The investigation of these patches has always been with the thermal 

 transducers, although several attempts have been made to correlate this 

 data with observed fluctuations in acoustic transmissions due to scattering 

 by the patches (e.g., References 11, 12). 



The question arises as to whether a knowledge of the distribution 

 of sound speed in these patches would be of value and whether current 

 velocimeters are suitable instruments to investigate them. 



The patches cause a transmitted acoustic signal to fluctuate 

 in intensity by + 6 db due to scattering. However, the distribution 

 and size of the patches are functions of both space and time. Thus, it 

 seems unlikely that any finer data would be of value in a tactical situation. 



For scientific or survey purposes, two problems arise in 

 measuring the sound velocity in patches. These are 



1. Most currently used instruments measure during vertical transects. 

 How could they be adapted to measure the horizontal changes? 



2. How can the spatial and temporal behavior of the patches be 

 distinguished and recorded. 



It seems quite feasible to adapt current instruments to such 

 studies by towing at fixed depths. One variation would be to use a 

 velocimeter together with an isotherm follower system and measure changes in 

 velocity along an isotherm. The ship velocity would necessarily be quite 

 low. Another possibility would be to use free-swimming vehicles such as 

 the University of Washington Applied Physics Laboratory Self Propelled 

 Underwater Research Vehicles, already equipped to perform this task. The 

 time response of the instruments appears perfectly adequate for all 

 likely spatial or temporal rates of change of temperature or salinity. 



14 



artbur 2D.Hittle.3htr. 



