Soil moisture inversion from X-band SAR and scatterometer data of vegetation fields

The polarimetric radar backscatters of a soybean field were measured using the ground-based X-band polarimetric scatterometer (HPS) in an angular range from 20° to 60° in 2009 and 2010. The backscattering coefficients were also obtained using the COSMO-SkyMed (Spotlight mode, HH mode) from July to October 2010. The backscattering coefficients of the soybean field were computed using the first-order RTM with field-measured input parameters. It was found that the estimated backscattering coefficients agree quite well with the field-measured radar backscattering coefficients. The surface scattering from the underlying soil surface was retrieved. Then, the soil moisture of the soybean field could be retrieved from the surface scattering using the empirical surface scattering model. The extracted soil moisture contents were compared with the in-situ measured soil moisture contents.