Surface Topography and Mixed Pixel Effects on the Simulated L-band Brightness Temperatures

The impact of topography and mixed pixels on L-band radiometric observations over land has not been properly quantified so far. With this purpose, simulations have been performed with an upgraded version of the Soil Moisture and Ocean Salinity (SMOS) End-to-end Performance Simulator (SEPS). The brightness temperature (T_B) generator of SEPS has been improved to include a 100 m-resolution land cover map (21 uses) and a 30 m-resolution digital elevation map of the Catalonian Region (NE Spain). The high resolution T_B generator allows to assess the errors in the soil moisture retrieval algorithms due to limited spatial resolution, and to set the basis for the development of pixel disaggregation techniques. Variation of the local incidence angle as seen from SMOS, shadowing, and atmospheric effects (up- and down-welling radiation) due to surface topography have been analyzed. Results are compared to T_B values computed under the assumption of an ellipsoidal Earth