Lagrangian Measurement of Waves and Near Surface Turbulence from Acoustic Instruments

Abstract

We demonstrate high-resolution measurements of upper ocean flow and turbulence using a Lagrangian drifter. A spherical buoy as a quasi-wave following drifter mitigate the contaminations induced by wave orbital velocities and motion-induced disturbances. The platform, with dimensions of 1.13 m diameter and 4.30 m overall length, is modified to include an Acoustic Doppler Velocimeter to measure time series of velocity fluctuations, a GPS logger, two GoPro video cameras to estimate both platform orientation and sea surface topography evolution, and a 5-beam Acoustic Doppler Current Profiler to collect near the surface velocity profiles. Results are reported from a 2-hour test deployment in November 2014, off Karmøy, Norway. This flexible measuring system is designed for a wide range of air-sea interaction studies, including the effect of wave breaking on the upper ocean variability. Such process understanding is of interest for the estimation of loads on fixed and floating offshore structures, and for efficient and optimal design of offshore platforms.