Surface Current Mapping with High Frequency RADAR
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Transcript of Surface Current Mapping with High Frequency RADAR
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Surface Current Mapping with High Frequency RADAR
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Applications
• Search and rescue
• Navigation
• Pollution Tracking (Oil spills, red tides, …)
• Recreational boating
• Fishing
• Assimilation into numerical circulation models to improve nowcast/forecast capabilities
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Study Area & Antenna Sites
Source: U.S. Geological Survey(www.seamless.usgs.gov/viewer)
Source: http://www.cbbt.com/
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Chesapeake Bay Bridge Tunnel (CBBT)
Ocean View Community Beach (VIEW)
AT OUR FIELD SITES
25.4 MHz CODAR Standard Range
Antennas with co-located Tx/Rx
MiniMac Field Computers
Cell phone/Cable modem connections
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Operating Costs
• Equipment (antenna, computer, electronics enclosure, software) roughly 150K / site
• Power / network connections / access to the site – CBBT $220/ month– VIEW $100/ month
• Technician• Additional costs: Pattern measurements
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Data Products Updated Hourly
Sub-tidal Flow
Trajectories
(http://www.lions.odu.edu/org/cbc)
Time Series
Hourly Velocity
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Shipping Channels
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HF RADAR National Network
UCSD, Scripps Institute http://cordc.ucsd.edu/projects/mapping/maps
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½ λ
f = 25MHzλ=12m Water speed is determined using the
frequency shift, fs, in the return signal.
fobs=25 + f
s
f=25
Ocean waves with strongest return signal
Antenna
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Radial Current Velocities… are combined on a grid
Mapping requires at least two antennas!
A single antenna measures only one component of the water velocity, thespeed of the water moving directly towards or away from it.
Radial vectors are output in range bins of 1.5 km and directional bins of 5 degrees.
The grid is designed by the operator.
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Grid for Total Current Vectors
2 km Grid courtesy ofCORDC National Network
Preserves orthogonality
Red points fail stability angle requirements
Baseline
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Gridpoint
2.5 km
Radial Current Velocities
Total Current Velocities
Around each grid point… Combine Radial Vectors (Least Squares Average)
+ Grid
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Data Quality
Calibration and Radial Coverage
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Antenna Patterns Radial Coverage
CBBT
VIEW
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Challenges
• At a 360° site, antenna pattern measurement is essential
• Antenna isolation
• Summertime heat
• Interference (Natural & Man-made)
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• Baseline (consistency)
• Tide
• Moored ADCP
• Towed ADCP
Data Validation by Comparison
Photo Source: NOAA OSTEP report
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Baseline Comparisons
Ideal antenna patterns Measured antenna patterns
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Tidal Analysis
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Moored ADCP Comparison
Site Mean S.DevCape Henry 16.2 14.0Thimble Shoals 13.2 11.2York Spit 13.9 10.0
Red line = CODARBlue line = NOAA ADCPBlack = |NOAA-CODAR|
Difference Statistics
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• Bistatic system: enhance coverage by using precise timing so that Rx can receive sea scatter from another transmitter (e.g. on a buoy)
• RiverSonde
• Ship detection
• Shallow water waves
CODAR Current Research & Development
Source: CODAR Research & Development poster
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Our Future Plans• Incorporate data into GIS;
map with other regional spatial data
• Continue to work with trajectories/ plume tracking
• Model comparisons• Outreach (VA Aquarium,
education)• Web page & product
development– Shipping channels– Ocean View beaches
ChesROMS model output
AVHRR SST Daily Composite, September 24, 2007
from NOAA Coastwatch
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Acknowledgements
• Larry Atkinson and Jose Blanco
• CIT, MACOORA, NOAA
• CODAR support
• Advice and assistance from numerous other HF RADAR operators