Evolution of Design Method Against Random Waves Statistical Properties and Spectral of Sea Waves Transformation and Deformation of Random Sea Waves Design of Breakwaters Design of Coastal Dikes and Seawalls Probabilistic Design of Harbor Facilities Harbor Tranquility and Vessel Mooring Hydraulic Model Tests with Random Waves Theoretical Description of Random Sea Waves Statistical Theory of Irregular Waves Techniques of Random Wave Analysis 2D Computation of Wave Transformation with Random Breaking and Nearshore Currents Statistical Analysis of Extreme Waves Prediction and Control of Beach Deformation Processes.

Random seas and design of maritime structures

The Galician coast (NW Spain) is a region that is strongly influenced by the presence of low pressure systems in the mid-Atlantic Ocean and the periodic passage of storms that give rise to severe sea states. Since its wave climate is one of the most energetic in Europe, the objectives of this paper were twofold. The first objective was to characterize the most extreme wave height events in Galicia over the wintertime of a two-year period (2015–2016) by using reliable high-frequency radar wave parameters in concert with predictions from a regional wave (WAV) forecasting system running operationally in the Iberia-Biscay-Ireland (IBI) area, denominatedIBI-WAV. The second objective was to showcase the application of satellite wave altimetry (in particular, remote-sensed three-hourly wave height estimations) for the daily skill assessment of the IBI-WAV model product. Special attention was focused on monitoring Ophelia—one of the major hurricanes on record in the easternmost Atlantic—during its 3-day track over Ireland and the UK (15–17 October 2017). Overall, the results reveal the significant accuracy of IBI-WAV forecasts and prove that a combined observational and modeling approach can provide a comprehensive characterization of severe wave conditions in coastal areas and shows the benefits from the complementary nature of both systems.

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Extreme Wave Height Events in NW Spain: A Combined Multi-Sensor and Model Approach.

High-frequency radars : physical limitations and recent developments

This paper presents results of a trial of a Pisces HF radar system aimed at assessing its use as a component of a wave-monitoring network being installed around the coasts of England and Wales. The radar system has been operating since December 2003 and the trial continued to June 2005. The data have been processed in near-real time and displayed on a website. Radar measurements of the directional spectrum and derived parameters are compared with those measured with a directional waverider and with products from the Met Office, United Kingdom, operational wave model. Radar measurements of currents and winds are also compared with Met Office model products and, in the case of winds, with the QuikSCAT scatterometer. Statistics on data availability and accuracy are presented. The results demonstrate that useful availability and accuracy in wave and wind parameters are obtained above a waveheight threshold of 2 m and at ranges up to 120 km at the radar operating frequencies (7-10 MHz) used. Waveheight measurements above about 1 m can be made with reasonable accuracy (e.g., mean difference of 2.5% during January-February 2004). Period and direction parameters in low seas are often contaminated by noise in the radar signal. The comparisons provide some evidence of wave model limitations in offshore wind and swell conditions

Operational Wave, Current, and Wind Measurements With the Pisces HF Radar

Data Analysis Methods in Physical Oceanography fills a real need for a single-volume summary of such methods suitable for both graduate teaching and research use. It is very successful in meeting its primary objective—to be a practical guide to oceanographic data collection and analysis that provides the reader with a solid understanding of both logistical difficulties and data analysis theory. The writing is clear and succinct. Furthermore, the book's coverage is even broader than the title suggests. The first 158 pages summarize physical oceanographic data collection methods from the obvious to the obscure. Because of its broad scope, it is sometimes less complete than one might wish with regard to new developments. Even when this is true, however, references to a fuller treatment are usually provided.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/99EO00074

Data Analysis Methods in Physical Oceanography

Since all ocean wave components contribute to the second-order scattering of a high-frequency radio wave by the sea surface, it is theoretically possible to estimate the ocean wave spectrum from first- and second-order scattering in the Doppler spectrum measured with an HF ocean radar. To extract the wave spectral information, however, it is necessary to solve a nonlinear integral equation. This paper describes in detail how to solve the nonlinear integral equation without linearization or approximation. We show that the problem of solving the nonlinear integral equation can be converted into a nonlinear optimization problem. An algorithm to find the optimal solution is described. Examples of the algorithm applied to simulated data and measured data are shown. The wave frequency spectrum can be estimated even if the Doppler spectrum is available in only a single direction. In this case, however, the solution of the two-dimensional wavenumber spectrum tends to converge to a spectrum that is symmetrical to the beam direction. Even if the wave spectrum is dominant in a single direction, the solution may give two peaks in the wavenumber spectrum. One of them is the true peak and the other is the mirror image of it with respect to the beam direction. This ambiguity can be avoided by using Doppler spectra measured in at least two different directions. Although there is still some room for improvement in the practical application of this method, it can be applied to estimate the wave directional spectrum up to a rather high frequency, or Bragg frequency.

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Nonlinear inversion of the integral equation to estimate ocean wave spectra from HF radar

A method to estimate ocean wave directional spectra using a high-frequency (HF) ocean radar was developed. The governing equations of wave spectra are integral equations of first- and second-order radar cross sections, the wave energy balance equation, and the continuity equation of surface winds. The parameterization of the source function is the same as that in WAM. Furthermore, the method uses the constraints that wave spectral values are smooth in both wave frequency and direction and that the propagation terms are small. The unknowns to be estimated are surface wind vectors at radial grids whose centers are the radar position, and wave spectral values at radial and wave frequency–direction grids. The governing equations are discretized in the radial and wave frequency–direction grids and are converted into a nonlinear minimization problem. Identical twin experiments showed that the present method can estimate wave spectra and dynamically extrapolate wave spectra, even in an inhomogeneous wav...

https://journals.ametsoc.org/doi/pdf/10.1175/JTECH1836.1

Ocean Wave Directional Spectra Estimation from an HF Ocean Radar with a Single Antenna Array: Methodology

Observations of sea surface currents by HF radar were carried out in the Bungo Channel in summer 1992. The current ellipses of M2 constituent obtained by the observational results agree quite well with those obtained by the ADCP observations, showing that the accuracy of the HF radar measurements is of the same level as ADCP. The results revealed the current structures and their change with the Kyucho in detail. The Kyucho is influenced by the complicated coastal geometry and does not propagate straightly into the Bungo Channel. It propagates further inward after charging the coastal bays with warm water. The current directions change largely, since the currents turn around the stagnant region in the bay filled with the warm water. The northward intrusion begins to be weakened in the southern part of the channel, while it still persists in the northern part. The northward current speeds of the observed Kyucho are about 50 cm/s and sometimes attain 60 to 70 cm/s.

Observation of the Kyucho in the Bungo Channel by HF Radar

We investigated ocean surface current variability in the region east of Okinawa Island in the spring of 1998 using in situ and remotely sensed data including surface velocity estimates inferred from HF ocean radars. Most previous studies utilizing HF ocean radars were limited to shallow continental shelves. In contrast, most of the observation area in this study was in the open ocean. During the observation period the HF ocean radars sampled a region where anticyclonic and cyclonic mesoscale eddies were adjacent to each other. The HF-radar-derived ocean currents agree with those measured by a current meter. The surface currents were highly variable in both time and space and were affected by the eddy field in the offshore region. The current field was related to the near-surface water temperature. For example, a local temperature rise was often associated with northeastward flows. The surface currents in regions shallower than about 1000 m had a significant correlation with local wind forcing. Our HF ocean radars often detected a strongly convergent zone, which was different in character from those described in previous studies in that it was in the deep ocean. From other data such as National Oceanic and Atmospheric Administration advanced very high resolution radiometer imagery, we concluded that the convergent zone was due to mesoscale eddy fronts.

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Surface current variability east of Okinawa Island obtained from remotely sensed and in situ observational data

[1] A method of estimating ocean wave directional spectra using a]high-frequency (HF) radar with a single antenna array was applied to actual ocean data. This method incorporates the wave energy balance equation and the continuity equation of wind vectors into the inversion method to solve the integral equation which relates a Doppler spectrum to wave spectra. This method uses dynamic extrapolation to estimate wave spectra at positions where the signal-to-noise (SN) ratio in Doppler spectra is not high. The agreement of wave heights with in situ observation is good. Additionally, there is a correlation between radar-estimated sea surface winds and winds near the HF radar observation area. The method under consideration was found to be able to estimate wave directional spectra in swell conditions.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2005JC002881

Yukiharu Hisaki

Papers

Nonlinear inversion of the integral equation to estimate ocean wave spectra from HF radar

Ocean Wave Directional Spectra Estimation from an HF Ocean Radar with a Single Antenna Array: Methodology

Observation of the Kyucho in the Bungo Channel by HF Radar

Surface current variability east of Okinawa Island obtained from remotely sensed and in situ observational data

Ocean wave directional spectra estimation from an HF ocean radar with a single antenna array: Observation