Wolff, Tatro, and Megehee 



completely, however, in the Mediterranean or any other area where the 

 water conditions approach isothermal and a half-channel sound velo- 

 city profile results. Possibly the addition of a deeper temperature 

 parameter will allow the extension of this system to cover these cases. 



EFFECTS OF CURRENT BOUNDARIES 



Near current and water mass boundaries the horizontal gradients 

 of temperature and salinity, and thus sound velocity, become quite 

 large. To investigate the effects of these large local gradients, a 

 highly detailed cross -section of the Gulf Stream taken with 

 expendable BT's by Sippican and the Woods Hole Oceanographic 

 Institution was digitized into 71 profiles. Figure 14 shows the cross 

 section used, and the locations of the sources which were initially 

 considered. Sources 1 and 2 were in a cold secondary front which 

 extended up to about 150 meters. Sources 3 and 4 were taken on the 

 warm side of the Main Gulf Stream wall and run through the wall. 

 Source 4 was also run away from the wall into an area of fairly homo- 

 geneous water. Sources 5 and 6 are on the cold side of the main wall 

 and were also run through the wall. In all cases, a convergence zone 

 was formed; however, they were generally broader and more diffuse 

 than the well defined zones found in an area of horizontal homogeniety, 

 and in many cases did not reach the surface. Figure 15 shows the 

 convergence zone formed from source 4 running through the Gulf 

 Stream wall. On this plot the depth scale is from to 2000 feet 

 rather than to 500 as before. The convergence zone formed is a 

 subsurface one at approximately 25 nautical miles. Figure 16 shows 

 a run from the same source in the opposite direction. In this case a 

 surface convergence zone is formed at 33.7 nautical miles. 



CONCLUSIONS 



Based on the Ray Trace runs which have been described here and 

 others of a similar nature, the following conclusions have been 

 drawn: 



1 . The micro-structure in the sound velocity profile is 

 essentially self-cancelling. It does not affect the convergence zone 

 parameters . 



2. In areas of reasonable horizontal homogeniety it is possible 

 to predict convergence zone range by empirical methods if the 

 temperature structure is known. 



3. In areas of high local horizontal gradients, convergence 



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