Characteristics of Short-term Changes of Infragravity Wave Components Observed along Japanese Coasts

Abstract

The characteristics of infragravity waves are different depending on the frequencies and the sea areas. We analyzed wave height data of four components (30-60s, 60-300s, 300-600s and 600s-) of infragravity waves compiled by the NOWPHAS system. The spectral characteristics of the changes of the longest component (600s-) with the time lapse are very different from those of shorter components. The wave height longevities of the longer components are smaller than those of the shorter components. The wave height longevities in the southern areas are larger than those in the northern areas. When only the longest component develops and the shorter components do not, the significant wave height does not increase.