that for very short waves energy can be rapidly transferred 

 to higher wavenumbers through gravity-capillary interactions, 

 which satisfy the Bragg resonance conditions already at 

 second order (cf. Phillips, I966). In this case, the energy 

 sink could be viscosity acting on extremely short waves. 

 Estimates indicate that this could remove all the energy 

 supplied to the wave field for wind speeds up to a few m/s , 

 but at higher winds energy is presumably lost over a broader 

 band of wavenumbers through white capping. The resolution 

 of these questions is fundamental for the application of 

 microwave techniques , which sense primarily the very short 

 surface waves and are therefore critically dependent on the 

 ability to predict the energy level in this wavenumber range 

 as a function of the wind-sea spectrum and the local wind 

 speed. 



6. STATISTICAL DESCRIPTION OF BACKSCATTER 



In order to discuss further the implications of wave 

 dynamics for the remote sensing problem, we first review 

 briefly the concepts and models developed to interpret 

 microwave measurements of the sea surface. It is found 

 that these models lead naturally to the same questions that 

 arose in the consideration of the wave energy balance. For 

 simplicity, we restrict the discussion to active microwave 

 techniques. Microwave temperature measurements are also 



25-27 



