Salinity is one of the factors driving ocean circulation. For a long time, it was measured only in situ, thus leading to a somehow sparse sampling in time and/or areas. Now, since 3 years (SMOS mission, ESA; 1 year and a half for Aquarius, NASA), satellite measurements of salinity have been available.  However, those need to be calibrated, and need supplementary information to be interpreted.
Thus an international programme, SPURS, including several field campaign has been launched. In particular, the French STRASSE cruise took place from August 16 to September 13, 2012 on board the RV Thalassa (French IFREMER and Spanish IEO agencies) with the middle of the North Atlantic subtropical gyre in focus, where salinity is at its highest (with low precipitations, high evaporation).

During this campaign a key aspect for the project was to identify a suitable region within the Sea Surface Salinity (SSS) maximum region for the in situ investigation. SMOS gridded Sea Surface Salinity provided information on the large scale spatial distribution of SSS for the days preceding the beginning of the campaign. To include the effects of the mesoscale dynamics on the spatial distribution of salinity, the satellite salinity were merged in real-time using surface geostrophic velocities derived from altimetry. This allowed to obtain a higher-resolution SSS map, from which it was possible to successfully identify the best area (35-36°W, 25.5-26.5°N) for the STRASSE field campaign. Preliminary results from in situ observations confirm the high-resolution SSS map thus obtained.  This pilot study is an example of how altimetry and Lagrangian tools (filament computation) may serve in the future for integrating novel satellite data (like SSS) and in situ observations.