Experiments on the Radar Backscatter of Snow

The 1-8-GHz microwave active spectrometer (MAS) system was used to measure the backscatter response from ground covered with a relatively thin layer of snow (up to 15 cm) in the 1975 winter. Except for one dry snow data set, the results of this experiment pertain to wet snow conditions. The scattering coefficient was measured for all linear polarization combinations at angles of incidence between nadir and 70°. The ground truth data consisted of soil moisture, soil and air temperatures, snow depth, snow density, and snow water equivalent. The results of the experiment indicate that the radar sensitivity to the total snow water equivalent increases in magnitude with increasing frequency and is almost angle independent for angles of incidence higher than 30°, particularly at the higher frequencies. In the 50-70° angular range in the 6-8-GHz frequency range, the sensitivity is typically around -0.4 dB/0.1 g/cm2 of the snow water equivalent and the associated linear correlation coefficient has a magnitude of about 0.8.