| Summary: | International audience The circumpolar northern colder climate zone (boreal zone/tundra) 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 the first space-borne passive L-band microwave (1.4 GHz) radiometer on board. 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 zone the SMOSHiLat project has been evoked in the framework of ESA's Changing Earth Science Network. 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 Institue, FMI), and Gludsted, Denmark (Hydrologic OBsErvatory, HOBE). Based on this database the L-MEB model is adapted for organic soils encountered in Northern regions and tested in the SMOS soil moisture prototype retrieval algorithm in view of its implementation in the operational one
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