Using microwave radar for soil moisture inversion under soybean canopies

The successful radar mapping of soil moisture under vegetation canopies would be a boon to agriculture, global climate change studies, water resource management and other areas. Toward this end, a series of polarimetric radar measurements of soybeans over the entire growing season of 1996 were made at L and C-band at the Long Term Ecological Research site at the Kellogg Biological Station, Hickory Corners, MI. The radar data obtained has been successfully modeled with a simplified radiative transfer expression, including the dependence of the VV,HH, and cross-polarized backscattering coefficients on the angle of incidence, vegetation water mass, vegetation height, and volumetric soil moisture. In addition, a simple inversion model based on the forward model has been obtained which yields vegetation water mass and volumetric soil moisture for select polarization and frequency combinations.