Persistence of Wave Heights 



Table C5 shows the number of times in 1992 when the specified wave height was equaled or 

 exceeded at least once during each day for the duration (consecutive days). Data for 1985 through 

 1992 are averaged and given in Table C6. An example is shown below: 



Height 

 m 















Consecut 



ive 



Day(s) or Longer 







1 

 18 



2 



15 



3 



4 

 14 



5 

 13 



6 

 12 



7 



8 

 11 



9 



10 



10 11 12 13 14 15 

 9 8 



16 17 



7 



18 19+ 



0.5 



1.0 



50 



34 



24 



21 



18 



14 



12 



8 



7 



3 2 







1.5 



41 



19 



8 



6 



2 



1 















2.0 



22 



9 



5 



1 



















2.5 



10 



5 



2 





















3.0 



6 



1 























3.5 





1 























4.0 



1 

























This example indicates that wave heights equaled or exceeded 1.0 m 50 times for at least 1 day; 34 

 times for at least 2 days; 24 times for at least 3 days, etc. Therefore, on 16 occasions the height 

 equaled or exceeded 1.0 m for 1 day exactly (50 - 34 = 16); on 10 occasions for 2 days; on 3 

 occasions for 3 days, etc. Note that the height exceeded 1 m 50 times for 1 day or longer, while 

 heights exceeded 0.5 m only 18 times for this same duration. This change in durations occurred 

 because the longer durations of lower waves may be interspersed with shorter, but more frequent, 

 intervals of higher waves. For example, one of the times that the wave heights exceeded 0.5 m for 

 16 days may have represented three times the height exceeded 1 m for shorter durations. 



Spectra 



Monthly spectra for the pressure gage (Gage 111) are presented in Figure C8. The plots show 

 "relative" energy density as a function of wave frequency. These figures summarize the large number 

 of spectra for each month. The figures emphasize the higher energy density associated with storms, 

 as well as the general shifts in energy density to different frequencies. As used here, "relative" 

 indicates the spectra have been smoothed by the three-dimensional surface drawing routine. 

 Consequently, extremely high- and low-energy density values are modified to produce a smooth 

 surface. The figures are not intended for quantitative measurements; however, they do provide the 

 energy density as a function of frequency relative to the other spectra for the month. 



Monthly and annual wave statistics for Gage 111 for 1992 and for 1985 through 1992 are 

 presented in Table C7. 



Figure C9 plots monthly time histories of wave height and period. 



C2 



Appendix C Wave Data for Gage 1 1 1 



