thumbnail

Accuracy of a pulse-coherent acoustic Doppler profiler in a wave-dominated flow

Journal of Atmospheric and Oceanic Technology

By:
and
DOI: 10.1175/1520-0426(2004)021<1448:AOAPAD>2.0.CO;2

Links

Abstract

The accuracy of velocities measured by a pulse-coherent acoustic Doppler profiler (PCADP) in the bottom boundary layer of a wave-dominated inner-shelf environment is evaluated. The downward-looking PCADP measured velocities in eight 10-cm cells at 1 Hz. Velocities measured by the PCADP are compared to those measured by an acoustic Doppler velocimeter for wave orbital velocities up to 95 cm s-1 and currents up to 40 cm s-1. An algorithm for correcting ambiguity errors using the resolution velocities was developed. Instrument bias, measured as the average error in burst mean speed, is -0.4 cm s-1 (standard deviation = 0.8). The accuracy (root-mean-square error) of instantaneous velocities has a mean of 8.6 cm s-1 (standard deviation = 6.5) for eastward velocities (the predominant direction of waves), 6.5 cm s-1 (standard deviation = 4.4) for northward velocities, and 2.4 cm s-1 (standard deviation = 1.6) for vertical velocities. Both burst mean and root-mean-square errors are greater for bursts with ub ??? 50 cm s-1. Profiles of burst mean speeds from the bottom five cells were fit to logarithmic curves: 92% of bursts with mean speed ??? 5 cm s-1 have a correlation coefficient R2 > 0.96. In cells close to the transducer, instantaneous velocities are noisy, burst mean velocities are biased low, and bottom orbital velocities are biased high. With adequate blanking distances for both the profile and resolution velocities, the PCADP provides sufficient accuracy to measure velocities in the bottom boundary layer under moderately energetic inner-shelf conditions.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Accuracy of a pulse-coherent acoustic Doppler profiler in a wave-dominated flow
Series title:
Journal of Atmospheric and Oceanic Technology
DOI:
10.1175/1520-0426(2004)021<1448:AOAPAD>2.0.CO;2
Volume
21
Issue:
9
Year Published:
2004
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Atmospheric and Oceanic Technology
First page:
1448
Last page:
1461
Number of Pages:
14