Exploring D-Pol-InSAR Coherence Regions for Snow Water Equivalent Estimation

Abstract

The interferometric phase difference measured with Differential Interferometric Synthetic Aperture Radar (D-InSAR) is used to estimate the snow layer change in terms of Snow Water Equivalent (SWE) occurring in the time between the two interferometric acquisitions. However, due to the 2π ambiguity of the measured phase difference only a wavelength dependent range of SWE changes can be retrieved unambiguously. In this study, the effect of the polarization of the D-InSAR measurements on the SWE change estimates is investigated. A Differential Polarimetric Interferometric SAR (D-Pol-InSAR) approach is proposed to model Pol-InSAR coherences that can potentially contribute to overcome limitations in SWE change estimations. The effect of snow layer changes on the Pol-InSAR coherence regions is investigated, revealing the difference of change in snow layer depth and anisotropy. Based on a D-Pol-InSAR model, a SWE change retrieval is proposed, that optimizes snow layer depth, density and anisotropy in the context of modelled and measured coherence regions using airborne SAR data acquired over the Woergetal valley, Austria from interferograms from the 03.03.2021/06.03.2021 and 06.03.2021/19.03.2021. This allows to improve the SWE estimation performance compared to the conventional single polarization approach for larger snowfall events causing 2π phase ambiguities.