Spatiotemporal characteristics analysis of atmospheric delay in spaceborne SAR based on IRI2020 and ERA5

Spaceborne synthetic aperture radar (SAR) plays a crucial role in mapping tasks. However, atmospheric delay at the meter level significantly limits the improvement of its geometric accuracy. This study utilizes IRI2020 and ERA5 data, using Sentinel-1 image parameters as an example, to analyze the spatiotemporal distribution characteristics of SAR atmospheric delay. The results indicate that atmospheric delay exhibits significant temporal and spatial variability. During the spring and autumn, the atmospheric delay distribution in both hemispheres shows symmetry, with a concentration in low-latitude regions and a gradual decrease toward the poles. Neutral atmospheric delay is minimally affected by temporal variations, while ionospheric delay experiences significant temporal fluctuations. In summer, ionospheric delay is mainly concentrated around the equator and to the north, whereas in winter, it is more pronounced south of the equator. Daytime atmospheric delay is higher than nighttime delay, peaking around midday. In terms of overall atmospheric delay, the difference between the hemispheres is smaller in spring and autumn. In the northern hemisphere, the atmospheric delay is largest in summer and smallest in winter, whereas the southern hemisphere, the opposite trend is observed, with the smallest atmospheric delay in summer and the largest in winter. For the Sentinel-1 satellite, the study finds that the primary source of SAR atmospheric delay is the neutral atmospheric delay, while the impact of ionospheric delay is relatively minor. This research provides significant theoretical foundations and practical guidance for atmospheric correction of SAR imagery, high-precision positioning, and InSAR-based surface deformation monitoring applications.