L-band microwave (1.4 GHz) brightness temperature (TB) observations of the Soil Moisture and Ocean Salinity (SMOS) satellite are used to retrieve global soil moisture data, taking advantage of the large difference between the dielectric constant of dry soil and water. The retrieval is based on the L-band Microwave Emission of the Biosphere (L-MEB) model using tuning parameters derived from study sites in dry and temperate climate zones. Thus, the aim of the SMOSHiLat project (ESA’s STSE Changing Earth Science Network) is to improve our understanding of L-band emissions and supporting SMOS data quality in more northern climate zones covered by pronounced organic surface layers. A database is created including L-band TB and dielectric constant measurements of organic-rich soils, mainly from (1) Sodankylä, Finland (Finish Meteorological Institute), and (2) Gludsted, Denmark (HOBE). Additional organic samples are available from Islay, Scotland, and the West Siberian Plain, Russia. The L-band dielectric constant measurements conducted at the IMS Laboratory (Bordeaux, France), show no distinct variability between a range of humus types encountered in the four regions. Due to the increased bound water fraction in porous organic material dielectric constants are consistently lower than measured in the underlying sandy mineral soils. Hence, one function was fitted through all organic soil moisture – dielectric constant couples, and tested in L-MEB by means of the tower-based ELBARA radiometer dataset acquired at the Research Center Jülich using Danish organic-rich soil. The derived relation proved satisfactory, and consequently, was implemented in the SMOS Soil Moisture Level 2 Prototype Processor (SML2PP). First runs were conducted over the Sodankylä test site and compared with retrieved soil moisture using the Dobson and Mironov dielectric mixing models. Results demonstrated significantly wetter retrieved soil moisture when using the organic fit function. This is in better agreement with an in situ surface soil moisture network average from measurements specifically calibrated for organic material and representative for prevailing land cover and soil types. Further test runs over other sites are planned in the near future. In this presentation, the SMOSHiLat project will be presented with special focus on the SML2PP studies.< Réduire