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Neutral atmospheric delay in interferometric synthetic aperture radar applications: Statistical description and mitigation

Emardson, T. R. and Simons, M. and Webb, F. H. (2003) Neutral atmospheric delay in interferometric synthetic aperture radar applications: Statistical description and mitigation. Journal of Geophysical Research B, 108 (B5). Art. No. 2231. ISSN 0148-0227. https://resolver.caltech.edu/CaltechAUTHORS:20130715-140303173

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Abstract

Variations in the refractive index of the atmosphere cause variations in satellite-based interferometric synthetic aperture radar (InSAR) observations. We can mitigate tropospheric effects by averaging N-independent interferograms. Because the neutral atmosphere is uncorrelated at timescales longer than 1 day, using this technique statistically reduces the variance, σ^2, of the noise by a factor of N. Using zenith neutral atmospheric delays from Global Positioning System (GPS) data from the Southern California Integrated GPS Network, we find that the average variance depends on the distance between observations, L, and height difference, H, as σ = c L^α + kH with estimated values for c, α, and k of about 2.5, 0.5, and 4.8, respectively, where σ is in mm and L and H are in km. We expect that the value of α is largely site-independent but the value of c will depend on the water vapor variability of the area of interest. This model is valid over a range of L between approximately 10 and 800 km. Height differences between 0 and 3 km have been used in this analysis. For distances of 100 and 10 km with negligible height differences, σ is estimated to be approximately 25 and 8 mm, respectively. For a given orbit revisit time and image archive duration, we calculate the number and duration (assumed constant) of interferograms required to achieve a desired sensitivity to deformation rate at a given length scale. Assuming neutral atmosphere is the dominant source of noise, a 30° look angle, and an image revisit time of 7 days, detection of a deformation rate of 1 mm yr^(−1) over distances of 10 km requires about 2.2 years of continuous observations. Given our results, we suggest a data covariance structure to use when using InSAR data to constrain geophysical models.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1029/2002JB001781 DOIUNSPECIFIED
http://onlinelibrary.wiley.com/doi/10.1029/2002JB001781/abstractPublisherUNSPECIFIED
ORCID:
AuthorORCID
Simons, M.0000-0003-1412-6395
Additional Information:© 2003 by the American Geophysical Union. Received 23 January 2002; revised 19 December 2002; accepted 31 January 2003; published 3 May 2003. The authors thank Ken Hurst for the processing of the GPS data and D. Dong and S. Wu for helpful discussion. We also thank K. Feigl, R. F. Hanssen, and F. Sigmundsson for constructive reviews. This research was in part supported by the Swedish Foundation for International Cooperation in Research and Higher Education (STINT) and performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. We acknowledge the Southern California Integrated GPS Network and its sponsors, the W. M. Keck Foundation, NASA, NSF, USGS, and SCEC.
Funders:
Funding AgencyGrant Number
Swedish Foundation for International Cooperation in Research and Higher Education (STINT)UNSPECIFIED
Southern California Integrated GPS NetworkUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
NASAUNSPECIFIED
NSFUNSPECIFIED
USGSUNSPECIFIED
Southern California Earthquake Center (SCEC)UNSPECIFIED
Subject Keywords:radar interferometry; troposphere; InSAR; crustal deformation
Issue or Number:B5
Record Number:CaltechAUTHORS:20130715-140303173
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20130715-140303173
Official Citation:Emardson, T. R., M. Simons, and F. H. Webb, Neutral atmospheric delay in interferometric synthetic aperture radar applications: Statistical description and mitigation, J. Geophys. Res., 108(B5), 2231, doi:10.1029/2002JB001781, 2003
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:39370
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:15 Jul 2013 21:53
Last Modified:03 Oct 2019 05:06

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