TRANSMISSION WITH NECATIVE GRADIENTS NEAR SURFACE 



119 



RAY DIAGRAM 



»- 80 



100 



BO 



4680 4930 4980 



SOUND VELOCITY IN FT PER SEC 



DATE 

 TIME 



7-7-1943 



BT CLASS CHARLIE 



WATER DEPTH 610 FM 



SEA 



SWELI 



WIND 



2000 4000 6000 



RANGE IN YARDS 



Figure 35. Sample transmission anomaly plot. 



creases linearly with range out to long ranges. Sample 

 types of these two curves are shown in Figures 34 and 

 35, respectively. With each figure is included a 

 smoothed temperature-depth plot and a correspond- 

 ing ray diagram. 



The relative number of straight-line anomaly 

 curves for different hydrographic conditions has been 

 investigated." The number of straight-line graphs 

 was found for different values of the temperature dif- 

 ference from to 30 ft and for different values of the 

 computed limiting range at the hydrophone depth 

 used. The results of this study are given in Table 1. 

 The accuracy with which observed curves could be 

 fittted by straight lines has already been discussed in 

 Section 5.2 where the high probability of straight-line 

 graphs in isothermal water was also pointed out. 



The classification of bathythermograms into 

 MIKE, CHARLIE, and NAN patterns on the basis 

 of the temperature difference from to 30 ft has al- 

 ready been discussed in Section 5.1.4. These patterns 

 are indicated in Table 1; the dividing line between 

 NAN and CHARLIE patterns, usually defined as 

 1/100 of the surface temperature, is about 0.7 F for 



Table 1. 

 graphs. 



Relative number of straight-line anomaly 



