significantly since there are few unimodal directional distributions at high 

 frequencies (see Figure 23). Compared to Figure 25, it appears that the 

 tendency is for unimodal, high-frequency directional distributions to have 

 peaks more nearly around the shore -normal direction. Overall, however, the 

 differences between Figures 25 and 26 are slight. 



Directional Spread 



218. Figure 27 shows the distribution of directional spreads Ad^ 

 where all data are considered. A distribution of A9 is given for each 

 frequency which is identified through the subscript n . The interest here is 

 how these distributions compare to each other and to the distribution of bulk 

 spread parameter shown in Figure 16. At the low frequencies (except the 

 lowest) in Figure 27, the range of spreads is from about 15 to 50 deg. The 

 peaks of the spread distributions at low frequencies is in the range 25 to 



30 deg. As frequency increases, the range of spreads increases and the peaks 

 in the distributions shift to greater values. At the highest frequencies 

 (bottom row) , spreads range from about 5 deg to 90 deg and peaks in the 

 distributions are in the region 40 to 45 deg. 



219. Compared to the bulk results of Figure 16, where the range was 20 

 to 60 deg and the peak was at 40 deg, it is seen that low frequencies have a 

 narrower range with lower peak values. Higher frequencies have a wider range 

 with slightly higher peak values. In composite, which results in the bulk 

 spread estimates, the ranges and peaks are averaged (by integrating the 

 frequency- direction spectrum with respect to frequency) so that the net result 

 falls between the extremes. At none of the frequencies are the distributions 

 exceptionally different from the bulk result; that is, all spread distribu- 

 tions are single-peaked, most of the cases fall in the range 20 to 60 deg, and 

 most probable spread angles are in the range 25 to 45 deg. 



220. It is noted that here, again, there are very few cases with very 

 small directional spreads. Thus, these wave fields are far from uni- 

 directional, a result consistent with the bulk representation. In the high 

 frequencies at the bottom part of Figure 27, there is a tendency for an 

 increase in the incidence of very broad spreads, with a significant number 

 exceeding 60 deg at the highest frequencies. These large spreads are likely 



91 



