30.10.2023: New version of SMOS freeze and thaw product released

The SMOS freeze and thaw processor has been updated to version 3.00. All data have been re-processed. The new reprocessed and operational data are available on the FMI dissemination server and can be downloaded here.

SMOS FT product version 2.01 data are archived here.

26.10.2023: Release of new user documents

New versions of the user documents are published. The documents can be found in the "Documents" section.

19.10.2023: Release of a new SMOS freeze and thaw product version

A new product Version 3 will be available on 30 October 2023, including several scientific enhancements and product format update. The product will be available on the ESA and FMI dissemination servers. More details on the upcoming version 3 product can be found in the ESA Earth Online news.

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The SMOS FT Service generates a daily information on the Northern hemisphere soil state using as input data the SMOS daily gridded level 3 brightness temperatures (data provided byCentre Aval de Traitement des Données SMOS - CATDS). The Service uses two ancillary datasets: ECMWF 2m air temperature data and NSIDC IMS snow cover data. The data are provided in The Equal-Area Scalable Earth Grid (EASE2-Grid) at 25 km x 25 km resolution. The product start date is July 1st 2010.

The soil freeze/thaw algorithm uses a threshold detection approach. The detection of the soil state is determined by comparing each observation to empirically predefined frozen and thawed ground references. Winter and Summer estimates are further regulated by air temperature reanalysis data. The output product has three categories for the soil state: frozen, partially frozen and thaw.

Before using the product, please read the ReadMe-first Technical Note (RM-TN). For detailed information on the algorithm, please check the Algorithm Theoretical Baseline Document (ATBD). Information on the product content is provided in Product Description Document (PDD). The latest versions of these documents are available in Document section in this web page.

The users are encouraged to give feedback on the product. Please, let us know if any errors on data set is suspected or if there are any regional or temporal inconsistencies with in-situ observations or model estimates. The User’s feedback section provides a channel for direct feedback input. Alternatively, users may contact FMI Project manager for matters concerning the data quality.

In issues related to data access either at FMI servers or at ESA servers, please contact the dissemination support via email provided in Contact section.

When applying the data for commercial, educational or scientific works and publications, please use the following citation:
Rautiainen, K., Parkkinen, T., Lemmetyinen, J., Schwank, M., Wiesmann, A., Ikonen, J., Derksen, C., Davydov, S., Davydova, A., Boike, J., Langer, M., Drusch, M., and Pulliainen, J. 2016. SMOS prototype algorithm for detecting autumn soil freezing, Remote Sensing of Environment, 180, 346-360. DOI: 10.1016/j.rse.2016.01.012