On the Importance of the Exact Nonlinear Interactions in the Spectral Characterization of Rogue Waves

2018 ◽  
Author(s):  
Sonia Ponce de León ◽  
Alfred R. Osborne ◽  
Carlos Guedes Soares
Keyword(s):  
Wave Spectrum ◽  
Wave Model ◽  
Rogue Waves ◽  
Clear Understanding ◽  
Nonlinear Interactions ◽  
Wave Interactions ◽  
Nonlinear Part ◽  
Wave Dynamics ◽  
Spectral Wave Model ◽  
Future Work

This work is focused on the analysis of the wave action equation with full 4-wave interactions (Snl4). For this purpose, we have applied a state-of-the-art spectral wave model (Wave Watch III), using an exact method for the calculation of the full nonlinear Boltzmann interactions in the evolution of the wave spectrum. We emphasize the use of the exact WRT method [Van Vledder, 2006] for the computation of the Snl4 interactions instead of the approximate DIA method. The WRT algorithm includes the full Boltzmann integrations. We discuss how the WRT method is important in any assessment of rogue waves in the ocean and discuss how the enhanced spectral peak assists the formation of rogue waves packets. We demonstrate how the most nonlinear part of the peak of the spectrum is reduced in amplitude when the nonlinear interactions are instead computed using the DIA interactions. These results suggest that a clear understanding of the physics of nonlinear interactions and of rogue wave dynamics requires the use of the full Boltzmann interactions. Future work would include faster WRT computations so that practical forecasting/hindcasting can become possible using the full four-wave interactions.

Projected Changes in the Occurrence of Extreme and Rogue Waves in Future Climate in the North Atlantic

2017 ◽  
Author(s):  
Odin Gramstad ◽  
Elzbieta Bitner-Gregersen ◽  
Erik Vanem
Keyword(s):  
North Atlantic ◽  
Wave Spectrum ◽  
Wave Model ◽  
Rogue Waves ◽  
Wave Climate ◽  
Future Climate ◽  
The North ◽  
Wave Parameters ◽  
The Future ◽  
The North Atlantic

We investigate the future wave climate in the North Atlantic with respect to extreme events as well as on wave parameters that have previously not been considered in much details in the perspective of wave climate change, such as those associated with occurrence of rogue waves. A number of future wave projections is obtained by running the third generation wave model WAM with wind input derived from several global circulation models. In each case the wave model has been run for the 30-year historical period 1971–2000 and the future period 2071–2100 assuming the two different future climate scenarios RCP 4.5 and RCP 8.5. The wave model runs have been carried out by the Norwegian Meteorological Institute in Bergen, and the climate model result are taken from The Coupled Model Intercomparison Project phase 5 - CMIP5. In addition to the standard wave parameters such as significant wave height and peak period the wave model runs provided the full two-dimensional wave spectrum. This has enabled the study of a larger set of wave parameters. The focus of the present study is the projected future changes in occurrence of extreme sea states and extreme and rogue waves. The investigations are limited to parameters related to this in a few selected locations in the North Atlantic. Our results show that there are large uncertainties in many of the parameters considered in this study, and in many cases the different climate models and different model scenarios provide contradicting results with respect to the predicted change from past to future climate. There are, however, some situations for which a clearer tendency is observed.

Application of Data Assimilation for a Spectral Wave Model on Unstructured Meshes

2006 ◽  
Author(s):  
Tai-Wen Hsu ◽  
Shan-Hwei Ou ◽  
Jian-Ming Liau ◽  
Jaw-Guei Lin ◽  
Chia-Chuen Kao ◽  
...  
Keyword(s):  
Data Assimilation ◽  
Wind Wave ◽  
Wave Spectrum ◽  
Wave Model ◽  
Wave Period ◽  
Optimal Interpolation ◽  
Sequential Method ◽  
Significant Wave ◽  
Spectral Wave Model ◽  
Buoy Data

The effect of the data assimilation of buoy data in the wind wave model (WWM) for wind wave simulations in both deep and shallow water regions developed by Hsu et al. [2005] is investigated. Following Lionello et al. [1992], the sequential method is implemented, where analyzed wave spectra and significant wave fields were assimilated by optimal interpolation (OI), then the analyzed values were used to reconstruct the wave spectrum. This paper examines the results of the assimilation of wave spectrum, significant wave height and significant wave period in a nearshore WWM model. The WWM model underestimates the wave period because it incorrectly applies past wave field data. The analysis has provided useful indications of the shortcomings of the WWM model. In summary, the OI approach is shown to be a reliable assimilation scheme in the WWM model.

The physics of ocean wave evolution within tropical cyclones

2021 ◽  
Author(s):  
Ali Tamizi ◽  
Jose-Henrique Alves ◽  
Ian R. Young
Keyword(s):  
Tropical Cyclone ◽  
Tropical Cyclones ◽  
Critical Role ◽  
Wave Model ◽  
Wave Interactions ◽  
Wave Evolution ◽  
Spectral Wave Model ◽  
Wind Sea ◽  
Buoy Data

AbstractA series of numerical experiments with the WAVEWATCH III spectral wave model are used to investigate the physics of wave evolution in tropical cyclones. Buoy observations show that tropical cyclone wave spectra are directionally skewed with a continuum of energy between locally generated wind-sea and remotely generated waves. These systems are often separated by more than 900. The model spectra are consistent with the observed buoy data and are shown to be governed by nonlinear wave-wave interactions which result in a cascade of energy from the wind-sea to the remotely generated spectral peak. The peak waves act in a “parasitic” manner taking energy from the wind-sea to maintain their growth. The critical role of nonlinear processes explains why one-dimensional tropical cyclone spectra have characteristics very similar to fetch-limited waves, even though the generation system is far more complex. The results also provide strong validation of the critical role nonlinear interactions play in wind-wave evolution.

Predicting Extreme Waves From Wave Spectral Properties Using Machine Learning

2019 ◽  
Author(s):  
Odin Gramstad ◽  
Elzbieta Bitner-Gregersen
Keyword(s):  
Machine Learning ◽  
Spectral Properties ◽  
Wave Spectrum ◽  
Wave Model ◽  
Rogue Waves ◽  
Wave Steepness ◽  
Extreme Waves ◽  
Learning Methods ◽  
Wave Statistics ◽  
Machine Learning Methods

Abstract An important question in the context of rogue waves is whether the statistical properties of individual waves, and in particular the probability of extreme and rogue waves, can be linked to the properties of the underlying wave spectrum of the relevant sea state. It has been suggested that a narrow wave spectrum (in frequency or direction) combined with a large wave steepness may lead to increased occurrence of extreme waves. Parameters based on the ratio of the wave steepness to the spectral band-widths have therefore been suggested as indicators of increased probability of extreme waves. However, for realistic ocean conditions the success of such parameters seems to be questionable. In this paper, we investigate relations between short-time wave statistics and wave spectral properties by using machine learning methods that can take a much wider range of spectral properties, or even the entire directional wave spectrum, into account. Numerical simulations with a nonlinear wave model that provides phase-resolved wave information are combined with wave spectra from a spectral wave model. Machine learning methods are then employed to investigate how well the wave statistics can be predicted from knowledge about the wave spectrum. The results are discussed in the context of existing parameters suggested as indicators of rogue waves, as well as with respect to potential warning against sea states in which extreme waves are expected to occur, based on wave-forecast from spectral wave models.

scholarly journals INTERACTIVE AND IMMERSIVE COASTAL HYDRODYNAMIC SIMULATION

2018 ◽  
pp. 63
Author(s):  
Patrick J. Lynett ◽  
Sasan Tavakkol
Keyword(s):  
Open Access ◽  
Boundary Conditions ◽  
Wave Model ◽  
Water Velocity ◽  
Model Parameters ◽  
Wave Interactions ◽  
Hydrodynamic Simulation ◽  
Wave Dynamics ◽  
Physical Variables ◽  
Language Environment

In this presentation, we will discuss the development and application of a GPU-based Boussinesq-type wave model. The novelty of this approach is that it is meant to serve the primary purpose of being interactive – allowing the user to modify the boundary conditions and model parameters as the model is running, and to see the effect of these changes immediately. To accomplish this, the model is coded in a shader language environment, and our physical variables (e.g. ocean surface elevation, water velocity) are represented in the model as textures, which can be rapidly rendered and visualized via a GPU. This software can help scientists better understand nearshore wave dynamics as it allows them to observe wave interactions in real-time and modify the boundary conditions and model parameters as the model is running to see the effect of these changes immediately. The model is named “Celeris”, and is released under the GNU (open-source, open-access) license.

Forty years of global wave hindcasts using the observation-based source terms: validation and geophysical applications

2020 ◽  
Author(s):  
Qingxiang Liu ◽  
Alexander Babanin ◽  
Erick Rogers ◽  
Stefan Zieger
Keyword(s):  
Empirical Studies ◽  
Mixed Layer Depth ◽  
Wave Spectrum ◽  
Wave Model ◽  
Global Scale ◽  
Gas Transfer ◽  
Fifth Generation ◽  
Spectral Wave Model ◽  
Wave Parameters ◽  
Wave Induced

<p>Forty years (1979-2019) of global wave hindcasts are developed with the third generation spectral wave model WAVEWATCH III® using the state-of-the-art observation-based source term parameterizations (i.e., ST6) and the advanced irregular-regular-irregular (IRI) 1/4 grid system. The wave model has been forced with two distinct wind databases sourced from the latest NCEP Climate Forecast System (CFS) and the fifth generation of the ECMWF climate reanalyses (ERA5), together with the ice concentration available from the EUMETSAT OSI SAF (version 2). The hindcasts not only include traditional integral wave parameters (e.g., wave height, period) but also provide various novel parameters such as the dominant wave breaking probability, wave-induced mixed layer depth and whitecap coverage that are derived from wave spectrum based on previous theoretical and empirical studies. Wave parameters are extensively validated against observations from in-situ buoys and satellite altimeters on a global scale. Possible applications of these hindcasts in the fields of freak waves, sea spray and air-sea gas transfer will also be discussed.</p>

scholarly journals Energy Spectra of Ensemble of Nonlinear Capillary Waves on a Fluid

2021 ◽  
Vol 9 (12) ◽  
pp. 1422
Author(s):  
Elena Tobisch ◽  
Alexey Kartashov
Keyword(s):  
Kinetic Equation ◽  
Energy Spectrum ◽  
Wave Spectrum ◽  
Capillary Waves ◽  
Energy Spectra ◽  
Dynamic Equations ◽  
Turbulent Regime ◽  
Nonlinear Interactions ◽  
Wave Interactions ◽  
Energy Cascades

The problem of spectral description of the nonlinear capillary waves on the fluid surface is discussed. Usually, three-wave nonlinear interactions are considered as a major factor determined by the energy spectrum of these waves in the kinetic wave turbulent regime. We demonstrate that four-wave interactions should be taken into account. In this case, there are two possible scenarios for the transfer of energy over the wave spectrum: kinetic and dynamic. The first is described by the averaged stochastic interaction of waves using the kinetic equation, while the second is described by dynamic equations written for discrete modes. In this article, we compare the time scales, spectral shapes, and other properties of both energy cascades, allowing them to be identified in an experiment.

scholarly journals Evaluating the accuracy and uncertainty of atmospheric and wave model hindcasts during severe events using model ensembles

2021 ◽  
Author(s):  
Ali Abdolali ◽  
Andre van der Westhuysen ◽  
Zaizhong Ma ◽  
Avichal Mehra ◽  
Aron Roland ◽  
...  
Keyword(s):  
Extreme Event ◽  
Numerical Models ◽  
Model Performance ◽  
Ground Truth ◽  
Wave Model ◽  
Atmospheric Model ◽  
Stationary Source ◽  
Source Point ◽  
Spectral Wave Model ◽  
Model Ensembles

AbstractVarious uncertainties exist in a hindcast due to the inabilities of numerical models to resolve all the complicated atmosphere-sea interactions, and the lack of certain ground truth observations. Here, a comprehensive analysis of an atmospheric model performance in hindcast mode (Hurricane Weather and Research Forecasting model—HWRF) and its 40 ensembles during severe events is conducted, evaluating the model accuracy and uncertainty for hurricane track parameters, and wind speed collected along satellite altimeter tracks and at stationary source point observations. Subsequently, the downstream spectral wave model WAVEWATCH III is forced by two sets of wind field data, each includes 40 members. The first ones are randomly extracted from original HWRF simulations and the second ones are based on spread of best track parameters. The atmospheric model spread and wave model error along satellite altimeters tracks and at stationary source point observations are estimated. The study on Hurricane Irma reveals that wind and wave observations during this extreme event are within ensemble spreads. While both Models have wide spreads over areas with landmass, maximum uncertainty in the atmospheric model is at hurricane eye in contrast to the wave model.

scholarly journals Wave Directions in a Narrow Bay

2010 ◽  
Vol 40 (1) ◽  
pp. 155-169 ◽  
Author(s):  
Heidi Pettersson ◽  
Kimmo K. Kahma ◽  
Laura Tuomi
Keyword(s):  
Wave Model ◽  
Wave Climate ◽  
Spectral Peak ◽  
Step Size ◽  
Weakly Nonlinear ◽  
Spectral Wave Model ◽  
Directional Coupling ◽  
Directional Wave ◽  
The Baltic ◽  
The Waves

Abstract In slanting fetch conditions the direction of actively growing waves is strongly controlled by the fetch geometry. The effect was found to be pronounced in the long and narrow Gulf of Finland in the Baltic Sea, where it significantly modifies the directional wave climate. Three models with different assumptions on the directional coupling between the wave components were used to analyze the physics responsible for the directional behavior of the waves in the gulf. The directionally decoupled model produced the direction at the spectral peak correctly when the slanting fetch geometry was narrow but gave a weaker steering than observed when the fetch geometry was broader. The method of Donelan estimated well the direction at the spectral peak in well-defined slanting fetch conditions, but overestimated the longer fetch components during wave growth from a more complex shoreline. Neither the decoupled nor the Donelan model reproduced the observed shifting of direction with the frequency. The performance of the third-generation spectral wave model (WAM) in estimating the wave directions was strongly dependent on the grid resolution of the model. The dominant wave directions were estimated satisfactorily when the grid-step size was dropped to 5 km in the gulf, which is 70 km in its narrowest part. A mechanism based on the weakly nonlinear interactions is proposed to explain the strong steering effect in slanting fetch conditions.

scholarly journals Wave power assessment in Faroese waters using an oceanic to nearshore scale spectral wave model

Energy ◽  
2021 ◽  
pp. 121404
Author(s):  
Bárður Joensen ◽  
Bárður A. Niclasen ◽  
Harry B. Bingham
Keyword(s):  
Wave Model ◽  
Wave Power ◽  
Spectral Wave Model
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