Roughness Effects on the L-band Emission of Bare Soils: The T-REX Field Experiment

Soil roughness is an important parameter whose effects on soil emissivity at L-band have not been satisfactorily quantified so far. This paper presents the preliminary results of the Terrain-Roughness Experiment (T-REX), which was carried out in Agramunt, Spain, during the fall of 2004. Four identical sets, each of them having four plots with different plough but the same soil type, were measured. Two profiles per soil plough were acquired, one parallel and the other perpendicular to the antenna frame. Since the purpose of T-REX 2004 was to analyze the impact of surface roughness on the received signal, the soil was not irrigated. Results show that the soil emissivity increases as the soil roughness increases. The horizontal polarization seems to be more sensitive to roughness than the vertical polarization for fields with a tillage direction perpendicular to the antenna reference frame. Emissivity at horizontal polarization decreases as the incidence angle increases, while the trend for the vertical polarization is almost constant when the soil is dry.