Comparison of Ers Sar Data Derived Soil Moisture Distributions with Svat-model Results

Within the frame of the ESA-project GeoBIRD soil moisture was determined from ERS-1/2 beased microwave backscatter measurements in three different European test sites. The semi empirical IGGF-model (Rombach and Mauser [1]) was used together with a geographical information system to derive the soil-moisture under the land covers maize, cereals and meadows. The IGGF-model takes into account land-use, biomass and soil-type to convert the ERSmeasurements of different surfaces into dielectric constants of the top soil layer, which are then converted into soilmoisture. The SVAT and land surface process model PROMET-V (PROcess oriented Modular Environment and Vegetation model (PROMET-V, Schneider and Mauser [7],[9]) was used to model the spatial and temporal development of the energy budget, the soil moisture and the plant growth before and during the ERS-overflights. The measured soilmoisture derived by the IGGF-model was compared both to field measurements and to the results of the SVAT-model. The results show, that the correspondance between ERS-measurements using the IGGF-model and field measurements are generally high. The spatial distribution and the soil-moisture level, which resulted from the SVAT-model PROMET show considerable correspondance with the ERS-measurements. Nevertheless discrapencies are due to incomplete soilinformation.