Abstract
Accelerometers, which can be installed inside a floating platform on the sea, are among the most commonly used sensors for operational ocean wave measurements. To examine the non-stationary features of ocean waves, this study was conducted to derive a wavelet spectrum of ocean waves and to synthesize sea surface elevations from vertical acceleration signals of a wave buoy through the continuous wavelet transform theory. The short-time wave features can be revealed by simultaneously examining the wavelet spectrum and the synthetic sea surface elevations. The in situ wave signals were applied to verify the practicality of the wavelet-based algorithm. We confirm that the spectral leakage and the noise at very-low-frequency bins influenced the accuracies of the estimated wavelet spectrum and the synthetic sea surface elevations. The appropriate thresholds of these two factors were explored. To study the short-time wave features from the wave records, the acceleration signals recorded from an accelerometer inside a discus wave buoy are analysed. The results from the wavelet spectrum show the evidence of short-time nonlinear wave events. Our study also reveals that more surface profiles with higher vertical asymmetry can be found from short-time nonlinear wave with stronger harmonic spectral peak. Finally, we conclude that the algorithms of continuous wavelet transform are practical for revealing the short-time wave features of the buoy acceleration signals.
Highlights
Wind-generated gravity waves are among the most significant phenomena on the ocean
We aim to develop a complete procedure of wavelet-based algorithm which is capable of obtaining a wavelet spectrum and sea surface elevations from buoy acceleration records
Accelerometers, which are commonly used in the airline industry, are among the most useful sensors for ocean wave measurements
Summary
Wind-generated gravity waves are among the most significant phenomena on the ocean. the mechanics and features of these types of waves are highly complex and random because of the combined influences of meteorological, hydrological, oceanographic and topographical factors.Studies of wind-generated gravity waves have continued ever since their contributions to water wave mechanics were recognised more than a century ago. Wind-generated gravity waves are among the most significant phenomena on the ocean. The mechanics and features of these types of waves are highly complex and random because of the combined influences of meteorological, hydrological, oceanographic and topographical factors. Studies of wind-generated gravity waves have continued ever since their contributions to water wave mechanics were recognised more than a century ago. To increase our practical knowledge of wind-generated gravity waves field measurements must be performed, but most measurement sensors are only suitable for use nearshore or in shallow water areas. Apart from remote sensing devices, moored buoys and vessels are the only platforms suitable for wave measurement in deep water areas [1]. Data buoys have been the most popular means of operational wave monitoring since the 1970s [2]
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