A wave prediction framework based on machine learning and the third generation wave model

2021 ◽  
pp. 1-14
Author(s):  
Shuai Liu ◽  
Xinshu Zhang
Keyword(s):  
Short Term Memory ◽  
Wave Spectrum ◽  
Wave Model ◽  
Absolute Error ◽  
Ocean Waves ◽  
Accurate Prediction ◽  
Third Generation ◽  
Wave Condition ◽  
Machine Leaning ◽  
Error Percentage

Abstract To predict the evolution of wave spectrum in real ocean, a machine leaning framework is developed by training a long short-term memory (LSTM) neural network on a physics-based third generation wave model (Simulating WAve Nearshore, SWAN). Considering the realistic ocean waves are usually mixtures of windsea and swells, the wave spectrum is partitioned using a watershed algorithm, such that the windsea and swells are analysed and predicted separately. Four parameters are selected to capture the wave spectrum of each systems, including the significant wave height Hs, peaked wave period Tp, mean propagation direction Qm and directional spreading width sq. The results demonstrate the machine leaning model can achieve accurate prediction of wave condition, the MAEPs (mean absolute error percentage) of 1-hour prediction are less than 5.9%, 3.3%, 3.5% and 3.3% for Hs, Tp, Qm and σθ respectively, and accurate prediction of wave spectra is achieved. Even for 10-hour prediction, satisfactory results are obtained, e.g. the MAEP of Hs is less than 15.5%. The effects of output size (i.e. prediction duration), input data size (i.e. number of delays), as well as different combinations of input features on predictions of wave condition are examined.

Implementing New Nonlinear Term in Third Generation Wave Models

2014 ◽  
Author(s):  
Odin Gramstad ◽  
Alexander Babanin
Keyword(s):  
Kinetic Equation ◽  
Spread Spectrum ◽  
Time Scale ◽  
Source Term ◽  
Wave Spectrum ◽  
Wave Model ◽  
Third Generation ◽  
Spectral Evolution ◽  
Linear Interaction ◽  
Wavewatch Iii

The non-linear interaction term is one of the three key source functions in every third-generation spectral wave model. An update of physics of this term is discussed. The standard statistical/phase-averaged description of the nonlinear transfer of energy in the wave spectrum (wave-turbulence) is based on Hasselmann’s kinetic equation [1]. In the derivation of the kinetic equation (KE) it is assumed that the evolution takes place on the slow O(ε−4) time scale, where ε is the wave steepness. This excludes the effects of near-resonant quartet interactions that may lead to spectral evolution on the ‘fast’ O(ε−2) time scale. Generalizations of the KE (GKE) that enable description of spectral evolution on the O(ε−2) time scale [2–4] are discussed. The GKE, first solved numerically in [4], is implemented as a source term in the third generation wave model WAVEWATCH-III. The new source term (GKE) is tested and compared to the other nonlinear-interaction source terms in WAVEWATCH-III; the full KE (WRT method) and the approximate DIA method. It is shown that the GKE gives similar results to the KE in the case of a relatively broad banded and directional spread spectrum, while it shows somewhat larger difference in the case of a more narrow banded spectrum with narrower directional distribution. We suggest that the GKE may be a suitable replacement to the KE in situations where ‘fast’ spectral evolution takes place.

Towards a unified framework for maximum wave computation from numerical models: outcomes from the LATEMAR project.

2020 ◽  
Author(s):  
Alvise Benetazzo ◽  
Francesco Barbariol ◽  
Paolo Pezzutto ◽  
Luciana Bertotti ◽  
Luigi Cavaleri ◽  
...  
Keyword(s):  
Numerical Models ◽  
Wave Spectrum ◽  
Wave Model ◽  
Ocean Waves ◽  
Unified Framework ◽  
Sea State ◽  
Large Wave ◽  
Wavewatch Iii ◽  
Wave Models ◽  
The Impact

<p>Reliable prediction of oceanic waves during severe marine storms has always been foremost for offshore platform design, coastal activities, and navigation safety. Indeed, many damaging accidents and casualties during storms were ascribed to the impact with abnormal and unexpected waves. However, predicting extreme wave occurrence is a challenging task, at first, because of their inherent randomness, and because the observation of large ocean waves, of primary importance to assess theoretical and numerical models, is limited by the costs and risks of deployment during severe open-ocean sea-state conditions.</p><p>In the context of the EU-based Copernicus Marine Environment Monitoring Service (CMEMS) evolution, the LATEMAR project (https://www.mercator-ocean.fr/en/portfolio/latemar/) aimed at improving the modelling of large wave events during marine storms. Indeed, at present, operational systems only provide average and peak wave parameters, with no information on individual waves whatsoever. However, developments of the state-of-the-art third-generation wave models demonstrated that using the directional wave spectrum moments into theoretical statistical models for wave extremes, forecasters are able to accurately infer the expected shape and likelihood of the maximum waves during storms.</p><p>The main purpose of the activity is therefore to provide the wave models WAM and WAVEWATCH III with common procedures to explicitly estimate the maximum wave heights for each sea state. LATEMAR achieved this goal by: performing an extensive assessment of the model maximum waves using field observations collected from an oceanographic tower; comparing WAM and WAVEWATCH III maximum wave estimates in the Mediterranean Sea; investigating the sensitivity of the maximum waves on the main sea state parameters. All model developments and evaluations resulting from this research project will be directly applicable to the wave model forecasting systems to expand their catalogue.</p>

Ocean Surface Modeling in Vary Wind Field

2011 ◽  
Vol 480-481 ◽  
pp. 1452-1456
Author(s):  
Li Bo ◽  
Zhong Yi Li ◽  
Yue Jin Zhang
Keyword(s):  
Wind Field ◽  
Wave Spectrum ◽  
Wave Model ◽  
Ocean Surface ◽  
Ocean Waves ◽  
Surface Modeling ◽  
Ocean Wave ◽  
Statistical Characteristics ◽  
Linear Wave ◽  
Wave Models

In ocean surface modeling a popular method of wave modeling is making use of ocean wave spectrum, which is a physical wave model and based on linear wave theories. The ocean waves produced in this way can reflect the statistical characteristics of the real ocean well. However, few investigations of ocean simulation have been focused on turbulent fluid under vary wind field in this way, while all ocean wave models are built with the same wind parameters. In order to resolve the problem of traditional method, we proposed a new method of dividing the ocean surface into regular grids and generating wave models with different parameters of wind in different location of view scope. The method not only preserves the fidelity of statistical characteristics, but also can be accelerated with the processing of GPU and widely used in VR applications.

scholarly journals Previsão de Ondas Oceânicas por Ensemble: Uma Revisão e Estudo de Caso

2006 ◽  
Vol 33 (1) ◽  
pp. 117
Author(s):  
LEANDRO FARINA
Keyword(s):  
Wave Model ◽  
Ocean Waves ◽  
Empirical Orthogonal Functions ◽  
Ensemble Prediction ◽  
Third Generation ◽  
Prediction System ◽  
Extreme Wave ◽  
Orthogonal Functions ◽  
Ensemble Prediction System ◽  
Realistic Case

The ensemble numerical prediction of ocean waves is considered and all published works on this new topic in Geosciences are reviewed. A Wave Ensemble Prediction System is described where a global third-generation wave model is adopted. Twenty members are generated by a method based on Empirical Orthogonal Functions and a particular realistic case where several extreme wave events occurred is analysed.

scholarly journals Numerical simulation of wave spectrum during a typhoon

2021 ◽  
Vol 290 ◽  
pp. 02019
Author(s):  
Congying Kong ◽  
Hao Liu
Keyword(s):  
Growth Process ◽  
Wind Waves ◽  
Wave Spectrum ◽  
Wave Model ◽  
Third Generation ◽  
Wavewatch Iii ◽  
Directional Spectrum ◽  
The Third ◽  
Sea Area ◽  
The Relationship

The third-generation wave model WAVEWATCH-III was used to numerically simulate the wave under the influence of a typhoon in the coastal area of China. The wave spectrum at the buoy point was output, and the characteristics of the wave spectrum were analyzed. The change of the wave spectrum during the typhoon process reflected the growth process of typhoon formation, development and extinction. The relationship between the wave spectrum and the wind direction was intuitively shown by the directional spectrum, indicating the coexistence of wind waves and swells in the sea area during the typhoon process.

scholarly journals Observation-Based Source Terms in the Third-Generation Wave Model WAVEWATCH III: Updates and Verification

2019 ◽  
Vol 49 (2) ◽  
pp. 489-517 ◽  
Author(s):  
Qingxiang Liu ◽  
W. Erick Rogers ◽  
Alexander V. Babanin ◽  
Ian R. Young ◽  
Leonel Romero ◽  
...  
Keyword(s):  
Power Law ◽  
Wave Spectrum ◽  
Wave Model ◽  
Wave Period ◽  
Bulk Wave ◽  
Third Generation ◽  
Source Terms ◽  
Frequency Wave ◽  
Wavewatch Iii ◽  
The Third

AbstractThe observation-based source terms available in the third-generation wave model WAVEWATCH III (i.e., the ST6 package for parameterizations of wind input, wave breaking, and swell dissipation terms) are recalibrated and verified against a series of academic and realistic simulations, including the fetch/duration-limited test, a Lake Michigan hindcast, and a 1-yr global hindcast. The updated ST6 not only performs well in predicting commonly used bulk wave parameters (e.g., significant wave height and wave period) but also yields a clearly improved estimation of high-frequency energy level (in terms of saturation spectrum and mean square slope). In the duration-limited test, we investigate the modeled wave spectrum in a detailed way by introducing spectral metrics for the tail and the peak of the omnidirectional wave spectrum and for the directionality of the two-dimensional frequency–direction spectrum. The omnidirectional frequency spectrum E(f) from the recalibrated ST6 shows a clear transition behavior from a power law of approximately f−4 to a power law of about f−5, comparable to previous field studies. Different solvers for nonlinear wave interactions are applied with ST6, including the Discrete Interaction Approximation (DIA), the more expensive Generalized Multiple DIA (GMD), and the very expensive exact solutions [using the Webb–Resio–Tracy method (WRT)]. The GMD-simulated E(f) is in excellent agreement with that from WRT. Nonetheless, we find the peak of E(f) modeled by the GMD and WRT appears too narrow. It is also shown that in the 1-yr global hindcast, the DIA-based model overestimates the low-frequency wave energy (wave period T > 16 s) by 90%. Such model errors are reduced significantly by the GMD to ~20%.

The evolution of large ocean waves: the role of local and rapid spectral changes

2006 ◽  
Vol 463 (2077) ◽  
pp. 21-48 ◽  
Author(s):  
R.S Gibson ◽  
C Swan
Keyword(s):  
Wave Spectrum ◽  
Wave Model ◽  
Ocean Waves ◽  
Order Theory ◽  
Second Order ◽  
Large Wave ◽  
Wave Event ◽  
Focused Wave ◽  
Wave Models ◽  
Directional Sea States

This paper concerns the formation of large-focused or near-focused waves in both unidirectional and directional sea-states. When the crests of wave components of varying frequency superimpose at one point in space and time, a large, transient, focused wave can occur. These events are believed to be representative of the largest waves arising in a random sea and, as such, are of importance to the design of marine structures. The details of how such waves form also offer an explanation for the formation of the so-called freak or rogue waves in deep water. The physical mechanisms that govern the evolution of focused waves have been investigated by applying both the fully nonlinear wave model of Bateman et al . (Bateman et al . 2001 J. Comput. Phys . 174 , 277–305) and the Zakharov's evolution equation (Zakharov 1968 J. Appl. Mech. Tech. Phys . 9 , 190–194). Aspects of these two wave models are complementary, and their combined use allows the full nonlinearity to be considered and, at the same time, provides insights into the dominant physical processes. In unidirectional seas, it has been shown that the local evolution of the wave spectrum leads to larger maximum crest elevations. In contrast, in directional seas, the maximum crest elevation is well predicted by a second-order theory based on the underlying spectrum, but the shape of the largest wave is not. The differences between the evolution of large waves in unidirectional and directional sea-states have been investigated by analysing the results of Bateman et al . (2001) using a number of spectral analysis techniques. It has been shown that during the formation of a focused wave event, there are significant and rapid changes to the underlying wave spectrum. These changes alter both the amplitude of the wave components and their dispersive properties. Importantly, in unidirectional sea-states, the bandwidth of the spectrum typically increases; whereas, in directional sea-states it decreases. The changes to the wave spectra have been investigated using Zakharov's equation (1968). This has shown that the third-order resonant effects dominate changes to both the amplitude of the wave components and the dispersive properties of the wave group. While this is the case in both unidirectional and directional sea-states, the consequences are very different. By examining these consequences, directional sea-states in which large wave events that are higher and steeper than second-order theory would predict have been identified. This has implications for the types of sea-states in which rogue waves are most likely to occur.

Sea State Estimation Based on Ship Motions Measurements and Data Fusion

2013 ◽  
Author(s):  
Céline Drouet ◽  
Nicolas Cellier ◽  
Jérémie Raymond ◽  
Denis Martigny
Keyword(s):  
Data Fusion ◽  
State Estimation ◽  
Wave Height ◽  
Significant Wave Height ◽  
Wave Spectrum ◽  
Ocean Waves ◽  
Ship Motions ◽  
Sea State ◽  
Significant Wave ◽  
X Band

In-service monitoring can help to increase safety of ships especially regarding the fatigue assessment. For this purpose, it is compulsory to know the environmental conditions encountered: wind, but also the full directional wave spectrum. During the EU TULCS project, a full scale measurements campaign has been conducted onboard the CMA-CGM 13200 TEU container ship Rigoletto. She has been instrumented to measure deformation of the ship as well as the sea state encountered during its trip. This paper will focus on the sea state estimation. Three systems have been installed to estimate the sea state encountered by the Rigoletto: An X-band radar from Ocean Waves with WAMOS® system and two altimetric wave radars from RADAC®. Nevertheless, the measured significant wave height can be disturbed by several external elements like bow waves, sprays, sea surface ripples, etc… Furthermore, ship motions are also measured and can provide another estimation of the significant wave height using a specific algorithm developed by DCNS Research for the TULCS project. As all those estimations are inherently different, it is necessary to make a fusion of those data to provide a single estimation (“best estimate”) of the significant wave height. This paper will present the data fusion process developed for TULCS and show some first validation results.

Variational Wave Data Assimilation in a Third-Generation Wave Model

1994 ◽  
Vol 11 (5) ◽  
pp. 1350-1369 ◽  
Author(s):  
Miriam M. De Las Heras ◽  
Gerrit Burgers ◽  
Peter A. E. M. Janssen
Keyword(s):  
Data Assimilation ◽  
Wave Model ◽  
Third Generation ◽  
Wave Data ◽  
Variational Wave
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