HF radar measurements of long ocean waves

Lipa, Belinda; Barrick, Donald E.; Maresca, Joseph W.

doi:10.1029/jc086ic05p04089

Cited by 35 publications

(10 citation statements)

References 16 publications

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“…Since narrow band swell on the open ocean always spans a sector exceeding 4 ø, these spikes could never contain enough energy to be seen. Further proof of this is evident from the many cases of long-wave propagation examined by Lipa et al [1980], where four second-order Doppler peaks are always seen; the comer reflector condition would produce only two such peaks. (For example, for swell slightly approaching the radar such that /• ß • < 0, these peaks would be positioned one on the positive side of each Bragg line.…”

Section: Discussionmentioning

confidence: 94%

“…The reason for this is that the second-order Doppler structure is sensitive to the directional properties of long waves. Inclusion of this dependence in the analysis results in more accurate Lipa et al [1980], whose analysis of the considerable amount of data is extensive and draws heavily upon the models and methods presented here. Our purpose in this paper is to derive and present simple models and methods that have been proven against data, along with a discussion of how and when to use them.…”

Section: Discussionmentioning

confidence: 99%

“…In the other extreme, waves are generated locally or in a storm area whose distance from the observer is not much different from the dimensions of the radar scattering patch; this is somewhat analogous to being in the near field of an antenna. We take as an example the situation existing at a recent coastal HF radar experiment at Pescadero, California [Lipa et al, 1980], where the dominant ocean waves were generated in a storm zone with the approximate dimensions 650 km x 740 km, with the storm center about 1250 km from the radar.…”

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confidence: 99%

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Methods for the extraction of long‐period ocean wave parameters from narrow beam HF radar sea echo

Lipa¹,

Barrick²

1980

Radio Science

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This paper describes inversion methods for HF radar sea echo Doppler spectra, giving parameters of the ocean wave spectrum in the important long-wavelength region. Radar spectra exhibiting very narrow spikes in the higher-order structure adjacent to the first-order lines are indicative of ocean wave components with a single dominant wavelength. In the simplest method of interpretation these components are assumed to be unidirectional; in this case we show how to extract wave period, direction, and rms wave height. If this simple model does not provide a good fit to the data or if the radar side bands have the form of broad peaks, we use a model for the wave spectrum with a cardioid distribution in direction and a Gaussian distribution in wave frequency. Parameters identifiable from this model include the rms wave height, dominant direction and period, and the angular spread in the direction and frequency distributions. In normal surface wave experiments the major source of error or noise is the random surface height of the sea; we describe the resulting statistics of the radar spectrum and trace the propagation of uncertainty to the derived ocean parameters. INTRODUCTIONCrombie [1955] discovered the mechanism behind high-frequency (HF) radar sea scatter nearly 25 years ago by spectrally analyzing the received time series. Using the gravity wave dispersion equation that relates the velocity to the square root of the ocean wavelength, he correctly deduced that the two sharp, symmetrically positioned Doppler peaks were produced by those ocean wave trains exactly half the radio wavelength, moving toward and away from the radar. We now call these prominent peaks the 'Bragg lines,' since the mechanism producing them is the first-order Bragg effect. When theories confirmed this mechanism [Wait, 1966;Barrick, 1972] and showed that the strength of these echo peaks is proportional to the heights of the corresponding Bragg-scattering ocean wave trains, scientists became enthusiastic about the prospect of using HF radars to measure sea state parameters. In order to make direct observations of the long ocean waves that are the essence of 'sea state' using this first-order Bragg effect, one This paper is not subject to U.S. copyright. Published in 1980 by the American Geophysical Union. would have to operate the radar at lower MF; huge antenna size requirements, heavy spectrum utilization in this region, and ionospheric problems all dictate against such a system [Barrick, 1977b; Barrick and Lipa, 1979a]. At mid and upper HF the first-order Bragg peaks are produced by the less interesting shorter waves, and hence using these alone, radio oceanographers resigned themselves to extracting only wind direction information because the short waves align themselves quickly with the wind [Long and Trizna, 1973; Stewart and Barnum, 1975].The more sophisticated radar systems and digital signal processors of the mid-1960's showed a lowerlevel spectral continuum surrounding the first-order Bragg peaks that was definitely established as sea ...

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Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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Methods for the extraction of long‐period ocean wave parameters from narrow beam HF radar sea echo

Lipa¹,

Barrick²

1980

Radio Science

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“…Skywave radar measurements of significant wave height, ocean wave spectra [Maresca and Carlson, 1978a, b, 1979Maresca and Georges, 1980;Lipa et al, 1980], and the mean surface wind velocity [Maresca and Carlson, 1977, 1978a, b, 1979 were also made for hurricanes Anita and Babe and were compared to measurements made at NOAA Data Buoy Office (NDBO) data buoys EB71 and EB04. Agreement between the radar-and buoy-measured wind speeds was within +2 m/s (10%), and agreement between the wind direction measurements was within 10 ø.…”

Section: Copyright ¸ 1981 By the American Geophysical Unionmentioning

confidence: 99%

Tracking Hurricane Anita by HF skywave radar

Maresca¹,

Carlson²

1981

J. Geophys. Res.

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Hurricane Anita was tracked across the Gulf of Mexico from August 29, 1977, to September 2, 1977, by using an HF skywave radar. The radar position estimates were made from California, three to five times per day, at the SRI‐operated Wide Aperture Research Facility (WARF). The storm center was located by using the WARF‐derived ocean surface wind direction maps. Seventeen independent wind maps were used to develop the WARF‐derived track. The WARF‐derived positions were compared to coincident temporal positions on the official track produced by the National Hurricane Center, and the relative agreement was 19 km.

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“…High‐frequency (HF) sky wave over‐the‐horizon radars (OTHRs) have been developed in many countries and employed in various civil and military applications [e.g., Barrick et al , 1967; Croft , 1967, 1972; Ahearn et al , 1974; Headrick and Skolnik , 1974; Rao , 1974, 1975; Georges , 1980; Maresca and Georges , 1980; Lipa et al , 1981; Earl and Ward , 1987; Anderson and Lees , 1988]. Basically, there are two types of HF sky wave OTHRs, one using monostatic interpulse phase‐modulated system and the other utilizing a bistatic frequency modulation continuous wave (CW) system.…”

Section: Introductionmentioning

confidence: 99%

Ionospheric Doppler and echo phase measured by the Wuhan Ionospheric Oblique Backscattering Sounding System

2007

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[1] Wuhan Ionospheric Oblique Backscattering Sounding System (WIOBSS) is a highfrequency (HF) sky wave over-the-horizon radar developed for ionospheric research and HF channel management. This radar, located in Wuhan (30.35°N, 114.33°E) has been under construction by the Ionosphere Lab of Wuhan University since 2002. WIOBSS uses long coded pulses and pulse compression to achieve good sensitivity and measures the bitemporal ionospheric response, channel scattering function, and phase of echoes simultaneously and then displays the processed data as ionograms and Dopplionograms in real time. Bitemporal ionospheric response is a matrix composed of the ionospheric transmission function with delay and time variables, while the scattering function shows the spectrum of the received signals as a function of the delay and Doppler coordinates, and is obtained by the Fourier Transform of the bitemporal ionospheric response over the time variable. The application of pulse compression and coherent integration allows WIOBSS to measure ionospheric Doppler with high resolution and very low power. A method is developed to get phase data directly from the bitemporal ionospheric response. The measured phase is strung in a series and then divided into linear and nonlinear components. The angular frequency of the linear component is in direct proportion to ionospheric Doppler velocity while the fluctuation of the nonlinear component includes the information of Doppler velocity spread. The phase method based on pulse impression is able to obtain the statistic Doppler information from weak backscattered echoes in short detection time.

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HF radar measurements of long ocean waves

Cited by 35 publications

References 16 publications

Methods for the extraction of long‐period ocean wave parameters from narrow beam HF radar sea echo

Methods for the extraction of long‐period ocean wave parameters from narrow beam HF radar sea echo

Tracking Hurricane Anita by HF skywave radar

Ionospheric Doppler and echo phase measured by the Wuhan Ionospheric Oblique Backscattering Sounding System

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