth of 28 m with a significant sea-swell wave height of 7 m and to O(0.1) m at the most southern location at a water depth of 34 m with a significant sea-swell wave height of 5 m. These appreciable IG wave heights in O(30) m water depth represent a lower bound for the expected maximum IG wave heights given the fact that in the present analysis only a fraction of the full IG frequency range is considered. Comparisons with the predicted bound IG waves show that these can contribute substantially to the observed total IG wave height during storm conditions. The ratio between the predicted bound- and observed total IG variance ranges from 10% to 100% depending on the location of the observations and the timing during the storm. The ratio is typically high at the peak of the storm and is lower at both the onset and waning of the storm. There is significant spatial variability in this ratio between the stations. It is shown that differences in the directional spreading can play a significant role in this. Furthermore, the observed variability along the Dutch coast, with a substantially decreased contribution of the bound IG waves in the south compared to the northern part of the Dutch coast, are shown to be partly related to changes in the mean sea-swell wave period. For the southern part of the Dutch coast this corresponds to an increased difference with the typically assumed equilibrium boundary condition although it is not clear how much of the free IG-energy is onshore directed barring more sophisticated observations and/or modeling.

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Section: Discussionmentioning

confidence: 95%

North Sea Infragravity Wave Observations

Reniers

Naporowski

Tissier

et al. 2021

JMSE

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“…Other deep water infragravity generation mechanics have also been proposed, such as atmospheric forcing by wind speed fluctuations (de Jong & Battjes, 2004;Vrećica et al, 2019) and IG-tidal interactions (Sugioka et al, 2010). By linking the arrival of FIG waves at oceanic sites to the landfall of energetic sea-swell waves at distant coastal regions, most deep water observations of IG energy have been explained by radiation of FIG waves at distant shorelines (e.g., Bogiatzis et al, 2020;Godin et al, 2014;Harmon et al, 2012;Neale et al, 2015;Tonegawa et al, 2018).…”

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confidence: 99%

Free Infragravity Waves in the North Sea

2021

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Infragravity waves are low‐frequency surface waves that can impact a variety of nearshore and oceanic processes. Recent measurements in the North Sea showed that significant bursts of infragravity energy occurred during storm events. Using a spectral wave model, we show that a substantial part of this energy was radiated from distant shorelines where it was generated by the incident sea‐swell waves. These radiated infragravity waves can cross the North Sea basin and reach distant shorelines. The origin of the infragravity wave energy varied between the different storms, and particularly depends on where largest sea‐swell waves made landfall. Along the coastlines of the North Sea, shoreward directed infragravity waves that originate from a remote source were non‐negligible during storm events. This suggests that radiated infragravity waves can potentially contribute to coastal dynamics and hazards away from their region of generation.

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Infragravity wave amplification by isolated topography: Field observations and semi-analytical modeling

Liao

Paniagua-Arroyave

et al. 2022

Applied Ocean Research

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Infragravity Wave Generation by Wind Gusts

Cited by 8 publications

References 29 publications

North Sea Infragravity Wave Observations

North Sea Infragravity Wave Observations

Free Infragravity Waves in the North Sea

Infragravity wave amplification by isolated topography: Field observations and semi-analytical modeling

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