Directional Wave Spectra From Heave/Pitch/Roll Data Buoys

Directional wave data measured by the NORWAVE heave/pitch/roll buoys moored on the Norwegian Continental Shelf has been used to consider in more detail the shape and spreading of the directional wave distribution of developing seas and long distance swell trains. The traditional cosine-2s distribution is rejected in favour of a family of wrapped stable distributions. By the use of a simple sufficient test multimodal distributions are found to occur, as expected, most frequently at lower wave frequencies. Simultaneous current measurements have been carried out near to the buoy locations and the effect of local currents on the measured dispersion relation has been studied. Although certain agreement with theory is seen, the presence of other effects shrouds the details making absolute agreement difficult.