isostropy is assumed, then the spectral densities in one hori- 

 zontal direction would represent the spectrum in any horizontal 

 direction; thus the numerical value of slope is the same as for 

 the log-log plot of U(h) vs frequency. 



The slopes were found by visually fitting a straight line 

 through the central part of the log -log points of the power 

 spectrum. The visually fitted curve for section Q data (fig. 35) 

 has a slope of -1.36, which lies close to the -1.67 curve. The 

 data from section Q are approximately average for the area under 

 consideration. The slope values for all the data sections are 

 listed (table 5). 



To obtain an overall plot of power spectrum, 25 sets of data 

 for the shallower isotherm are averaged together and plotted 

 (fig. 36). A similar average power spectrum for the deeper iso- 

 therm is also included. Since these data are for a wide range of 

 towing directions and cover different areas, they may be con- 

 sidered representative power spectrum curves. 



The averaged curves show no distinct peaks in the central 

 part of the limited frequency range (0.05-0. 30 cpm). Both 

 curves have a slope which approximates the -5/3 reference 

 curve, and this close relationship may be indicative of turbulent 

 motion in accordance with the Kolmogorov theory. There are, 

 however, small peaks in both average power spectra around 

 0.15 cpm (0.66 mile) and 0.3 cpm (0.33 mile) in the shallower 

 isotherm spectrum, which indicates these to be the dominant 

 frequencies. Individual power spectrum curves have more sig- 

 nificant breaks in this frequency range, but at varying frequencies, 

 which are nearly smoothed out in the average plot (fig. 36). 



TABLE 5. SLOPE OF LOG-LOG RELATIONSHIP BETWEEN 



POWER SPECTRUM AND FREQUENCY OF DEPTH 

 OF ISOTHERM IN MAIN THERMOCLINE (SHALLOW) 

 AND ISOTHERM BELOW MAIN THERMOCLINE 

 (DEEP) (Continued on page 68) 



Section 



Shallow Iso- 

 therm Slope 

 M 



Deep Iso- 

 therm Slope 



M 



A 



-1.19 



-1.75 



B 



-1.74 



-1.91 



67 



