Semi-empirical dissipation source functions for ocean waves: Part I, definition, calibration and validation

New parameterizations for the spectra dissipation of wind-generated waves are proposed. The rates of dissipation have no predetermined spectral shapes and are functions of the wave spectrum and wind speed and direction, in a way consistent with observation of wave breaking and swell dissipation properties. Namely, the swell dissipation is nonlinear and proportional to the swell steepness, and dissipation due to wave breaking is non-zero only when a non-dimensional spectrum exceeds the threshold at which waves are observed to start breaking. An additional source of short wave dissipation due to long wave breaking is introduced to represent the dissipation of short waves due to longer breaking waves. Several degrees of freedom are introduced in the wave breaking and the wind-wave generation term of Janssen (J. Phys. Oceanogr. 1991). These parameterizations are combined and calibrated with the Discrete Interaction Approximation of Hasselmann et al. (J. Phys. Oceangr. 1985) for the nonlinear interactions. Parameters are adjusted to reproduce observed shapes of directional wave spectra, and the variability of spectral moments with wind speed and wave height. The wave energy balance is verified in a wide range of conditions and scales, from gentle swells to major hurricanes, from the global ocean to coastal settings. Wave height, peak and mean periods, and spectral data are validated using in situ and remote sensing data. Some systematic defects are still present, but the parameterizations yield the best overall results to date. Perspectives for further improvement are also given.Comment: revised version for Journal of Physical Oceanograph

Global to Channel Scale Water Level Forecasting and Analysis

A multi-step process to creating better grids and to get to a global tidal model for ADCIRC 1. Process of merging shoreline databases together for better mesh development. 2. High resolution optimal meshes for the US East and Gulf of Mexico coasts 3. Hindcast of Hurricane Irma using ADCIRC + SWAN (to learn about how system performs) 4. Development of 30m and 120m meshes for the US East and Gulf Coasts 5. ADCIRC global tidal model developmen

Direklesende ontledingsmetodes vir die edelmetale

Tesis (M. Sc.) -- Universiteit van Stellenbosch, 1964.Full text to be digitised and attached to bibliographic record

Physics of 'saturation-based' dissipation functions proposed for wave forecast models

The dissipation term is one of the three most important source functions of the radiative transfer equation employed by all spectral wave models to predict the wave spectrum. In this paper, the issue of physics of such dissipation functions is discussed. It is argued that the physics presently utilized in the models do not adequately describe currently known features of the wave dissipation process, and the dissipation functions, to a great extent, remain a residual tuning term in spite of important experimental progress in wave breaking studies. A recently suggested 'saturation-based' dissipation function and its connections with the experimental physics are analyzed in detail

Extra-Tropical Multi-Model Guidance: Winter Storm Riley 2018

Extra-Tropical Multi-Model Guidance for Winter Storm Riley, 201

Nonlinear waves on collinear currents with horizontal velocity gradient

Analytical and experimental research of wave dynamics on adverse and following currents with horizontal-velocity gradient, was conducted. Laboratory tests were carried out at the Tainan Hydraulics Laboratory of the National Cheng Kung University of Taiwan, where a special setup aimed at accelerating/decelerating currents was designed, constructed and employed. In the case of accelerating adverse currents, the wave behaviour is strongly nonlinear and leads to downshifting of the wave energy which allows the waves to penetrate the blocking current. For the case of decelerating currents, linear behaviour should lead to amplification of wave amplitude and increase in steepness, which is indeed observed, but downshifting also happens if the initial waves are steep enough. Such results point out to the physics which is presently not accounted for in wave forecast models

Operational forecasts of wave-driven water levels and coastal hazards for US Gulf and Atlantic coasts

Abstract Predictions of total water levels, the elevation of combined tides, surge, and wave runup at the shoreline, are necessary to provide guidance on potential coastal erosion and flooding. Despite the importance of early warning systems for these hazards, existing real-time meteorological and oceanographic forecast systems at regional and national scales, until now, have lacked estimates of runup necessary to predict wave-driven overwash and erosion. To address this need, we present an approach that includes wave runup in an operational, national-scale modeling system. Using this system, we quantify the contribution of waves to potential dune erosion events along 4,700 km of U.S. Atlantic and Gulf of Mexico sandy coastlines for a one-year period. Dune erosion events were predicted to occur at over 80% of coastal locations, where waves dominated shoreline total water levels, representing 73% of the signal. This shows that models that neglect the wave component underestimate the hazard. This new, national-scale operational modeling system provides communities with timely, local-scale (0.5 km resolution) coastal hazard warnings for all wave conditions, allowing for rapid decision-making related to safety and emergency management. The modeling system also enables continued research into wave-driven processes at a broad range of coastal areas