Ongoing research project |

Soil Moisture and Ocean Salinity (SMOS)

SMOS is the second Earth Explorer Opportunity mission developed as part of the European Space Agency (ESA) Living Planet programme. The SMOS mission provides two-dimensional interferometric radiometer measurements of L-band (1.4 GHz) brightness temperature from a satellite in polar orbit. At this frequency the atmosphere is almost transparent and surface emission is strongly related to soil moisture over continental surfaces, salinity and surface state of the oceans, and to the thickness of sea ice (

SMOS was successfully launched and put into orbit on the 2nd of November 2009.

The key objectives of the SMOS mission are to:

  • Improve our understanding of the global water cycle.
  • Contribute to the improvement in weather and seasonal-climate forecasting.

ECMWF plays a major role in developing and implementing the use of SMOS brightness temperature data in NWP models. ECMWF’s contribution to the SMOS mission is two-fold:

  • Development of a data monitoring system for the SMOS near real time product to provide a timely quality check for ESA and the SMOS calibration and validation teams
  • Assimilation of SMOS brightness temperature data in ECMWF's global NWP system through the Surface Data Assimilation System (SDAS) based on the Extended Kalman Filter. This system is currently being tested with the active microwave METOP/ASCAT surface soil moisture data.

One main component of the monitoring is the observation operator that transforms model fields (soil moisture and ocean salinity) into observation equivalent (brightness temperatures).

To this end the CMEM (Community Microwave Emission Modelling Platform) has been developed at ECMWF. More information on ECMWF SMOS.

The usefulness of SMOS data for measuring the thickness of thin sea ice and strong winds over the ocean is also being investigated.


Lars Isaksen

Joaquin Munoz Sabater

European Space Agency