II- 6 



Scattering from the surface of the ocean poses a very different prob- 

 lem. The spectrum of the ocean surface covers a large range of wavelengths. 

 Ordinary ocean waves range in order of magnitude between wavelengths of one 

 meter to those of 100 meters. Small ripples may be of the order of one centi- 

 meter, and tidal waves may be as long as 1000 kilometers. The ocean surface is 

 a stochastic function, varying both in space and in time. A realistic description 

 of this surface involves the space-time spectrum, and the interaction between 

 the spatial and temporal components cannot be ignored. As is well known, sur- 

 face waves of different lengths propagate at different speeds. 



To obtain an understanding of scattering from this surface, one usually 

 studies a very much simplified model. In fact, the most widely used idealization 

 is the reflection of a plane wave from a stationary sinusoidal surface, a problem 

 first posed by Lord Rayleigh. Figure II- 1 shows a plane wave propagating towards 

 the sinusoidal surface. 



Z = h cos p X 







/ 



v; 



^ 



-■ — ^^ y^ ^ 



^\^ ~~- 





t' ■ 



-"// 



\\^\ ^^ 



--^ 



^ 



/ // 



\ \ ^x 



^~^Y2 



cose:«<- / 



/ / 



/ / 



> / 



\ \ 



\ 



' mc 



A— 



/ 



Y-2 



\ 



\ 



Y-1 



\. .,„ 



FIGURE II- 1 SCATTERING OF A PLANE WAVE BY A SINUSOIDAL SURFACE 



S-7001-0307 



