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SECURITY CLASSIFICATION OF THIS PAGEfWhan Data Enterad) 



Analysis is done in both the frequency and the time domain. The fast 

 Fourier transform (FFT) spectral analysis procedure is shown to possess limi- 

 tations in resolution of frequency and phase. Phases are shown to be subject 

 to erratic variations. Shortcomings of the FFT procedure are circumvented by 

 using a multiple regression screening (MRS) technique to identify frequency, 

 amplitude, and phase for major constituents in the frequency domain. 



The time domain analysis is designed to extract wave grouping information 

 directly from the time series. A wave group is conceptualized as a small area 

 of sea surface containing relatively high energy. Groups are identified as 

 sections of the time series in which the local variance is high relative to 

 the variance of the complete record. Local variance is computed over a time 

 approximately equal to twice the peak spectral period. Fluctuations in local 

 variance provide information on both the intensity and time scale of wave 

 grouping. A new dimensionless parameter indicative of wave grouping is 

 defined as the ratio of standard deviation of local variance fluctuations to 

 variance of the time series . The autocorrelation between individual wave 

 heights, between periods, and between amplitudes is also considered. The 

 autocorrelation between successive heights ranged from about 0.2 to 0.5. 



Analyses of the data are used to test the following six hypotheses about 

 the nature of ocean waves : 



(a) Spectral components are sometimes discrete and are not smeared 

 over a broad continuous spectrum. 



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

 nonrandom way. 



(c) The detailed spectral shape may be partially explained by the 

 theory of Benjamin and Feir (1967). 



(d) Waves in deep water tend to be organized so that high waves 

 occur in groups . 



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

 the period and steepness of the waves. 



(f) The extent of grouping in each time series and the modulation 

 period are related to certain features of the spectrum. 



Evidence supporting the hypotheses leads to the conclusion that some com- 

 monly held conceptions of ocean waves, including the notion of a random wave 

 field represented by a continuous random-phase spectrum, are open to serious 

 question. 



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