Sensitivity of L-band Brightness Temperatures to Soil Roughness Parameterization. the Smosrex Case Study

The Soil Moisture and Ocean Salinity (SMOS) satellite mission of the European Space Agency (ESA), scheduled for launch in summer 2009, responds to the growing need for an accurate estimate of the root-zone soil water content. SMOS will operate at L-band frequencies, where the microwave signal is more sensitive to the soil water content. The European Centre for Medium-Range Weather Forecasts (ECMWF) is preparing to integrate this new data in its data assimilation chain ([1]). In this context, ECMWF has developed the Comunity Microwave Emission Model (CMEM) forward operator ([2]) to simulate the top of the atmosphere brightness temperatures (TB) in frequencies ranging from 1 GHz to 20 GHz as a function of the land surface conditions and vegetation. CMEM has a modular design and permits the combination of different parameterizations for each component of the soil microwave emission. [2] and [3] found that the Kirdyashev parameterization for the vegetation optical thickness was the best for the TB simulation. But little investigation was undertaken in the choice of the soil roughness model. A study over the SMOSREX field site [4] demonstrates that the calibration of this component is likely to be the most important in the microwave simulation. This paper investigates which soil roughness parameterization available in CMEM reproduces more accurately the observed TB. This study concentrates in the year 2004 using the operational configuration. Some results are showed in this paper.