Since the surface ducts were practically isothermal the major cause of varia- 

 tion in acoustical velocity within them arose from the increase of pressure with 

 depth. Figures B -5, B-6, B-7, andB-8 show the sonic velocity profiles calcu- 

 lated from the bathythermograph data of both ships obtained at two -hour inter- 

 vals in the two regions . The numbers on the profiles correspond to the position 

 numbers in Figures B-l and B-2. 



Based on these figures, the mean velocity gradients in the surface channels in 

 the two regions were 0.02 sec"-*- in the Boundary Region and 0.013 sec"* in the 

 Transition Water Region. Since the coefficient for the change of sonic velocity 

 with pressure is 0.018 sec"* and since the intrinsic error of the coefficient 

 when derived from bathythermograph measurements in an isothermal channel 

 of 200 feet depth is approximately 0.01 sec" 1 , it is hard to distinguish the 

 acoustic velocity profiles in the two areas . 



Table B-l presents the parameters used in the theoretical computations, the 

 notation being that of Reference (2) . The values were obtained from the velocity 

 profile by a rather gross averaging since the quality and quantity of data did not 

 justify further refinement . 



TABLE B-l 

 PARAMETERS USED IN THE NORMAL MODE CALCULATIONS 



C (ft/sec) Z a (ft) Y (sec _1 ) Yl (sec -1 ) 



Area I 4970.7 207.5 .0201 -.196 



Area II 4965.0 225.0 .0134 -.213 



B-9 



3rtbur Zn.HittlcJnr. 



