Separation of wind sea and swell from nearshore ocean wave spectra

Coexistence of wind sea and swell often results in double-peaked spectra. Separation and identification of the wave energies of wind sea and swell from the measured spectra allow us to have a more realistic description of the sea state, which is of great importance to offshore structure design, safety of marine operation, and the study of wind wave dynamics. This paper describes a method based on the peak frequency of a steepness function to separate the wave energies of wind sea and swell from the omnidirectional wave spectra. Using the PM spectral model for the wind sea spectrum, the separation frequency is derived from the peak frequency of the steepness function. This steepness method does not rely on the availability of the information of wind velocities and wave directions and can be easily implemented for operational uses. Verification results using wave data collected of Seoguipo in Korea are presented.