A wavelet-based test for swell stationarity

The temporal behaviour of swell is examined using the wavelet transform, and a test of stationarity using the wavelet transform is described. The method is demonstrated on time series data from a Directional Waverider buoy deployed at Duck, North Carolina, and it is shown that non-stationary sea states are usually associated with local wind-sea growth rather than significant changes in the swell component, which can be considered stationary for at least as long as the 160-min records. This is close to the 3-h duration that is typically assumed for a stationary sea state. The stationary character of swell is an important result for offloading from an LNG barge to carrier.