Table XII. Mean velocities (cm/sec) for various depths 

 computed using Helland-Hansen's technique 



* These velocities were northward. 



and 9538 or 9543 and 9544. Drogue number 

 6 passed between stations 9537 and 9538 or 

 9543 and 9544. Drogue 7 was set to the west 

 of drogue number 6 and it drifted between 

 stations 9536 and 9537 or 9542 and 9543. Be- 

 cause the density distribution changed in the 

 time interval between the occupation of sta- 

 tions 9535 and 9540 and stations 9541 and 

 9546, the average drogue velocities were com- 

 pared with the dynamic height anomalies and 

 the corresponding velocities from both occupa- 

 tions. 



Reid (1963) stated that drogues should be 

 tracked for more than 48 hours before the 

 velocities are compared with the geostrophic 

 flow because of the short period fluctuations in 

 flow and positioning errors. Although the 

 maximum time interval that a drogue was 

 tracked was 9 hours, it is felt that a meaning- 

 ful comparision can be made since the hori- 

 zontal position errors were small. 



DISCUSSION 



As indicated in Figure 32, the dynamic to- 

 pography changed significantly from 16 to 18 

 April 1966. This caused the variations observed 

 in the volume transports. The radar ranges 

 and bearings taken on the drogues and the 

 reference buoy insured that the position errors 

 and hence uncertainty in calculating both the 

 drogue and geostrophic velocities were mini- 

 mized. Because of this, the average drogue 

 speeds and the calculated geostrophic velocities 



have been directly compared. The average 

 drogue speed was calculated by averaging the 

 drogue speed without considering the direc- 

 tion. It was recognized that velocity is a vector 

 quantity and should be averaged in compon- 

 nent form and the averaged components then 

 used to form the average velocity vector. It 

 was felt that the added accuracy was not com- 

 mensurate with the added complexity involved. 

 The speeds have been arthmetically averaged 

 and no weighting has been done to compensate 

 for difi'erent observational time intervals. 



Drogues 1 and 2 were set approximately 12 

 hours after stations 9536 and 9537 were oc- 

 cupied and approximately 36 hours before sta- 

 tions 9542 and 9543 were occupied. The 

 trajectories of drogues 1 and 2 and the velocity 

 information in Table 6 indicate a rather 

 strong (40cm/sec) southerly flow. This is not 

 as indicated by the dynamic heights calculated 

 for stations 9536 and 9537. The occupations 

 of this section 36 hours later showed a weak 

 (llcm/sec) velocity southward. The last 

 drogue velocities measured indicated a velocity 

 of 21cm/sec and 14cm/sec respectively for the 

 15 meter and 40 meter drogues. Initially the 

 geostrophic velocity did not correspond to the 

 measured velocity in this case, but at the end 

 there was an indication that dynamics were 

 adjusting to indicate a velocity similar to that 

 measured. 



Drogue 5 was anomalous because it indicated 

 the highest velocity (120cm/sec) and had the 

 highest average velocity (81cm/sec). The other 

 100 meter drogue had an average speed of 

 56cm/sec compared with a calculated geo- 

 strophic current of 47cm/sec. 



Hence the agreement between drogue 6 and 

 the geostrophic current was considered satis- 

 factory, and the agreement between drogue 5 

 and the calculated currents was considered to 

 be poor. Drogue 5 was observed for only 4 

 hours, and it was set approximately 23 hours 

 before the oceanographic observations were 

 taken from which the velocity calculations 

 were done. The agreement between the average 

 velocity of drogue 5 and the 100 meter 

 geostrophic velocity calculated between sta- 

 tions 9537 and 9538 was also poor. Drogue 

 5 apparently measured some irregular motion. 

 The average speed of drogue 7 agreed satis- 

 factorily with geostrophic velocities computed 



23 



