necessary for wave forecasts to consider the complex nature of 

 ocean waves as they present themselves to an observer at sea. Fur- 

 ther theoretical work and observations well suited to support new 

 ideas are needed to compile the knowledge which may lead us step by 

 step to a satisfactory solution of all the problems about ocean waves 

 and their generation. 



2) Energy transfer from wind to waves 



The energy transfer A from wind to rough ocean waves depends 

 at a given wind velocity upon the pushing and dragging forces which 

 act at the sea surface, and therefore it depends upon the present 

 state of wave development itself. In this way, the actual roughness 

 conditions of the air-sea interface become important with regard to 

 the problem. The effective wind force T may always be split up into 

 a component Z'^ acting normally to the "wavy" interface, and into a 

 component T". acting in the tangential direction, as represented in 

 Fig. 10 which shows a schematic profile of a rough wavy surface. 



At present, it seems very difficult to estimate the real dis- 

 tribution of both of these components (T*., and "C. ) over the wave 

 profile with the necessary degree of accuracy, especially when the 

 rough irregular forms of ocean waves are considered. Therefore, an 

 attempt has been made to split up the resultant effective resistance 

 of the actual rough sea-surface into a "pressure-resistance" and 

 a "friction-resistance." This has been done for practical reasons 

 by considering the smooth form of the wavy air-sea interface and 

 approximating it by a "general wave prof ile"(" Haupt prof il ^>» G. 

 Neumann [8]). The resistance of the "rough" superpositions on 

 this general profile, which would have to be counted as "pressure- 



47 



