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Published December 2015 | Supplemental Material + Published
Journal Article Open

InSAR bias and uncertainty due to the systematic and stochastic tropospheric delay

Abstract

We quantify the bias and uncertainty of interferometric synthetic aperture radar (InSAR) displacement time series and their derivatives, the displacement velocities, by analyzing the systematic and stochastic components of the temporal variation of the tropospheric delay. The biases due to the systematic seasonal delay depend on the SAR acquisition times, whereas the uncertainties depend on the standard deviation of the random delay, the number of acquisitions, the total time span covered, and the covariance of the time series of the stochastic delay between a pixel and the reference. We study the contribution of the wet delay to the InSAR observations along the western India plate boundary using (i) Moderate Resolution Imaging Spectroradiometer precipitable water vapor, (ii) stratified tropospheric delay estimated from the ERA-I global atmospheric model, and (iii) seven Envisat InSAR swaths. Our analysis indicates that the amplitudes of the annual delay vary by up to ~10 cm in this region equivalent to a maximum displacement bias of ~24 cm in InSAR line of sight direction between two epochs (assuming Envisat IS6 beam mode). The stratified tropospheric delay correction mitigates this bias and reduces the scatter due to the stochastic delay. For ~7 years of Envisat acquisitions along the western India plate boundary, the uncertainty of the InSAR velocity field due to the residual stochastic wet delay after stratified tropospheric delay correction using the ERA-I model is in the order of ~2 mm/yr over 100 km and ~4 mm/yr over 400 km. We discuss the implication of the derived uncertainties on the full variance-covariance matrix of the InSAR data.

Additional Information

© 2015 American Geophysical Union. Received 3 AUG 2015; Accepted 23 NOV 2015; Accepted article online 27 NOV 2015; Published online 28 DEC 2015. The MODIS PWV data of NASA's Aqua and Terra satellites were obtained using the Jet Propulsion Laboratory's Online Services for Correcting Atmosphere in Radar (OSCAR). The SAR raw data from ESA's Envisat satellite were obtained using UNAVCO's Seamless SAR archive (SSARA). We thank Brian Mapes from the UM Atmospheric Sciences Department and Shimon Wdowinski for discussions. This study was funded by grants from NASA's Earth Science division and the National Science Foundation's tectonics program to F.A. (NNX09AD22G and EAR-1019847).

Attached Files

Published - Fattahi_et_al-2015-Journal_of_Geophysical_Research__Solid_Earth.pdf

Supplemental Material - jgrb51407-sup-0001-supinfo.pdf

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Fattahi_et_al-2015-Journal_of_Geophysical_Research__Solid_Earth.pdf
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Additional details

Created:
August 20, 2023
Modified:
October 18, 2023