Simulation of wave-current interactions under hurricane conditions using FVCOM: The impact on wave and current fields
The effect of wave-current interactions on both the wave and current fields under hurricane conditions is investigated through the application of the unstructured-grid finite-volume community ocean model (FVCOM) coupled with the unstructured-grid surface wave model (SWAVE) in the North Atlantic Ocean. The model domain ranges from 20oN to 70oN and from 80oW to 30oW, which provides a large enough area to study the progression of wave-current interactions during hurricanes Juan (2003) and Bill (2009), in both deep and shallow waters. Simulations of ocean and wave parameters in each hurricane are shown to compare well with buoy and satellite altimeter observations, in terms of winds, significant wave heights, wave energy spectra and wave directions. Significant modulation of wave-current interactions on significant wave heights shows a dipole-like positive and negative alternative pattern. The effect of currents on significant wave heights is shown to reach 0.4 m for hurricane Juan and 1.0 m for hurricane Bill. The effects of waves on currents is shown to reach 0.5 m/s. Simulation of wave-current interactions is also shown to improve the wave energy spectrum simulation at the peak of the storm, through the comparison with the buoy observations. The default bulk formula for the wind stress in FVCOM-SWAVE coupled model gives increasing values for the drag coefficient with increasing wind speed, while the setting of a limiting cap for the drag coefficient can clearly reduce the overestimation of the maximum significant wave heights at the spectral peak.
Differences of the ratios of the swaths of significant wave heights for FVCOM-SWAVE minus SWAVE, during the passages of (a) Juan (left, unit: %) and (b) Bill (right, unit: %). Circles indicate the hurricane center location every 6 hours; black lines represent 200 m and 2000 m isobaths. Differences less than 0.05 m are not plotted.