• Dickey, T. D., A. J. Plueddemann, and R. A. Weller, 1998: Current and water property measurements in the coastal ocean. The Sea—Ideas and Observations on Progress in the Study of the Seas, K. H. Brink and A. R. Robinson, Eds., Vol. 10, The Global Coastal Ocean, John Wiley and Sons, 367–398.

  • Frye, D., N. Hogg, and C. Wunsch, 2004: A long duration mooring for ocean observation. Sea Technol., 45 , 2939.

  • Gilboy, T. P., T. D. Dickey, D. E. Sigurdson, X. Yu, and D. Manov, 2000: An intercomparison of current measurements using a vector measuring current meter, an acoustic Doppler current profiler, and a recently developed acoustic current meter. J. Atmos Oceanic Technol., 17 , 561574.

    • Search Google Scholar
    • Export Citation
  • Heinmiller, R. H., and R. G. Walden, 1973: Details of Woods Hole moorings. Tech. Rep. WHOI-73–71, Woods Hole Oceanographic Institution, 23 pp.

  • Irish, J. D., A. J. Plueddemann, and S. J. Lentz, 1995: In-situ comparisons of moored acoustic Doppler profilers with conventional VACM and VMCM current meters. Proc. IEEE Fifth Working Conf. on Current Measurements, IEEE, St. Petersberg, FL, 59–64.

  • McCullough, J. R., 1975: Vector averaging current meter speed and calibration technique. Tech. Rep. WHOI-75-44, Woods Hole Oceanographic Institution, 41 pp.

  • McKee, T. K., E. A. Francis, and N. G. Hogg, 1981: Compilation of moored current-meter data from three topographic experiments: The Bermuda microstructure array, the island trapped waves array and the Gibbs Fracture Zone array. Tech. Rep. WHOI-81-68, Woods Hole Oceanographic Institution, 41 pp.

  • Weller, R. A., and R. E. Davis, 1980: A vector measuring current meter. Deep-Sea Res., 27 , 565581.

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Performance of a New Generation of Acoustic Current Meters

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  • 1 Woods Hole Oceanographic Institution, Woods Hole, Massachusetts
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Abstract

As part of a program aimed at developing a long-duration, subsurface mooring, known as Ultramoor, several modern acoustic current meters were tested. The instruments with which the authors have the most experience are the Aanderaa RCM11 and the Nortek Aquadopp, which measure currents using the Doppler shift of backscattered acoustic signals, and the Falmouth Scientific ACM, which measures changes in travel time of acoustic signals between pairs of transducers. Some results from the Doppler-based Sontek Argonaut and the travel-time-based Nobska MAVS are also reported. This paper concentrates on the fidelity of the speed measurement but also presents some results related to the accuracy of the direction measurement. Two procedures were used to compare the instruments. In one, different instruments were placed close to one another on three different deep-ocean moorings. These tests showed that the RCM11 measures consistently lower speeds than either a vector averaging current meter or a vector measuring current meter, both more traditional instruments with mechanical velocity sensors. The Aquadopp in use at the time, but since updated to address accuracy problems in low scattering environments, was biased high. A second means of testing involved comparing the appropriate velocity component of each instrument with the rate of change of pressure when they were lowered from a ship. Results from this procedure revealed no depth dependence or measurable bias in the RCM11 data, but did show biases in both the Aquadopp and Argonaut Doppler-based instruments that resulted from low signal-to-noise ratios in the clear, low scattering conditions beneath the thermocline. Improvements in the design of the latest Aquadopp have reduced this bias to a level that is not significant.

Corresponding author address: Dr. Nelson Hogg, Woods Hole Oceanographic Institution, MS 21, Woods Hole, MA 02543. Email: nhogg@whoi.edu

This article included in the In Honor of Carl Wunsch special collection.

Abstract

As part of a program aimed at developing a long-duration, subsurface mooring, known as Ultramoor, several modern acoustic current meters were tested. The instruments with which the authors have the most experience are the Aanderaa RCM11 and the Nortek Aquadopp, which measure currents using the Doppler shift of backscattered acoustic signals, and the Falmouth Scientific ACM, which measures changes in travel time of acoustic signals between pairs of transducers. Some results from the Doppler-based Sontek Argonaut and the travel-time-based Nobska MAVS are also reported. This paper concentrates on the fidelity of the speed measurement but also presents some results related to the accuracy of the direction measurement. Two procedures were used to compare the instruments. In one, different instruments were placed close to one another on three different deep-ocean moorings. These tests showed that the RCM11 measures consistently lower speeds than either a vector averaging current meter or a vector measuring current meter, both more traditional instruments with mechanical velocity sensors. The Aquadopp in use at the time, but since updated to address accuracy problems in low scattering environments, was biased high. A second means of testing involved comparing the appropriate velocity component of each instrument with the rate of change of pressure when they were lowered from a ship. Results from this procedure revealed no depth dependence or measurable bias in the RCM11 data, but did show biases in both the Aquadopp and Argonaut Doppler-based instruments that resulted from low signal-to-noise ratios in the clear, low scattering conditions beneath the thermocline. Improvements in the design of the latest Aquadopp have reduced this bias to a level that is not significant.

Corresponding author address: Dr. Nelson Hogg, Woods Hole Oceanographic Institution, MS 21, Woods Hole, MA 02543. Email: nhogg@whoi.edu

This article included in the In Honor of Carl Wunsch special collection.

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