In-situ measurements of the effects of wave breaking on near-surface turbulence
Abstract
Surface waves, and in particular breaking waves, are a critical component of air-sea interaction. They modulate energy and momentum transfer between the atmosphere and ocean, aid in gas transfer, and are a source of aerosols. Wave fields in the open ocean evolve according to the radiative transfer equation, which has three source terms, wind input, non-linear wave-wave interactions, and dissipation. Of these, dissipation is the least well understood, but is thought to be frequently dominated by wave breaking. We present R/P FLIP-based measurements of near-surface turbulent kinetic energy (TKE) dissipation taken during the ONR RaDyO program south of Hawaii in 2009 and the HiRes program off the coast of California in 2010. During these experiments, stereo video of sea surface temperature structure was captured by a pair of long-wave IR cameras. Using particle imaging velocimetry (PIV) on these data, we are able to reconstruct the surface vorticity field. We have developed a new technique to extract TKE dissipation from these vorticity fields which is un-contaminated by the orbital velocities of irrotational waves. An important statistic of breakers, Λ(c), the distribution of crest length per unit area of sea surface as a function of breaker speed c, is measured using both IR and visible imagery. The properly scaled 5th moment of Λ(c) gives a remotely-sensed estimate of dissipation by wave breaking (Kleiss and Melville, 2010), which can then be related to the in-situ TKE dissipation measurements. This comparison will help to better understand the role of breaking in wave dissipation and as a source of ocean surface turbulence, mixing and air-sea fluxes.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.A31C0044S
- Keywords:
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- 4504 OCEANOGRAPHY: PHYSICAL / Air/sea interactions;
- 4568 OCEANOGRAPHY: PHYSICAL / Turbulence;
- diffusion;
- and mixing processes;
- 4572 OCEANOGRAPHY: PHYSICAL / Upper ocean and mixed layer processes;
- 4594 OCEANOGRAPHY: PHYSICAL / Instruments and techniques