FALSE WAVES IN WAVE RECORDS

A methodology to define discrete waves from free sea surface elevation time series is presented. The method allows an objective discriminati on of false waves among small waves, avoiding the use of arbitrary cri teria associated with zero-up-crossing, zero-down-crossing, or other d efinitions. The method uses the Hilbert Transform and the representati on of the time series in the complex plane. A discrete wave correspond s to a 2pi phase-advance in the complex plane. The waves between zero crossings which do not show a 2pi phase advance are considered false w aves. Wave rider buoy records, measured off the west coast of Portugal , were employed in assessing some of the statistical implications of t his methodology.