Microwave L‐band Dielectric Constant and Brightness Temperature Estimates of Organic‐Rich Soils in the Boreal Zone
Résumé
Climate Variables of the ESA's Climate Change Initiative. It constitutes a major uncertainty in climate and hydrological models, which are currently the best tools to simulate the ongoing human-induced climate changes. Hence, global soil moisture observations of good temporal resolution and quality are of high relevance. The ESA's Earth Explorer Soil Moisture and Ocean Salinity (SMOS) mission carries the first space-borne passive L-band microwave (1.4 GHz) radiometer on board, operating at the preferred frequency for soil moisture retrieval. It acquires global brightness temperature (TB) data every three days, from which surface soil moisture is retrieved, based on the inversion of the L-band Microwave Emission of the Biosphere (L-MEB) radiative transfer model. To account for the impact of roughness and vegetation, in L-MEB several land cover-dependent tuning parameters are implemented, which exclusively stem from study sites in the dry and temperate climate zones. Environmental conditions in the vast northern boreal zone are different. Prevailing land cover types include coniferous forest, heath- and wetlands with pronounced organic surface litter layers. The emission contributions of litter have been identified, but more knowledge is needed to take them into account in the modeling. This conference contribution presents the above-mentioned L-band dielectric constant and brightness temperature database from the Sodankylä test site in Northern Finland. Comparisons of modeled and measured dielectric constant estimates are shown. Furthermore, comparisons of modeled brightness temperatures as well as ELBARA, HUT-2D, and SMOS brightness temperature estimations are illustrated. Finally, an outlook is given on the planned model development.