Further analysis of the 17 horizontal-temperature-gradient 

 fields (obtained from the smoothed temperature structures) pro- 

 vides added support for the existence of a dominant frequency of 

 oscillation. More than 600 wavelength measurements at two 

 depths throughout the 17 horizontal gradient fields were made and 

 the mean wavelength was found to be 0.72 mile ( f= 0. 14 cycle 

 per minute) with a standard deviation of 0. 07 mile. The horizon- 

 tal bars in the histogram of figure 12 display the mean wavelength 

 for each of the 17 sample areas, and the vertical lines show the 

 mean wavelength and the standard deviation as derived from the 

 ensemble averages . It should be observed that the mean wave- 

 length (0.72 mile) for all the sample areas is in good agreement 

 with the results of the spectral analysis (0.67 mile) for Cruises 4 

 and 8. However, the histogram gives no indication of the shorter 

 wavelengths (0.4 and 0.3 mile) as shown in the average spectral 

 curves for Cruises 4 and 8. 



These results indicate that there is a dominant frequency 

 of oscillation in the thermal structure of the ocean with a wave- 

 length of about 0.7 mile. The frequency spectrum under investi- 

 gation here indicates that this result combined with the relation 

 of the magnitudes of the vertical and horizontal gradients could 

 be utilized as the foundation for a simplified predictive model of 

 the horizontal-temperature gradients of the sea. The consistency 

 of these results over widely separated geographic areas leads to 

 the speculation that they are characteristic of the world ocean. 



27 



