HAMILTON: TIME VARIATIONS OF SOUND SPEED OVER LONG PATHS IN THE OCEAN 



DISCUSSION 



Dr. A. O. Sykes (Office of Naval Research) : What do you read for 

 the cutoff on the records in Figure 11? 



Mr. Hamilton: You go through a learning cycle to determine what 

 fits the data and gives nice results [ laughter] . If the delta range 

 is large in data such as this, the sources of error are few: 1) the 

 shot boat position and the SOFAR detonation depth/time in the trans- 

 ponder array; 2) the SOFAR charge did not sink vertically; 3) the 

 SOFAR signal cutoff timing; 4) something in the physics of sound trans- 

 mission is not understood. It was never necessary to use either 2 

 or 4 to explain away inconsistent data. 



Dr. D. C. Stickler (Applied Research Laboratory) : Can you 

 speculate about the origin of the six-month period in your sound-speed 

 program? 



Mr. Hamilton : There has been a recent series of papers by Jacobsen 

 of RPI in JASA discussing ocean Rossby waves and their effect on acous- 

 tics. Rossby waves are similar to the 200nm diameter eddies seen by 

 the Mid-Ocean Dynamics Experiment in 1974 between Bermuda and the 

 Bahamas. That six-month variation is about the period of these 

 eddies as they move westward a few kilometers per day. 



Dr. Sykes: How far apart in time were the pre- and post- SOFAR 

 shots used to calibrate the missile impact area? And how closely do 

 the speeds correlate? Is it a matter of a day or so? 



Mr. Hamilton : No, they were approximately two hours before and 

 after missile impact. 



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