MODERN SPECTRAL WAVE HINDCASTING APPLIED TO THE ANALYSIS OF COASTAL PROCESSES

Recent advances in wave modeling and wave hindcasting have had a major influence on coastal engineering design practice. The wind-wave generation model WaveWatch3 (WW3), coupled with 30 years of meteorological data from the re-analysis of the global climate forecast system, gives coastal scientists the ability to develop accurate hindcasts of the wave field at any particular time and any particular place. WW3 models the growth, dissipation, and propagation of the spectral wave energy in each computational cell of an ocean basin domain. The wave field at any given location can be composed of many different wave types over a range of frequencies. Earlier wave propagation models were only capable of outputting one wave height per time step by summing the total energy of the spectrum. To be useful when multiple wave fields are present, spectral wave energy must be separated into its components by the technique of spectral partitioning. Partitioning the spectrum can show multiple wave events existing at the same time and allows a more accurate representation of the sea state.

Applying the partitioning technique to spectral data allows for the identification of low energy swell hidden by energetic short period wind waves. For example, using standard parametric techniques in Hawaii, low amplitude southern swell is typically masked by trade wind waves, or trade wind wave energy is added to southern swell resulting in an overprediction of wave height. The errors that result have a direct effect on quantifying the wave climate that shapes the south shore of Oahu. The partitioned data set may even uncover a source a wave energy that is typically obscured by prevailing conditions.

The partitioned data set is often critical for coastal engineering design analysis. A more accurate representation of the deepwater wave climate leads to improved understanding of the waves that impact a specific area of the coast. Extreme wave height analysis is more accurate, and modeling the transformation of individual spectral components to the shoreline allows a better understanding of these components on coastal processes.