Ocean Wave Measurement Using GPS Buoys

AbstractThe observation of ocean wave parameters is necessary to improve forecasts of ocean wave conditions. In this paper, we investigate the viability of using a single GPS receiver to measure ocean-surface waves, and present a method to enhance the accuracy of the estimated wave parameters. The application of high-pass filtering to GPS data in conjunction with directional wave spectral theory is a core concept in this article. Laboratory experiments were conducted to test the viability and accuracy measurements of wave parameters made by a single GPS receiver buoy. These tests identified an error of less than 1% for the rotational arm measurement (wave height) and an error of 1% in verifications of the wave direction and wave period, and showed a 0.488 s bias; this is sufficiently accurate for many specific purposes. These results are based on the best cut-off frequency value derived in this study. A moored-sea GPS buoy on the Taiwanese coast was used to estimate the GPS-derived wave parameters. Our results indicate that data from a single GPS receiver, processed with the presented method to reduce the error of the estimated parameters, can provide measurements of ocean surface wave to reasonable accuracy.

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Investigation of the Anisotropic Patterns in the Altimeter Backscatter Measurements Over Ocean Wave Surfaces

Frontiers in Earth Science ◽

10.3389/feart.2021.731610 ◽

2021 ◽

Vol 9 ◽

Author(s):

Xi-Yu Xu ◽

Ke Xu ◽

Maofei Jiang ◽

Bingxu Geng ◽

Lingwei Shi

Keyword(s):

Wave Model ◽

Ocean Surface ◽

Ocean Waves ◽

Ocean Wave ◽

Altimeter Data ◽

Wave Surface ◽

Wave Direction ◽

Backscatter Coefficient ◽

Wave Surfaces ◽

Operational Modes

This article attempts to analyze the influence of the anisotropic effects of the ocean wave surface on SAR altimetry backscatter coefficient (Sigma-0) measurements, which has not been intensively addressed in publications. Data of Sentinel-3A, Cryosat-2, and Jason-3 altimeters allocated by the WW3 numeric wave model were analyzed, and the patterns of Sigma-0 with respect to the wave direction were acquired under ∼2 m significant wave height. The ocean waves were classified into six categories, among which the moderate swell and short win-wave cases were analyzed intensively. Swell-dominated ocean surface shows less randomness than the wind-wave-dominated ocean surface. Clear and significant sinusoid trends are found in the Sigma-0 and SSB patterns of both operational modes (SAR mode and PLRM mode) of the Sentinel-3A altimeter for the moderate swell case, indicating the sensitivity of Sigma-0 and SSB measurements to the anisotropic features of the altimeter measurements. The anisotropic pattern in the Sentinel-3A PLRM Sigma-0 is somewhat counterintuitive, but the analysis of Jason-3 altimeter data would show similar results. Additionally, by comparing the anisotropic patterns of two orthogonally polarized SAR altimeters (Sentinel-3A and Cryosat-2), we could draw the conclusion that the Sigma-0 measurements are not sensitive to the polarization mode. As for the SSHA patterns, no clear sinusoid could be identified for the moderate swell. A possible explanation is that the SSB pattern may be overwhelmed in the complicated factors that can influence the SSHA pattern.

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Ocean Wave Information Retrieval Using Simulated Compact Polarized SAR from Radarsat-2

Journal of Sensors ◽

10.1155/2018/1738014 ◽

2018 ◽

Vol 2018 ◽

pp. 1-12 ◽

Cited By ~ 1

Author(s):

Xiaochen Wang ◽

Yun Shao ◽

Lu She ◽

Wei Tian ◽

Kun Li ◽

...

Keyword(s):

Wave Field ◽

Ocean Surface ◽

Ocean Wave ◽

Wave Direction ◽

National Data ◽

Slope Spectrum ◽

Field Information ◽

Wave Slope ◽

Good Agreement

The main objective of this paper is to demonstrate the capability of compact polarized (CP) synthetic aperture radar (SAR) to retrieve ocean wave field parameters. Souyris’ and Nord’s algorithms are used to carry out the reconstruction of CP SAR pseudo quad-polarized data for the ocean surface under both the circular transmit linear receive (CTLR) and π/4 mode. The results show that, for the CP reconstruction, Nord’s algorithm has a better convergence ability than Souyris’. In addition, the investigation of the reconstruction accuracy shows that the CTLR mode is superior to the π/4 mode, in terms of ocean surface reconstruction. It is, therefore, concluded that the reconstructed parameters of CP CTLR mode data by Nord’s algorithm adapt to retrieve ocean wave information. The ocean wave slope spectrum and other main wave parameters are also calculated from reconstructed CP data and compared with measurements from in situ National Data Buoy Center (NDBC) matched-up buoys. Comparison of CP SAR-based wave field information with buoy outputs also shows good agreement in the case of dominate wave height, wave direction, and wave period, with biases of 0.36 m, 17.96°, and 0.88 s, respectively.

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Modeling Microseism Generation by Inhomogeneous Ocean Surface Waves in Hurricane Bonnie Using the Non-Linear Wave Equation

Remote Sensing ◽

10.3390/rs10101624 ◽

2018 ◽

Vol 10 (10) ◽

pp. 1624

Author(s):

Joshua Wilson

Keyword(s):

Wave Equation ◽

Surface Wave ◽

Surface Waves ◽

Ocean Surface ◽

Linear Wave ◽

Linear Wave Equation ◽

Ocean Surface Waves ◽

Non Linear ◽

Hurricane Bonnie ◽

Ocean Surface Wave

It has been shown that hurricanes generate seismic noise, called microseisms, through the creation and non-linear interaction of ocean surface waves. Here we model microseisms generated by the spatially inhomogeneous waves of a hurricane using the non-linear wave equation where a second-order acoustic field is created by first-order ocean surface wave motion. We treat range-dependent waveguide environments to account for microseisms that propagate from the deep ocean to a receiver on land. We compare estimates based on the ocean surface wave field measured in hurricane Bonnie in 1998 with seismic measurements made roughly 1000 km away in Florida.

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Microwave Specular Measurements and Ocean Surface Wave Properties

Sensors ◽

10.3390/s21041486 ◽

2021 ◽

Vol 21 (4) ◽

pp. 1486

Author(s):

Paul A. Hwang ◽

Thomas L. Ainsworth ◽

Jeffrey D. Ouellette

Keyword(s):

Surface Wave ◽

Ocean Surface ◽

Closed Form Expression ◽

Wind Condition ◽

High Wind ◽

Ocean Surface Waves ◽

Wind Speeds ◽

Surface Measurements ◽

Ocean Surface Wave ◽

Reference Measurements

Microwave reflectometers provide spectrally integrated information of ocean surface waves several times longer than the incident electromagnetic (EM) wavelengths. For high wind condition, it is necessary to consider the modification of relative permittivity by air in foam and whitecaps produced by wave breaking. This paper describes the application of these considerations to microwave specular returns from the ocean surface. Measurements from Ku and Ka band altimeters and L band reflectometers are used for illustration. The modeling yields a straightforward integration of a closed-form expression connecting the observed specular normalized radar cross section (NRCS) to the surface wave statistical and geometric properties. It remains a challenge to acquire sufficient number of high-wind collocated and simultaneous reference measurements for algorithm development or validation and verification effort. Solutions from accurate forward computation can supplement the sparse high wind databases. Modeled specular NRCSs are provided for L, C, X, Ku, and Ka bands with wind speeds up to 99 m/s.

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First Observations of Microbaroms with Single Absolute Barometers

Journal of Atmospheric and Oceanic Technology ◽

10.1175/2011jtecha1526.1 ◽

2011 ◽

Vol 28 (7) ◽

pp. 933-943 ◽

Cited By ~ 3

Author(s):

Ganesh K. Subramanian ◽

Andreas Muschinski

Keyword(s):

Surface Wave ◽

Atlantic Ocean ◽

Surface Waves ◽

Frequency Spectrum ◽

Ocean Surface ◽

Upper Atmosphere ◽

Ocean Surface Waves ◽

Equilibrium Spectrum ◽

Ocean Surface Wave ◽

First Time

Abstract The first observations of microbaroms with single absolute barometers are presented and discussed. Microbaroms are pulses of atmospheric infrasound emitted by ocean surface waves. They can propagate over thousands of kilometers through the atmosphere, and they can reach altitudes well into the upper atmosphere before they are refracted down to the earth’s surface. Typical microbarom periods are 5 s, typical wavelengths are 1.5 km, and typical surface amplitudes are 100 mPa (1 μbar). The data presented here were collected during the 2-week period from 26 February through 10 March 2008 in Amherst, Massachusetts, which is located about 150 km away from the Atlantic Ocean. The authors report for the first time, to the best of their knowledge, an f−5 microbarom frequency spectrum, which is consistent with Phillips’s f−5 ocean surface wave equilibrium spectrum.

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