DInSAR measurement of soil moisture

Differential interferometric sythetic aperture radar (DInSAR) measurements using the European Remote Sensing 2 (ERS-2) satellite in a high-plains region of Colorado show intriguing spatial variations in millimeter-scale path-length change that may correspond to variations in soil moisture of a few percent by volume, in both farm fields and uncultivated terrain. The observed signal is hypothesized to result from both changes in penetration depth and the swelling of clay-rich soils, both due to changes in soil moisture. Comparisons with our field measurements of soil moisture cannot conclusively verify this, but strong support is found from prior and complementary research as well as the visual correlation with hydrological features such as stream channels and watershed boundaries on a 50-m scale. Detection of these subtle signals was facilitated using a digital elevation model with high vertical accuracy. If our interpretations are correct, C-band DInSAR is a promising new tool for the remote sensing of soil moisture in a variety of terrain.