TRANSMISSION THROUGH A THERMOCLINE 



117 



< 



o 



z 

 < 



lA 

 l/> 



z 

 < 



20 



40 



I HYDROPHONE DEPTH tiS30 FT 



II 50 Sh -=100 FT 



in IOOSh<200 FT 



IV 200* h«300 FT 



V 300Sh£400 FT 



I 



1000 2000 



RANGE IN YARDS 



3000 



Figure 30. Average transmission anomalies for iso- 

 thermal layer 40 to 80 feet thick. 

 



20 



40 



I HYDROPHONE DEPTH h= 



II 50= h -100 FT 

 in' I00 = h-=200FT 



IV 200Sh-=300FT 



V 300ShS400 FT 



I I I 



30 FT 



1000 2000 



RANGE IN YARDS 



3000 



Figure 31. Average transmission anomalies for iso- 

 thermal layer more than 80 feet thick. 



the thermocline, is significantly lower than curves IV 

 and V, with the hydrophone between 120 and 360 ft 

 below the top. Curve II apparently combines some 

 runs with the hydrophone above the layer with 

 others below the layer and is thus intermediate be- 

 tween curve I (hydrophone in the isothermal layer) 

 and curve III (hydrophone below top of thermocline). 

 In Figure 31, curves III, IV, and V agree with each 

 other, and apparently represent an average anomaly 

 curve for a hydrophone below the thermocline. In 

 agreement with equation (13), the anomalies are not 

 so great as those found for a hydrophone just below 

 a shallow layer. An analysis relating the average trans- 

 mission anomaly below a thermocline to changes in 

 the depth and sharpness of the thermocline might 

 give more useful information than can be obtained 

 with the temperature code used in Figures 30 and 31. 



5.3.5 Transmission at 60 kc 



The only other frequency for which data are avail- 

 able on transmission below the thermocline is 60 kc. 



RANGE IN YARDS 

 1000 2000 3000 



4000 



o 



UJ 



o 



o 



z 

 o 



z 

 < 



Figure 32. Average transmission anomalies at 60 kc, 

 above and below thermocHne. 



1000 2000 



" o RANGE IN YARDS 



Figure 33. Difference in transmission 

 above and below thermocline. 



3000 



anomalies 



The average transmission anomalies both in the 

 isothermal water above the thermocline and in the 

 thermocUne are shown in Figure 32. The difference 

 between these curves at 1,000 and 2,000 yd is plotted 

 in Figure 33; for comparison, the corresponding dif- 

 ferences at 24 kc are also shown, which were taken 

 from Figure 24. On the ray theory, these two curves 

 should be identical if do is the same for the two fre- 

 quencies, since the increased divergence resulting 

 from downward bending should be independent of 

 frequency. The agreement between the 24-kc crosses 

 and the 60-kc circles in Figure 33 is not too close; 

 however, such a comparison of data cannot be reliable 

 unless the measurements were made under similar 

 thermal conditions. 



