Derivation of hydrological parameters from ENVISAT ASAR wide swath data

Spatially distributed information about the current state of the land surface can be obtained from remote sensing measurements. These may be used with great benefit for the understanding of hydrological processes on the landscape level, where in situ measurements must fail due to lacking spatial coverage. The potential to quantify soil moisture conditions of the top soil layer, as well as the derivation of snow parameters by means of active microwave imagery has been successfully demonstrated in numerous studies. In contrast to earlier and rather experimental research efforts, data acquired from the ENVISAT ASAR sensor firstly enables to continuously monitor large areas with high temporal frequency and high spatial resolution. The different operation modes of ASAR allow the derivation of soil moisture maps on both, the field and the regional scale. The paper presents new methods to derive soil moisture and snow covered area information from ASAR wide swath (WSM) datasets. The presented approaches allocate a robust, yet practicable and reliable technique to derive near-surface soil moisture and snow patterns, being the key prerequisite for an operational application in hydrologic modelling.