Polarimetric emissivity of vegetation-covered soils: simulation results

Soil moisture can be determined by L-band radiometry. Because of the long electromagnetic wavelength -21 cm- surface roughness effects are small. In principle, vegetation effects are also small, but they cannot be neglected if the observation angle is large and/or the vegetation cover is thick or dense. In addition, coherent effects may appear because the distance between scatterers becomes comparable to the electromagnetic wavelength. In this paper we investigate the effect on the four Stokes elements (T_v, T_h, U and V) of a vegetation cover consisting of individual trunks over a tilted rough surface. Simulated results show the known trends for T_v and T _h: higher brightness temperatures for dry soils than for moist soils, and lower difference T_v-T_h for vegetation covered soils than for bare soils. The third and fourth Stokes parameters (U, V) show a more erratic behavior highly dependent on the vegetation geometry (orientation of scatterers), increasing at large observation angles and with peak amplitudes of a fraction of a Kelvin