Characterization of the high frequency wave spectrum tail measured by a floating lidar buoy

The high-frequency tail of wave spectra derived from motion sensors installed on floating LiDAR buoys is affected by the hydrodynamic response of the platform, which is typically larger and dynamically different from conventional waverider buoys. This reduced motion response leads to an underestimation of short-period wave energy and can bias wave parameters that depend on an accurate representation of the spectral tail. This paper presents a method to identify the frequency range over which this attenuation occurs and to correct the measured spectral density without relying on independent benchmark measurements. The approach is based on a statistical analysis of deviations between buoy-measured spectra and several physically consistent reference spectra, including numerical wave model outputs and parameterized empirical spectra, under carefully selected wind-sea dominated conditions. A correction of the high-frequency tail is formulated using a JONSWAP spectrum for representing the expected spectral decay under the analysed conditions. The correction is applied directly to the measured spectra, and its impact on integrated wave parameters is evaluated. Results show that the correction significantly reduces biases in spectral periods, with mean absolute differences reduced by approximately 26–54% depending on the parameter considered. In addition, wave spectra derived from a seabed-mounted ADCP are analysed to assess their behaviour at high frequencies and their suitability for comparison with surface-based measurements.