casting sea state are based essentially on the earliest American re- 

 port on a method for forecasting sea and swell by H, U. Sverdrup and 

 collaborators In 194-2, later revised and published by H, U. Sverdrup 

 and W. H, Munk [l]. Its publication stimulated further investiga- 

 tions of wind and sea state relationships, so that more comprehensive 

 empirical data were soon available. 



' Upon surveying the results of investigations up to the present, 

 we find a lack of knowledge with respect to certain aspects, sometimes 

 as it seems, to basic problems. There is the question of the 

 "characteristic" waves, or those waves existing at a certain wind 

 velocity when the sea is fully arisen, and also on the period, wave 

 length and height of waves. First, we must know the characteristic 

 pattern under different conditions at a sea surface which has complex 

 wave motion. The definition of the "significant wave" given by Sver- 

 drup and Munk is not very satisfactory. It is a statistical defin- 

 ition which takes merely a certain average for the highest waves and 

 approximately the wave length of the longest wave present at the sea 

 surface. The steepness of these waves, when fully developed, is 

 about 1:46 (ratio of wave height to wave length), but there are much 

 steeper waves present with a velocity of propagation smaller than 

 the wind velocity. These characteristic "seas" cause the broken 

 appearance of the sea surface and obscure to a large degree the 

 presence of longer and flatter waves. 



Furthermore, there are some questions about the energy transfer 

 from wind to waves and about the growth of the waves under the action 

 of wind. What type of pattern of sea surface (wave heights and 

 lengths) is to be expected when a wind of a certain mean velocity 

 has blown over the sea surface for one, two, three or more hours? 



