COHERENCE 



To study the spatial coherence of 

 internal waves, two-dimensional hori- 

 zontal thermal measurements are made 

 as the waves move shoreward in the 

 vicinity of the tower. This is done with 

 a circular thermistor array 450 feet in 

 diameter. The temperature signals from 

 the array are recorded on the tower in 

 analog and digital form. 



Several long periods of continuous 

 coherence data have been compiled, to- 

 gether with simultaneous recordings of 

 acoustic transmission loss information. 

 Preliminary analysis indicates that the 

 beam width of the direction of internal 

 wave propagation is about 0.4 radian. 

 Other information reveals that internal 

 waves of high frequency are coherent for 

 distances of over half a wavelength. 



Observation and measurement of 

 the orientation and movement of sea- 

 surface slicks also provide information 

 on the coherence of internal waves. 



Internal wave coherence is investigated with this 

 circular array of 48 sensors. The array is installed 

 in a horizontal plane at mid-depth, 30 feet from the 

 sea floor and 700 feet southwest of the tower. At 

 this location the tower is too far away to affect the 

 internal wave structure. Each sensor is cable- 

 connected to the tower. 



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