m No. 3i|2 



The 2 m peak rises above the O.5 and 1 m spectrum curves, below 0.25 

 cps . This is indicative that oscillations occurred dioring the different 

 sampling periods which were not stationary. This is further suggested by 

 the mean values of the horizontal component which vary from I3.6 to 21.6 cm 

 sec"l, indicating a low frequency meandering motion. 



The secondary peak is at O.UOO cps (T - 2.5 seconds) and is characteristic 

 of the wind waves observed at the time of measurement. In this wind wave fre- 

 q^uency band and upwards to the cutoff frequency, the spectral density decreases 

 markedly with depth. This shows that the motions in this band (O.^O - 2.50 

 cps or 2.5 - O.k sec period) are of stationary character. In other words, the 

 spectral characteristics of the wind wave motions seem not to have changed 

 over the period of sampling, whereas the lower frequency motions apparently 

 show marked variations or trends. The auto spectra function of the vertical 

 velocity component fw(f ) is similar to the function ^(f ) . The low fre- 

 quency peak again shows indication that slowly varying motions occurred of 

 frequencies in the range from 0.10 - 0.25 cps. 



The wind wave peak occurs at about O.UO - O.5O cps, indicating a slightly 

 lower frequency peak than the U spectra. 



The 0.5 m spectra indicate a lingering of energy existing in the region 

 from the wind wave peak out to the cutoff value of 2.5 cps. That is, the 

 §-[](f) curve for 0.5 m tends to flatten out at a value of O.5 cm^ sec~l between 

 2.30 - 2.50 cps, whereas in this same frequency range the $]j(f) curve drops to 

 about 0.05 cm^ sec~l as seen in figure 10. 



Both sets of spectra indicate the presence of the wind waves at fre- 

 quencies centered at k.O - 5*0 cps and an exponential decrease in the variance 

 contribution at this band. 



Both the variances and spectra of the U and ¥ component at 2 m are similar, 

 This could indicate that at the sea surface the turbulent wave motions cause 

 artificial perturbations on the meters and distort the spectra of the motions. 

 At a deeper depth this gives a truer picture of the wind wave oscillatory 

 patterns. Thus at the depths beneath the O.5-I m levels, means are available 

 for faithfully reproducing gross orbital motions of the particles. 



Wave measiJirements in a variety of meteorological conditions are being 

 continued at Buzzards Bay Entrance Light Station, and further results of 

 these "open ocean" measurements will be reported at a later date. 



Round Hill Field Station of MIT is being funded from MJOS to utilize 

 and study the potential of the Buzzards Tower for making wind stress measure- 

 ments. It is hoped to coordinate wind and wave momentum flux measurements to 

 provide a better understanding of the interactions and transfer of energy 

 between the wind and ocean and hence provide dynamic pressure and acceleration 

 data for the design specifications of high speed vehicle and hydrofoil systems. 



11 



