Soil moisture retrieval using L-band time-series SAR data from the SMAPVEX12 experiment

The algorithms for retrieving soil moisture contents within the top 5 cm of the soil using the L-band multi-polarized radar data from the future Soil Moisture Active and Passive (SMAP) mission were applied to the data sets obtained by the recent aircraft field campaign in Winnipeg Canada in 2012 (SMAPVEX12), and the algorithm performance was evaluated. Two algorithms are: the time-series inversion of radar scattering forward models "data-cubes" and the change detection method. The SMAPVEX12 data sets include airborne synthetic aperture radar (SAR) data and ground-based measurements of soil and vegetation. These data were collected over fields with diverse crops and a wide range of moisture and vegetation conditions. In general, volumetric soil moisture and backscattering coefficients showed a positive relationship and the vegetation effects were significant for corn and beans. Assessed over all available fields of corn, beans, pasture, and wheat, the data-cube time-series inversion resulted in a retrieval rmse of 0.050 to 0.090 cm(3)/cm(3), and correlations of 0.5 to 0.9. Compared with the change detection approach, the data-cube inversion performed better in the presence of significant vegetation growth.