Bridging the gap between surface salinity satellites: SMOS and Aquarius

Abstract

The SMOS (Soil Moisture and Ocean Salinity) mission of the European Space Agency (ESA) consists of a satellite with a L-band microwave synthetic aperture radiometer to retrieve ocean surface salinity (SSS) and soil moisture. Almost simultaneously, a second mission, this time from NASA, has been developed to produce a new salinity-sensing satellite, called Aquarius, that includes both a L-band radiometer and a scatterometer. While SMOS was launched November 2009, Aquarius is scheduled for launch in 2011. While the two satellites use different technological approaches that result in slightly different measurement resolutions, the issues regarding product generation and validation remain analogous. Some of the main technical issues to address for the proper intercomparison are: 1) the different spatial footprint that makes direct single image comparison difficult; 2) the need of image reconstruction algorithms; 3) the distinct noise levels expected; 4) the different spatial and temporal averaging scales needed for noise reduction; 5) the errors introduced by auxiliary data. Three primary interaction tasks are described: I) the identification of optimal/worse settings for each satellite based on the comparison with in situ and model data; II) the production of best estimates of satellite-measured global salinity maps using Optimal Interpolation; and III) the use of remote measurements in applications (e.g., involvement in the SPURS project to study the North Atlantic SSS maximum). SPURS (Salinity Processes in the Upper-ocean Regional Study) will try to characterize the main processes associated with the maintenance and evolution of the SSS maximum during an intensive field campaign to take place during 2012. SSS satellite information will help constrain the large-scale structure and its temporal evolution. Meanwhile, the availability of sufficient in situ observations will provide an outstanding opportunity for satellite data validation