Application of S-Transforms to the Study of Modulational Interactions of Waves

Records of storms in the North Sea are analyzed for evidence that wave groups may be composed of independently propagating components. The Stockwell transform (S-Transform) is used to obtain time-frequency contour plots of wave energy for simulated idealized, interacting wave groups. Additionally, simulated groups with independent directional components, are analyzed using both the S-transform and the Iterative Maximum Likelihood Method to resolve the directions and frequency. Both techniques are applied to the analysis of North Sea storm data obtained from a 3-point array showing that real wave groups can be formed of interacting components that may be propagating in different directions.