Researchers

Jim Thomson

Principal Oceanographer

AIRS Department

APL-UW

Associate Professor, Civil and Environmental Engineering

Joe Talbert

Field Engineer II

AIRS Department

APL-UW

Alex De Klerk

Field Engineer I

AIRS Department

APL-UW

Chris Bassett

Research Assistant

AIRS Department

APL-UW

Michael Schwendeman

Research Assistant

AIRS Department

APL-UW

Seth Zippel

Research Assistant

AIRS Department

APL-UW

Curtis Rusch

Research Assistant

AIRS Department
APL-UW

Funding

NSF

ONR

SWIFT

Surface Wave Instrument Float with Tracking

Measuring Waves, Winds, Turbulence, and Ambient Noise at the Ocean Surface

The Surface Wave Instrument Float with Tracking (SWIFT) is a free drifting system to measure waves, winds, turbulence, and ambient noise at the ocean surface. A key feature is the ability to move with the wave motion, thereby maintaining a near-surface range and filtering the wave orbital velocities. SWIFT is being used in studies of breaking wave energy dissipation, wave–ice dynamics in the Arctic, and characterization at marine energy sites.

Wave breaking dissipation observed by SWIFT drifters

Thomson, J., "Wave breaking dissipation observed by SWIFT drifters," J. Atmos. Ocean. Technol., 29, 1866-1882, doi:10.1175/JTECH-D-12-00018.1, 2012.

More Info

1 Dec 2012

Energy dissipation rates during ocean wave breaking are estimated from high-resolution profiles of turbulent velocities collected within 1 m of the surface.The velocity profiles are obtained from a pulse-coherent acoustic Doppler sonar on a wave-following platform, termed a Surface Wave Instrument Float with Tracking, or "SWIFT", and the dissipation rates are estimated from the structure function of the velocity profiles. The purpose of the SWIFT is to maintain a constant range to the time-varying surface and thereby observe the turbulence in breaking crests (i.e., above the mean still water level). The Lagrangian quality is also useful to pre-filter wave orbital motions and mean currents from the velocity measurements, which are limited in magnitude by phase-wrapping in the coherent Doppler processing. Field testing and examples from both offshore whitecaps and nearshore surf breaking are presented. Dissipation is elevated (up to 10-3 m2 s-3) during strong breaking conditions, which are confirmed using surface videos recorded onboard the SWIFT. Although some velocity contamination is present from platform tilting and heaving, the structure of the velocity profiles is dominated by a turbulent cascade of eddies (i.e., the inertial sub-range). The noise, or uncertainty, in the dissipation estimates is shown to be normally distributed and uncorrelated with platform motion. Aggregated SWIFT measurements are shown to be useful in mapping wave breaking dissipation in space and time.

More About This Research

Videos + Websites

Graduate student researcher Seth Zippel tests SWIFT performance in arctic waters in advance of planned missions during the Marginal Ice Zone experiments in 2014.

Wave field observations at the Columbia River bar by SWIFT drifters from the R/V Oceanus. A video by Micha Hilliard, narrated by Jim Thomson.

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