Potential of ASAR-ENVISAT for estimating near surface soil moisture in a sloping terrain of a Himalayan watershed

Abstract

Soil moisture estimation is considered to be one of the important parameters in hydrological studies. The extraction of information on near surface soil moisture from the synthetic aperture radar is well established. The available Advanced Synthetic Aperture Radar (ASAR) data onboard ENVISAT with multi-incidence and multi-polarization mode for soil moisture estimation on sloping terrain was investigated. Empirical models were developed to estimate near surface soil moisture in the fallow agricultural fields by incorporating the effects of surface roughness using multi-incidence angle ASAR data. Medium incidence angle (IS-4) with VV polarization of ASAR data had higher correlation coefficient to volumetric soil moisture content. The ratio of medium (IS-4) to high incidence (IS-6) angle could further reduce the effect of surface roughness. The effect of topography on the radar data is taken care by calculating local incidence angle derived from ASTER DEM data. The VV polarization in the sloping terrain provided better results in comparison to VH polarization.