ance of the sea surface. The shapes of the power spectra will be 
discussed first at the high frequency end and then at the low fre- 
quency end in terms of what power spectra are possible. This will 
also permit a discussion of the appearance of the sea surface as 
a by-product. 
Equation (11.16) and (11.24) combined with the discussion 
given in the paragraphs on the potential function and the velocity 
field show from equation (11.25) (if [a,( 4 ,0)1° has a series ex- 
pansion) that the constant, C,, must be less than the value given 
in (11.26). For wy, equal to 27, C, must be less than 117,6007r, 
and the largest possible value for the term (when pw equals 27) 
is equal to 117, 6001r/(2r)* or 236 cm* sec. With the above value 
for Cay the power between 27 and 37 as computed irom (11.25) with 
different limits of integration is very nearly 328 cm’, and there 
is little power above the value 37. 
At the high end of the frequency spectrum, then, the spectrum 
must die down in amplitude at least as fast as C,/u 4. For moderate 
values of » , the spectrum can get to be quite high but it must 
always satisfy equation (11.24). 
Equation (11.21) applies to the low end of the frequency spect- 
rum. Especially in the source region, it states that the flow of 
energy across the forward edge of the storm must be bounded. Some 
results from the formulas given in Chapter 9 also apply here. For 
a wave system over a fetch 250 km long, seventeen hours after the 
winds cease, the power spectrum at the edge of the fetch will no 
longer contain values of » less than 21/5. Waves therefore die 
down in the storm area very rapidly as soon as the winds cease 
16 
