Emissivity of vegetation: theory and computational aspects

Abstract

Direct formulas to compute the absorption cross section of lossy dielectric discs in the Physical Optics approximation, and cylinders in the Infinite Length approximation, are derived and their validity is checked by means of the Forward Scattering Theorem. These formulas are helpful in modeling microwave emissivity from vegetation. Due to enhanced directivity of large cylinder bistatic patterns, an exact computation of emissivity of those cylinders would require a tremendous amount of computational resources. In this paper it is demonstrated that for a layer of cylinders large with respect to the wavelength, the absorption cross section direct formula allows to compute emissivity in a simple way and with acceptable accuracy.