Duration-limited growth method for wind sea and swell separation of directional wave spectrum

The separation of wind sea and swell is crucial for advancing wave dynamics research, improving wave forecasting, and optimizing the design of coastal and offshore structures. In this study, we highlight the limitations of the widely used wave age method for separating two-dimensional wind sea and swell. Specifically, under strong wind conditions, waves require extended durations to reach full development—an aspect not accounted for by the wave age method, which assumes fully developed seas and thus tends to overestimate wind sea. Furthermore, changes in wind direction and wave refraction in shallow waters can lead to misclassification. To overcome these issues, we propose a novel algorithm for directional spectral separation, grounded in wind wave growth theory and incorporating wave refraction effects. The proposed method improves separation accuracy and delivers more consistent results across a range of wave conditions.