K 



24 12 8 6 



7 

 6 



5 - 



4 - 



3 - 



2 - 



1 - 



•— PERIOD (HR) 

 3 2 



1.5 



1.2 



_ 



1 1 



7'"" 1 I 1 i 



1 1 1 



1 1 1 1 1 1 1 1 



1 



_ 



\\^ 







.... DRIFT <;TATI0M 1 



_ 



npiFT STATION 1 



DRIFT STATION 3 



- 



\ Y; 

 \ W 



\\\ 









- 



- 



\\ 



\\ 



\\ 



\ 



\ 







- 



- 





ts^ 







- 



- 





1 



^^^^vr:^-^ 









1 



1 



10 

 HARMONICS 



15 



20 



Figure 5. Meon amplitude spectrum for the upper 780 meters at Drift Stations 1, 2, and 3- 



Drift Stations 2 and 3 



In October 1963, USS MARYSVILLE studied the situation closer to the 

 coast by making measurements with the thermistor chain at Drift Stations 2 and 

 3, near Sixty Mile Bank. Each observation was 24 hours long (2145 hours to 

 2130 hours, 15-16 October; 2345 to 2330, 16 - 17 October) . In the first 

 measurement the drift was about 15 miles in 24 hours (approximately 32 cm/sec) ; 

 in the second, drift was negligible. Doppler shifting appeared to be very small 

 in the tidal range. Representative hydrographic data for both stations are 

 given in table 2. 



Each isotherm was subjected to a harmonic analysis. Their mean depths 

 were 32, 40, 45, 49, 56, 76, 102, 142, and 173 meters. The sampling rate was every 

 15 minutes. Mean values of the computed amplitudes, A^ , are shown in figure 5 

 as a function of the harmonics (lower scale) or the periods (upper scale). It can 

 be seen from these_curves that the tidal periods govern the spectrum. We get 

 mean amplitudes, A^ , of about 6 meters for both the diurnal and semidiurnal in- 

 ternal tides in the upper 180 meters, and this is in good agreement with station 

 1. For comparison, figure 6 shows the predicted tidal curve at San Diego, 

 California, from 10 to 17 October 1963. The tides are mainly diurnal at the 

 beginning and strongly semidiurnal at the end of the period. It therefore seems 

 reasonable to expect internal tides of both periods to be present at all times, 



30 



