A review of the latest improvements in the L-MEB Model (SMOS mission)
Résumé
The L-MEB (L-band Microwave Emission of the Biosphere) is the forward model used in the operational SMOS algorithm. This model is based on a well-known zero-order solution of the radiative transfer equations: the so called Ƭ-ῳ model, where the optical depth Ƭ accounts for extinction effects within the canopy and the single scattering albedo ῳ accounts for scattering effects. L-MEB includes several parameterisations which were developed specifically to account for the multiangular and bi-polarization capabilities of the SMOS TB observations in the retrieval process. A detailed description of the L-MEB model and the analysis of soil moisture retrievals over a variety of crops have been given in Wigneron et al. (2007, 2010). Since then, the model has been implemented in the SMOS algorithm which produced time series of the Level 2 (Kerr et al., 2012, delivered by ESA) and Level 3 (Kerr et al., 2013, delivered by CATDS) SM products, since the beginning of 2010. These SM products have been evaluated against numerical modelling products (ECMWF SM-DAS-2, MERRA-Land) and in situ data from large SM networks included in the SMOS cal/val initiative. Moreover, the model was evaluated in a series of experimental campaigns based on field (SMOSREX, MELBEX, Upper Danube, etc.) or airborne measurements (NAFE-06, Australia; CAROLS, France; etc.). Eventually, numerical and physical models were used to develop new parameterizations of the soil roughness (Lawrence et al., 2013), soil permittivity (Mironov et al., 2012) and vegetation effects. Based on this very dense scientific activity, some major changes have been made and some future improvements of the L-MEB model have been proposed. This communication makes a review of the most significant changes.