Determination of ocean surface wave shape from forward scattered sound

TitleDetermination of ocean surface wave shape from forward scattered sound
Publication TypeJournal Article
Year of Publication2016
AuthorsWalstead SP, Deane GB
JournalJournal of the Acoustical Society of America
Date Published2016/08
Type of ArticleArticle
ISBN Number0001-4966
Accession NumberWOS:000383916100016
Keywordsfield-measurements; profiles; receivers; reflected acoustic pulses; sea-surface; spectra

Forward scattered sound from the ocean surface is inverted for wave shape during three periods: low wind, mix of wind and swell, and stormy. Derived wave profiles are spatially limited to a Fresnel region at or near the nominal surface specular reflection point. In some cases, the surface wave profiles exhibit unrealistic temporal and spatial properties. To remedy this, the spatial gradient of inverted waves is constrained to a maximum slope of 0.88. Under this global constraint, only surface waves during low wind conditions result in a modeled surface multipath that accurately matches data. The power spectral density of the inverted surface wave field saturates around a frequency of 8 Hz while upward looking SONAR saturates at 1 Hz. Each shows a high frequency spectral slope of -4 that is in agreement with various empirical ocean wave spectra. The improved high frequency resolution provided by the scattering inversion indicates that it is possible to remotely gain information about high frequency components of ocean waves. The inability of the inversion algorithm to determine physically realistic surface waves in periods of high wind indicates that bubbles and out of plane scattering become important in those operating scenarios. (C) 2016 Acoustical Society of America.

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