Design and performance of a self-contained fan-beam ADCP

• Published in: IEEE journal of oceanic engineering Vol. 26; no. 2; pp. 252 - 258
• Main Authors: Plueddemann, A.J., Terray, E.A., Merewether, R.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.04.2001; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acoustic beams; Acoustic measurements; Acoustic transducers; Acoustical measurements and instrumentation; Acoustics; Azimuth; Backscatter; Beams (radiation); Circulation; Current measurement; Electronics; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Horizontal; Instruments; Marine; Microorganisms; Physics; Sea measurements; Sea surface; Transducers; Transduction; acoustical devices for the generation and reproduction of sound; Underwater sound; Wind speed; Doppler sonar; Acoustic measurement; Sea current; Surface current; Side scan sonar; Velocity distribution; Langmuir circulation; Underwater acoustics; Ultrasonic transducer
• ISSN: 0364-9059; 1558-1691
• DOI: 10.1109/48.922791

Recent field studies have shown the utility of acoustic Doppler current profilers (ADCPs) with fan-shaped transducer beam patterns (narrow in azimuth and broad in elevation) for the measurement of oceanic surface currents. For wind speeds greater than about 3 m/spl middot/s/sup -1/, the acoustic backscatter is dominated by microbubbles in the upper few meters of the water column, and beams intersecting the surface from below effectively map out horizontal profiles of near-surface current. This paper describes the design and performance of a self-contained, fan-beam ADCP consisting of RD Instruments 300 kHz BroadBand electronics mated to a specially designed transducer head, and intended for long-term deployment on conventional oceanographic moorings. The instrument operated successfully during two field deployments, providing horizontal profiles of near-surface velocity with precision of about 1 cm/spl middot/s/sup -1/ and horizontal resolution of about 5 m. Profiles were obtained once per minute during 20 min "burst" samples each hour. The usable horizontal range varied with wind speed from about 100 to 200 m. Distinct convergence patterns indicative of Langmuir circulation were evident in the cross-wind velocity field during strong forcing events. Time-range maps and horizontal wavenumber spectra of velocity showed evolution of the strength and dominant scale of the circulation during these events.