Algorithm Theoretical Basis Document (ATBD) for the SMOS Level 4 Root Zone Soil Moisture

The aim of the report is to present the theoretical basis and the implementation of the SMOS Level 4 Root zone Soil moisture (L4-RZSM) product implemented at CATDS. The document contains a general introduction containing a description of the SMOS mission, the CATDS processing center and the presentation of the root zone soil moisture variable. This is followed by an overview of the algorithm and a description of the theoretical basis. The last part concerns the operational implementation at CATDS.