Synthetic aperture radar

A synthetic aperture radar (SAR) is an active microwave sensor capable of imaging the amount of backscattered signal per unit area - the normalized radar cross section (NRCS). NRCS depends on the size and geometry of roughness elements on the scale of the radar wavelength at the Earth surface.

Over a calm ocean surface, the returned NRCS is limited because radar pulses are reflected away from the SAR at an angle equal to the angle of incidence. As the wind picks up, roughness in the form of capillary and short-gravity waves is generated by the surface wind stress. The dominant scattering mechanism is then diffuse and known as Bragg scattering. The relation of NRCS to the local wind speed and direction and to the radar viewing geometry forms the key principle in ocean wind retrievals from SAR.

Page updated  by   04.11.2009


Merete Badger
Senior scientist
Wind Energy (VEA)
Dir tel+45 46775002