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Sea Surface Salinity

Sea Surface Salinity (SSS) is an Essential Climate Variable (ECV) that plays a fundamental role in the density-driven global ocean circulation, the water cycle, and climate. The satellite SSS observation from the Soil Moisture and Ocean Salinity (SMOS), Aquarius, and Soil Moisture Active Passive (SMAP) missions have provided an unprecedented opportunity to map SSS over the global ocean since 2010 at 40-150km scale with a revisit every 2 to 3 days. This observation capability has no historic precedent and has brought new findings concerning the monitoring of SSS variations related with climate variability such as El Niño-Southern Oscillation, Indian Ocean Dipole, and Madden-Julian Oscillation, and the linkages of the ocean with different elements of the water cycle such as evaporation and precipitation and continental runoff. It has enhanced the understanding of various ocean processes such as tropical instability waves, Rossby waves, mesoscale eddies and related salt transport, salinity fronts, hurricane haline wake, river plume variability, cross-shelf exchanges. There are also emerging use of satellite SSS to study ocean biogeochemistry, e.g. linked to air-sea CO2 fluxes.

Following the success of the initial oceanographic studies implementing this new variable, the European Space Agency (ESA) funded a new Climate Change Initiative (CCI) Sea Surface Salinity (SSS) project (2018-2020). The CCI+SSS project (2018-2020) aims at generating improved calibrated global SSS fields over 10 years period (2010-2019) from all available satellite L-band radiometer measurements, extended at regional scale to 2002-2019 from C-band radiometer measurements. It will fully exploit the ESA/Earth explorer SMOS mission complemented with SMAP and AQUARIUS satellite missions. The project gathers teams involved in earth observation remote sensing, in the validation of satellite data and in climate variability study.

CCI SSS will provide data products that are specifically adapted to climate applications (i.e. include information on accuracy and uncertainty within the data). Furthermore, this project will explore the need to improve the performance of current SSS algorithm retrievals and directly contribute to climate science studies submitted to the next International Panel on Climate Change (IPCC) Annual Review for climate change in 2020.

Project Team


The CCI SSS project team comprises of nine scientific and industrial partners from the United Kingdom, France, Spain, Germany and Luxemburg. The following companies make up this consortium:

  • ARGANS Ltd. (United Kingdom)
  • Laboratoire d'Océanographie et du Climat (LOCEAN) (France)
  • Laboratoire d'Océanographie Physique et Spatiale (LOPS) (France)
  • Institut français de recherche pour l'exploitation de la mer (IFREMER) (France)
  • ACRI-ST (France)
  • AdwäisEO (Luxemburg)
  • Ocean Data Lab (ODL) (France)
  • Institut des sciences de la mer de Barcelona (ICM-CSIC) (Spain)
  • National Oceanography Centre (NOC) (United Kingdom)
  • Universitat Hamburg (UoH) (Germany)

With additional support from the following external partners:

  • NASA's Jet Proplusion Laboratory (JPL) (U.S.A.)
  • NASA's Goddard Space Flight Center (GSFC) (U.S.A.)
  • Remote Sensing Systems (RSS) (U.S.A.)






Latest News


First CCI+SSS maps now available HERE

The first version of satellite Sea Surface Salinity (SSS) maps produced by the ESA CCI (Climate Change Initiative) SSS project by combining SMOS-CATDS, AQUARIUS and SMAP SSS are now available. This new data set underlines with an unprecedented precision the spatio-temporal variability of the SSS over the 2010-2018 period, especially those related to the fresh water river outflows (e.g. Amazon, Mississippi, see image below). Systematic differences between SSS obtained from the various instruments and under various geometries have been homogenised  using a methodology similar to the one developed and implemented at CATDS (Centre Aval de Traitement des Données SMOS).

We are very keen to get User feedback. Users can give feedback either via mail or via the online user feedback form


See more on data description and access onto:

See ESA announcement










The"Salinity Science Seminar"  will take place in Hamburg, Germany  from 26 to 27 September, 2019.

This Meeting will be a joint effort of the University of Hamburg and the LOCEAN and will focus on actual research and bring together recent expertise of data assimilation and salinity processes based on models and ocean salinity observations as well as validation studies and feedback regarding the new CCI+SSS product.

To view the agenda and register visit the Seminar website.


CCI SSS Documentation


Document Version Milestone Date
User Requirement Document (URD) v1r4 MS#01 03/01/2019
Product Specification Document (PSD) v1r6 MS#01 24/04/2019
Data Access Requirement Document (DARD) v1r4 MS#01 23/04/2019
Algorithm Development Plan (ADP) v1.1 MS#02 19/12/2019
Product Validation and Algorithm Selection Report (PVASR) v1.1 MS#02 13/12/2019
Algorithm Theoretical Basis Document (ATBD) v1.3 MS#02 19/12/2019
End to End Uncertainty Budget (E3UB) v1.2 MS#02 19/12/2019
Product Validation Plan (PVP) v1.1 MS#02 04/12/2019
Systems Requirement Document (SRD) v1.1 MS#02 06/12/2019
Systems Specification Document (SSD) v1.1 MS#02 05/12/2019
System Verification Report (SVR) v1.1 MS#02 11/12/2019
Product User Guide (PUG) v1.2 MS#03 05/03/2020

Product Validation and Intercomparison Report 


v1.1 MS#03 07/04/2020

Climate Assessment Report


v1.1 MS#03 10/04/2020


CCI+SSS open source code in Github





Data Sources


Data pertaining to this project is sourced by the CCI Open Data Portal and visual analysis of the data is provided through the CCI Toolbox.


Useful Links

Websites related to ESA’s SMOS mission:

  • SMOS ESA EO Mission
  • ARGANS SMOS [Level 2]
  • Centre Aval de Traitement des Données SMOS (CATDS) [Level 3+]
  • Barcelona Expert Center (BEC) [Level 3+]
  • SMOS Pilot-Mission Exploitation Platform (PiMEP)

Websites related to NASA’s Aquarius, SMAP and SPURS missions:

  • Physical Oceanography Distributed Active Archive Center (PO.DACC) [Level 1+]




Contact Information


Project Leaders:

  • Scientific Leaders: Jacqueline Boutin and Nicolas Reul.
  • Project Manager: Rafael J. Catany (

ESA Technical Officers:




Password protected site. Contact Project Manager to get access to this space.


Frequently Asked Questions

  • What is SSS?
    • SSS stands for Sea Surface Salinity. For more information please refer to the Useful Links section above.
  • Where can I find SSS data?
    • Links to data provided by this project can be found in the Data section above. Alternative data sources can be found in the Useful Links section above.
  • What is CCI?
    • CCI stands for the Climate Change Initiative. The CCI is a programme initiated by ESA. For more information please refer to the CCI home page.
  • What is ECV?
    • ECV stands for Essential Climate Variable. For more information please refer to the ECV Inventory page.
  • What is ESA?
    • ESA stands for the European Space Agency. For more information please refer to the ESA home page.
  • What is EO?
    • EO stands for Earth Observation.