Assimilation of ERS SAR wave spectra in an operational wave model

1998 ◽  
Vol 103 (C4) ◽  
pp. 7887-7900 ◽  
Author(s):  
Lars-Anders Breivik ◽  
Magnar Reistad ◽  
Harald Schyberg ◽  
Jens Sunde ◽  
Harald E. Krogstad ◽  
...  
Keyword(s):  
Wave Model ◽  
Wave Spectra

scholarly journals WAVE AND SEAFLOOR SPECTRA PREDICTIONS WITH THE COUPLED SWAN-NSEA MODELING SYSTEM

2020 ◽  
pp. 57
Author(s):  
Allison Penko ◽  
Erick Rogers ◽  
Joseph Calantoni
Keyword(s):  
Underwater Acoustics ◽  
Roughness Parameter ◽  
Wave Model ◽  
Wave Spectra ◽  
Dynamic Feedback ◽  
Layer Model ◽  
Sediment Wave ◽  
Coastal Morphology ◽  
Wave Forcing ◽  
Biologic Activity

The existence and evolution of bedforms on the seafloor have significant effects in the areas of oceanography, marine geophysics, and underwater acoustics including the transport of sediment, wave energy attenuation, and seabed sonar scattering and penetration. Here, we present a wave-seafloor modeling system that couples a spectral seafloor boundary layer model (NSEA) with an operational wave model (SWAN) that includes the dynamic feedback between the predicted wave spectra and the wave generated bedforms on the seafloor through a bottom roughness parameter. NSEA is a seafloor spectral model that uses hydrodynamic input forcing forecasted by the wave model SWAN to predict the evolving seafloor spectra given a sediment grain diameter and an estimation of the biologic activity. The system can be used to determine the spatially and temporally varying bottom roughness under given wave forcing important for coastal morphology and acoustic applications.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/u66k6lZbEbw

scholarly journals Assimilation of decomposed in-situ directional wave spectra into a numerical wave model on typhoon wave

2013 ◽  
Vol 1 (4) ◽  
pp. 3967-3989
Author(s):  
Y. M. Fan ◽  
H. Günther ◽  
C. C. Kao ◽  
B. C. Lee
Keyword(s):  
Data Assimilation ◽  
Forecast Accuracy ◽  
Wave Model ◽  
Sequential Data ◽  
Wave Spectra ◽  
Typhoon Wave ◽  
Independent Observations ◽  
Directional Wave ◽  
Numerical Wave

Abstract. The purpose of this study was to enhance the accuracy of numerical wave forecasts through data assimilation during typhoon period. A sequential data assimilation scheme was modified to enable its use with partitions of directional wave spectra. The performance of the system was investigated with respect to operational applications specifically for typhoon wave. Two typhoons that occurred in 2006 around Taiwan (Kaemi and Shanshan) were used for this case study. The proposed data assimilation method increased the forecast accuracy in terms of wave parameters, such as wave height and period. After assimilation, the shapes of directional spectra were much closer to those reported from independent observations.

WAVERYS : A CMEMS global wave reanalysis during the altimetry period

2020 ◽  
Author(s):  
Stephane Law Chune ◽  
Lotfi Aouf ◽  
Alice Dalphinet ◽  
Bruno Levier ◽  
Yann Drillet
Keyword(s):  
Large Scale ◽  
Surface Current ◽  
Wave Model ◽  
Grid Resolution ◽  
Wave System ◽  
Wave Spectra ◽  
Ocean Reanalysis ◽  
Wave Data ◽  
Directional Wave ◽  
Wave Reanalysis

<p><strong>As part of the Copernicus Marine Core service, WAVERYS is the multi-year wave reanalysis that aims to provide global wave data with a grid resolution of 1/5°. The wave reanalysis covers the period of 1993-2018 and provides 3-hourly classical integrated wave parameters describing the sea state at the ocean surface. The wave model used is the V4 version of the model MFWAM, which is driven by atmospheric forcing (winds and ice fraction) from ECMWF ERA5 reanalysis. This latter has showed a significant improvement regarding to the previous reanalysis ERA-Interim. WAVERYS includes the assimilation of altimeters wave data available during the period starting from Topex-Poseidon until Sentinel-3A missions. Directional wave spectra from Synthetic Aperture Radar (SAR) of Sentinel-1A and 1B missions are also assimilated. This is the first time that such directional wave spectra are used in a global wave reanalysis.</strong></p><p><strong>Further, WAVERYS uses a 3 hour surface current forcing provided by ocean reanalysis GLORYS12 implemented by Mercator-Ocean in the frame of Copernicus Marine Service with a grid resolution of 1/12°. The wave reanalysis is high skilled for ocean regions with dominant wave-currents interactions. Preliminary validation tests have shown improvement by 15% in scatter index for large scale high currents areas. This paper will give detailed characteristics of the wave system and will insist on the benefits of taking into account ocean currents and a physics calibrated for realistic swell propagation.</strong></p><p> </p>

Experimental and Numerical Statistics of Storm Wave Forces on a Monopile in Uni- and Multidirectional Seas

2017 ◽  
Author(s):  
Signe Schløer ◽  
Henrik Bredmose ◽  
Amin Ghadirian
Keyword(s):  
Wave Model ◽  
Wave Theory ◽  
Peak Frequency ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Wave Forces ◽  
Wave Spectra ◽  
Higher Harmonics ◽  
Storm Wave ◽  
Multidirectional Wave

Experiments with both uni- and multidirectional wave realizations with a stiff pile subjected to extreme wave forces are considered. Differences in crest heights and force peaks resulting from directional spread waves are analysed. The wave realizations are reproduced numerically in the fully nonlinear wave model OceanWave3D. The numerical reproductions compare well to the experiments. Only for the largest forces significant differences are seen, which is due to a very simple breaking filter applied in OceanWave3D. In the wave spectra, the higher harmonics occur for smaller frequencies than the straight multiples of the peak frequency. Further, the higher harmonics of the multidirectional wave spectra contain less energy. Both effects can be explained by the second order wave theory. Finally, the computed wave kinematics are used to investigate the dynamic response of an offshore wind turbine. The excitation of the first natural frequency is largest for the unidirectional wave realizations, as the higher harmonics are largest for these realizations.

scholarly journals Comparison of Envisat ASAR Ocean Wave Spectra with Buoy and Altimeter Data via a Wave Model

2009 ◽  
Vol 26 (3) ◽  
pp. 593-614 ◽  
Author(s):  
Jian-Guo Li ◽  
Martin Holt
Keyword(s):  
Wave Height ◽  
Spectral Characteristics ◽  
Wave Model ◽  
Ocean Wave ◽  
Global Ocean ◽  
Altimeter Data ◽  
Wave Spectra ◽  
Envisat Asar ◽  
Comparison Results ◽  
Wave Heights

Abstract The Advanced Synthetic Aperture Radar (ASAR) on board the Envisat satellite is an important resource for observation of global ocean surface wave spectra. However, assessment of this valuable dataset is not straightforward as a result of a lack of other independent ocean wave spectral observations. The radar altimeter (RA-2) on board the same satellite measures ocean wave height at the same time as the ASAR but at a location about 200 km distant. A small number of moored buoys produce one-dimensional (1D) ocean wave spectra but few ASAR spectra fall on the buoy positions in a given period. Indirect comparison of the Envisat ASAR 2D wave spectra with the RA-2 wave heights and 1D spectra of three selected buoys from July 2004 to February 2006 is facilitated by a wave model, which provides coherent spatial and temporal links between these observations. In addition to the conventional significant wave height (SWH), four spectral subrange wave heights (SRWHs) are used to illustrate the spectral characteristics of these observations. A comparison of three Envisat ASAR 2D spectra with the closest model and buoy spectra is also attempted to illustrate the qualities of these different observations and to demonstrate the restrictions to their direct comparison. Results indicate that these three independent observations are in good agreement in terms of SWH, though the Envisat ASAR shows the largest variance. Comparison of SRWHs indicates that the ASAR spectra agree well with buoy and model in moderately long waves, but the ASAR instrument does not resolve high-frequency waves, especially along the satellite track.

scholarly journals ON SPECTRUM CALIBRATION FOR NEARSHORE WAVE TRANSFORMATION

2018 ◽  
pp. 50
Author(s):  
Zhong Peng ◽  
Jill Bradon
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Wave Spectrum ◽  
Wave Model ◽  
Accurate Solution ◽  
Least Square ◽  
Wave Transformation ◽  
Wave Spectra ◽  
Wave Modelling ◽  
Spectrum Calibration

A ‘shape-focus’ method is proposed for wave spectrum calibration. In this method calibration factors at each frequency bin are derived from measured and modelled data using a least square error approach. Modelled wave spectra are calibrated using the shape-focus method and then applied to a SWAN wave model to simulate nearshore wave transformation. Nearshore wave spectra are then compared with measurements. Results show that spectrum calibration with the shape-focus method improves wave data accuracy significantly for both significant wave height and mean wave periods, thus provides a more accurate solution to calibrating wave spectra for nearshore wave modelling.

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