High-Resolution Forward Modeling of Sentinel-1 Observations at High Altitude in Complex Topography

Sentinel-1 C-band SAR observations over the high-altitude Senator Beck Basin in Colorado show spatial patterns strongly modulated by local topography. An uncalibrated coupled snow hydrology-radiative transfer model driven by downscaled atmospheric reanalysis data (30-m, 15-min) was applied to simulate the spatial and temporal evolution of the backscattering behavior of the seasonal snowpack without vegetation. Model simulations were corrected to capture the impact of complex topography on the viewing geometry. The moisture-attenuated background backscattering field was estimated from a small number of averaged summertime measurements under snow-free conditions. The comparison between the results shows good agreement (< 3 dB) between simulated and observed backscattering fields except in very steep slopes (> 25°). Localized higher discrepancies at lower elevations and relatively flat terrain can be unambiguously attributed to underestimation of snowfall in the reanalysis data.