The circumpolar cold temperate (boreal) climate zone is covered by pronounced organic soils. Due to above-average rising temperatures in the higher northern latitudes, a large amount of these important carbon sinks might be released, possibly causing a significant positive feedback on global warming. Thus, there is a strong need to monitor hydrologic processes in these regions.

The ESA’s Soil Moisture and Ocean Salinity (SMOS) mission carries onboard the first space-borne passive L-band microwave (1.4 GHz) radiometer. It acquires global brightness temperatures (TB) from which surface Soil Moisture is retrieved, taking advantage of the very large difference between the dielectric constant of dry soil and water at this frequency. The retrieval algorithm is based on the L-band Microwave Emission of the Biosphere (L-MEB) model which uses tuning parameters derived from study sites in dry and warm temperate climate zones.

In order to improve our understanding of L-band emissions of organic soil surface layers and thus supporting the quality of SMOS data in the northern colder climate zones the SMOSHiLat project has been evoked. It aims at creating a database including L-band TBs and dielectric constant values of soils, mainly from two northern study sites in Sodankylä, Finland (Finnish Meteorological Institute, FMI), and Gludsted, Denmark (Hydrologic OBsErvatory, HOBE). L-band dielectric constants are quantified by modeling from calibrated soil moisture measurements input to a dielectric model for organic soils, as well as direct measurements from collected samples (wave-guide and cavity techniques). Using these estimates, L-band TBs will be modeled by means of a physically-based radiative transfer model to supplement the tower-based radiometer observations from both study sites. Based on this database a surface emission model adapted for organic soils is developed and tested in the SMOS soil moisture prototype retrieval algorithm in view of its implementation in the operational one.