When considering the growth of the sea under the influence of 

 wind action, many possibilities of generation have to be taken into 

 accoimt. It happens very often that the wind encounters an "old 

 sea," has to destroy it (or partly destroy it) and to generate a 

 new wave motion. Therefore, allowances must be made for waves that 

 are present when the wind starts blowing. Or, in another case, the 

 wind may increase with time and the "sea" grows slowly with this in- 

 creasing wind speed. However the simplest case is where the wind in 

 the generating area is constant in time and space and begins to 

 blow over an undisturbed water surface. First we shall assume a 

 wind field of constant velocity and direction in the following con- 

 siderations. 



The present approach to wind waves forecasting deals with the 

 growth of the complex sea in the area of wave formation depending 

 upon the wind velocity, the stretch of water over which the wind 

 has blown (the fetch), and the length of time the wind has blown 

 over the fetch (the duration). A first attempt was made to take 

 into account the composite nature of wind generated waves as in- 

 dicated in Chapter I of this paper. It seems that the development 

 of composite wind generated wave motion from small steep waves to 

 the case of fully arisen sea is not a continuous process. Discon- 

 tinuities are to be expected in certain states of composite wave 

 formation, because the relatively short "sea" is to be found as a 

 characteristic steep, breaking wave in all further stages of ocean 

 wave patterns up to fully developed sea. Probably we have to assume 

 these rather steep, breaking waves in all higher stages of develop- 

 ment so that longer waves with a higher amount of energy may be 



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