High‐Resolution Soil Moisture Evolution in Hyper‐Arid Regions: A Comparison of InSAR, SAR, Microwave, Optical, and Data Assimilation Systems in the Southern Arabian Peninsula

Abstract

AbstractWe present an analysis of a 3‐year time series of Synthetic Aperture Radar (SAR) imagery covering the southern Arabian Peninsula, spanning two devastating typhoons that impacted the region in 2018. The limited vegetation and precipitation in the area allows for clear separation of soil moisture changes from other factors that typically also affect microwave imagery. We generate soil moisture proxies from Interferometric SAR (InSAR) coherence and compare them with a range of other soil moisture products. We estimate the decay timescale over which the surface returns to its pre‐storm state for each event and data type, and find that the radar coherence‐based timescales tend to be longer than those for the other products. We also find that the coherence‐based timescales of the two events differ from each other in a manner that is consistent with seasonal temperature fluctuations and the total rainfall that occurred each time. The higher spatial resolution of the InSAR coherence results and differing sensitivity to the vertical distribution of soil moisture complements the other more temporally dense products, particularly in regions of high heterogeneity along the edge of the storm and within regions where the surface properties change dramatically over small spatial scales. As the frequency and strength of tropical cyclones increase, and as already scarce water resources are utilized further in arid regions, InSAR coherence data constitutes another tool that researchers can use to expand our understanding of these challenges.