Turbulent structure under short fetch wind waves

Abstract

Momentum transfer from wind forcing into the ocean is complicated by the presence of surface waves. Wind momentum and energy are partitioned into wave growth, wave breaking, and wave forcing of the ocean surface layer. The purpose of this study was to support the ONR Coupled Boundary Layers and Air-Sea Transfer program by making very high spatial resolution profile measurements of the 3-D velocity field into the crest-trough region of wind-forced surface gravity waves, and study the low-frequency turbulent motions below the waves. The overarching goal is to improve model parameterization of how momentum is imparted on the ocean via wind-driven processes. At the Salinas River, in California, the Bistatic Coherent Acoustic Doppler Velocity Profiler and Thies Clima Ultrasonic 3-D Anemometer were deployed to capture the above-surface and subsurface velocity fields simultaneously to explore three main objectives: 1) determine the wave energy decay with depth and confirm the wavenumber, 2) determine the observed wind stress and calculate the wind stress using a bulk formula to identify any variations as a result of this estuarine environment, and 3) determine the turbulent stresses in the water column below the waves, and confirm the presence of Langmuir circulations and determine their advection and scaling.