On Shipboard Marine X-Band Radar Near-Surface Current ‘‘Calibration’’

The ocean wave signatures within conventional noncoherent marine X-band radar (MR) image sequences can be used to derive near-surface current information. On ships, an accurate near-real-time record of the near-surface current could improve navigational safety. It could also advance understanding of...

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Bibliographic Details
Published in:Journal of atmospheric and oceanic technology 2015-10, Vol.32 (10), p.1928-1944
Main Authors: Lund, Björn, Graber, Hans C, Hessner, Katrin, Williams, Neil J
Format: Article
Language:English
Subjects:
Accuracy
Air-sea interaction
Antennas
Calibration
Differential global positioning system
Doppler radar
Doppler sonar
Errors
Estimates
Global positioning systems
GPS
Gravity waves
Gyrocompasses
Hurricanes
Navigational safety
Ocean waves
Oceans
Profilers
Radar
Radar imaging
Radar signatures
Ship speed
Ships
Superhigh frequencies
Trigonometric functions
Typhoons
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Summary:The ocean wave signatures within conventional noncoherent marine X-band radar (MR) image sequences can be used to derive near-surface current information. On ships, an accurate near-real-time record of the near-surface current could improve navigational safety. It could also advance understanding of air–sea interaction processes. The standard shipboard MR near-surface current estimates were found to have large errors (of the same order of magnitude as the signal) that are associated with ship speed and heading. For acoustic Doppler current profilers (ADCPs), ship heading errors are known to induce a spurious cross-track current that is proportional to the ship speed and the sine of the error angle. Conventional mechanical gyrocompasses are very reliable heading sensors, but they are too inaccurate for shipboard ADCPs. Within the ADCP community, it is common practice to correct the gyrocompass measurements with the help of multiantenna carrier-phase differential GPS systems. This study shows how a similar multiantenna GPS-based ship heading correction technique stands to improve the accuracy of MR near-surface current estimates. Changes to the standard MR near-surface current retrieval method that are necessary for high-quality results from ships are also introduced. MR and ADCP data collected from R/V Roger Revelle during the Impact of Typhoons on the Ocean in the Pacific (ITOP) program in 2010 are used to demonstrate the MR currents’ accuracy and reliability.
ISSN:0739-0572
1520-0426
DOI:10.1175/JTECH-D-14-00175.1