Paul Tregoning: Environmental Geodesy
Geodesy-related Student Projects
Variations in water resources in regional drainage basins
GRACE satellites in orbit around the Earth (Courtesy NASA/JPL-Caltech) |
The Gravity Recovery and Climate Experiment (GRACE) space gravity
mission now provides the capability to measure temporal mass variations
of the Earth at sub-continental scales. Thus, it is now possible to
estimate water resources at drainage-basin scales.
Studies of temporal variations in water of the Murray-Darling and other large-scale drainage basins are underway. Linking such large-scale information with hydrologic data provides a powerful monitoring capability for Australia's water resources. PublicationsLeblanc, M., P. Tregoning,, G. Ramillien, S. Tweed, A. Fakes, 2009. Basin scale, integrated observations of the early 21st Century multi-year drought in southeast Australia, Water Resources Res., 45, W04408, doi:10.1029/2008WR007333. (pdf) |
Quantifying sea level change
Satellite altimetry measures global sea level (Courtesy NASA/JPL-Caltech) |
Sea levels change as a result of thermal expansion of the oceans under
a warming climate but also through the exchange of water between the
oceans and the continents/atmosphere. An increase in snow accumulation
requires a reduction in ocean volume, whereas melting of continental
ice causes an increase in ocean volume; therefore an increase in
sea level.
Satellite altimetry is used to measure sea surface heights, from which sea level variations can be deduced. Improvements to the geodetic reference frame, orbit estimation of altimeter satellites and calibration/validation of altimeters are required in order to estimate accurate rates of sea level variations. |
Modelling atmospheric effects
Mean improvement in height estimate produced by using accurate surface pressure when analysing GPS data |
The propagation of radio signals through the Earth's atmosphere is still the
most limiting factor in determining accurate height estimates from GPS and
VLBI analyses. Recent advances in developing time-varying mapping functions
(such as the VMF1 developed by Johannes Boehm in Vienna) and the use of
more accurate a priori hydrostatic delays have made significant
improvements.
Future research in this area includes modelling asymmetric variations in the atmosphere, variations in atmospheric pressure tides, improved atmospheric pressure loading models and improved modelling of the a priori atmospheric delays. |
Selected relevant publications
Tregoning, P. and C. Watson,
Atmospheric effects and spurious signals in GPS analyses,
J. Geophys. Res., , in press
pdf
Boehm, J., P.J. Mendes Cerveira, H. Schuh, P. Tregoning, 2007. The impact of mapping functions for the neutral atmosphere based on numerical weather models in GPS data analysis, IAG Symopsium Series, P. Tregoning and C. Rizos (Eds), 130, 837-843.
pdf
Tregoning, P. and T. A. Herring, 2006. Impact of a priori zenith hydrostatic delay errors on GPS estimates of station heights and zenith total delays, Geophys. Res. Lett., 33, doi:10.1029/2006GL027706.
pdf
Boehm, J., A. E. Niell, P. Tregoning, H. Schuh, 2006. The GMF: A new empirical mapping function based on numerical weather model data, Geophys. Res. Lett., 33(7), doi:10.1029/2005GL025546.
pdf