InSAR Tropospheric Correction Maps Generated From GPS and Weather Model Data: Application to Envisat and ALOS Interferograms in Southern California

We describe a system under development for providing tropospheric delay maps from GPS and weather model data as part of a NASA Advanced Information Systems Technology project. We build on GPS zenith tropospheric delay (ZTD) estimates routinely produced with excellent temporal resolution (5 minutes to 1 hour) by Scripps Institution of Oceanography and Jet Propulsion Laboratory while generating daily position solutions for approximately 1300 continuous GPS stations in western North America. The spatial resolution is enhanced by including water vapor fields from weather forecast products. The GPS and weather model data are combined such that the GPS values are preserved at the locations of the GPS stations and weather model data is more strongly weighted farther away from GPS stations. We account for variations in topography when interpolating the corrections to a 6-arcsecond grid. The correction maps, which improve the ability to estimate interseismic deformation and distinguish different fault mechanisms, will soon be available to investigators via the GPS Explorer portal. Tests of the system have been extended to include ALOS interferograms, complementing our earlier tests on Envisat interferograms. We apply the correction maps to short-interval interferograms to isolate atmospheric variation as the dominant signal, and expect that a successful correction map reduces RMS from the original interferogram. Results are favorable for GPS corrections; inclusion of weather model data yields further improvements in some, but not all, of the cases examined.