PART VI: BULK DIRECTIONAL CHARACTERISTICS 



179. The most important objective of the present study is to charac- 

 terize the directional properties of the total energy in the set of observa- 

 tions that has been made. This characterization is done with the bulk 

 parameters defined above in two ways: (a) the distribution of a property which 

 indicates its range and most probable values; and (b) correlations between 

 parameters to see how they relate as well as intercomparisons between para- 

 meters for the same property where two definitions have been given (e.g., peak 

 direction and directional spread) . 



Peak Direction 



180. Two parameters were isolated to obtain a general concept of the 

 range and probability of occurrence of the direction of wave approach: 



(a) 9 pD , the direction of the maximum spectral density in the frequency- 

 direction spectrum, S(f,6) ; and (b) ^p.ios > ^^^ direction of maximum energy 

 in the integrated direction spectrum, S(6) . The two parameters are distinct 

 in that the former indicates the direction of the most energetic peak of all 

 frequencies and directions, whereas the latter indicates the direction of 

 dominant overall wind wave energy. 



181. Figure 10 shows the distribution of ^p,FD > computed by summing 

 the number of cases where peak direction fell within discrete direction arcs 

 and normalizing the result by the total number of cases to find the percent of 

 cases in each arc. The directional spectra were already discretized into d^ 

 = 2-deg arcs, and this made a convenient division for the distribution 

 calculation. All 1,046 cases from the first year's collection were con- 

 sidered. At this stage, no distinction was made as to other parameters of the 

 wave field (energy level, spread, etc.) 



182. Figure 10 indicates that peak direction ranges generally across a 

 120 -deg arc from 60 to -60 deg. The main peak in the distribution is in the 

 direction range of 6 to -20 deg, i.e., from roughly shore normal to slightly 

 south of shore normal. This range is consistent with the fact that the 

 observation set is dominated by low- energy, day-to-day sea states. These 

 consist primarily of low- frequency waves which have likely propagated across 

 the continental shelf from the open, deep Atlantic. The shelf break, which is 



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