A semi-empirical backscattering model at L-band and C-band for a soybean canopy with soil moisture inversion

Radar backscatter measurements of a pair of adjacent soybean fields at L-ba nd and C-band are reported. These measurements, which are fully polarimetri c, took place over the entire growing season of 1996, To reduce the data ac quisition burden, these measurements were restricted to 45 degrees in eleva tion and to 45 degrees in azimuth with respect to the row direction. Using the first order radiative transfer solution as a form for the model of the data, four parameters were extracted from the data for each frequency/polar ization channel to provide a least squares fit to the model. Ebr inversion, particular channel combinations were regressed against the soil moisture a nd area density of vegetation water mass. Using L-band cross-polarization a nd VV-polarization, the vegetation water mass can be regressed with an R-2 = 0.867 and a root mean square error (RMSE) of 0.0678 kg/m(2), Similarly, w hile a number of channels, or combinations of channels, can be used to inve rt for soil moisture, the best combination observed, namely, L-band VV-pola rization, C-band HV- and VV-polarizations, can achieve a regression coeffic ient of R-2 = 0.898 and volumetric soil moisture RMSE of 1.75%.