Although there was considerable variability in changes in the 

 vertical angle expressed in the 70th and 50th percentiles - slope, 

 the results show that the 70th percentile - angle varies from 16 to 

 56 minutes. In general the slope becomes a little less when run- 

 ning from San Diego toward Honolulu where the vertical gradients 

 are weaker and the internal waves are larger. The slopes of the 

 deeper isotherm are usually less than the one in the main thermo- 

 cline where the vertical gradients are stronger. The average 

 slope of the latter is around half a degree. 



The slopes of the 50th percentile - slope plotted in the lower 

 part of figure 5 necessarily show lower angles with an average 

 slope of around 16 minutes. This condition undergoes a great deal 

 of variation with a tendency for lower median angles toward 

 Honolulu. 



Autocorrelation of Depth Values 



Another approach to measuring subsurface temperature var- 

 iability is by means of autocorrelation coefficients . By using the 

 same haK-minute isotherm depth data, autocorrelations were com- 

 puted for each leg of the cruise and each selected isotherm. Suc- 

 cessive pairs of points at equal but overlapping time intervals were 

 correlated with each other and the process repeated for each time 

 interval, increasing by one-half minute steps from one half a min- 

 ute to 72 minutes, or 144 lags. Autocorrelation, R^ , was com- 

 puted for increasing intervals. A, of 304 feet (half minute), using 

 the expression: 



(F-A) V i.x. ,- y) X. y; X. , 



^ ' ^-^ I i+X ^^ I ^-' z + A 



1=1 



i-1 



i=l 



#-A 



(F-A) Y, X, - 



i=l 



'n-x 



2 



1 



P. 



Ul, 







li=l J 







N-X 



{N-X) D X. 



1=1 



i + X 



N-X 



Ex 



i=l 



i+X 



where A = 0, 1, 2, 144 lag intervals, N - total number of 



depth recordings in a run. N is usually 1440, and A is 



N_ 

 10' 



16 



