Over land

Water and energy fluxes at the surface/atmosphere interface are strongly dependent upon Soil Moisture. Evaporation, infiltration and runoff are driven by moisture while soil moisture in the vadose zone governs the rate of water uptake by vegetation. Soil moisture is thus a key variable in the hydrologic cycle. Soil moisture, and its spatio-temporal evolution as such, is an important variable for numerical weather and climate models, and should be accounted for in hydrology and vegetation monitoring.

For the Oceans

Sea Surface Salinity plays an important role in the Northern Atlantic sub polar area, where intrusions with a low salinity influence the deep thermohaline circulation and the meridional heat transport. Variations in salinity also influence the near-surface dynamics of tropical oceans, where rainfall modifies the buoyancy of the surface layer and the tropical ocean-atmosphere heat fluxes. Salinity fields and their seasonal and inter-annual variabilities are thus tracers and constraints on the water cycle and on the coupled ocean-atmosphere models.

Even though both moisture and salinity are used in predictive atmospheric, oceanographic, and hydrologic models, no capability exists to date to measure directly and globally these key variables. SMOS is aimed at filling this gap through the implementation of a mission that has the potential to provide globally, frequently, and routinely this information. It is also expected that the SMOS mission will provide significant information on vegetation water content, which will be very useful for regional estimates of crop production.

Finally, significant research progress are expected over the cryosphere, through improving the assessment of the snow mantle, and of the multi-layered ice structure. These quantities are of significant importance to the global change issue. Research on sea ice will also be carried out.