Section 3.23 and by Kinsman (1965), National Academy of Sciences (1963), 

 and Neumann and Pierson (1966). 



For the distribution of significant wave heights as defined by the 

 data reduction procedures at CERC (Thompson and Harris, 1972), the data 

 fit a modified exponential distribution of form 



fH>h.) = ^ 



"s "s min 



(4-6) 



where Hg is the significant height, Hg the significant height of in- 

 terest, Hg Yrrin is the approximate "minimum significant height," and a 

 is the significant wave height standard deviation. This equation depends 

 on two parameters, Hg ^yi and a which are related to the mean height, 



H = H . + a . (4-7) 



I^ ^s min °^ ° ^^® "°^ available, but the mean significant height, 

 Hg is known, then an approximation to the distribution of (4-6) can be 

 obtained from the data of Thompson and Harris (1972, Table 1), which 

 suggest 



H.^.-„ - 0.38 H^ . (4-8) 



This approximation reduces Equation 4-6 to a one-parameter distribution 

 depending only on mean significant wave height 



f(h^>h> 



1.61 H —0.61 H 



s s 



". 



(4-9) 



Equation 4-9 is not a substitute for the complete distribution function, 

 but when used with the wave-gage data on Figure 4-12, it provides an 

 estimate of higher waves with agreement within 20 percent. Greater 

 scatter would be expected with visual observations. 



4.34 OFFICE STUDY OF WAVE CLIMATE 



Information on wave climate is necessary for understanding local 

 littoral processes. Usually, time does not permit obtaining data from 

 the field, and it is necessary to compile information in an office study. 

 The primary variables of engineering interest for such a compilation are 

 wave height and direction. 



Shipboard observations covering conterminous U.S. coasts and other 

 ocean areas are available as summaries (Summary of Synoptic Meterological 

 Observations, SSMO) through the National Technical Information Service, 

 Springfield, Va. 22151. See Harris (1972) for a preliminary evaluation 

 of this data for coastal engineering use. 



4-35 



