LABORATORY BACKSCATTER MEASUREMENTS OVER UREA ICE WITH A SNOW COVER AT KU BAND

Indoor laboratory facilities were used to measure radar backscatter at Ku band (13.9 GHz) over urea ice, which has been shown to be structur ally similar to sea ice. Data were collected at angles of incidence fr om normal to 55 degrees, over very thin (0 to 9 cm) ice, snow-covered ice, and ice with a flooded snow cover. The laboratory proved to be us eful in creating and controlling specific physical properties of ice w hile keeping all other variables constant, a difficulty with measureme nts collected in the field. It was found that surface scattering and t he dielectric constant are the dominant factors that cause variations (up to 15 dB) in the measured backscatter. The addition of a snow cove r increased the surface roughness of the smooth ice, increasing the ba ckscatter at 20 degrees incidence angle by about 11 dB and decreasing the backscatter at normal incidence by about 6 dB. The subsequent floo ding of this snow layer increased the backscatter at all angles of inc idence due to the increased dielectric constant of the wet slush layer . These results indicate the importance of the snow layer in influenci ng the surface characteristics of the ice sheet, which in turn modifie s the backscattered signal.