Sea Surface Salinity - Remote Sensing

Sea Surface Salinity Remote Sensing

at CATDS Ocean Salinity Expert Center

(CEC-OS)

Legend: Annual Average Sea Surface Salinity map at 0.25°x0.25° resolution deduced from SMOS satellite data for the year 2010

About the CATDS Salinity Expert Center

The CATDS Salinity Expeertise Center is a research group including members from the following french Laboratories:

-Laboratoire d'Océanographie Spatiale at the French Institute of Research for the Exploitation of the Sea (Ifremer) ,

-Brest/Radar division of the french company Collect Localisation Satellite,

-Laboratoire d’Océanographie et du Climat : Expérimentation et Approches Numériques (LOCEAN), UMR 7159 CNRS/UPMC/IRD/MNHN, Paris, France

-Laboratoire d'Etude en Géophysique et Océanographie Spatiale (LEGOS) , OMP, CNRS, IRD, Université de Toulouse, Toulouse, France

Our activities are focused on the challenge of Sea Surface Salinity (SSS) Remote Sensing from space.

In particular, our team is strongly involved in the scientific algorithm development and data exploitation of the ESA's Soil Moisture and Ocean Salinity (SMOS) satellite mission. Members of our group thus work as two Expert Support Laboratories for ESA level 2 ocean salinity products. This activity is conducted in close collaboration with the spanish ICM-CSIC laboratories, as well as with the UK/ARGANS company which is in charge of the prototype processor development and maintenance.Our research activities on SMOS data also includes providing some feedback to the SMOS Level 1 image reconstruction processing (calibration, quality validation).

Ifremer hosts the Centre Aval de Traitement des Données SMOS (CATDS), which is the french ground segment for the SMOS Level 3 and 4 data, developped in collaboration with CNES and the CESBIO laboratory. In this context, our team is in charge of the CATDS Salinity Expertise center (C-ECOS). This center is piloted and developed in collaboration with several national partners, in particular with our collegues from LOCEAN/IPSL and LEGOS laboratories. In this context, the prototype Level 3 and 4 algorithms that are tested in the C-ECOS and found to produce the best SSS products will then be turned into operational processing chains by the french companies CAP-GEMINI and ACRI-ST.

Finally, we are also collaborating with our US collegues involved in the NASA Aquarius/SAC-D satellite mission. Aquarius is another focused satellite mission to measure global Sea Surface Salinity that was launched in 2011. By providing feedback results from SMOS mission, we thus support the scientific algorithm development of the mission and we prepare the synergies between SMOS and Aquarius data in close collaboration with our US collegues.

More generally, we are using multiple sensor & associated data sets (low frequency microwave radiometers, ocean color, sea surface temperature, wind, wave, altimeter products, model and in situ data..) to develop new scientific algorithms, synergetic data methodologies and computing techniques that tentatively best map salinity at the surface of the oceans. The principal scientific objective is to make global SSS measurements over the ice-free oceans with 150-km spatial resolution, and to achieve a measurement error less than 0.2 (PSS-78 [practical salinity scale of 1978]) on a 30-day time scale, taking into account all sensors and geophysical random errors and biases. Salinity is indeed a key indicator of the strength of the hydrologic cycle because it tracks the differences created by varying evaporation and precipitation, runoff, and ice processes. These variables lead to important dynamical consequences for oceanic currents and mixing that influence the ocean’s capacity to absorb, transport, and store heat, freshwater, and carbon dioxide. Many of the processes governing the role of salinity in the modulation of upper-ocean mixing in both tropical and high-latitude regions are neither well understood nor adequately represented in climate models.

Our research activity is thus part of a national and international effort to provide the scientific community with new data sets usefull for ocean circulation modeling, climate studies, bio-optics and bio-chemistry of the ocean.