Surface materials and landforms as controls on InSAR permanent and transient responses to precipitation events in a hyperarid desert, Chile

Abstract

Ground-based monitoring and remote sensing of extreme rain events in the hyperarid Atacama Desert, Chile, reveal a complex relationship between precipitation, soil types and interferometric synthetic aperture radar (InSAR) coherence. These integrated analyses allow examination of temporal and spatial variations of the soil moisture response between locations dominated by sulfate soils and those with immature, silicate-mineral soils. The radar dataset captures at least four separate rain events within the 2015-2017 timeframe, two of which were regionally devastating. The lack of vegetation in this region allows us to discriminate between contributions to the InSAR coherence from permanent changes of the landscape (e.g., erosion or deposition) and transient changes associated with soil moisture variability. The spatial distribution and character of the transient InSAR response depends strongly on soil type, and is remarkably repeatable between rain events. The areas that experienced permanent changes included river channels, steep slopes, playas, and sites of anthropogenic activity, such as roads, mines, or telescope construction. Ground-based observations of soil moisture after each event also exhibit a strong dependence on soil type. The observations presented here demonstrate how InSAR data can constrain variations in soil moisture with high spatial resolution over large regions, complementing the higher-sensitivity but sparser field sites and enabling discrimination of inter-event variability and analysis of longer-term changes in soil mineralogy in arid regions.