Local Analysis of Wave Fields Produced From Hindcasted Rogue Wave Sea States

Abstract

Global-scale wave climate models, such as WAVEWATCH III, are widely used in oceanography to hindcast the sea state that occurred in a particular geographic area at a particular time. These models are applied in rogue-wave science for characterizing the sea states associated with observations of rogue waves (e.g., the well known “Draupner” [1] or “Andrea” [2] waves). While spectral models are generally successful in providing realistic representations of the sea state and are able to handle a large number of physical factors, they are also based on a very coarse grained representation of the wave field and therefore unsuitable for a detailed resolution of the wave field and refined wave-height statistics. On the other hand, local wave models based on first-principle fluid dynamics equations (such as the Higher Order Spectral Method) are able to represent wave fields in detail, but in general they are hard to interface with the full complexity of real-world sea conditions. This paper displays our efforts in coupling these two types of models in order to enhance our understanding of past extreme events and provide scope for rogue wave risk evaluation. In particular, high resolution numerical simulations of a wave field similar to the “Andrea” wave one are performed, allowing for accurate analysis of the event.

Rogue events in spatiotemporal numerical simulations of unidirectional waves in basins of different depth

“…In particular, the relation between the BFI index and the wave statistics is not confirmed in fully nonlinear simulations of unidirectional waves by Chalikov (2009). Besides simulations of model spectra, the direct numerical simulations are used to reconstruct the sea condition on the basis of hindcasting data (Bitner-Gregersen et al 2014;Dias et al 2015).…”

Real world ocean rogue waves explained without the modulational instability

“…Evidence that such extremes can occur in nature is provided, among others, by the Draupner and Andrea events, which have been extensively studied over the last decade123456. Several physical mechanisms have been proposed to explain the occurrence of such waves7, including the two competing hypotheses of nonlinear focusing due to third-order quasi-resonant wave-wave interactions8, and purely dispersive focusing of second-order non-resonant or bound harmonic waves, which do not satisfy the linear dispersion relation910.…”

Are Rogue Waves Really Unexpected?

“…Horizontal line denotes the observed maximum crest height 1.62H s . Wave parameters H s 5 9.2 m, T m 5 13.2 s, depth d 5 70 m (Magnusson and Donelan 2013), skewness l 3 ; 0.15, and excess kurtosis l 40 ; 0.1 (Dias et al 2015). Average wave parameters are taken from Tayfun (2006) and Tayfun and Fedele (2007), in particular skewness l 3 ; 0.23 and excess kurtosis l 40 ; 0.11. amplitude.…”

“…In particular, the Andrea wave was measured on 9 November 2007 by a system of four Optech lasers placed on a square array (LASAR) mounted on the Ekofisk platform in the North Sea in a water depth of d 5 74 m (Magnusson and Donelan 2013). In the last decade, the properties of the Draupner and Andrea waves have been extensively studied (Dysthe et al 2008;Osborne 1995;Magnusson and Donelan 2013;Bitner-Gregersen et al 2014;Dias et al 2015; and references therein). In the last decade, the properties of the Draupner and Andrea waves have been extensively studied (Dysthe et al 2008;Osborne 1995;Magnusson and Donelan 2013;Bitner-Gregersen et al 2014;Dias et al 2015; and references therein).…”

“…As a specific application here, we capitalize on the numerical simulations of the Andrea sea state (Bitner-Gregersen et al 2014;Dias et al 2015) and examine the unexpectedness of the Andrea wave in detail. We also study the effects of nonstationarity and stochastic dependence among successive waves.…”