Some work on persistence of surface channels has been carried out from 



BT measurements (Reference 10) and several surveys of the deep sound 



channel have been referenced. The main requirement for such surveys 



is that the instruments used are accurate and have a good depth capability, 



to at least 5000 meters. This accuracy must be good in both the relative 



sense, to ensure that -r- is known, and the absolute sense. In such 

 dz 



survey work much valuable information could be obtained on various problems 

 such as horizontal variations, interfaces, internal waves and the sea 

 bottom. For surveys, temperature and salinity should be measured as well 

 as sound velocity. SVTP systems are commonly used. 



D. Problem Areas 



1. The velocity of Sound in Ocean Patches 



It is well known that while the temperature variations in the 

 vertical direction tend to exhibit a layer structure, the horizontal 

 variations, due to the turbulence in the upper layer, are more in the 

 nature of random patches. The patch size spectrum ranges from diameters 

 of the order of the layer depth (i.e., about 50 meters) to small diameters 

 which correspond to the dissipation of the thermal structure by molecular 

 heat conduction. Details of the temperature variations are given in 

 References 10, 11; generally a dominant patch diameter of the order of 

 twice the measurement depth is noted until the thermocline depth is 

 reached. The temperature fluctuations are generally less than 1°C but 

 may be sufficiently large to be of the order of 1 - 2°C. The spectrum 

 of patch size apart from the largest might be expected to follow the well 

 known Kolmogorov distribution law for turbulent eddies. 



13 



Arthur ZD.IUttleJnr. 



