Correction of tropospheric effects in SAR interferometry: a comparison of ERA-Interim, ERA-5 and HRES Global Atmospheric Models

Since the 1970s, Interferometric Synthetic Aperture Radar is commonly used in Earth Sciences to construct high resolution topographic maps or to study surface displacements. The recent launch of new satellites such as Sentinel-1 constellation allows to routinely derive dense deformation maps with millimetre precision thanks to high revisit frequency and wide swath coverage (300 km wide). However, the accuracy of InSAR is still limited by atmospheric noise, as atmospheric delays may lead to subcentimeter biases in measurements. Global Atmospheric Models (GAMs) allow to compute tropospheric delay maps and correct interferograms from atmospheric delays. In the light of the development of these models over the last ten years, where spatio-temporal resolutions became finer and models more accurate, we propose a quantitative comparison of recent GAMs. We first describe how to correct interferograms from atmospheric delays and present three GAMs used in this paper: ERA-5, ERA-Interim and HRES. We then perform a statistical comparison of the performances of atmospheric corrections. We finally discuss the contribution of the enhanced spatio-temporal resolution of ERA-5, the latest global reanalysis from ECMWF, arguing that improving the spatial resolution is key toward better predictions of atmospheric delays in SAR interferometry.