Ocean surface currents mapped by radar

Barrick, Donald E.; Evans, Michael; Weber, B. L.

doi:10.1109/ccm.1978.1158377

Cited by 104 publications

(131 citation statements)

References 6 publications

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“…The achieved range of the radar system is typical for the operating frequency used. The HFRs used within "PRISMA" were based on an early CODAR design developed at NOAA (Barrick et al 1977) and had been modified at the University of Hamburg. In contrast to more recent systems, like the CODAR SeaSonde (Lipa et al 2006) and the WERA system (Gurgel et al 1999a, b), these systems transmitted pulses of electromagnetic waves for range resolution and four receive antennas arranged in a square for finding the azimuth of the echoes.…”

Section: Hfr Observationsmentioning

confidence: 99%

“…Two of them, Schirmer et al (1994) and Carbajal and Pohlmann (2004), could be considered as precursors of the present paper. The former study estimated tidal ellipses for different tidal constituents from "Coastal Ocean Dynamics Applications Radar" (CODAR; Barrick et al 1977) measurements carried out in the German Bight showing clearly that the input of freshwater and, in general, baroclinic effects favored clockwise rotation in this region. The major changes occurred in the neighbourhood of the openings of the embayments.…”

Section: Introductionmentioning

confidence: 99%

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Tidal and wind-driven surface currents in the German Bight: HFR observations versus model simulations

Port

Gurgel

Staneva³

et al. 2011

Ocean Dynamics

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Tidal and wind-driven surface currents in the German Bight between shallow mudflats of the North Frisian islands and the island of Helgoland are studied using coastal high-frequency radar (HFR) observations and hindcasts from a primitive equation numerical model. The setup of the observational system is described, and estimates of expected measurement errors are given. A quantitative comparison of numerical model results and observations is performed. The dominant tidal components are extracted from the two data sources using tidal harmonic analysis and the corresponding tidal ellipses are defined. Results show that the spatial patterns of different tidal ellipse parameters are consistent in the two data sets. Model sensitivity studies with constant and variable salinity and temResponsible Editor: Aida Alvera-Azcárate This article is part of the Topical Collection on Multiparametric observation and analysis of the Sea A. Port (B) ICBM,

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Section: Hfr Observationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Tidal and wind-driven surface currents in the German Bight: HFR observations versus model simulations

Port

Gurgel

Staneva³

et al. 2011

Ocean Dynamics

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“…HF radars can deliver real-time data at relatively high spatial resolutions (300-1500 m) and can be installed, operated, and maintained in all weather conditions at a reduced cost compared with satellite or in situ sensor technology. HF radars are used routinely to measure ocean surface currents (e.g., Barrick 1977b;Wyatt et al 2006;Parks et al 2009) , ocean wave spectra (e.g., Barrick 1977a, c;Wyatt 1986;Gurgel et al 2006;Haus et al 2010), and even wind direction (e.g., Heron and Rose 1986;Harlan and Georges 1994;Wyatt et al 2006). However, the measurement of wind speed still poses a challenge.…”

Section: Introductionmentioning

confidence: 99%

Wind-speed inversion from HF radar first-order backscatter signal

et al. 2011

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Land-based high-frequency (HF) radars have the unique capability of continuously monitoring ocean surface environments at ranges up to 200 km off the coast. They provide reliable data on ocean surface currents and under slightly stricter conditions can also give information on ocean waves. Although extraction of wind direction is possible, estimation of wind speed poses a challenge. Existing methods estimate wind speed indirectly from the radar derived ocean wave spectrum, which is estimated from the second-order sidebands of the radar Doppler spectrum. The latter is extracted at shorter ranges compared with the first-order signal, thus limiting the method to short distances. Given this limitation, we explore the possibility of deriving wind speed from radar first-order backscatter signal. Two new methods are developed and presented that explore the relationship between wind speed and wave generation at the Bragg frequency matching that of the radar. One of the methods utilizes the absolute energy level of the radar first-order peaks while the second method uses the directional spreading of the wind generated waves at the Bragg frequency. For both methods, artificial neural network analysis is performed to derive the interdependence of the relevant parameters with wind speed. The first method is suitable for application only at single locations where in situ data are available and the network has been trained for while the second method can also be used outside of the training location on any point within the radar coverage area. Both methods require two or more radar sites and information on the radio beam direction. The methods are verified with data collected in Fedje, Norway, and the Ligurian Sea, Italy using beam forming HF WEllen RAdar (WERA) systems operated at 27.68 and 12.5 MHz, respectively. The results show that application of either method requires wind speeds above a minimum value (lower limit). This limit is radar frequency dependent and is 2.5 and 4.0 m/s for 27.68 and 12.5 MHz, respectively. In addition, an upper limit is identified which is caused by wave energy saturation at the Bragg wave frequency. Estimation of this limit took place through an evaluation of a year long database of ocean spectra generated by a numerical model (third generation WAM). It was found to be at 9.0 and 11.0 m/s for 27.68 and 12.5 MHz, respectively. Above this saturation limit, conventional second-order methods have to be applied, which at this range of wind speed no longer suffer from low signal-to-noise ratios. For use in operational systems, a hybrid of first- and second-order methods is recommended

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“…By transmitting an electromagnetic wave and using surface gravity waves as target, an HF radar measures the direction and intensity of surface currents: when a Bragg scattering coherent resonance occurs (Crombie 1955), the echo recorded by the receiving antenna displays a peak in the signal spectrum (Barrick et al 1977), with a Doppler effect shift revealing the presence of a current beneath the gravity waves. The system installed in the GoN is composed of monostatic, direction-finding systems with a three-element crossed loop/monopole antennas used to transmit and receive the signals.…”

Section: Hf Radar Networkmentioning

confidence: 99%

Multiplatform observation of the surface circulation in the Gulf of Naples (Southern Tyrrhenian Sea)

et al. 2011

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The Gulf of Naples (Southern Tyrrhenian Sea) is a highly urbanised area, where human activities and natural factors (e.g. river runoff, exchanges with adjacent basins) can strongly affect the water quality. In this work we show how surface transport can influence the distribution of passively drifting surface matter, and more in general if and how the circulation in the basin can promote the renovation of the surface layer. To this aim, we carried out a multiplatform analysis by putting together HF radar current fields, satellite images and modelling tools. Surface current fields and satellite images of turbidity patterns were used to initialise and run model simulations of particle transport and diffusion. Model results were then examined in relation to the corresponding satellite distributions. This integrated approach permits to investigate the concurrent effects of surface dynamics and wind forcing in determining the distribution of passive tracers over the basin of interest, identifying key mechanisms supporting or preventing the renewal of surface waters as well as possible areas of aggregation and retention.

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Ocean surface currents mapped by radar

Cited by 104 publications

References 6 publications

Tidal and wind-driven surface currents in the German Bight: HFR observations versus model simulations

Tidal and wind-driven surface currents in the German Bight: HFR observations versus model simulations

Wind-speed inversion from HF radar first-order backscatter signal

Multiplatform observation of the surface circulation in the Gulf of Naples (Southern Tyrrhenian Sea)

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