Mitigation of Tropospheric Effects on X-band InSAR Time-Series Datasets over Nicaraguan Volcanoes
Abstract
Interferometric Synthetic Aperture Radar (InSAR) studies of surface ground deformation are often plagued by tropospheric artefacts, which are the result of phase delays due to spatiotemporal variations of the refractivity of air within the troposphere. Suggested methods to correct for these tropospheric phase delays include empirical and predictive techniques, such as estimation of a linear relation between topography and phase, and using meteorological datasets respectively.
In this study, we examine the applicability of global weather reanalysis models (GWRMs) and an empirical linear correction method for removing the tropospheric component to COSMO-SkyMed (X-band) interferograms covering two different volcanic types in Nicaragua: the Telica stratovolcano (elevation 1,036 m, 23:30 UTC acquisition time) and the Masaya caldera (elevation 635m, 11:40 UTC acquisition time). Our study utilizes three GWRMs according to their availability over Nicaragua, and temporal and spatial resolutions: 1) the European Centre for Meteorological and Weather Forecasting (ECMWF) ERA5 (~30 km, hourly); 2) HRES products (14 km, every 6 hours; accessible through the Generic Atmospheric Correction Online Service, GACOS); and 3) the National Center for Environmental Prediction North American Regional Reanalysis (NARR) (~32 km, every 3 hours). Atmospheric phase screens are created from these GWRMs to account for the tropospheric phase delay and are then subtracted from the interferometric phase. The corrected interferograms are then linearly inverted using the Small BAseline Subset (SBAS) time-series technique to produce a time-series of ground deformation. Statistical assessment of the GWRM corrected interferograms and time-series results is performed to determine the accuracy of the corrections. We validate this analysis using cGPS time-series for stations located on the volcanoes. Preliminary results suggest that while higher temporal resolution in GWRMs is important in improving the tropospheric delay estimate, the spatial resolution still takes precedent in removing tropospheric phase delays. We envision that the results from this study will help future researchers using InSAR data in tropical regions to determine which tropospheric correction method is most applicable for their research.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.G13B0542S
- Keywords:
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- 1209 Tectonic deformation;
- GEODESY AND GRAVITY;
- 1211 Non-tectonic deformation;
- GEODESY AND GRAVITY;
- 1240 Satellite geodesy: results;
- GEODESY AND GRAVITY;
- 1241 Satellite geodesy: technical issues;
- GEODESY AND GRAVITY