Assessment of Two SMOS Sea Surface Salinity Level 3 Products Against Argo Upper Salinity Measurements

Since the launch of the Soil Moisture and Ocean Salinity (SMOS), different sea surface salinity (SSS) level 3 (L3) research products have been developed by several institutions, including the Barcelona Expert Centre (BEC) in Spain and the Centre Aval de Traitement des Données SMOS (CATDS) in France. This letter assesses the performances of BEC “Ocean Reprocessing Campaign 2012001” L3 data and CATDS Version 2 (V02) L3 data by comparing both of them with Argo upper salinity measurements (within 5-m depth). Twenty-month data from May 2010 to December 2011 are selected for the study. Through computing differences and root-mean-square errors of the differences between BEC and Argo data as well as between CATDS V02 and Argo data at each 1° ×1° grid point, it is observed that CATDS V02 data are of better quality along coasts and in high latitudes than BEC data owing to different-SSS-bias mitigation such as applying a correction with respect to the climatology in 5° ×5° boxes and using the same ocean target transformation for the whole processing. In open ocean, however, both SMOS data sets perform very well. Several regions are picked out to conduct the time series comparisons, and the results are similar.