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Ocean surface current measurements by WERA HF-radars: Hawaii & Adriatic

Cedric Chavanne Pierre Flament University of Hawaii, USA. Ocean surface current measurements by WERA HF-radars: Hawaii & Adriatic. Overview. HOME: Hawaiian Ocean Mixing Experiment Characteristics Calibrations Validations Tidal currents Mesoscale currents

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Ocean surface current measurements by WERA HF-radars: Hawaii & Adriatic

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  1. Cedric Chavanne Pierre Flament University of Hawaii, USA Ocean surface current measurements by WERA HF-radars: Hawaii & Adriatic

  2. Overview • HOME: Hawaiian Ocean Mixing Experiment • Characteristics • Calibrations • Validations • Tidal currents • Mesoscale currents • AMEX: Adriatic Mesoscale Experiment • Characteristics • Problems • Conclusions

  3. HOME • 2 sites with 16 Rx antennas • 16 MHz, 125 kHz continuous chirp • 9 months (sep 2002 – may 2003) • 9-min acquisitions every 20 min • Moored ADCPs Kauai Oahu

  4. Spatial coverage Daytime: 130km Nightime: 90km

  5. Koolina

  6. Kaena

  7. Calibrations • transmitter on R/V Wyrtki • Continuous sinusoid at 16 MHz • Passive listening by radar • Ship position by differential GPS

  8. Phases vs azimuth (Kaena)

  9. Beamformed direction – true direction (GPS) Beam-steering error

  10. Example of spectra (Kaena)

  11. Auto-validation

  12. Comparison with ADCP C1

  13. M2 tidal current ellipses POM model WERA

  14. M2 tidal currents and isopycnal displacement(POM model, Merrifield and Holloway, 2002)

  15. Mesoscale currents (3-day low-pass filtered) Longitudinal section (at 21.3N) Latitudinal section (at 158.4W) V U U V

  16. Mesoscale currents (3-day low-pass filtered

  17. AMEX • 1 site with 16 Rx antennas: Goro • 2 sites with 4 & 6 Rx antennas: Ravenna &Bartolo • 16 MHz, 125 kHz continuous chirp • 2 years (nov 2002 –nov 2004) • 12-min acquisitions every 30 min

  18. 55 km 65 km Spatial coverage 110 km 90 km

  19. Example of spectra (Ravenna)

  20. Mean and standard deviation of radial currents

  21. Time series of radial currents

  22. Conclusions • WERA has great flexibility of operation:beamforming or direction finding, wide range of working frequencies, signal processing in software • Beamforming is a more robust technique than Direction Finding and gives a greater range • Beamforming enables to measure waves, but we have not tested it yet ...

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