where S(fp) is the peak value of th

where S(fp) is the peak value of the corresponding 1D wave spectrum of a target wave system with a peak frequency fp and SPM(fp) is the peak value of the PM spectrum with the same peak frequency. A wave system is considered to be wind sea if &＞1, illustrating that the wave system meets the condition of the overshoot phenomenon; otherwise, it is swell. The target wave system must be transformed to the corresponding 1D spectrum by integrating over the direction domain before the identification process. It should be noted that this method is based on the condition that a wave system is overshot rather than the wave growth status defined by wave age; thus, the advantage is that it does not require wind information.