Stories of the Finnish Arctic Expertise
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Soil freeze and thaw data service to boost climate change assessment

Finnish Meteorological Institute (FMI) is now providing global and continuous information on soil freeze and thaw.

Soil frost is 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 landmasses. 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 European Space Agency 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 originates from deeper soil layers compared to instruments operating at higher frequencies.

"The 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.

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

Data available from 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. 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 on the product can be found from the SMOS FMI service portal.

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