In most of the generation cases studied, the time deriv- 

 ative in the energy balance equation was small compared with 

 the convective term. By dimensional arguments, Kltaigorod- 

 skii (1962) has shown that the nondimensional wave spectrum 



E(fu*/g) = g~^u^(f) should reduce in this case to 

 a universal function of the nondimensional fetch 



X = (fetch) '9/^* > where the friction velocity 



u^ = (momentum t transferred across the air-sea 



interface/density of air) . The dependence of the scale 



A , 



parameters on x is shown in Fig. 4. Note that a de- 



A 



creases with x , m contrast to Phillips' original dimen- 

 sional argument, which predicts a universally constant a 

 This is in accordance with the interpretation of the source 

 function given below which indicates that the f depen- 

 dence in this part of the spectrum is not dominated by white 

 capping, as assumed by Phillips, but rather by a balance 

 between the energy Input from the atmosphere and the energy 

 transfer to other wave components through wave-wave inter- 

 actions . 



The shape parameters showed considerable scatter, but 

 no systematic variation with fetch [5]. VJlthin the uncer- 

 tainties of this variability (attributed to the gustiness of 

 the wind), the wave spectra could be regarded as self simi- 

 lar over the range of fetches of the experiment. 



The smoothed dependence of the five spectral parameters 



A 



on nondimensional fetch x defined a mean evolution of 



25-13 



