in local variance, referred to as the LVTS, provide information on both the 

 intensity and the time scale of wave grouping. The LVTS is used to define a 

 new parameter which is indicative of wave grouping. Autocorrelation between 

 individual wave heights is also considered as an indicator of wave grouping. 



Analyses of the selected data from the three sites are used to test six 

 hypotheses about the nature of ocean waves. The hypotheses and the evidence 

 obtained in this study for or against them are as follows: 



( 1) Spectral components are sometimes discrete and are not 

 smeared over a broad continuous spectrum. MRS analysis is used to 

 identify evidence of a fine structure in the spectral representation 

 of ocean wave records. The structure is sufficiently detailed to be 

 transparent to most spectral analysis procedures applied to field 

 records. Thus, the continuous spectra often reported in field stud- 

 ies may be generated by analysis procedures rather than by physical 

 processes. Evidence is also found that the amplitude of MRS constit- 

 uents defining the structure is highly variable in time. 



(2) Spectral components are sometimes related in a deterministic, 

 nonrandom way. MRS constituents with about the same frequency are 

 matched between records from each site. Phases of matched constit- 

 uents show strong evidence of nonrandom behavior. These records 

 provide evidence that the phase relationship among constituents is 

 relatively invariant. 



(3) The detailed spectral shape may be partially explained by 

 Benjamin and Feir's (1967) theory, which provided a theoretical basis 

 for expecting discrete, detailed structure in a spectrum. Frequency 

 spacings between MRS constituents in the swell data are shown to be 

 reasonably consistent with BF theory. The frequency range covered by 

 constituents in the sea data is reasonably consistent with expecta- 

 tions from the BF theory. The amplitude structure is not clearly 

 consistent with BF theory. Also, the variability of amplitude struc- 

 ture between records is not predicted by BF theory. 



(4) Waves in deep water tend to organize so that high waves occur 

 in groups. An investigation of the time series, autocorrelation 

 between individual wave heights and the LVTS, along with a review of 

 the literature, indicates high waves often tend to occur in groups. 

 Evidence also indicates that grouping characteristics can be highly 

 variable over short time intervals. 



(5) The modulation period of wave groups is sometimes related to 

 the period and steepness of the waves. The LVTS is used to show that 

 a modulation period computed from the peak frequency and steepness of 

 the waves is comparable to the time between wave groups, despite con- 

 siderable scatter. Modulation frequency computed by Benjamin and 

 Feir (1967) and by Longuet-Higgins (1980) is shown to compare favor- 

 ably with field data, though closer agreement is indicated with the 

 more refined stability criteria established through a higher order of 

 approximation by Longuet-Higgins. 



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