99.93 



8 10 12 14 16 18 20 30 



Wave Height, Crest to Trough, ft 



Fig. 13 Distribution of the Heights of Ocean Waves at Weather Station C, 52° N 37° W, North Atlantic 



Ocean 



(This distribution is based on 12,365 observations naade over a period of 4'A yr by U.S. Weather Bureau personnel.) 



volving only a change in scale from the distribu- 

 tion of periods, Fig. 14. 



Observations of significant wave heights in 

 the Pacific Ocean made by merchant vessels 

 have also been studied (13). Although these 

 data are not as extensive or systematic as the 

 Weather Bureau data for the North Atlantic 

 Ocean, the indication is that the cumulative 

 distribution functions of significant wave heights 

 in the Pacific Ocean are approximately log 

 normal. 



The log-normal distribution of "significant" 



wave heights may be thought of as a distribution 

 of E where each value of E corresponds to a defi- 

 nite sea state which may be alternatively speci- 

 fied by a significant wave height, if it may be 

 assumed that the Rayleigh distribution holds for 

 the distribution of individual wave heights in a 

 given sea state. This assumption appears to be 

 justified (11). On the basis of this assumption it 

 is possible to arrive at the long-term distribution 

 of wave heights (as apart from significant wave 

 heights) in accordance with the following ap- 

 proach. 



19 



