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On the skewness of sea-surface elevation

Published online by Cambridge University Press:  21 April 2006

M. A. Srokosz
Affiliation:
Institute of Oceanographic Sciences, Wormley, Godalming, Surrey, England, and Department of Applied Mathematics and Theoretical Physics, Silver Street, Cambridge
M. S. Longuet-Higgins
Affiliation:
Institute of Oceanographic Sciences, Wormley, Godalming, Surrey, England, and Department of Applied Mathematics and Theoretical Physics, Silver Street, Cambridge

Abstract

Surface skewness is a statistical measure of the vertical asymmetry of the air-sea interface – exemplified by the sharp crests and rounded troughs of surface gravity waves. Some authors have proposed a constant ratio between surface skewness and the ‘significant slope’ of the waves. Here it is shown theoretically that no such simple relation is to be expected.

Wave records are of at least two different types; Eulerian (as made with a fixed probe) or Lagrangian (as with a free-floating buoy). The corresponding statistical properties are examined. At first sight it might appear that the degree of skewness in corresponding records would be different. However it is shown that to lowest order the skewness is invariant; only the apparent mean level is different, at second order.

Type
Research Article
Copyright
© 1986 Cambridge University Press

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