Skip Navigation
USGS - science for a changing world

Woods Hole Coastal and Marine Science Center

The Massachusetts Bay Internal Wave Experiment, August 1998: Data Report

Skip navigational side bar

ADCP Corrections

The current observations at Site B made with the bottom-mounted upward-looking Acoustic Doppler Current Profiler (ADCP) differ significantly from currents measured by the point current meters during periods when the short-wavelength internal waves are present, except within about 20 m from the instrument (Scotti and others, 2005). These periods are flagged with high error velocities, defined as the difference between the vertical velocities estimated from each pair of beams, by the standard ADCP algorithm. The algorithm assumes that the current field is spatially uniform over the distance separating the beams, and combines data from opposite beams to determine the horizontal and vertical velocities. The ADCP fails to correctly determine the components of the velocity in earth coordinates during passage of the short-wavelength internal waves because the standard algorithm combines beam components that, at a given time, are sampling different phases of the wave, violating the assumption of spatial homogeneity. However, the individual velocity measurements in beam coordinates are uncorrupted. Scotti and others (2005) show that measurements from the four spatially-diverging beams and the backscatter intensity signal can be used to calculate the propagation direction and celerity of the internal waves. Once this information is known, a modified beam-to-earth transformation that combines appropriately lagged beam measurements can be used to obtain current estimates in earth coordinates that compare well with point current measurements made by the FSI and VMCM current meters.

The following MATLAB .mat files contain corrected ADCP current observations for 2-hour intervals following the start of each internal wave event.

Site B Lagged Data Site C Lagged Data

The following .nc files contain corrected ADCP current observations for 2-hour intervals following the start of each internal wave event, merged into the original file with data from periods with no internal waves.

Site B (All Times) Site C (All Times)

Jump to top of page
Return to field experiment. Go on to sediment texture.
Skip Navigation

Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo USAGov logo U.S. Department of the Interior | U.S. Geological Survey

URL: woodshole.er.usgs.gov/pubs/ds-85/WEBPAGES/adcp_errors.html
Page Contact Information: WHSC Webmaster
This page last modified on Monday, 24-Nov-2014 11:29:02 EST