Evaluation of Wide-Swath InSAR Tropospheric Delay Estimation Methods over the Altyn Tagh Fault

Abstract

In recent years, wide-swath (WS) interferometric synthetic aperture radar (InSAR) technique that has the potential to produce continental-scale maps has been widely used in geological disaster survey and crustal deformation monitoring. However, the impact of tropospheric delay greatly limits its accuracy in mapping small amounts of ground deformation over large spatial areas. Three common used methods, that is ECMWF (European Centre for Medium-Range Weather Forecasts), GACOS (generic atmospheric correction online service for InSAR) and topography-correlated linear relationship, are evaluated to investigate their statistical performance with WS InSAR time series derived from Envisat ASAR ScanSAR and Sentinel-1 TOPOSAR modes over the western segment of the Altyn Tagh Fault. The results show that the GACOS correction method is superior to the other two methods and performs best in capturing both topography-correlated and turbulent mixing tropospheric delays. For Envisat ASAR and Sentinel-1 datasets, the mean reduction of phase standard deviation after GACOS correction can reach 68.1% and 54.5% respectively. The linear correction method can perform relatively well in large-scale areas with rough topography when vertical atmospheric stratification dominates the tropospheric delay. Due to a lack of ground meteorological observation, ECMWF products with limited spatial and temporal resolution cannot accurately reveal the local details. As a fast, robust and effective online service for tropospheric delay estimation and correction, GACOS products can provide critical and reliable support for global InSAR users in large-scale geological disaster applications.