An investigation of wave-induced momentum flux through phase averaging of open ocean wind and wave fields
Citable URI
https://hdl.handle.net/1912/5687Location
Monterey, CADOI
10.1575/1912/5687Keyword
Wave mechanics; Atmospheric waves; Surface wavesAbstract
This thesis presents an investigation of the influence of the dominant, wind-driven, surface
waves on the vertical flux of horizontal momentum in the marine surface layer over open
ocean conditions. Through a procedure which involves phase averaging the wind fields at the
period of the dominant waves, the wave-induced component of the atmospheric fluctuations
is isolated and vertical profiles of mean wave-induced momentum flux are computed.
Previous investigators have used phase averaging to remove the turbulence from an
oscillatory signal, but the absence of a monochromatic wave field in open ocean conditions
complicates this approach. This difficulty is overcome by choosing only the time periods
characterized by the most monochromatic-like waves present and filtering those sections of
wind data with a narrow band-pass filter centered around the dominant wave frequency before
beginning the phase averaging process.
The analysis is carried a step further by investigating the dependence of wave-induced
momentum flux on sea state through bin averaging according to wave age. This results in a
set of profiles which express the ratio of wave-induced momentum flux to the total flux as a
function of the wave age parameter c/U10. These profiles all tend to zero with height, and
remain negligible at all heights over fully developed seas. Over younger seas, this ratio
becomes increasingly more positive (corresponding to a positive value for - uw) with
decreasing wave age; while over older seas, this ratio becomes increasingly more negative
with increasing wave age. This provides strong quantitative evidence that there is a
significant flux of momentum to the atmosphere from decaying waves, and a transfer of
atmospheric momentum to developing waves.
Description
Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 1996
Suggested Citation
Thesis: Wetzel, Suzanne W., "An investigation of wave-induced momentum flux through phase averaging of open ocean wind and wave fields", 1996-09, DOI:10.1575/1912/5687, https://hdl.handle.net/1912/5687Related items
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