hindcasts. In this way the poor initial conditions improved as time 

 duration became a part of the output and as the swell was gradually 

 introduced into the computations. 



In addition to this problem, results obtained from the original 

 machine program indicated that there were the following problems needing 

 solution: 



1. A better spectral model 



2. A better growth function for 3-tLOurly intervals 



3- A proper assumption for the natiire of the high-freq.uency end of 

 the spectrum 



k. A proper dissipation function for the spectrum. 



Taken together these four problems would make a formidable task for 

 any individual effort but by a team assault they were all finally 

 solved so that the end product gave acceptable though not perfect results. 



After having tried several different spectral models, the new non- 

 directional spectrum developed at New York University was programmed and 

 showed very good results for the Eastern Worth Atlantic Ocean when com- 

 pared to the wave observations taken by shipborne recorders on weather 

 ships. Also later tests with weather ships wave observations in the 

 Western Atlantic and with wave staff observations at Argus Island gave 

 similarly good results. 



To determine the proper growth function it was first necessary to 

 use an equation for the maximum spectrum that could be generated, assuming 

 an infinite fetch, infinite dixration, and certain directional effects 

 found in other studies. ^'^•' The form of the equation used was 



(9) A2(f, d ) = _Ci__ expf-CgD^] 4f4«..0-*-r0.5 + 0.82 e:q) 

 2 TT f !? ^ -' I. '• 



(-0.5D" )7 cos( 0.03^^9065 p-j_) + 0.32 exp (-0.50"^) cos (O.O69813 fi)! 



for 90°— /p,|and zero otherwise and 



where D = I9 . 08 



2TffVI^ 



P]_ : direction from the wind direction 



Af - incremental frequency 



J^9 = incremental direction 



f = frequency in cycles per second 



Vig.R = wind speed in knots at 19*5 ni height 



Ci and C2 = constants 



36 



