for some of the differences at the frequencies above 0.11 hertz. The Wave-Track 

 results show a problem in defining directions in the lower frequency range. The 

 extent of the frequency range for this problem seems to vary from run to run. The 

 authors believe this is due to the hydrodynamic phase lag reflected primarily in 

 the tilt channels. This lag may be greater for the longer waves that have a 

 smaller orbital differential over the depth of the buoy than for shorter waves. 



The spreading angles of the directional waves for the buoys can be seen in the 

 lower graph of these figures. The spreading for the Wave-Track buoy data is con- 

 sistently high in the lower frequency range, including the peak frequency at times. 

 The spreading then drops to a lower level, still above that for the WAVEC data, in 

 the middle frequencies. Finally, the spreading increases in the upper frequencies. 

 A reasonable amount of spreading occurs in a range around the peak frequency for 

 the WAVEC buoy data. Different spreading functions were used to calculate WAVEC 

 and Wave-Track spreading angles. 



The high level of spreading in the lower frequencies of the Wave-Track data may 

 be due to the buoy's response to non-unidirectional orbital velocities in the long 

 waves. Forrestal, et al. noted a complicated flow field in a large wave during 

 Hurricane Delia. Three current meters were strung in the water column. The upper 

 current meter measured the greatest horizontal velocities to be in the east-west 

 direction; however, the velocities in the north-south direction were not negli- 

 gible. The velocities can flow in a horizontally eliptical manner, and so the 

 corresponding movement of the buoy stem can be in an eliptical manner, rather than 

 linearly unidirectional. 



This trial provided two opportunities to measure changing sea conditions over 

 periods of several hours. In the first case, for Runs 10-25, wave data were 

 measured from 0820 to 18U3 on 15 May 1982. Middle frequency waves were coming out 

 of the west (250-270 degrees) throughout the day, while some higher frequency wind 

 driven waves were coming from the south (180-190 degrees). As the day progressed, 

 the energy in the mid frequencies generally increased, with some fluctuations, 

 until the last run. The energy in the waves that were closely aligned with the 

 wind, i.e., south, continued to increase, with a corresponding increase in period. 

 This can also be seen in the directions, as the ramp between the west and the 

 south shifts to the left and becomes less steep. This is more clearly seen in the 

 mean directions of WAVEC data than the Wave-Track data. 



11 



