ABSTRACT

Atmospheric heterogeneity mainly exposes itself as tropospheric-phase delay in Satellite Interferometric Synthetic Aperture radar (InSAR) observations, which smears or even overshadows the deformation component of InSAR measurements. In this study, we estimated the performance of four Global Atmospheric Models (GAMs), i.e. European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis v5 (ERA5), ERA-Interim (ERA-I), Modern-Era Retrospective analysis for Research and Applications v2 (MERRA2) and Generic Atmospheric Correction Online Service for InSAR (GACOS), for tropospheric-phase delay reduction in InSAR applications in the Tibetan plateau, of which ERA5 is the latest GAM released by ECMWF. We demonstrated the effectiveness of Atmospheric Phase Screen (APS) correction using the four GAMs for more than 700 Sentinel-1 Terrain Observation by Progressive Scans interferograms covering two study areas in the southern (R1) and northwest margins (R2) of the Tibetan plateau. Topography-correlated signals have been widely observed in these interferograms, which are most likely due to the APS effects. We calculated the Standard Deviations (SD) and Pearson’s Correlation Coefficients (r) between InSAR Line of Sight measurements and topography before and after applying APS correction. The results show that the SDs of non-deformation areas from the GAMs decrease to approximately 4 mm from around 10 mm and 12 mm originally on average for R1 and R2, respectively, and the r after the APS correction are reduced below 0.4 from around 0.8 for the selected interferometric pairs. In addition, as the newly released GAM, ERA5 has similar performance with GACOS products and outperforms other models generally. This suggests that GAMs, particularly ERA5, have great potential in the APS correction for InSAR applications in the Tibetan plateau.

摘要

在卫星干涉合成孔径雷达（InSAR）观测中，大气异质性主要表现为对流层相位延迟，这会掩盖甚至掩盖InSAR测量的变形分量。在这项研究中，我们估算了四种全球大气模型（GAM）的性能，即欧洲中距离天气预报中心（ECMWF）再分析v5（ERA5），ERA临时（ERA-I），现代时代的回顾性分析研究和应用程序v2（MERRA2）和InSAR通用大气校正在线服务（GACOS），用于减少青藏高原InSAR应用中的对流层相位延迟，其中ERA5是ECMWF发布的最新GAM。我们通过累进扫描干涉图对青藏高原南部（R1）和西北边缘（R2）的两个研究区域进行了700多个Sentinel-1地形观测，证明了使用四种GAM校正大气相位幕（APS）的有效性。在这些干涉图中，已广泛观察到与地形相关的信号，这很可能是由于APS效应所致。我们计算了标准偏差（SD）和皮尔逊相关系数（r）在进行APS校正之前和之后的InSAR视线测量与地形之间。结果表明，来自GAM的非变形区域的SD分别从R1和R2的原始平均值分别从大约10 mm和12 mm减小到大约4 mm，并且APS校正后的r从大约0.8减小到0.4以下。对于选定的干涉对。此外，作为新发布的GAM，ERA5与GACOS产品具有相似的性能，并且总体上胜过其他型号。这表明GAM，特别是ERA5，在青藏高原InSAR应用的APS校正中具有巨大潜力。