SAR observations and modeling of the C-band backscatter variability due to multiscale geometry and soil moisture

The effect of the multiscale surface geometry on the sensitivity of C band synthetic aperture radar (SAR) data to soil moisture is studied. The experimental data consist of C-band SAR images of an agricultural site, including fields with various combinations of three distinct roughness components from small to large scale. The backscatter variability due to surface roughness has been analyzed. The effect of random roughness associated with soil clods is never less than 2 dB, and the effect of a row pattern can be as strong as 10 dB. In addition, the periodic drainage topography induces a backscatter variability due to soil moisture variation and drainage relief. The results indicate that airborne C-band SAR data cannot be easily inverted into soil moisture data. However, with ERS-1 or Radarsat data at an incidence angle of about 20°, the effect of random and periodic roughness can be reduced to about 2 dB if the look angle is less than 50°