A third-generation numerical wave model to compute random, short-crested waves in coastal regions with shallow water and ambient currents (Simulating Waves Nearshore (SWAN)) has been developed, implemented, and validated. The model is based on a Eulerian formulation of the discrete spectral balance of action density that accounts for refractive propagation over arbitrary bathymetry and current fields. It is driven by boundary conditions and local winds. As in other third-generation wave models, the processes of wind generation, whitecapping, quadruplet wave-wave interactions, and bottom dissipation are represented explicitly. In SWAN, triad wave-wave interactions and depth-induced wave breaking are added. In contrast to other third-generation wave models, the numerical propagation scheme is implicit, which implies that the computations are more economic in shallow water. The model results agree well with analytical solutions, laboratory observations, and (generalized) field observations.

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A third-generation wave model for coastal regions: 1. Model description and validation

The sections in this article are


1
Radiometers

2
Radar Scattering

3
Radar Scatterometers

4
Radar Altimeters

5
Ground-Penetrating Radars

6
Imaging Radars

7
Real-Aperture Radars

8
Synthetic-Aperture Radars

Microwave Remote Sensing

Review of several recent ocean surface wave models finds that while comprehensive in many regards, these spectral models do not satisfy certain additional, but fundamental, criteria. We propose that these criteria include the ability to properly describe diverse fetch conditions and to provide agreement with in situ observations of Cox and Munk [1954] and Jahne and Riemer [1990] and Hara et al. [1994] data in the high-wavenumber regime. Moreover, we find numerous analytically undesirable aspects such as discontinuities across wavenumber limits, nonphysical tuning or adjustment parameters, and noncentrosymmetric directional spreading functions. This paper describes a two-dimensional wavenumber spectrum valid over all wavenumbers and analytically amenable to usage in electromagnetic models. The two regime model is formulated based on the Joint North Sea Wave Project (JONSWAP) in the long-wave regime and on the work of Phillips [1985] and Kitaigorodskii [1973] at the high wavenumbers. The omnidirectional and wind-dependent spectrum is constructed to agree with past and recent observations including the criteria mentioned above. The key feature of this model is the similarity of description for the high- and low-wavenumber regimes; both forms are posed to stress that the air-sea interaction process of friction between wind and waves (i.e., generalized wave age, u/c) is occurring at all wavelengths simultaneously. This wave age parameterization is the unifying feature of the spectrum. The spectrum's directional spreading function is symmetric about the wind direction and has both wavenumber and wind speed dependence. A ratio method is described that enables comparison of this spreading function with previous noncentrosymmetric forms. Radar data are purposefully excluded from this spectral development. Finally, a test of the spectrum is made by deriving roughness length using the boundary layer model of Kitaigorodskii. Our inference of drag coefficient versus wind speed and wave age shows encouraging agreement with Humidity Exchange Over the Sea (HEXOS) campaign results.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/97JC00467

A unified directional spectrum for long and short wind-driven waves

Ocean waves are a huge, largely untapped energy resource, and the potential for extracting energy from waves is considerable. Research in this area is driven by the need to meet renewable energy targets, but is relatively immature compared to other renewable energy technologies. This review introduces the general status of wave energy and evaluates the device types that represent current wave energy converter (WEC) technology, particularly focusing on work being undertaken within the United Kingdom. The possible power take-off systems are identified, followed by a consideration of some of the control strategies to enhance the efficiency of point absorber-type WECs. There is a lack of convergence on the best method of extracting energy from the waves and, although previous innovation has generally focused on the concept and design of the primary interface, questions arise concerning how best to optimize the powertrain. This article concludes with some suggestions of future developments.

https://journals.sagepub.com/doi/pdf/10.1243/09576509JPE782

A review of wave energy converter technology

New parameterizations for the spectral dissipation of wind-generated waves are proposed. The rates of dissipation have no predetermined spectral shapes and are functions of the wave spectrum and wind speed and direction, in a way consistent with observations of wave breaking and swell dissipation properties. Namely, the swell dissipation is nonlinear and proportional to the swell steepness, and dissipation due to wave breaking is nonzero only when a nondimensional spectrum exceeds the threshold at which waves are observed to start breaking. An additional source of short-wave dissipation is introduced to represent the dissipation of short waves due to longer breaking waves. A reduction of the wind-wave generation of short waves is meant to account for the momentum flux absorbed by longer waves. These parameterizations are combined and calibrated with the discrete interaction approximation for the nonlinear interactions. Parameters are adjusted to reproduce observed shapes of directional wave spect...

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Semiempirical Dissipation Source Functions for Ocean Waves. Part I: Definition, Calibration, and Validation

: The data for the spectra of fully developed seas obtained for wind speeds from 20 to 40 knots as measured by anemometers on two weather ships are used to test the similarity hypothesis and the idea that, when plotted in a certain dimensionless way, the power spectra for all fully developed seas should be of the same shape as proposed by Kitaigorodskii (1961). Over the important range of frequencies that define the total variance of the spectrum within a few percent, the transformed plots yield a non-dimensional spectral form that is nearly the same over this entire range of wind speeds within the present accuracies of the data. However, since slight variations of the wind speed have large effects on the location of this non-dimensional spectral form, inaccuracies in the determination of the wind speed at sea allow for some latitude in the final choice of the form of the spectrum. Also since the winds used to obtain the non-dimensional form were measured at a height greater than ten meters, the problem of relating the spectral form to a standard anemometer height arises. The variability introduced by this factor needs to be considered. The results, when errors in the wind speed, the sampling variability of the data, and the anemometer heights are considered, suggest a spectral form that is a compromise between the various proposed spectra and that has features similar to many of them.

A proposed spectral form for fully developed wind seas based on the similarity theory of S. A. Kitaigorodskii

Various criteria pertaining to the synoptic situation are presented in order to determine when a fully developed wind-generated sea might be found in the North Atlantic Ocean. Four hundred and sixty wave records, corresponding to various synoptic situations, were digitized and analyzed spectrally as a first step in the preparation of a climatology of ocean wave spectrums. The wave records were taken by the ocean weather ships of the United Kingdom by means of a Tucker shipborne wave recorder. Selected subsets from the available spectrums based on these synoptic criteria were averaged in order to produce spectrums for various wind speeds. These selected subsets were examined to see if they came from the same population by means of the Kolmogorov-Smirnov test, and the results show that, within the accuracy expected, the samples chosen represent fully developed seas. A second subset chosen at random without using these criteria was tested, and the results showed that wind speed alone does not properly characterize the sea state. A nested family of spectrums was obtained for wind speeds of 20, 25, 30, 35, and 40 knots in which the frequency of the maximum appeared to be inversely proportional to the wind speed and the significant height was proportional to the square of the wind speed. The spectrums and the results deducible from them yield results that appear to be a compromise among the various published theoretical forms for the spectrums and the equations for the significant height of a fully developed sea.

Estimates of the Power Spectrums for Fully Developed Seas for Wind Speeds of 20 to 40 Knots

Abstract : As a part of the problem of developing numerical wave forecasting procedures for the North Atlantic Ocean, selected sequences of the weather maps for the North Atlantic for which wave data were known to be available were studied in detail for the five year period beginning in April 1955 and ending in March 1960. Data from a hurricane in September 1961 were also analyzed. Certain dates and times of observations were selected for a variety of reasons for study. For these dates and times, the National Institute of Oceanography provided copies of the wave records that were obtained by the OWS Weather Explorer and by the OWS Weather Reporter. In total, about 800 wave records were provided, and a complete spectral analysis is planned for about 400 of these records. Data are presented in tabular and graphical form of the results of these analyses. The total number of spectra given is 290.

/pdf/wave-spectra-estimated-from-wave-records-obtained-by-the-ows-yb070meub1.pdf

Wave spectra estimated from wave records obtained by the OWS Weather Explorer and the OWS Weather Reporter / by L. Moskowitz, W. J. Pierson Jr., E. Mehr.

Lionel Moskowitz

Papers

A proposed spectral form for fully developed wind seas based on the similarity theory of S. A. Kitaigorodskii

Estimates of the Power Spectrums for Fully Developed Seas for Wind Speeds of 20 to 40 Knots

Wave spectra estimated from wave records obtained by the OWS Weather Explorer and the OWS Weather Reporter / by L. Moskowitz, W. J. Pierson Jr., E. Mehr.