A Doppler spectral method of identifying water and ice in marginal-ice-zone imagery

Complex synthetic aperture radar (SAR) imagery at C-band and X-band were acquired in and near the marginal-ice-zone on March 26 1989 in the Greenland Sea. The authors specially process this imagery to obtain Doppler spectra from two backscatter regions: (1) newly forming ice inside a tongue shaped region called the Odden and (2) open water adjacent to the Odden. They observe Doppler bandwidth broadening from the water imagery compared to the spectral width backscattered from the ice. A model is developed describing this broadening in terms of the platform motion, and the short and long ocean waves. They claim this broadening is primarily due to random sub-resolution velocities within a SAR resolution cell caused by the short ocean waves. The bandwidth broadening is extracted as Δfˆ_a≈40 Hz at C-band and Δfˆ_a≈55 Hz at X-band. The corresponding scene correlation times are 2τ_c≈22 ms at C-band and 16 ms at X-band. The measured ice bandwidth due to the platform motion (155 m/s) is approximately 118 Hz at both C-band and X-band