Ocean science news, explainers, and statistics covering marine environments, currents, climate, coasts, seafloor research, and the changing global ocean.
Deep-water and shallow-water waves are classified by comparing water depth with wavelength, not by judging whether the sea looks deep or shallow. A wave behaves as a deep-water wave when depth is greater than half its wavelength. It behaves as a shallow-water wave when depth is less than one-twentieth of its wavelength. Between those limits…
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Significant wave height is the average height of the highest one-third of waves measured during a sampling period. It is reported from trough to crest and commonly appears as “seas” in marine forecasts. The value summarizes the larger part of an irregular wave field, but it is not the maximum wave that can occur. The…
Average wave period summarizes the broader mix of waves recorded during a sampling interval. Dominant wave period identifies the period associated with the strongest peak in the wave-energy spectrum. The numbers can differ because the ocean usually carries several wave systems at once, with energy spread across many frequencies rather than concentrated in identical crests.…
Wave height measures the vertical distance from a trough to the next crest. Wavelength measures the horizontal distance between matching points on successive waves, usually crest to crest or trough to trough. One describes how tall a wave is, while the other describes how widely its repeating shape is spaced across the water. The two…
