Evaluation of Near Surface Climatology in Atmospheric Delay Estimation for Application in SAR Interferometry

Microwave signal propagation caused by spatiotemporal differences of dry and wet atmospheric content results in an effect known as atmospheric delay. Atmospheric delay is a main source to obscure the land deformation signal derived from Interferometry. A very sparsely distributed GPS network is continually measuring atmospheric delay. However, as climatology parameters show strong spatiotemporal variability, the GPS derived delays are not interpolatable. Instead, InSAR community utilizes climatologic profiles provided by models or reanalysis. This process is time consuming and suffers from the lack of accuracy in terms of spatial and temporal resolutions. In this study, based on a statistical method, we try to link the total delay and near surface climatology. Using four years of hourly climatological profiles from ERA-5 reanalysis (2017–2020), we investigated the vertical autocorrelation within climatological parameter and dry and wet delay profiles within 25 barometric pressure levels (until 13.5 km). The analysis shows that, at about 3.5 km altitude, the accumulated Q, and accordingly, wet delay reaches maximum and remains unchanged upward. However, T and dry delay continue to decrease and increase respectively. We evaluate the results using GNSS GPS total zenith path delay (ZPD) for three stations in the region of study. GPS total zenith path delay showed a mean RMS value of 28 mm and 23 mm with bulk and near surface climatology respectively.