| Summary: | In the context of the European Space Agency's (ESA) Soil Moisture and Ocean Salinity (SMOS) mission, we present a study of the emission of rough surfaces at 1.4 GHz and the effects of moisture and temperature gradients. Surface roughness has been studied in some depth in the literature as it is a key influencing parameter on ground emission. A new approach for the calculation of rough surface scattering and emission at L-band has recently been validated for the case of scattering from a single layer rough surface of Gaussian autocorrelation function [3]. This approach relies on the use of ANSYS's numerical computation software HFSS (High Frequency Structure Simulator), which in turn solves Maxwell's equations using the Finite Element Method (FEM). The interest of this approach is that it can be extended to calculate the emission and scattering of complicated multilayer media, including features such as volume effects, gradients effects and inclusions, as well as rough surfaces. This is therefore especially useful for the problem of the emission from soil-litter systems in forests. At L band, volume effects in the upper layer of soil should be taken into account. In particular, moisture or thermal phenomena lead to the presence of gradients. In this paper we present the work we have done to use FEM (Finite Element Method) method to compute thermal effects and water infiltration effects in ground. Coupling electromagnetic and thermal computation we are able to study scattering of media such as permafrost or effects of rapid changes in temperature condition. It can also be very useful for global observations with a frequent repeat coverage (future NASA Soil Moisture Active/Passive mission SMAP). In the present study we firstly present the effects of water infiltration in ground (as moisture gradients) on the emissivity and bi-static scattering coefficient of soil. Then we will present results of computations on soils partially or completely frozen.
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