The angular variation 



In order to study the angular variation of the spectrum, the results shown 

 in figure lloZO were employed. Radii at 5 degree intervals were superimposed 

 on the figure by overlays. The plane of the directional spectrum was thus di- 

 vided into small areas bounded by arcs of two circles and two adjacent radii. 

 Two adjacent circles bounded 36 such small areas, and the areas are tabulated 

 in Table H,4. Since the effect of the circles in breaking the squares up into sul^* 

 areas had already been computed, it was not too difficult to compute the effect 

 of the radii since each small area had to have a known value. The percentages 

 which resulted were then multiplied by the appropriate U(r5 s) values and sum- 

 med for each small area. The number thus obtained is an estimate of the con- 

 tribution to the total E value of the short crested sea for spectral components 



1 1 



with frequencies between 2TT{k -— )/96 and 2-ir(k +-^)/96 and with directions be- 



2 ^ 



tween 9 and B + 5° as k varies from 11 through 27 and as varies from -90° 



to +85°. The results of this computation are shown in figure 11.22. The white 

 noise estimate has been removed by subtracting {A/36)(l/800)(1.08) from each 

 value. 



The curves are erratic, mainly due to sampling variation, but there is a 

 rather definite indication of the presence of a swell for curves corresponding 

 to k = 11 through 17. The swell was removed by estimating the shape that the 

 curve would have had, had the swell not been there. 



This estimate is shown by the dashed lines in figure 11.22. Tables 11.6 



and 11,7 show the resolution of the data into frequency and direction intervals. 



201 



