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

Hisaki, Yukiharu

doi:10.1029/2005jc002881

Cited by 21 publications

(15 citation statements)

References 29 publications

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“… Wyatt et al [1999] demonstrated that such dual‐site inversion methods can obtain reliable wave spectral estimates when compared with moored buoys. Hisaki [2005] has produced wave spectral estimates using a blend of single site radar observations and a wave model. This hybrid approach is likely to be quite useful for extending the range of HF wave observations, but is of limited use for focused wave studies because the wave field has been assumed to take a specified form.…”

Section: Methodsmentioning

confidence: 99%

Surface current effects on the fetch‐limited growth of wave energy

Haus

2007

J. Geophys. Res.

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[1] To study the fetch-limited growth of wind wave energy over a region with significant lateral shear of the current field, this study exploited data obtained from two linear phased-array High Frequency (HF) radar systems. Both the near-surface currents and wave energy and period were mapped over the highly sheared inshore boundary of the Florida Current. The wave energy growth during two periods when the winds were steady for >12 hours and were directed offshore was computed over a range of fetches from 5 to 45 km. The observed energy growth rates were significantly ($50 %) lower than predicted by the Donelan et al. (1992) empirical formulation over the high vorticity region. The reduced growth rate was consistent with a shift of the wind stress direction into the current direction due to refraction of the wave field. Dimensionless wave energy increased by as much as 100% over neighboring values when the vertical component of the surface current vorticity was a global minimum. While trapping and enhancement of wave energy is predicted by wave ray theory, it has never before been confirmed within the Florida Current with coincident wave and current measurements.

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Section: Methodsmentioning

confidence: 99%

Surface current effects on the fetch‐limited growth of wave energy

Haus

2007

J. Geophys. Res.

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“…Thus, these factors all deserve more study. Another challenging problem is how to inverse the directional wave spectra from the second-order radar echoes, which can give more information of ocean waves than significant waveheight, as what had been done by some other authors [8][9][10][11][12] . The study is under progress now.…”

Section: Resultsmentioning

confidence: 97%

“…Therefore, the significant waveheight can be derived from the integral of the secondorder echo spectra. In the following years, Lipa et al [8] , Wyatt [9] , Howell et al [10] , Hisaki [11] and Green et al [12] proposed several methods to obtain directional wave spectrum through the inversion of Barrick's second-order nonlinear equation. All methods would provide more comprehensive information on directional wave spectrum.…”

Section: Introductionmentioning

confidence: 99%

Experimental determination of significant waveheight by OSMAR071: Comparison with results from buoy

Shao

et al. 2009

Wuhan Univ. J. Nat. Sci.

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OSMAR071 is the latest product of the OSMAR (ocean state monitor and analysis radar) series of high frequency surface wave radar (HFSWR), which was developed by the Radiowave Propagation Laboratory of Wuhan University. It adopts a modified Barrick waveheight inversion model. The modifications are introduced to improve the model's performances under the effect of noises and interferences and in the case of broad beam radar detection. The two unknown coefficients in the modified model are figured out by fitting the HFSWR significant waveheight results to those output from a wave buoy located in the radiating coverage of the radar site. The model is applied to inverse the waveheights from radar data for the duration from Dec. 1st, 2008 to Feb. 25th, 2009, and then the radar waveheights are compared with the buoy measurements. Results show that the rms difference between radar-derived significant waveheights and those from the buoy is 0.38 m and the correlation coefficient between the two series is 0.66. This study describes OSMAR071 observation of significant waveheight with relatively satisfactory accuracy during about three months.High frequency surface wave radar (HFSWR) operated in the HF band (3-30 MHz), as the name suggests, employs the ground wave mode of radio wave propagation, in which the radar signal is guided by a good conducting surface such as the ocean surface to follow a path that essentially matches the earth's curvature. It is capable of all-weather remote sensing of large-area ocean surface dynamics with relatively high precision [1] . After more than 40 years' development, its capability of current detection has been considered to satisfy the requirements for routine marine observations while its wind and wave outputs have not reached the matched status [2] . Currents information can be extracted from the broadening of the Bragg peaks (which are also called as the first-order peaks) in the sea echoes' Doppler spectra. The second-order continuum which contain the information of waves and winds is relatively weak (20-40 dB lower than the Bragg peaks) and susceptible to the effect of noise and interference, so the extraction of waves and winds information is difficult [3] and the corresponding inversion theory and technology are still currently under development. Much progress has been made to understand the relationship between the Doppler spectrum of the radar backscatter signals and the ocean wave spectrum [4] . In 1977 Barrick proposed an inversion model of significant waveheight [5] , which can work robustiously in practice [6,7] . It is different from several other algorithms, which relate the inversion of wave spectra to the second-order sea echoes directly. Therefore, the significant

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“…In the experiments we did not consider all types of data available for regional modeling. In particular, directional spectra (with a coarser resolution and larger uncertainties) can be obtained from high-frequency radars (Graber and Heron 1997;Hisaki 2005) and spaceborne (Tison et al 2008;Ren et al 2010) platforms. Simplifying assumptions have been also made in configuring WAM: the background currents (;0.2-0.4 m s 21 ) were assumed to be negligible in comparison with the wave velocities (;5-10 m s 21 ) of the major spectral peak and stationary conditions at the open boundaries were specified due to relatively short period of model integration.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Adjoint-Free Variational Data Assimilation into a Regional Wave Model

Panteleev

Yaremchuk

Rogers

2015

Journal of Atmospheric and Oceanic Technology

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A variational data assimilation algorithm is developed for the ocean wave prediction model [Wave Model (WAM)]. The algorithm employs the adjoint-free technique and was tested in a series of data assimilation experiments with synthetic observations in the Chukchi Sea region from various platforms. The types of considered observations are directional spectra estimated from point measurements by stationary buoys, significant wave height (SWH) observations by coastal high-frequency radars (HFRs) within a geographic sector, and SWH from satellite altimeter along a geographic track. Numerical experiments demonstrate computational feasibility and robustness of the adjoint-free variational algorithm with the regional configuration of WAM. The largest improvement of the model forecast skill is provided by assimilating HFR data (the most numerous among the considered types). Assimilating observations of the wave spectrum from a moored platform provides only moderate improvement of the skill, which disappears after 3 h of running WAM in the forecast mode, whereas skill improvement provided by HFRs is shown to persist up to 9 h. Spaceborne observations, being the least numerous, do not have a significant impact on the forecast skill but appear to have a noticeable effect when assimilated in combination with other types of data. In particular, when spectral data from a single mooring are used, the satellite data are found to be the most beneficial as a supplemental data type, suggesting the importance of spatial coverage of the domain by observations.

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

Cited by 21 publications

References 29 publications

Surface current effects on the fetch‐limited growth of wave energy

Surface current effects on the fetch‐limited growth of wave energy

Experimental determination of significant waveheight by OSMAR071: Comparison with results from buoy

Adjoint-Free Variational Data Assimilation into a Regional Wave Model

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