Validation of SMOS level 3 soil moisture data
Résumé
The SMOS ground segment “CATDS” (Centre Aval de Traitement des Données SMOS) has been delivering level 3 data, which are temporal aggregated products (1-day, 3-day, 10-day, monthly average). The retrieval is based on a modified version of ESA level 2 soil moisture processor to account for multi-orbit retrievals, correlated vegetation optical depth, projection on the EASE Grid. The soil moisture retrieval has evolved and improved since its first version and major changes lead to reprocessing campaigns to obtain homogeneous time series, i.e. data done using one processor. Three campaigns have been done so far at the CATDS and the last one, referred to as reprocessing RE03, uses the last calibrated brightness temperatures (version 620 for ESA level1C, version 280 for CATDS level3TB) and the last soil moisture processor (version 620 for EASE level 2 SM and version 280 for CATDS level 2 SM). The new set of products will be available in Spring 2015. The validation of SMOS data (level 2 and 3) has been a constant activity since the beginning of the mission. It consists in evaluating the performances of these products by comparing them at various climate areas like for example in Australia, West Africa, Denmark, France, in the US. It is done for every release to insure that the new data are consistent and closer to in-situ observations, as for instance when it was decided to switch the dielectric constant model. The aim of this communication is then to present data from the RE03 campaign and to discuss the changes and improvements of the new releases. A first analysis over a week (sept. 2013) shows that the new soil moisture values (RE03 version V280) are globally lower than the previous version by 0.01 m3/m3. This result is preliminary and the analysis will be extended to a longer time period.