Abstract
The accuracy and applications of synthetic aperture radar interferometry (InSAR) are severely suppressed by tropospheric error. Numerical Weather Models (NWMs) and GPS-derived tropospheric delays have been widely used to correct the tropospheric error considering their complete spatial coverage or high accuracy. However, few studies focus on the fusion of both NWMs and GPS for the tropospheric error correction. In this study, we used the Weather Research and Forecasting (WRF) to obtain NWMs with a higher spatial-temporal resolution of 3 km and 20 s from both ERAI (79 km and 6 h) and ERA5 (0.25° and 1 h). After that, we utilized the WRF Data Assimilation (WRFDA) system to assimilate the GPS ZTD into these enhanced NWMs and generate merged NWMs products. The tropospheric correction effectiveness from different NWMs products was evaluated in a case in the Pearl River Delta region of China. The results showed that all the NWMs products could correct the stratified component in the interferogram but could not mitigate the turbulence well, even after improving the spatial-temporal resolution. As for the trend component, the merged NWMs products showed obvious superiority over other products. From the statistics perspective, the stdev of the interferogram decreased further over 20% by the merged NWMs products than other products when using both ERAI and ERA5, indicating the significant effectiveness of GPS ZTD assimilation.
Highlights
Synthetic aperture radar interferometry (InSAR) has demonstrated a powerful measurement capability in a wide range of applications such as earthquake deformation [1], land subsidence [2], and volcanic activity monitoring [3,4]
Assimilation, and reanalysis-based Weather Research and Forecasting (WRF) with Global Positioning System (GPS) zenith total delay (ZTD) assimilation, will be compared at both GPS station locations in Section 3.1 and interferogram pixels in Sections 3.2 and 3.3
The datum discrepancy between GPS and interferogram is eliminated by setting the atmospheric delay difference at station DLSH to zero
Summary
Synthetic aperture radar interferometry (InSAR) has demonstrated a powerful measurement capability in a wide range of applications such as earthquake deformation [1], land subsidence [2], and volcanic activity monitoring [3,4]. The former method generally assumes atmospheric error as temporal random noise [8] or as an elevation-dependent component [9,10], which either needs a large set of interferograms to separate deformation rate and noise or relies on the assumption of correlations between the deformation and elevation By contrast, the latter method, which is based on EAP, such as Global Positioning System (GPS) [11], Numerical Weather Models (NWMs) [12,13,14,15,16], and Moderate Resolution Imaging Spectroradiometer (MODIS) [17], can provide direct tropospheric delay correction and is more straightforward. This paper will make a preliminary study to investigate the performance of correcting InSAR atmospheric delay by combining NWMs and GPS ZTD.
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