scholarly journals Surface currents in the Alderney Race from high-frequency radar measurements and three-dimensional modelling

2020 ◽  
Vol 378 (2178) ◽  
pp. 20190494 ◽  
Author(s):  
G. Lopez ◽  
A.-C. Bennis ◽  
Y. Barbin ◽  
A. Sentchev ◽  
L. Benoit ◽  
...  
Keyword(s):  
High Frequency ◽  
Current Model ◽  
Three Dimensional ◽  
Surface Current ◽  
Tidal Energy ◽  
Phase Lag ◽  
Surface Currents ◽  
Entire Study ◽  
High Frequency Radar ◽  
Radar Measurements

Two weeks of high-frequency radar measurements collected at the Alderney Race are compared with the results of a three-dimensional fully coupled wave–current model. Spatial current measurements are rare in this site, otherwise well investigated through modelling. Thus, the radar measurements offer a unique opportunity to examine the spatial reliability of numerical results, and can help to improve our understanding of the complex currents in the area. Comparison of observed and modelled surface current velocities showed a good agreement between the methods, represented by root mean squared errors ranging from 14 to 40 cm s −1 and from 18 to 60 cm s −1 during neap and spring tides, respectively. Maximum errors were found in shallow regions with consistently high current velocities, represented by mean neap and spring magnitudes of 1.25 m s −1 and 2.7 m s −1 , respectively. Part of the differences between modelled and observed surface currents in these areas are thought to derive from limitations in the k-epsilon turbulence model used to simulate vertical mixing, when the horizontal turbulent transport is high. In addition, radar radial currents showed increased variance over the same regions, and might also be contributing to the discrepancies found. Correlation analyses yielded magnitudes above 0.95 over the entire study area, with better agreement during spring than during neap tides, probably because of an increase in the phase lag between radar and model velocities during the latter. This article is part of the theme issue ‘New insights on tidal dynamics and tidal energy harvesting in the Alderney Race’.

scholarly journals On the Performance of High Frequency Radar in the Western Mediterranean During the Record-Breaking Storm Gloria

2021 ◽  
Vol 8 ◽  
Author(s):  
Pablo Lorente ◽  
Jue Lin-Ye ◽  
Manuel García-León ◽  
Emma Reyes ◽  
Maria Fernandes ◽  
...  
Keyword(s):  
High Frequency ◽  
Mixed Layer Depth ◽  
Three Dimensional ◽  
Surface Current ◽  
Western Mediterranean ◽  
Ocean Model ◽  
Transport Processes ◽  
Instantaneous Rate ◽  
High Frequency Radar ◽  
The Impact

Storm Gloria (January 19–24, 2020) hit the NW Mediterranean Sea with heavy rainfall, strong easterly winds, and very high waves, causing structural damages and 13 fatalities. The low-lying Ebro Delta (ED) region was severely inundated, ruining rice fields and seaside promenades. A variety of Copernicus Marine Environment Monitoring Service (CMEMS) modeling and observational products were jointly used to examine the fingerprint of Gloria and the response of the upper oceanic layer. According to the results, Gloria can be interpreted as a high-impact once-in-a-decade metocean event where various historical records were beaten. The 99th percentile of several parameters (wind speed, significant wave height, wave period, and surface current velocity), derived from long-term observational time series, was persistently exceeded. The atmospheric surge, albeit not negligible, exerted a secondary role in ED. The ability of a high-frequency radar deployed in this region (HFR-ED) to characterize the striking features of the storm was quantified from both waves and circulation aspects. Consistent radar current observations were subsequently compared against the 5-day-ahead forecast of CMEMS Iberia-Biscay-Ireland (IBI) regional ocean model to determine, from an Eulerian perspective, the strengths and shortcomings in its predictive capabilities. Time-averaged maps of surface circulation, superimposed with fields of Instantaneous Rate of Separation (IROS), were derived to resolve flow features and identify areas of elevated particles dispersion, respectively. The mean and P99 values of IROS almost doubled the historical statistics in the vicinity of the northern Ebro hemidelta. Although IBI predicted moderately well basic features of the storm-induced circulation, results suggests that coastal transport processes, likely modulated by wave-current interactions, were not fully captured. Furthermore, current estimations from other two radar systems, overlooking immediate choke points like the Ibiza Channel and the Strait of Gibraltar, evidenced Gloria’s remote-effect in the anomalous circulation patterns observed, that altered the usual water exchanges between adjacent sub-basins. Finally, three-dimensional outcomes from IBI were used to elucidate the impact of this moving storm at different depth levels. Data analyses illustrated that Gloria caused a large increase in kinetic energy and a significant deepening of the mixed layer depth.

scholarly journals Observations of Surface Currents and Tidal Variability Off of Northeastern Taiwan from Shore-Based High Frequency Radar

2021 ◽  
Vol 13 (17) ◽  
pp. 3438
Author(s):  
Yu-Ru Chen ◽  
Jeffrey D. Paduan ◽  
Michael S. Cook ◽  
Laurence Zsu-Hsin Chuang ◽  
Yu-Jen Chung
Keyword(s):  
High Frequency ◽  
Tide Gauge ◽  
Surface Current ◽  
Sea Surface ◽  
Field Pattern ◽  
Surface Currents ◽  
High Frequency Radar ◽  
Synoptic Variability ◽  
Four Seasons ◽  
Frequency Components

A network of high-frequency radars (HFRs) has been deployed around Taiwan. The wide-area data coverage is dedicated to revealing near real-time sea-surface current information. This paper investigates three primary objectives: (1) describing the seasonal current synoptic variability; (2) determining the influence of wind forcing; (3) describing the tidal current field pattern and variability. Sea surface currents derived from HFR data include both geostrophic components and wind-driven components. This study explored vector complex correlations between the HFR time series and wind, which was sufficient to identify high-frequency components, including an Ekman balance among the surface currents and wind. Regarding the characteristics of mesoscale events and the tidal field, a year-long high-resolution surface dataset was utilized to observe the current–eddy–tide interactions over four seasons. The harmonic analysis results derived from surface currents off of northeastern Taiwan during 2013 are presented. The results agree well with the tidal parameters estimated from tide-gauge station observations. The analysis shows that this region features a strong, mixed, mainly semidiurnal tide. Continued monitoring by a variety of sensors (e.g., satellite and HFR) would improve the understanding of the circulation in the region.

scholarly journals Multistatic estimation of high-frequency radar surface currents in the region of Toulon

2020 ◽  
Vol 70 (12) ◽  
pp. 1485-1503
Author(s):  
Dylan Dumas ◽  
Anthony Gramoullé ◽  
Charles-Antoine Guérin ◽  
Anne Molcard ◽  
Yann Ourmières ◽  
...  
Keyword(s):  
High Frequency ◽  
Surface Currents ◽  
High Frequency Radar

The Integrated Ocean Observing System High-Frequency Radar Network: Status and Local, Regional, and National Applications

2010 ◽  
Vol 44 (6) ◽  
pp. 122-132 ◽  
Author(s):  
Jack Harlan ◽  
Eric Terrill ◽  
Lisa Hazard ◽  
Carolyn Keen ◽  
Donald Barrick ◽  
...  
Keyword(s):  
High Frequency ◽  
Surface Current ◽  
Water Quality Monitoring ◽  
Velocity Fields ◽  
Common Source ◽  
Integrated Network ◽  
High Frequency Radar ◽  
Radar Network ◽  
Network Status ◽  
Ocean Observing

AbstractA national high-frequency radar network has been created over the past 20 years or so that provides hourly 2-D ocean surface current velocity fields in near real time from a few kilometers offshore out to approximately 200 km. This preoperational network is made up of more than 100 radars from 30 different institutions. The Integrated Ocean Observing System efforts have supported the standards-based ingest and delivery of these velocity fields to a number of applications such as coastal search and rescue, oil spill response, water quality monitoring, and safe and efficient marine navigation. Thus, regardless of the operating institution or location of the radar systems, emergency response managers, and other users, can rely on a common source and means of obtaining and using the data. Details of the history, the physics, and the application of high-frequency radar are discussed with successes of the integrated network highlighted.

scholarly journals Characteristic Mode Analysis of surface current distributions on metallic structures exposed to HIRF- and DCI-excitations

2020 ◽  
Vol 18 ◽  
pp. 33-41
Author(s):  
Jan Ückerseifer ◽  
Frank Gronwald
Keyword(s):  
Three Dimensional ◽  
Surface Current ◽  
Resonance Region ◽  
Mode Analysis ◽  
Surface Currents ◽  
Characteristic Mode ◽  
Metallic Structures ◽  
Current Distributions ◽  
Characteristic Modes ◽  
Physical Quantities

Abstract. This paper treats Characteristic Mode Analyses of three-dimensional test objects in the context of EMC. Based on computed Characteristic Modes and mode-specific physical quantities, series expansions for HIRF- and DCI-induced surface currents are deduced. The contribution of single Characteristic Modes to surface currents at different test frequencies is analyzed. HIRF- and DCI-excitations are compared with regard to their surface current distributions in their resonance region determined by Characteristic Mode Analysis.

scholarly journals Investigations into Synoptic Spatiotemporal Characteristics of Coastal Upper Ocean Circulation Using High Frequency Radar Data and Model Output

2020 ◽  
Vol 12 (17) ◽  
pp. 2841
Author(s):  
Lei Ren ◽  
Nanyang Chu ◽  
Zhan Hu ◽  
Michael Hartnett
Keyword(s):  
Ocean Circulation ◽  
High Frequency ◽  
Numerical Models ◽  
Surface Current ◽  
Flow Fields ◽  
Surface Flow ◽  
Self Organizing Map ◽  
Eof Analysis ◽  
Surface Flows ◽  
High Frequency Radar

Numerical models and remote sensing observation systems such as radars are useful for providing information on surface flows for coastal areas. Evaluation of their performance and extracting synoptic characteristics are challenging and important tasks. This research aims to investigate synoptic characteristics of surface flow fields through undertaking a detailed analysis of model results and high frequency radar (HFR) data using self-organizing map (SOM) and empirical orthogonal function (EOF) analysis. A dataset of surface flow fields over thirteen days from these two sources was used. A SOM topology map of size 4 × 3 was developed to explore spatial patterns of surface flows. Additionally, comparisons of surface flow patterns between SOM and EOF analysis were carried out. Results illustrate that both SOM and EOF analysis methods are valuable tools for extracting characteristic surface current patterns. Comparisons indicated that the SOM technique displays synoptic characteristics of surface flow fields in a more detailed way than EOF analysis. Extracted synoptic surface current patterns are useful in a variety of applications, such as oil spill treatment and search and rescue. This research provides an approach to using powerful tools to diagnose ocean processes from different aspects. Moreover, it is of great significance to assess SOM as a potential forecasting tool for coastal surface currents.

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