A combined quality-control methodology in Ebro Delta (NE Spain) high frequency radar system

Abstract. Ebro River Delta is a relevant marine protected area in the western Mediterranean. In order to promote the conservation of its ecosystem and support operational decision making in this sensitive area, a three site standard-range (13.5 MHz) CODAR SeaSonde High Frequency (HF) radar was deployed in 2013. Since there is a growing demand for reliable HF radar surface current measurements, the main goal of this work is to present a combined quality control methodology. Firstly, one year-long (2014) real-time web monitoring of nonvelocity-based diagnostic parameters is conducted in order to infer both radar site status and HF radar system performance. Signal-to-noise ratio at the monopole exhibited a consistent monthly evolution although some abrupt decreases (below 10 dB), occasionally detected in June for one of the radar sites, impacted negatively on the spatiotemporal coverage of total current vectors. It seemed to be a sporadic episode since radar site overall performance was found to be robust during 2014. Secondly, a validation of HF radar data with independent in situ observations from a moored current meter was attempted for May–October 2014. The accuracy assessment of radial and total vectors revealed a consistently high agreement. The directional accuracy of the HF radar was rated at better than 8°. The correlation coefficient and RMSE values emerged in the ranges 0.58–0.83 and 4.02–18.31 cm s−1, respectively. The analysis of the monthly averaged current maps for 2014 showed that the HF radar properly represented basic oceanographic features previously reported, namely: the predominant southwestward flow, the coastal clockwise eddy confined south of Ebro Delta mouth or the Ebro River impulsive-type freshwater discharge. Future works should include the use of verified HF radar data for the rigorous skill assessment of operational ocean circulation systems currently running in Ebro estuarine region like MyOcean IBI.

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Evaluating the surface circulation in the Ebro delta (northeastern Spain) with quality-controlled high-frequency radar measurements

Ocean Science ◽

10.5194/os-11-921-2015 ◽

2015 ◽

Vol 11 (6) ◽

pp. 921-935 ◽

Cited By ~ 15

Author(s):

P. Lorente ◽

S. Piedracoba ◽

J. Soto-Navarro ◽

E. Alvarez-Fanjul

Keyword(s):

High Frequency ◽

Marine Protected Area ◽

Accuracy Assessment ◽

Surface Current ◽

Radar Data ◽

Western Mediterranean ◽

Hf Radar ◽

Ebro Delta ◽

Ebro River ◽

Surface Circulation

Abstract. The Ebro River delta is a relevant marine protected area in the western Mediterranean. In order to promote the conservation of its ecosystem and support operational decision making in this sensitive area, a three-site standard-range (13.5 MHz) CODAR SeaSonde high-frequency (HF) radar was deployed in December 2013. The main goal of this work is to explore basic features of the sea surface circulation in the Ebro deltaic region as derived from reliable HF radar surface current measurements. For this aim, a combined quality control methodology was applied: firstly, 1-year long (2014) real-time web monitoring of nonvelocity-based diagnostic parameters was conducted to infer both radar site status and HF radar system performance. The signal-to-noise ratio at the monopole exhibited a consistent monthly evolution, although some abrupt decreases (below 10 dB), occasionally detected in June for one of the radar sites, impacted negatively on the spatiotemporal coverage of total current vectors. It seemed to be sporadic episodes since radar site overall performance was found to be robust during 2014. Secondly, a validation of HF radar data with independent in situ observations from a moored current meter was attempted for May–October 2014. The accuracy assessment of radial and total vectors revealed a consistently high agreement. The directional accuracy of the HF radar was rated at better than 8°. The correlation coefficient and root mean square error (RMSE) values emerged in the ranges [0.58–0.83] and [4.02–18.31] cm s−1, respectively. The analysis of the monthly averaged current maps for 2014 showed that the HF radar properly represented basic oceanographic features previously reported, namely, the predominant southwestward flow, the coastal clockwise eddy confined south of the Ebro delta mouth, or the Ebro River impulsive-type freshwater discharge. The EOF analysis related the flow response to local wind forcing and confirmed that the surface current field evolved in space and time according to three significantly dominant modes of variability.

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Ice-edge detection from Japanese C-band radar and high-frequency radar coastal stations

Annals of Glaciology ◽

10.3189/2013aog62a007 ◽

2013 ◽

Vol 54 (62) ◽

pp. 59-64 ◽

Cited By ~ 2

Author(s):

K. Shirasawa ◽

N. Ebuchi ◽

M. Leppäranta ◽

T. Takatsuka

Keyword(s):

Sea Ice ◽

Edge Detection ◽

High Frequency ◽

Open Water ◽

Radar Data ◽

Hf Radar ◽

Sea Surface ◽

Geometrical Structures ◽

Overlapping Data ◽

Ice Edge

AbstractA C-band sea-ice radar (SIR) network system was operated to monitor the sea-ice conditions off the Okhotsk Sea coast of northern Hokkaido, Japan, from 1969 to 2004. The system was based on three radar stations, which were capable of continuously monitoring the sea surface as far as 60 km offshore along a 250 km long coastal section. In 2004 the SIR system was closed down and a sea surface monitoring programme was commenced using high-frequency (HF) radar; this system provides information on surface currents in open-water conditions, while areas with ‘no signal’ can be identified as sea ice. The present study compares HF radar data with SIR data to evaluate their feasibility for sea-ice remote sensing. The period of overlapping data was 1.5 months. The results show that HF radar information can be utilized for ice-edge mapping although it cannot fully compensate for the loss of the SIR system. In particular, HF radar does not provide ice concentration, ice roughness and geometrical structures or ice kinematics. The probability of ice-edge detection by HF radar was 0.9 and the correlation of the ice-edge distance between the radars was 0.7.

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Automated quality control of High Frequency radar data

2012 Oceans ◽

10.1109/oceans.2012.6404809 ◽

2012 ◽

Cited By ~ 9

Author(s):

H. Roarty ◽

M. Smith ◽

J. Kerfoot ◽

J. Kohut ◽

S. Glenn

Keyword(s):

Quality Control ◽

High Frequency ◽

Radar Data ◽

High Frequency Radar ◽

Automated Quality Control

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A Quality Control Method for Broad-Beam HF Radar Current Velocity Measurements

Journal of Marine Science and Engineering ◽

10.3390/jmse7040112 ◽

2019 ◽

Vol 7 (4) ◽

pp. 112 ◽

Cited By ~ 2

Author(s):

Lipa ◽

Barrick ◽

Whelan

Keyword(s):

Quality Control ◽

High Frequency ◽

Control Method ◽

Doppler Frequency ◽

Hf Radar ◽

Velocity Measurements ◽

Poor Agreement ◽

Broad Beam ◽

Radar Echo ◽

Basic Equations

This paper describes a method to provide quality control for radial velocity maps derived from radar echo voltage cross spectra measured by broad-beam high frequency radars. The method involves the comparison of voltage cross spectra measured at Doppler frequencies in the Bragg region with values predicted from basic equations defining the complex voltage cross spectra in terms of the measured antenna patterns and the radar cross section. Poor agreement at a given Doppler frequency indicates contamination of the spectra, usually due to interference; velocity results from that Doppler frequency are then eliminated. Examples are given of its application to broad-beam radars operating at four sites.

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Research on Polarization Cancellation of Nonstationary Ionosphere Clutter in HF Radar System

International Journal of Antennas and Propagation ◽

10.1155/2015/631217 ◽

2015 ◽

Vol 2015 ◽

pp. 1-12 ◽

Cited By ~ 5

Author(s):

Xingpeng Mao ◽

Hong Hong ◽

Weibo Deng ◽

Yongtan Liu

Keyword(s):

Surface Wave ◽

Time Domain ◽

High Frequency ◽

Interference Cancellation ◽

Radar System ◽

Experimental Results ◽

Hf Radar ◽

Oblique Projection ◽

Polarization Filter ◽

Wave Radar

Oblique projection polarization filter (OPPF) can be applied as an effective approach for interference cancellation in high-frequency surface wave radar (HFSWR) and other systems. In order to suppress the nonstationary ionosphere clutter further, a novel OPPF based clutter suppressing scheme is proposed in this paper. The polarization and nonstationary characteristic of the clutter are taken into account in the algorithms referred to as range-Doppler domain polarization suppression (RDDPS) and the range-time domain polarization suppression (RTDPS) method, respectively. The RDDPS is designed for weak ionosphere clutter and implemented in the range-Doppler domain directly, whereas the RTDPS algorithm is designed to suppress the powerful ionosphere clutter with a multisegment estimation and suppression scheme. About 15–23 dB signal to interference ratio (SIR) improvement can be excepted when using the proposed method, whereas the targets can be more easily detected in the range-Doppler map. Experimental results demonstrate that the scheme proposed is effective for nonstationary ionosphere clutter and is proven to be a practical interference cancellation technique for HFSWR.

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Skill Assessment of HF Radar–Derived Products for Lagrangian Simulations in the Bay of Biscay

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-16-0045.1 ◽

2016 ◽

Vol 33 (12) ◽

pp. 2585-2597 ◽

Cited By ~ 13

Author(s):

Lohitzune Solabarrieta ◽

Sergey Frolov ◽

Mike Cook ◽

Jeff Paduan ◽

Anna Rubio ◽

...

Keyword(s):

Ocean Circulation ◽

Temporal Distribution ◽

Surface Current ◽

Current Data ◽

Hf Radar ◽

Skill Assessment ◽

Open Boundary ◽

Data Series ◽

Bay Of Biscay ◽

Time Step

AbstractSince January 2009, two long-range high-frequency (HF) radar systems have been collecting hourly high-spatial-resolution surface current data in the southeastern corner of the Bay of Biscay. The temporal resolution of the HF radar surface currents permits simulating drifter trajectories with the same time step as that of real drifters deployed in the region in 2009. The main goal of this work is to compare real drifter trajectories with trajectories computed from HF radar currents obtained using different methods, including forecast currents. Open-boundary modal analysis (OMA) is applied to the radar radial velocities and then a linear autoregressive model on the empirical orthogonal function (EOF) decomposition of an historical data series is used to forecast OMA currents. Additionally, the accuracy of the forecast method in terms of the spatial and temporal distribution of the Lagrangian distances between observations and forecasts is investigated for a 4-yr period (2009–12). The skills of the different HF radar products are evaluated within a 48-h window. The mean distances between real trajectories and their radar-derived counterparts range from 4 to 5 km for real-time and forecast currents after 12 hours of simulations. The forecast model improves persistence (i.e., the simulations obtained by using the last available OMA fields as a constant variable) after 6 hours of simulation and improves the estimation of trajectories up to 28% after 48 hours. The performance of the forecast is observed to be variable in space and time, related to the different ocean processes governing the local ocean circulation.

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A Real-Time and Offline Quality Control Methodology for SeaSonde High-Frequency Radar Currents

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-11-00217.1 ◽

2012 ◽

Vol 29 (9) ◽

pp. 1313-1328 ◽

Cited By ~ 16

Author(s):

Simone Cosoli ◽

Giorgio Bolzon ◽

Andrea Mazzoldi

Keyword(s):

Quality Control ◽

Real Time ◽

Signal To Noise Ratio ◽

Radar Data ◽

Control Procedure ◽

Spectral Quality ◽

Quality Factors ◽

High Frequency Radar ◽

Minimization Procedure ◽

Control Methodology

Abstract A near-real-time and offline quality control methodology for SeaSonde systems is proposed. It is applied on radial current maps and is based on the determination of the signal-to-noise ratio (SNR) values of the Doppler lines that contribute to the hourly radial current at each range-bearing (R, θ) pair, under the assumption that SNR is a proxy for radar data quality. The retrieval of the sequence of Doppler lines is performed through a minimization procedure that takes advantage of the statistical descriptors output in the short-term radial maps. The separation of the contributing Doppler velocities into valid observations and anomalous velocities is based on their spectral quality factor and on a range-dependent noise threshold derived from statistics (average and standard deviation) of the signal amplitudes in the tails of the Doppler spectra. The final product of the quality control procedure is a radial current map, in which Doppler velocities are weighted by their SNR values and their spectral quality factors, and averaged to produce an output that is fully compatible with the proprietary software. This procedure is fast, despite the fact that a large number of combinations might be required during the retrieval of the Doppler lines, and effective, because it removes both evident spikes as well as Doppler velocities that are not clearly identified as anomalous velocities. In principle, this approach can be used to fill gaps in the radar coverage without the need for interpolation in time or space, proved that the Doppler velocities satisfy predetermined SNR constraints.

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Applying the Method of EOF Interpolation and 2dVar to Complete the Ocean Surface Current Data Obtained from HF Radar System

VNU Journal of Science Earth and Environmental Sciences ◽

10.25073/2588-1094/vnuees.4335 ◽

2018 ◽

Vol 34 (1S) ◽

Author(s):

Nguyen Thi Thu Mai ◽

Alexei Sentchev ◽

Tran Manh Cuong

Keyword(s):

Interpolation Method ◽

Surface Current ◽

Ocean Surface ◽

Radar Data ◽

Current Data ◽

Surface Flow ◽

Radar System ◽

Hf Radar ◽

High Frequency Radar ◽

Ocean Surface Current

Abstract: There are now over 350 high frequency radar (HF radar) stations operating on the coast of 37 countries around the world that allow the mapping of ocean surface current. However, observation from HF radars are often interrupted (loss of data) in both space and time due to signal inference, backscatters, ocean state.Therefore, in this study, we will present a method to improve the surface current data collected from HF radar system. Firstly, the radial surface current data will be filtered intermittently, then the result is interpolated over time and space by the orthogonal experimental EOF and the 2dVar bi-directional variable interpolation. In addition, the authors have initially applied 2dVar interpolation method to the HF radar data in Vietnam and received initial positive results. The methods used in this paper promise to be effective when applied to improve surface flow data obtained from HF radar stations in Vietnam in the future. Keywords:EOF interpolation, 2dVar, Iroise sea, HF radar, ocean surface current.

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