HR: 0800h
AN: G31A-0786    [Abstracts]
TI: On the Applicability of Taylor's ``Frozen-Flow'' Hypothesis to Spatial and Temporal Observations of Atmosphere Path Delay From InSAR and GPS
AU: * Onn, F
EM: phae@stanford.edu
AF: Department of Electrical Engineering, Stanford University, Stanford, CA 94305 United States
AU: Zebker, H A
EM: zebker@stanford.edu
AF: Department of Electrical Engineering, Stanford University, Stanford, CA 94305 United States
AB: Turbulent mixing of water vapor in the lower troposphere produces fluctuations of the spatio-temporal distribution of neutral atmosphere refractive index at microwave frequencies. These variations cause phase shifts in Interferometric Synthetic Aperture Radar (InSAR) images and Global Positioning System (GPS) signals. Here, we compare spatial observations of atmospheric phase shifts from a radar interferogram of Southern California with temporal measurements of atmospheric delay obtained from a network of continuous GPS receivers operating in the imaged area. We translate temporal observations to equivalent spatial samples of delay through Taylor's ``frozen-flow'' hypothesis. We use the ``frozen-flow'' hypothesis in conjuction with Kolmogorov turbulence theory to derive theoretical expressions for temporal and spatial power spectra and structure functions of atmosphere delay. We show that temporal and spatial power spectra and structure functions have similar theoretical forms and parameters. Further, the theoretical expressions for temporal power spectra and structure functions require knowledge of the magnitude and direction of wind about each GPS receiver, which we estimate from the timeseries of delays at each site. These wind estimates and the theoretical expressions are fit to computed power spectra and structure functions of delay derived from the GPS and InSAR data. The parameters derived from the least-squares fitting of temporal power spectra and structure functions from GPS are used to infer spatial models of power spectra and structure functions of interferometric phase. Comparison of these inferred models with computed spatial power spectra and structure functions from the InSAR phase residuals demonstrate the validity of applying Taylor's hypothesis to GPS and InSAR atmospheric delay measurements. This correspondence between measurements of atmosphere delay from the two datasets suggests that full timeseries of atmosphere path delay from GPS, as opposed to delay observations taken at the radar acquisition times only, can be used to mitigate atmospheric effects in radar interferograms.
DE: 1229 Reference systems
DE: 1243 Space geodetic surveys
DE: 1244 Standards and absolute measurements
DE: 1294 Instruments and techniques
DE: 1299 General or miscellaneous
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting