Observations and Measurements of Ocean Waves 

 (///L) r ~exp[-(gr/27rr 2 )] 



where v is the wind speed. 



The relation valid for the single wave components 



L== iH 



In 



53 

 (III. 5) 



(III. 6) 



can be substituted for the spectral wave steepness, and from (III. 3) with 

 a = 2tt/T we obtain the spectrum of the wave frequencies: 



2g 2 l 



dU T = W„da = -CggWa-texp 



o-r- 



da . 



(Ill, 6a) 



The constant C [sec -1 ] must be determined, similar to a respective constant 

 in Planck's Law of Radiation, from the total wave energy of the fully arisen 

 wind generated waves for a given wind velocity. Figure 32 shows for three 



005 



0-10 



0-15 



0-20 



0-25 



Fig. 32. Wave spectra for fully arisen sea at a wind speed of 20, 30 and 40 knots, respectively. 



different wind velocities the energy distribution W a =/(c) for a fully arisen 

 sea. The scale of the ordinate is proportional to the square of spectral wave 

 heights. 



Depending upon the wind velocity, the range of wave components with 

 a significant amount of energy covers a more or less broad band on the 

 /-scale, although all periods between and oo are theoretically possible. The 

 examples in Fig. 32 show that the relatively small wave energy, or the re- 

 latively small spectral wave heights for a 20 knot wind cover significant 



