Wave Observation Methods using High-frequency Ocean Radar

2020 ◽  
Vol 95 (sp1) ◽  
pp. 1273
Author(s):  
Jae-Seol Shim ◽  
Jung Hun Kim ◽  
Byung Sun Chang ◽  
In-Ki Min ◽  
Junghyun Choi ◽  
...  
Keyword(s):  
High Frequency ◽  
Observation Methods ◽  
Wave Observation ◽  
Ocean Radar

scholarly journals High-frequency ocean radar support for Tsunami Early Warning Systems

2018 ◽  
Vol 5 (1) ◽  
Author(s):  
Anna Dzvonkovskaya ◽  
Leif Petersen ◽  
Thomas Helzel ◽  
Matthias Kniephoff
Keyword(s):  
Early Warning ◽  
High Frequency ◽  
Early Warning Systems ◽  
Warning Systems ◽  
Tsunami Early Warning ◽  
Tsunami Early Warning Systems ◽  
Ocean Radar

scholarly journals Editorial for Special Issue “Ocean Radar”

2019 ◽  
Vol 11 (7) ◽  
pp. 834
Author(s):  
Weimin Huang ◽  
Björn Lund ◽  
Biyang Wen
Keyword(s):  
High Frequency ◽  
Wind Wave ◽  
Surface Wind ◽  
Sea Surface ◽  
Special Issue ◽  
Sea Surface Wind ◽  
Control Schemes ◽  
New Methodologies ◽  
Ocean Monitoring ◽  
Ocean Radar

This Special Issue hosts papers related to ocean radars including the high-frequency (HF) surface wave and sky wave radars, X-, L-, K-band marine radars, airborne scatterometers, and altimeter. The topics covered by these papers include sea surface wind, wave and current measurements, new methodologies and quality control schemes for improving the estimation results, clutter and interference classification and detection, and optimal design as well as calibration of the sensors for better performance. Although different problems are tackled in each paper, their ultimate purposes are the same, i.e., to improve the capacity and accuracy of these radars in ocean monitoring.

scholarly journals Interoperability of Direction-Finding and Beam-Forming High-Frequency Radar Systems: An Example from the Australian High-Frequency Ocean Radar Network

2019 ◽  
Vol 11 (3) ◽  
pp. 291 ◽  
Author(s):  
Simone Cosoli ◽  
Stuart de Vos
Keyword(s):  
High Frequency ◽  
Direction Finding ◽  
Coastal Monitoring ◽  
Vector Correlation ◽  
High Frequency Radar ◽  
Pointing Errors ◽  
Radar Systems ◽  
Radar Network ◽  
Vector Correlations ◽  
Ocean Radar

Direction-finding SeaSonde (4.463 MHz; 5.2625 MHz) and phased-array WEllen RAdar WERA (9.33 MHz; 13.5 MHz) High-frequency radar (HFR) systems are routinely operated in Australia for scientific research, operational modeling, coastal monitoring, fisheries, and other applications. Coverage of WERA and SeaSonde HFRs in Western Australia overlap. Comparisons with subsurface currents show that both HFR types agree well with current meter records. Correlation (R), root-mean-squares differences (RMSDs), and mean bias (bias) for hourly-averaged radial currents range between R = (−0.03, 0.78), RMSD = (9.2, 30.3) cm/s, and bias = (−5.2, 5.2) cm/s for WERAs; and R = (0.1, 0.76), RMSD = (17.4, 33.6) cm/s, bias = (0.03, 0.36) cm/s for SeaSonde HFRs. Pointing errors (θ) are in the range θ = (1°, 21°) for SeaSonde HFRs, and θ = (3°, 8°) for WERA HFRs. For WERA HFR current components, comparison metrics are RU = (−0.12, 0.86), RMSDU = (12.3, 15.7) cm/s, biasU = (−5.1, −0.5) cm/s; and, RV = (0.61, 0.86), RMSDV = (15.4, 21.1) cm/s, and biasV = (−0.5, 9.6) cm/s for the zonal (u) and the meridional (v) components. Magnitude and phase angle for the vector correlation are ρ = (0.58, 0.86), φ = (−10°, 28°). Good match was found in a direct comparison of SeaSonde and WERA HFR currents in their overlap (ρ = (0.19, 0.59), φ = (−4°, +54°)). Comparison metrics at the mooring slightly decrease when SeaSonde HFR radials are combined with WERA HFR: scalar (vector) correlations for RU, V, (ρ) are in the range RU = (−0.20, 0.83), RV = (0.39, 0.79), ρ = (0.47, 0.72). When directly compared over the same grid, however, vectors from WERA HFR radials and vectors from merged SeaSonde–WERA show RU (RV) exceeding 0.9 (0.7) within the HFR grid. Despite the intrinsic differences between the two types of radars used here, findings show that different HFR genres can be successfully merged, thus increasing current mapping capability of the existing HFR networks, and minimising operational downtime, however at a likely cost of slightly decreased data quality.

scholarly journals DIURNAL WIND-INDUCED MIXING IN A SEA SURFACE LAYER ON THE UPPER SIDE OF A STRONG NEARSHORE CURRENT WITH A HIGH-FREQUENCY OCEAN RADAR AND A MICRO-SCALE PROFILER

2007 ◽  
Vol 51 ◽  
pp. 1433-1438
Author(s):  
Masayuki NAGAO ◽  
Eisuke HASHIMOTO ◽  
Yoshio TAKASUGI ◽  
Shoichiro KOJIMA ◽  
Kenji SATOH ◽  
...  
Keyword(s):  
Surface Layer ◽  
High Frequency ◽  
Sea Surface ◽  
Micro Scale ◽  
Diurnal Wind ◽  
Ocean Radar

scholarly journals Improving Data Quality for the Australian High Frequency Ocean Radar Network through Real-Time and Delayed-Mode Quality-Control Procedures

2018 ◽  
Vol 10 (9) ◽  
pp. 1476 ◽  
Author(s):  
Simone Cosoli ◽  
Badema Grcic ◽  
Stuart de Vos ◽  
Yasha Hetzel
Keyword(s):  
Quality Control ◽  
Data Quality ◽  
Radial Velocity ◽  
High Frequency ◽  
Signal To Noise Ratio ◽  
Detection Threshold ◽  
Radial Beam ◽  
Control Procedures ◽  
Quantitative Analyses ◽  
Ocean Radar

Quality-control procedures and their impact on data quality are described for the High-Frequency Ocean Radar (HFR) network in Australia, in particular for the commercial phased-array (WERA) HFR type. Threshold-based quality-control procedures were used to obtain radial velocity and signal-to-noise ratio (SNR), however, values were set through quantitative analyses with independent measurements available within the HFR coverage, when available, or from long-term data statistics. An artifact removal procedure was also applied to the spatial distribution of SNR for the first-order Bragg peaks, under the assumption the SNR is a valid proxy for radial velocity quality and that SNR decays with range from the receiver. The proposed iterative procedure was specially designed to remove anomalous observations associated with strong SNR peaks caused by the 50 Hz sources. The procedure iteratively fits a polynomial along the radial beam (1-D case) or a surface (2-D case) to the SNR associated with the radial velocity. Observations that exceed a detection threshold were then identified and flagged. After removing suspect data, new iterations were run with updated detection thresholds until no additional spikes were found or a maximum number of iterations was reached.

scholarly journals The Traveling Wave Loop Antenna: A Terminated Wire Loop Aerial for Directional High-Frequency Ocean RADAR Transmission

2020 ◽  
Vol 12 (17) ◽  
pp. 2800
Author(s):  
Stuart John de Vos ◽  
Simone Cosoli ◽  
Jacob Munroe
Keyword(s):  
Radiation Pattern ◽  
High Frequency ◽  
Beam Width ◽  
Travelling Wave ◽  
Antenna Design ◽  
Frequency Noise ◽  
Design Development ◽  
Beam Radiation ◽  
International Telecommunication Union ◽  
Ocean Radar

In this paper we document the design, development, results, performance and field applications of a compact directive transmit antenna for the long-range High Frequency ocean RADAR (HFR) systems operating in the International Telecommunication Union (ITU) designated 4MHz and 5MHz radiodetermination bands. The antenna design is based on the combination of the concepts of an electrically small loop with that of travelling wave antenna. This has the effect of inducing a radiated wave predominantly in a direction opposed to that of energy flow on the antenna structures. We demonstrate here that travelling wave design allows for a more compact antenna than other directive options, it has straightforward feed-point matching arrangements, and a flat frequency and phase response over an entire radiodetermination band. In situ measurements of the antenna radiation pattern, obtained with the aid of a drone, correlate well with those obtained from simulations, and show between 8dB and 30dB front-to-back suppression, with a 3dB beam width in the forward lobe of 100∘ or more. The broad-beam radiation pattern ensures proper illumination over the ocean and the significant front-to-back suppression guarantees reduced interference to terrestrial services. The proposed antenna design is compact and straight forward and can be easily deployed by minimal modifications of an existing transmission antenna. The design may be readily adapted to different environments due to the relative insensitivity of its radiation pattern and frequency response to geometric detail. The only downside to these antennas is their relatively low radiation efficiency which, however, may easily be compensated for by the available power output of a typical HFR transmitter. Antennas based on this design are currently deployed at the SeaSonde HFR sites in New South Wales, Australia, with operational ranges up to 200 km offshore despite their low radiating efficiency and the extremely low output power in use at these installations. Due to their directional pattern, it is also planned to test these antennas in phased-array Wellen RADAR (WERA) systems in both the standard receive arrays: where in-band radio frequency noise of terrestrial origin is impacting on data quality, and in the transmit array: to possibly simplify splitting, phasing and tuning requirements.

scholarly journals Chiral gravitational effect in time-dependent backgrounds

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Kohei Kamada ◽  
Jun’ya Kume ◽  
Yusuke Yamada
Keyword(s):  
Gravitational Waves ◽  
Effective Action ◽  
High Frequency ◽  
Chemical Potential ◽  
Gravitational Effect ◽  
Magnetic Effect ◽  
Time Dependent ◽  
Chiral Magnetic Effect ◽  
Anomaly Equation ◽  
Wave Observation

Abstract Gravitational counterpart of the chiral magnetic effect, which is referred as the chiral gravitational effect, can also be of interest in a cosmological setup. In this study, we investigate this effect in the time-dependent chiral asymmetric fermion background and in the expanding spacetime by formulating the effective action of gravitational waves. We also analyze the anomaly equation to see how the backreaction from gravitational waves to thermal chiral plasma occurs. We find that the non-trivial time dependence of chiral chemical potential, which can be induced in some scenarios of baryogenesis, is the key ingredient of the chiral gravitational effect. It turns out that the “memory” of the effect is imprinted on the high frequency gravitational waves propagating in the plasma. Cosmological implications and potential effects on the gravitational wave observation are briefly discussed.

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