IV. SPECTRA, SPECTRAL SUMMARIES, AND SEA-SURFACE 

 ELEVATION DISTRIBUFION FUNCTION PARAMETERS 



1. High-Energy Wave Spectra . 



Since high-energy spectra are of greatest concern in most engineering 

 applications, plots of individual spectra containing the most energy for 

 each station are provided in Appendix A. Spectra are grouped by gage 

 location in the order listed in Table 1. The appendix includes 24 spec- 

 tra for each location, arranged and numbered in descending order of sig- 

 nificant height. 



Each plot in Appendix A shows the significant wave height, period 

 corresponding to the highest spectral peak, spectral-peakedtiess parameter 

 (Op), and number of major spectral peaks identified by the computer rou- 

 tine SMOOTH (App. D) . Spectral plots for days associated with tropical 

 storms and hurricanes are labeled accordingly. The energy density scale 

 can vary between plots. 



Pressure-gage spectra in Appendix A are cut off at high frequencies 

 above 0.33 hertz for the Great Lakes gages and 0.31 hertz for the Pt. 

 Mugu gage. Several of the Pt. Mugu high-energy spectra were obviously 

 overcon5)ensated for attenuation of pressure with depth so that the high- 

 frequency energy was much greater than the low- frequency energy. These 

 spectra were omitted from Appendix A. This problem can arise because 

 the high-frequency cutoff is constant while the compensation increases 

 as the depth of water over the gage increases with the tide. Thus, the 

 high-frequency end of the spectrum is sometimes overcompensated when 

 water levels are high. This problem did not arise with pressure-gage 

 spectra in the Great Lakes (where there is no tide) . 



Energy computed for wave periods longer than 30 seconds (frequencies 

 less than 0.043 hertz) does not directly represent wind-generated waves. 

 In some cases it is questionable whether such very long-period energy 

 has any physical meaning. Therefore, it was omitted from spectral plots 

 for the Great Lakes and Pacific coast locations and should be ignored in 

 plots for the Atlantic and gulf coast locations. 



Spectral plots for each location in Appendix A are followed by a table 

 which contains auxiliary data for each plot, including sequential number, 

 date, time, significant wave height, peak wave period, water depth, rela- 

 tive water depth (where Ln is the shallow-water wavelength for a wave 

 with frequency equal to the frequency of maximum spectral energy density), 

 ratio of significant wave height to water depth, wave steepness, ratio of 

 depth to gTp (which is related to wavelength) , spectral-peakedness pa- 

 rameter, and skewness and kurtosis of the distribution function of sea- 

 surface elevations. Wavelength used in the tables was computed in each 

 case from period corresponding to the highest spectral peak and the equa- 

 tions of linear wave theory. The largest ratio of significant wave height 

 to depth is 0.54. None of the significant height-to-depth ratios approach 

 the commonly used limit of 0.78. 



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