scholarly journals Measurement and Analysis of Ocean Current using High- Frequency (HF) Radar Observation in the Bali Strait

2021 ◽  
Vol 893 (1) ◽  
pp. 012053
Author(s):  
R Firdaus ◽  
E L Siadari ◽  
F Alfahmi
Keyword(s):  
Harmonic Analysis ◽  
High Frequency ◽  
Weather Condition ◽  
Current Data ◽  
Residual Current ◽  
Hf Radar ◽  
Ocean Current ◽  
Random Pattern ◽  
Residual Currents ◽  
Adcp Data

Abstract High-Frequency (HF) Radar is an instrument using radio waves to measure ocean currents and waves remotely. This technology has many advantages, including has unprecedented spatial and temporal resolution, can operate in any weather condition, and is not dangerous for the environment. However, HF Radar's research is still limited in Indonesia. This research aimed to analyze the tidal and residual current in the Bali Strait in July 2020. Radial velocity from two HF Radar sites is combined to obtain the total currents. Current data from HF Radar were compared with Acoustic Doppler Current Profiler (ADCP) data to investigate its accuracy. Surface current data were analyzed using harmonic analysis to separate tidal and residual currents. Comparison between HF Radar and ADCP data are in good agreement for meridional current with a very high correlation of 0.813 and a small RMSE value of 0.22 m/s. Harmonic analysis shows that the dominant currents are tidal currents. The current direction was northward (southward) at flood (ebb), with maximum northward (southward) velocities are 2.17 m/s (2.97 m/s), respectively. The residual current has a random pattern, slightly faster northward than southward, and has similar spectral with the wind.

scholarly journals Evaluating Radial Current Measurement of Multifrequency HF Radar with Multidepth ADCP Data during a Small Storm

2015 ◽  
Vol 32 (5) ◽  
pp. 1071-1087 ◽  
Author(s):  
Chen Zhao ◽  
Zezong Chen ◽  
Gengfei Zeng ◽  
Longgang Zhang ◽  
Fei Xie
Keyword(s):  
Wind Speed ◽  
Correlation Coefficient ◽  
Correlation Coefficients ◽  
Radar System ◽  
Hf Radar ◽  
Residual Currents ◽  
Radio Wavelength ◽  
Effective Depth ◽  
Different Depths ◽  
Adcp Data

AbstractA multifrequency high-frequency (MHF) radar system was designed and developed by Wuhan University in 2007. This system can simultaneously operate at four frequencies mainly in the 7.5–25-MHz band. This paper focuses on discussing the performances of an MHF radar system deployed along the coast of the East China Sea based on comparisons with multidepth ADCP datasets, which were obtained from ADCPs deployed at different locations in August 2010 during a small storm. The comparisons illustrate that radar-derived radial currents are correlated with ADCP data at mainly a 2–4-m depth with correlation coefficients over 0.95 and RMS differences less than 0.12 m s−1 for both operating frequencies. Bearing offsets at points A, C, and D are computed for different operating frequencies with magnitudes of 0°–11°.The capability of MHF radar to measure currents at different depths is explored. The results indicate that the effective depth of current measurements by MHF radar increases with decreasing operating frequency. A linear regression (with a regression coefficient of 0.0576) of the responses in the mean effective depth on the predictors in radio wavelength is obtained. The dominant semidiurnal and diurnal constituents are also analyzed. The radial current amplitudes of the M2 and K1 constituents are strong in this area during this experiment. The residual currents vary with wind speed, with a correlation coefficient of 0.52. A correlation coefficient of 0.79 between nontidal currents and the radial wind speed after a clockwise rotation of the wind vector by about 50° was obtained.

scholarly journals The Effects of High-Frequency Residual Currents on the Operation of Residual Current Devices

2021 ◽  
Vol 19 ◽  
pp. 67-72
Author(s):  
T. M. H. Slangen ◽  
◽  
B. R. F. Lustenhouwer ◽  
V. Cuk ◽  
J. F. G. Cobben
Keyword(s):  
High Frequency ◽  
Residual Current ◽  
Power Electronic ◽  
Leakage Currents ◽  
Important Conclusion ◽  
Large Power ◽  
Residual Currents ◽  
Safety Risks ◽  
Set Up ◽  
Frequency Current

This research investigates the effects of high frequency currents between 50 Hz and 150 kHz on the operation of Residual Current Devices (RCDs). Nowadays, the increasing amount of large power-electronic switching devices can be a source of both harmonics (<2 kHz) and supraharmonics (2-150 kHz) currents injected to the grid. This can have several effects and possibly lead to unwanted tripping of RCDs, due to high earth-currents that can be emitted by the devices. The question is if supraharmonics can also lead to misoperation or fail-to-operate conditions for the RCDs, potentially leading to serious safety risks. A set-up is developed to introduce both 50 Hz and highfrequency leakage currents. First, the 50 Hz tripping-current of the RCDs is tested under nominal conditions. Secondly, the tripping current for non-nominal frequencies (between 50 Hz and 150 kHz) is determined to verify the possibility for false tripping. Lastly, the 50 Hz tripping current for the RCD is tested in the presence of a high-frequency current. The most important conclusion is that RCDs of type A and AC have an increased fundamental (50 Hz) tripping current when there are HFcomponents present. This potentially results in a safety risk.

scholarly journals Examining the Accuracy of GlobCurrent Upper Ocean Velocity Data Products on the Northwestern Atlantic Shelf

2018 ◽  
Vol 10 (8) ◽  
pp. 1205 ◽  
Author(s):  
Hui Feng ◽  
Douglas Vandemark ◽  
Julia Levin ◽  
John Wilkin
Keyword(s):  
Gulf Of Maine ◽  
Ground Truth ◽  
Current Data ◽  
Hf Radar ◽  
Ocean Current ◽  
Upper Ocean ◽  
Dynamic Topography ◽  
Near Surface ◽  
Radar Networks ◽  
Study Results

This study provides a regional coastal ocean assessment of global upper ocean current data developed by the GlobCurrent (GC) project. These gridded data synthesize multiple satellite altimeter and wind model inputs to estimate both Geostrophic and Ekman-layer velocities. While the GC product was mostly devised and intended for open ocean studies, the present objective is to assess whether its data quality nearer the coast is suitable for other applications. The key ground truth sources are long-term mean and time series observations on the Northwestern Atlantic (NWA) shelf derived from Acoustic Doppler Current Profilers (ADCP) and high frequency (HF) radar networks in both the Mid-Atlantic Bight (MAB) and the Gulf of Maine (GoM). Results indicate that mean geostrophic currents across the MAB and the offshore GoM agree to roughly 10% in speed and 10 degree in direction with the in situ depth-averaged currents, with correlation levels of 0.5–0.8 at seasonal and longer time scales. Interior GoM comparisons at 5 coastal buoys show much less agreement. One likely source of GoM error is shown to be the GC mean dynamic topography near the coast. Comparison to near-surface MAB HF radar current measurements on the MAB shelf shows significant GC data improvement when including the surface Ekman term. Overall, the study results imply that application of GlobCurrent data may prove useful in coastal seas with broad continental shelves such as the MAB or Scotian shelf, but that large inaccuracies inside the GoM diminish its utility there.

scholarly journals Gap Filling of the CALYPSO HF Radar Sea Surface Current Data through Past Measurements and Satellite Wind Observations

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Adam Gauci ◽  
Aldo Drago ◽  
John Abela
Keyword(s):  
Oil Spills ◽  
Surface Current ◽  
Radar Data ◽  
Current Data ◽  
Hf Radar ◽  
Sea Surface ◽  
Machine Learning Techniques ◽  
Learning Techniques ◽  
Spatial Coverage ◽  
Essential Components

High frequency (HF) radar installations are becoming essential components of operational real-time marine monitoring systems. The underlying technology is being further enhanced to fully exploit the potential of mapping sea surface currents and wave fields over wide areas with high spatial and temporal resolution, even in adverse meteo-marine conditions. Data applications are opening to many different sectors, reaching out beyond research and monitoring, targeting downstream services in support to key national and regional stakeholders. In the CALYPSO project, the HF radar system composed of CODAR SeaSonde stations installed in the Malta Channel is specifically serving to assist in the response against marine oil spills and to support search and rescue at sea. One key drawback concerns the sporadic inconsistency in the spatial coverage of radar data which is dictated by the sea state as well as by interference from unknown sources that may be competing with transmissions in the same frequency band. This work investigates the use of Machine Learning techniques to fill in missing data in a high resolution grid. Past radar data and wind vectors obtained from satellites are used to predict missing information and provide a more consistent dataset.

Spatio-Temporal Deep Learning for Ocean Current Prediction Based on HF Radar Data

2019 ◽  
Author(s):  
Nathachai Thongniran ◽  
Peerapon Vateekul ◽  
Kulsawasd Jitkajornwanich ◽  
Siam Lawawirojwong ◽  
Panu Srestasathiern
Keyword(s):  
Deep Learning ◽  
Radar Data ◽  
Hf Radar ◽  
Ocean Current ◽  
Spatio Temporal

Backtracking drifting objects using surface currents from high-frequency (HF) radar technology

2012 ◽  
Vol 62 (7) ◽  
pp. 1073-1089 ◽  
Author(s):  
Ana Julia Abascal ◽  
Sonia Castanedo ◽  
Vicente Fernández ◽  
Raúl Medina
Keyword(s):  
High Frequency ◽  
Hf Radar ◽  
Surface Currents

High-Frequency and Passive Radar Designs for Homeland Security Applications

2011 ◽  
Vol 45 (3) ◽  
pp. 111-119 ◽  
Author(s):  
Magdy F. Iskander ◽  
Zhengqing Yun ◽  
Nuri Celik ◽  
Hyoungsun Youn ◽  
Nobutaka Omaki ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Homeland Security ◽  
High Frequency ◽  
Beam Steering ◽  
Antenna System ◽  
Hf Radar ◽  
Passive Radar ◽  
High Definition ◽  
Security Applications ◽  
The Impact

AbstractEmerging homeland security applications require low-cost and fast, deployable, high-frequency (HF) radar systems and the ability to operate in challenging terrain environments. With the need to cover as many border and coastal areas as possible, taking advantages of available transmitter resources to track targets using passive radar technologies is yet another area of research of considerable interest. In this paper, we describe the development of an HF radar system that meets these operational challenges, and we also highlight some recent implementation of the passive radar technology for homeland security applications. Specifically, we describe the design of a novel, electrically small HF antenna system consisting of three helical elements, one connected to the feed port while the other two are folded arms terminated with switchable loads. The antenna is 0.90-m (<3 feet) high with a small ground disk of 0.60 m (∼2 feet) diameter. The antenna is self-resonant at multiple frequencies (5.7, 16, 20.5, and 27.7 MHz) and with input impedance values that can be easily matched to a 50-Ω coaxial feed. Values of the electrical size ka range from 0.44 at 30 MHz down to 0.08 at 5.7 MHz. The achieved bandwidths range from 1.4% up to 12% and associated efficiencies range from 66.2% to 76% within the HF band (3‐30 MHz). As for the operational requirement in challenging terrain environments, a setup in a hilltop-type environment with a slope terrain and surface roughness was considered. A propagation modeling and ray-tracing approach was used to evaluate the impact of such terrain conditions on the effective interelement spacing of an HF radar antenna array and the subsequent impact on its beamforming and beam steering performance. It is shown that while the effect of the slope on the effective interelement spacing of the array could be very significant, diffraction effects from surface roughness resulted in a much smaller, but significant, error of about 18°. Results from some initial work on the implementation of passive radar technology, with focus on addressing the bandwidth requirement to ensure practical resolution values, are also described. It is shown that signals from wide-band transmitters (e.g., High Definition Television [HDTV] signals) rather than those from radio stations are required to provide acceptable range resolution. These as well as simulation and experimental results of the antenna design, and results from beamforming simulations illustrating the effect of a rough hilltop terrain on the HF radar performance are described.

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

2013 ◽  
Vol 54 (62) ◽  
pp. 59-64 ◽  
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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