net result wider than the spread at any given frequency. Hence, ^6ios would 

 tend to be greater than A^gw • 



195. For a bulk characterization, the parameter A^jpg will be used 

 from here on. It characterizes directional spread of the true (uniformly 

 integrated) total energy at the observation site. Since A^s„ is less 

 influenced by variations from frequency to frequency, it tends to miss the 

 full range of directions at which there is significant energy. This property 

 defeats the immediate purpose of characterizing overall directional spread. 



196. Correlations of A^jps with the conventional height, period, and 

 direction parameters are shown in Figures 19, 20, and 21, respectively. In 

 the height relationship (Figure 19), directional spread has its greatest range 

 at small E^^ . Smaller spreads tend to occur in the early stages of wind- 

 generated growth (see Figure 6) and in some cases of swell. Large spreads may 

 be caused by rapidly veering winds or when swell and wind- sea waves coexist 

 but from widely separated directions. These cases are the extremes and 

 generally occur at low energy. An interesting feature of Figure 19 is that 



O ° o 



8 



_o o 



0.0 20.0 40.0 60.0 80.0 100.0 



A0,os (deg) 



Figure 19. Correlation of directional spread with 

 characteristic wave height 



79 



