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Kurt L Polzin

Publications and source records attributed to Kurt L Polzin.

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A One-Dimensional Model for Investigating Scale-separated Approaches to the Interaction of Oceanic Internal Waves

High-frequency wave propagation in near-inertial wave shear has been considered fundamental in setting the spectral character of the oceanic internal wave continuum and for transporting energy to wave-breaking. We compare idealized ray tracing numerical results with metrics derived using a wave turbulence derivation for the kinetic equation and a path integral to study such scale-separated interactions. At small inertial wave amplitudes, all three provide consistent descriptions for the mean drift of wavepackets in the spectral domain and dispersion about that mean drift. Extrapolating our results to the background internal wavefield over-predicts downscale energy transports by an order of magnitude. At oceanic amplitudes, however, the numerics support diminished transport and dispersion that coincide with the mean drift time scale becoming similar to the lagged correlation time scale. Despite this decrease, numerical estimates of downscale energy transfer are still significantly larger than oceanic derived metrics. Our results support replacing the long standing interpretive paradigm of extreme scale-separated interactions with a more nuanced slate of 'local' interactions in the kinetic equation.

physics.ao-ph

Generalized Transport Characterizations for Short Oceanic Internal Waves in a Sea of Long Waves

Internal waves in the ocean interact in triads. Early work emphasized the importance of extreme-scale separated interactions in which two large wavenumber waves interact with one small wavenumber wave. More recent efforts have called this early paradigm into question. We use wave turbulence kinetic equation and the ray-tracing WKB technique to derive two versions of the corresponding Fokker-Planck (generalized diffusion) equation. We then use these Fokker-Planck equations to estimate the spectral energy flux towards dissipation (high wave numbers) we obtain different results: spectral transport of the kinetic equation Fokker-Planck equation is an order of magnitude larger than either observations or reported ray tracing estimates. This apparent contradiction stems from the difference between Eulerian and ray-path descriptions of these scale-separated interactions.

physics.flu-dyn