properties of a random moving surface can most efficiently be applied by 

 using the moments computed from the corrected spectrum obtained in this 

 study and allowing for the effects of the white noise and coluran errors. 



Winds 



The winds as observed by the R, V. Atlantis were measured by means of 

 a three cup anemometer and a wind vane. The three cup anemometer and the 

 vane were mounted at the end of the main boom above the upper laboratory of 

 the Atlantis at a height of 15 to 18 ft above sea leveL The dial of the ane- 

 mometer was read visually to get the wind speeds. The winds as observed 

 might have been a little high compared to undisturbed measurements over 

 open water due to the presence of the ship. 



The theory of the Neumann spectrum is based on observations of the 

 wind at a height of about 25 feet above the sea level. If a logarithmic wind 

 profile is used with a roughness coefficient of 0,75 cm (Neumann [1948]), 

 and if 15 feet is used for the anemometer height of the Atlantis, the 18.7 

 knot wind becomes a 20 knot wind at 25 feet. It becomes a 19.5 knot wind 

 if 18 feet is used. 



The theoretical spectra for 19 and 20 knots are also shown in figure 

 11,26. On consideration of the confidence bands of the composite spectrum, 

 especially near the peak where there are only 22 degrees of freedom, the 

 variability of the winds during the time when the 18.7 knot average was ob- 

 tained, and the compensating effects of the presence of the ship and the cor- 



249 



