On the determination of the upper limit frequency of infragravity waves

Abstract

Due to significant contribution of infragravity (IG) wave to coastal hydrodynamics, a number of studies have been carried out on the mechanisms of generation and development of IG waves. Along with deep understanding on the mechanisms of IG waves, accurate estimation of IG wave energy is crucial for clarifying various coastal processes. For estimating IG wave spectrum from observed data, it is required to specify the frequency range of IG waves. In case of the lower limit frequency of IG wave, the value between 0.003 Hz and 0.005 Hz is typically used. Meanwhile, the upper limit frequency has been chosen between 0.033 Hz to 0.05 Hz, primarily depending on location and prevalence of either wind wave or swell. Onthe east coast of Korea, selection of the lower limit frequency is not an issue if it is in that range. In contrast, wave height of IG wave largely depends on the upper limit frequency. Hence, it is necessary to propose an adequate guideline for determining the upper limit frequency of IG wave based on thorough analysis of the observed wave data. Using the data observed from multiple locations on the east coast of Korea over the years, we examined the adequacy of separation of spectral energy between IG wave and sea-swell bands to determine an upper limit frequency of IG wave. We applied the value of the upper limit as either constant or adaptively varying related to peak frequency of sea-swell band. Then compa