A fully polarimetric multiple scattering model for crops

This article describes an electromagnetic model which simulates the microwave polarimetric backscatter of agricultural fields. The model is based on radiative transfer theory and solves the relevant equation by means of a numerical algorithm, namely matrix doubling, which includes multiple scattering effects. The backscatter coefficient may be simulated for any pair of incidence and scattering elliptical polarizations; also, the phase difference between VV and HH channels is computed. Model simulations are compared with experimental results obtained at L band (1.2 GHz) by the NASA-JPL AIRSAR, in the framework of the MAC Europe '91 campaign, over sunflower fields belonging to an Italian site named Montespertoli. A satisfactory agreement is observed between predicted and measured polarimetric quantities of vegetated fields, while for bare soils (particularly at VV polarization) backscatter coefficients are overestimated, due to inaccuracies of surface models available at present.