6.6 On the variation of the effective breaking strength in oceanic sea states

Tuesday, 16 August 2016: 2:45 PM
Lecture Hall (Monona Terrace Community and Convention Center)
Christopher J. Zappa, Columbia University, Palisades, NY; and M. L. Banner, R. P. Morison, and S. E. Brumer

A spectral framework for quantifying the geometric/kinematic and dynamic/energetic properties of breaking ocean waves was proposed by Phillips in 1985. Phillips assumed a constant breaking strength coefficient to link the kinematic/geometric breaking crest properties to the associated excess energy and momentum fluxes from the waves to the upper ocean. However, a scale-dependent (spectral) breaking strength coefficient is needed, but is unavailable from measurements. In this paper, the feasibility of a parametric mean effective breaking strength coefficient valid for a wide range of sea states is investigated. All available ocean breaking wave data sets were analyzed and complemented with wave model behavior. Robust evidence is found supporting a single linear parameter relationship between the effective breaking strength and wave age or significant wave steepness. Envisaged applications for the effective breaking strength are described.
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