Radar measurements of wind and waves

Radio signals scattered from the sea surface are used to measure many things such as wind speed and direction, currents, current boundaries, and the directional ocean-wave spectrum. Yet the scatter itself really only senses ocean waves. In the case of HF signals, these waves have decameter wavelengths, but microwaves sense only shorter wavelets. All other processes must be inferred indirectly through their influence on these waves. Thus, it is critical to understand the nature of these influences and modulations if radio techniques are to fulfill their promise. Here we assess the modulation of wavelets by long waves, their relationship to wind, and finally, radio techniques useful at HF frequencies.