Earth Observation for Cryosphere, News

New global and continuous soil freeze-thaw data released to boost climate change assessment

ESA SMOS product family expands with a hemispheric cryosphere product, the SMOS Level 3 freeze and thaw soil state. This new product, provided by Finnish Meteorological Institute (FMI), gives daily information on soil frost; one of the key parameters in understanding global carbon and water cycle processes.

Approximately half of the Earth’s land surface is affected by seasonal soil freezing and thawing. Permafrost areas cover about one quarter of the land masses. Soil freezing influences surface energy balance, global water cycle and exchange rates of carbon with the atmosphere. Change in soil freeze period length has an effect on the permafrost degradation. The decrease in permafrost extent is likely to speed up the release of the methane from arctic and sub-arctic wetlands.

The ESA’s SMOS (Soil Moisture and Ocean Salinity) satellite, launched in November 2009, was the first in-orbit mission providing L-band passive microwave observations from space. With L-band the observed signal is originated from deeper soil layers compared to instruments operating at higher frequencies.

“SMOS instrument is particularly well suited for the detection of soil state. The freezing of free liquid water in soils increases the observed brightness temperature significantly providing a well detectable contrast in observations compared to the thaw soil condition,” says Kimmo Rautiainen, senior scientist at the Finnish Meteorological Institute. 

Susanne Mecklenburg, ESA’s SMOS mission manager, said “The systematic provision of this data opens up new opportunities for carbon cycle research. We are happy to see this operational service now started.”

Data available from year 2010 onwards

The SMOS soil freeze and thaw product, originally presented in 2016, was the first satellite-based L-band product providing daily information on the soil freeze and thaw state (Rautiainen et al., 2016). Within the frame of several ESA studies, the development of the original prototype product has now achieved an operational status providing a new addition to the ESA SMOS product family. The operational Level 3 freeze and thaw (L3FT) product is daily generated based on SMOS observations from CATDS (Centre Aval de Traitement des Données SMOS).

The dataset from year 2010 onwards can be accessed from the ftp service: . This dataset will be also available on the ESA SMOS Data Dissemination server in the coming months.

Further information:

Senior scientist Kimmo Rautiainen, Finnish Meteorological Institute, tel. +358 29 539 2045,

Further information on the product can be found from the SMOS FMI service portal:

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