of the maximum echo strength received at a constant range. Measure- 

 ments were made both on the first field trip by the writer and again 

 during the latter part of the field work by personnel experienced with the 

 procedure. The fluctuation amplitude of these measurements agreed in 

 both cases and the results of the latter observations are shown in figure 

 26. The bottom curve is the top curve normalized to a constant range of 

 1.3,150 yards by equation (2). The mean deviation, regardless of sign, for 

 these 24 normalized observations is 1.9 decibels. During the observation 

 period the wind increased from 16 kts at 1230 to 20 kts at 1400, and de- 

 creased to 8 kts at 1500. There is a slight correlation between the weather 

 conditions and the trend of the fluctuations and it is believed that a change 

 in the path-gain factor can partly account for the increased amplitude of 

 fluctuations between 1400 and 1500. A comparison of the observations of 

 figure 20 with those made by the Radiation Laboratory, Massachusetts 

 Institute of Technology, indicates that these fluctuations are certainly 

 within the expected magnitudes. It is concluded that, although the 

 measurement procedure is at best rather coarse, major trends in prop- 

 agation anomalies and changes should be detected by the technique 

 of matching the echo observed over a 30-second period. This time 

 series indicates, also, that the time-space fluctuation of an iceberg- 

 echo is comparable to that from a ship. The micro scintillations were 

 not measured. 



* _ 



40 — 



O CD 



UJ Q 



30 



5^40 



"■as 



30 



1600 



I'm ; i hk •_'('). — Time scries observations of reflected power at near constant range and 

 aspect from an ice formation. Curve A is the actual observation, B the 

 change in station on the target, and (' the power curve normalized to 

 constant, range. 



60 



