Comparison of Two Types of Wave Buoys: Linear and Second-Order Motion

Wave data from oceanographic buoys remains indispensable in offshore and coastal engineering. Modern wave buoys can produce semi-Lagrangian time histories of motion in three dimensions (one vertical and two horizontal) in addition to the standard statistical output. A recent study (Ding et al., 2023) reveals that, while the three translational motions of a wave buoy are dominated by the linear components, there is significant nonlinearity in the horizontal plane. This study uses field data from the Southern Ocean off Albany, Western Australia, measured from four closely spaced buoys: three Sofar Spotters and a Datawell Directional Waverider-4. The measured time histories measured by the different types of wave buoys in three orthogonal directions and the relationship between them have been systematically investigated, for the first time. Significant second-order components in both vertical and horizontal directions are observed.