Ocean Wave Spectra and Shtp Appltcattons 
probabilities were higher for the case of Ty = 15 sec. These were 
~1.5 percent and ~ 21 percent for a=0.4C and 0.1C, respecti- 
vely. 
Recently, Webb Institute analyzed a group of wave records 
measured at weather station I L°]. Preliminary unpublished results 
from these newly analyzed data indicate that the idealized two-para- 
meter spectral form does not agree well with the measured spectra. 
Figure 5 illustrates how the wave energy is improperly dis- 
tributed over the frequencies in the idealized spectrum when it is 
compared against the measured wave spectrum. The solid curve in 
the figure is the average measured spectrum calculated from some of 
the recently analyzed spectra Z . The other curves are the corres- 
ponding average idealized spectra calculated from three different de- 
finitions of T, as follows 
a = =T,(1) , 
(exore 
0 
oo 
en | —S,(w) dw 
WwW 
M 0 DASE T I: | 
hs ee) 26. 847 acy 
| Sp(w) d 
0 
co 
1 
f spte) a 7/2 . 
7 
eee, Ol | ee eee ———— = 
Dy le _ ety ad a 
0 
For an idealized spectrum, T, (1), T(-1), and T,(2) are the same 
by their definition. However, for a measured ocean spectrum the va- 
rious T,'s can be different. The differences reflect the departure of 
ESS 
