Deviations of the wave profile from sinusoidal occur even in deep 

 water for very steep waves as discussed previously. Spectra for such 

 waves can also be expected to show energy at multiples of the dominant 

 frequency. In such cases the spectral form is related to both wave 

 height and period. 



Because of expected systematic influences of wave height and period 

 on the shallow-water spectrum, spectra in this study were grouped into 

 sets by both significant height and period corresponding to the highest 

 spectral peak. Significant height and peak period are convenient because 

 they are comparable to height and period parameters used extensively in 

 past nonspectral wave analyses. 



Despite the groL5)ing, major differences between individual spectral 

 shapes in each set can still occur. Differences between spectra at one 

 location for several cases in which the significant height and peak 

 period were near the annual means are shown in Figure 6. The differences 

 in spectral shape between individual spectra in a set were greater than 

 the differences in the mean spectrum between sets in this study and in 

 Hoffman's (1974) study. However, any systematic characteristics of each 

 set should emerge in the mean spectrum and standard deviation if the 

 number of samples is sufficient. This does not imply that the mean 

 spectra necessarily represent characteristics. 



25,000 



20,000 



E 15,000 



10,000 



5,000 



SYMBOL 



TIME 



DATE 



0643 



26 Nov. 



1968 



204 1 



1 5 jon. 



1969 



0242 



17 Jan. 



1969 



0640 



24 Moy 



1969 



184 1 



25 Moy 



1969 



0042 



27 Moy 



1969 



0.2 0.3 



Frequency {Hz) 



0.5 



Figure 6. Several individual spectra in the same Hg - Tp group 



(Hg = 91 to 122 centimeters; Tp = 8.5 to 9.3 seconds). 

 Nags Head, North Carolina. 



24 



