Soil Moisture Variation Impact on Decorrelation Phase Estimated by Sentinel-1 Insar Data.

Soil moisture is an important component in investigations of land-surface climate and hydrology. Recently several methodologies and techniques have been proposed, allowing soil moisture retrieving from SAR remote sensing techniques at large scales. In this work we investigate the relation between the closure phases and the time varying soil moisture. We combine three interferograms obtained from three SAR images of the same area acquired at different times, to derive maps of bi-coherence and phase triplet. The results show that there is a linear correlation between the modelled phases derived from soil moisture measurements and the closure phases. The correlation coefficient was R-2=0.76 and R-2=0.86 for the descending and ascending passes, respectively. However, a scale effect of the closure phases was found when compared with the derived model phases. The scale is about 10% for both passes, meaning that the estimated closure phases underestimate the soil moisture changes.