抄録
It is well known that a correlation between infragravity wave heights and the properties of wind waves observed in offshore harbor. Hirasihi et al (1997) have proposed a function of infragravity wave spectrum related to a function of wind wave spectrum by a boundary frequency estimated with parameter: αl. The αl can be estimated with the square root of ratio of infragravity wave energy to total wave energy: RL. In this study, a related function between αl and RL for JONSWAP spectrum is proposed and it is confirmed that an averaged value of αl estimated with spectra observed in storm conditions at each observation station may overestimate the infragravity wave heights in calm conditions. Moreover, the related function between Ursell number and αl proposed Hirayama et al (2014) can estimate them with good accuracy.
