Estimation of snow water equivalent from L-band radar interferometry: simulation and experiment

Abstract

ABSTRACT The Snow Water Equivalent (SWE) is the main feature of a snowpack that determines its impact on the natural environment. Because microwaves penetrate through the snowpack, microwave remote sensing enables the measurement of depth and snow water equivalent. A promising tool for determining SWE is synthetic-aperture radar, which provides a high spatial resolution (from metres to tens of metres). This paper presents a theoretical and experimental study of snowpack sensing using radar interferometry. An approximate model of interferometric sensing based on the small perturbation method is proposed. As opposed to the well-known interferometric model, the proposed one takes into account microwave backscattering from the snow surface. We estimated the contribution of scattering from the snow surface to amplitude and interferometric phase values. Using Advanced Land Observing Satellite – 2 (ALOS-2) Phased Array type L-band Synthetic Aperture Radar – 2 (PALSAR-2), SWE was first determined by means of a radar interferometry method at a test site near Lake Baikal, Russia. The experiment consisted of comparing the phases of radar signals received when there was no snowpack (in September) and those in its presence (in February). We used a reference scatterer in the form of a trihedral corner reflector to calibrate the phase measurements. The SWE values were restored from the linear dependence between SWE and the interferometric phase. A comparison between the calculated and experimental data shows their good agreement.