Simulation of Low Energy Waves during Fair-Weather Summer Conditions in the Northern Gulf of Mexico: Effect of Whitecapping Dissipation and the Forcing Accuracy

Abstract

Simulating WAves Nearshore (SWAN) on a structured grid over the Louisiana shelf in the northern Gulf of Mexico is used to evaluate the performance of three different classes of formulations for quantifying wind input and whitecapping dissipation. The formulations include Komen based on the mean spectral parameters, Westhuysen based on the saturation concept of the wave groups, and the most recent observation-based physics package ST6. The evaluation was implemented for two summer months (July and August 2015) to assess these formulations for a low wave energy period. The modeling area consists of the Louisiana inner shelf with the offshore open boundary located beyond the continental shelf. The model was forced using the spatially variable Climate Forecast System Reanalysis (CFSR) wind field and wave parameters obtained from the NOAA’s WAVEWATCH-III (WWIII) model along the open boundaries. Simulated wave parameters and spectra regarding each formulation were evaluated and compared with measured wave data at NDBC stations; comparisons showed that the most appropriate formulation for the simulation of low energy waves for the study area to be ST6. The e performance of each whitecapping formulation was described by examining 1D/2D spectra and the source term balance at different met-ocean conditions during the simulation period. It was also shown that the inaccuracies in the input wind field and boundary conditions can substantially contribute to the model inaccuracy.