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Large scale SSS contrasts detected by SMOS and in situ SSS analysis in the tropical Pacific and Indian Oceans

posted Mar 6, 2013, 4:28 AM by Salinity CERSAT   [ updated Mar 7, 2013, 5:50 AM ]
Variability in the tropical Pacific and Indian Oceans  between 2010 and 2011 is very large linked to the ending 2009-2010 El Nino, 2010 strong La Niña and 2011 weak La Niña events, and to contrasted Indian Ocean Dipole (IOD) in 2010 and 2011 (see Figure below).
Figure 1: Time series of SST anomalies in the four Niño regions from in 2010-2011 and corresponding Indian Ocean Dipole (IOD) Index (SST difference between eastern and western equatorial Indian Ocean) from the Australian bureau of Meteorology.

The animation below is showing differences in the monthly averaged SSS between year 2011 and 2010 for all calendar months. Top panels show the ΔSSS=SSS2011-SSS2010 results obtained from objectively analyzed in situ data (ISAS products) and bottom ones from SMOS Level 3 data.




Large scale SSS variability is very consistently observed on SMOS SSS maps (1) compared with ISAS SSS maps (2) derived from in situ (ARGO floats and ship data) measurements, as seen on the film. SMOS anomalies are often more contrasted than ISAS anomalies due to fresher SMOS SSS in fresh regions associated with rain (Boutin et al., 2013). Signal is much noisier from January to May due to worse SMOS SSS quality during commissionning phase in January-May 2010, but nevertheless spatial structures of anomalies remain very consistent with ISAS maps.

(1) SMOS SSS maps are generated using ESA reprocessing version 5 as described in J. Boutin, N. Martin, G. Reverdin, X. Yin and F. Gaillard, Sea surface freshening inferred from
SMOS and ARGO salinity: Impact of rain, Ocean Sci., 9, 183-192, doi:10.5194/os-9-183-2013, 2013.

The latest version of the maps generated at CATDS/CEC-LOCEAN will be soon made available to CATDS users on the catds web portal ( A dedicated news explaining how to access these new CATDS/CEC research products will come very soon on the present web site.

(2) ISAS SSS maps are produced by the In Situ Analysis System version 6 at LPO (see


This is a collaborative study between LOCEAN  and IFREMER laboratories.