Spectral and angular ground-based radar backscatter measurements of Greenland snow facies

Snow facies, or melt zones, on the Greenland Ice Sheet are correlated with brightness patterns on spaceborne radar imagery. To better relate radar scattering signatures to individual zones, the authors investigate the relationship between radar scattering and firn physical properties. They operated surface-based radar systems at five different sites on the Greenland Ice Sheet. In the dry snow zone the angular variation of the backscattering coefficient indicates that at high incidence angles the return energy is dominated by volume scattering. They also observe a systematically higher backscattering coefficient when the physical temperature is low and all the other parameters are identical. In the wet snow zone the backscatter coefficient is temporally dependant as the temperature variations affect the moisture content and modifies the spectral backscattered energy. The snow and ice surface roughnesses determine the angular response. In the percolation zone, the backscatter coefficient is independent of the frequency and the angular response is also controlled by the ice structures (surface roughness, lenses, and pipes).