In general, wind sea refers to wave

In general, wind sea refers to waves that are still being developed by wind or are very near to the area they were generated. While swell are waves that have propagated away from the generating region, or when the phase velocities are higher than the wind speed, far from the effect of the wind that caused them (Ewans et al. 2004;Holthuijsen 2007; Semedo et al. 2009). Separation and identification of complex wave conditions into wind sea and swell provide us with detailed wave information that is important to both scientific research and engineering applications. Wind seas are generated locally and receive momentum from the wind in their growing process;therefore, a proper estimation of the wind sea is required for the study of wind sea dynamics, validating wave models, and air–sea interaction. With the slow energy attenuation rate, swells radiating from tsunamis or storms can travel long distances across the globe ocean;can have great significance on human activities such as nearshore structure design, marine operations, offshore industry, and coastal management; and may cause sensible beach erosion (Doong and Kao 2007; Ardhuin et al.2009; Kumar et al. 2011; de Farias et al. 2012).