SEA SURFACE 



x 30 



40 



,7 °;<v* 



SOUND 

 V\ /%, VELOCITY 



VI , L / \ < f P s > 



496 2 



• 16°';* A;\N '« '/ V- V ; \\ ■■ \ 49 



'V\ v . .A.a.ivA, Va\^ 9 , 



- / «. e« \,/- \ 



4954 > 



V> 



4944 



'- • A 



w 



W* v ' WV V\-^^a Va \r~w^ 



4935. 



W^v. 



V W 



1500 



1600 



1700 



1800 



2000 



TIME 



Small scale time fluctuations in sound velocity may be approxi matedfrom detailed thermal 

 structure, such as shown in this recording made in the summer of 1965. Since the salinity 

 range from surface to bottom is very small, the principal controlling factor is temperature. 

 Thus, from the detailed recordings of thermal structure and depth, the sound velocity 

 corresponding to each isotherm may be computed from the known temperature-salinity- 

 depth relationship. Such sound velocity detail is useful in the study of fluctuations in 

 acoustic transmission. 



u 

 10 









WINTER 



SUMMER / 



20 







30 



■ 





40 







50 



/ 



" 



4900 4950 5000 



SOUND VELOCITY (FT/SEC) 



The vertical sound velocity structure, like tempera- 

 ture, changes greatly from summer to winter. Thus 

 different acoustic transmission programs are sched- 

 uled to take advantage of the desired sound velocity 

 condition. 



59 



