obtained for this single, fixed frequency component over a range of wind speeds. 

 From these data it was possible for the first time to evaluate quantitatively the rela- 

 tive Importance and correctness of the wave growth theories previously mentioned . 

 The results supported the resonance theory of Phillips. They also showed that the 

 instability theory of Miles predicted rates of wave growth that were almost an order 

 of magnitude too low. 



The final condition is the one met by this work. Expanding on (ill). It is 

 sufficient that the wind field be at least weakly stationary over a reasonably large 

 region that encompasses the locations at which observations are to be made. The 

 amount of time, t, during which the wind should have been stationary depends on 

 the frequency component to be observed and the fetch distance at which the observa- 

 tion is to be made. This quantity may be apprc»<imated by the equation 



t= d (3) 



Vg(<-) 



with d equal to the maximum fetch distance for which the <»"-component would be 

 fully developed and both d and t » (Phillips, 1958a). For all frequencies which 

 satisfy (3) whose time for full development is less than that given by (3) with d 

 ando* given, equation (1) reduces to: 



Vg(<r,*) • V*F(o-,«^;^=G(o- ,<^,^. (4) 



By considering only the steady state fetch limited c«e, we have reduced the data 

 necessary to evaluate a and to F ( o" , '^,'x) and W (x). Without the aid of an 

 inordinate number of ships and/or oceanographic buoys, collection of even these data 

 would seem a formidable and, in fact, nearly impossible task. However, the relatively 

 fast (200 knot) airplane-altimeter arrangement provides on estimate of F (a , "P, "x), and 

 by working with uniform wind fields W (x) is reduces to W. Both of these simplifications 

 involve certain assumptions that will be justified in later sections. 



It is appropriate here to compare the work of Snyder and Cox (1 966) with the 

 present effort. Both experiments are similar In their intent and approach. Both obtain 

 their raw data from a moving platform and hence have their theoretical base in the 

 work of St. Denis and Pierson (1953) and Cartwright (1963). Both eventually arrive at 

 a final estimate of spectral growth. These estimates are logically compared by both 

 sets of authors against the predictions of various theories. Here the similarity ends. 

 Snyder and Cox observe, with relatively good accuracy, the growth of a single frequency 

 component over a range of wind speeds. On the other hand this work observes simultan- 

 eously the growth of a number of frequency components under a single wind condition. 

 The two sets of measurements essentially represent the Eulerian and LaGrangian view 

 poirui. A!?*^ dissimilar is the way in which the final estimates of spectral growth ore 



