Global validation of the ESA CCI+SSS products

The European Space Agency (ESA) Climate Change Initiative for Sea Surface Salinity (CCI+SSS) project aims at generating long-term, improved, calibrated global SSS fields from space. The project started in mid-2018 and in its first year has produced a 9-year dataset (2010-2018) from the three available L-band radiometer satellites (SMOS: Soil Moisture and Ocean Salinity; Aquarius; SMAP: Soil Moisture Active Passive) and validated it against in situ references (Argo and ISAS: In Situ Analysis System). The dataset is available at https://catalogue.ceda.ac.uk/uuid/9ef0ebf847564c2eabe62cac4899ec41.

The comparisons with in situ ground truth indicate much better performances than the ones obtained with a single satellite data product, with global precision against in situ references of 0.16 pss and 0.10 pss in areas with low variability. There is a very good agreement between the CCI dataset and references, including long-term stability, with differences within +-0.05 pss for global ocean within [40°S-20°N]. At higher latitude, we observe seasonal oscillation of the CCI SSS difference against references. The CCI SSS products uncertainty have been validated against references and show good agreement as long as the spatial representativeness is considered in presence of strong spatial gradients in salinity.