Abstract. Hydrologic processes, such as runoff production
or evapotranspiration, largely depend on the variation of soil
moisture and its spatial pattern. The interaction of electromagnetic
waves with the land surface can be dependant on
the water content of the uppermost soil layer. Especially in
the microwave domain of the electromagnetic spectrum, this
is the case. New sensors as e.g. ENVISAT ASAR, allow for
frequent, synoptically and homogeneous image acquisitions
over larger areas. Parameter inversion models are therefore
developed to derive bio- and geophysical parameters from
the image products. The paper presents a soil moisture inversion
model for ENVISAT ASAR data for local and regional
scale applications. The model is validated against in situ soil
moisture measurements. The various sources of uncertainties,
being related to the inversion process are assessed and
quantified.