National Oceanic and
Atmospheric Administration
United States Department of Commerce


FY 2004

Processing of subsurface ADCP data in the equatorial Pacific

Plimpton, P.E., H.P. Freitag, and M.J. McPhaden

NOAA Tech. Memo. OAR PMEL-125, NTIS: PB2004-105254, NOAA/Pacific Marine Environmental Laboratory, Seattle, WA, 41 pp (2004)

Near-surface ocean currents are measured with acoustic Doppler current profilers (ADCPs) in the equatorial Pacific as part of the Tropical Ocean-Atmosphere/Triangle Trans-Ocean (TAO/TRITON) Array. Four equatorial sites at 110°W, 140°W, 170°W, and 165°E are presently maintained by the Pacific Marine Environmental Laboratory (PMEL) using upward-looking 153.6 kHz narrowband RD Instruments' ADCPs. The depths of the ADCP velocity data are determined to an accuracy of 5 m using historical sound velocity profiles and transducer depths computed by three independent methods. The measured ADCP velocities are corrected using sound velocities computed at the ADCP transducer from in situ temperatures and salinities. Data contaminated by sidelobe interference from sea surface reflections are eliminated and the ADCP velocities are mapped by interpolation to standard 5-m depths. ADCP velocities and directions are compared with velocity time series at specific depths collected on nearby surface moorings with EG&G mechanical current meters and with Sontek Argonaut-MD current meters. Mean velocity differences in these comparisons are less than 5 cm s–1 and mean direction differences are less than 5°.

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