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J. R. Gemmrich, T. D. Mudge, and V. D. Polonichko

Abstract

A basic model relating the energy dissipation in the ocean mixed layer to the energy input into the surface wave field is combined with recent measurements of turbulent kinetic energy dissipation to determine the average phase speed of the waves acquiring energy from the wind. This phase speed and the square root of the corresponding wavelength are proportional to the vertically integrated dissipation. The calculations show that the maximum energy input occurs at the high-frequency end of the wave spectrum. Dissipation data from other investigators are used to estimate the effective phase speed between 0.55 and 0.72 m s−1 and corresponding wavelengths varying between 0.2 and 0.33 m for the waves receiving most of the energy.

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Michael L. Banner, Christopher J. Zappa, and Johannes R. Gemmrich

Abstract

There has been a recent upsurge in interest in quantifying kinematic, dynamic, and energetic properties of wave breaking in the open ocean, especially in severe sea states. The underpinning observational and modeling framework is provided by the seminal paper of O. M. Phillips. In this note, a fundamental issue contributing to the scatter in results between investigators is highlighted. This issue relates to the choice of the independent variable used in the expression for the spectral density of the mean breaking crest length per unit area. This note investigates the consequences of the different choices of independent variable presently used by various investigators for validating Phillips model predictions for the spectral density of the breaking crest length per unit area and the associated spectral breaking strength coefficient. These spectral measures have a central role in inferring the associated turbulent kinetic energy dissipation rate and the momentum flux to the upper ocean from breaking wave observations.

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