Analysis of abnormal wave groups in Hurricane Camille by the Hilbert Huang Transform method

The peculiarities of abnormal waves, appearing in a group of high waves are discussed on the basis of comparison with the characteristics of single abnormal waves. The field data are from hurricane Camille. The characteristics of reported abnormal waves and the sea states are reviewed and the appearance of abnormal waves is examined in connection with the group structure of sea waves using the Hilbert Huang Transformation (HHT) method. The HHT decomposition of single abnormal wave and abnormal wave groups has different peculiarities. There is a kind of focusing of decomposing functions at the crest and trough of the symmetrical abnormal waves, while they are phase shifted or out of phase at the trough of asymmetrical single abnormal waves. The time variations of the frequency and energy during the abnormal wave occurrence show that the energy covers wider frequency range in the case of single abnormal wave in contrast to abnormal wave group.