A global GPS data reprocessing strategy: Implications for the reference frame, orbital solutions, and trends in zenith delay parameters and total column water vapor (1994--2011).

摘要

The primary focus of this work is to derive a long-term global trends in precipitable water vapor using atmospheric path delays as observed by continuously operating GPS stations from 1994 to present. Atmospheric water vapor plays a key role in global climate change but the exact mechanics of this process is poorly understood. Measuring the atmospheric path delay between the GPS satellite and ground station, it is possible to estimate the total water vapor content as a derived quantity independent of hardware configuration or environmental factors at continuous GPS locations. Globally distributed continuous GPS stations have existed with sufficient density for climate studies since around 1994 making GPS derived atmospheric path delay an excellent tool for global water vapor studies. A global GPS data set of more than 1000 stations has been reprocessed from 1994 to present to ensure maximum homogeneity of satellite orbits, ground station coordinates, and thus atmospheric delay estimates. The observed mean trend in precipitable water vapor based on zenith total delay measurements at GPS station locations is small at 0.094 +/- 0.030 mm per decade while regional trends are often quite large w.r.t this mean trend, at times by an order of magnitude. Furthermore these large regional trends are polarized where positive trend regions are cancelled out by other negative trend regions. Precipitable water vapor estimates from the meteorological model ERA-Interim yield a mean trend over all land of 0.113 +/- 0.007 mm per decade and a mean trend of 0.078 +/- 0.017 mm per decade when restricted to GPS station locations only.