ANU Space Gravity Analysis

More information

Artist's rendering of the twin GRACE-FO satellites in orbit. Credit: NASA

The ANU GRACE software, developed in the Environmental Geodesy group at the Research School of Earth Sciences, is a suite of programs and scripts that processes the Level-1B data from the GRACE and GRACE Follow-On missions to estimate temporal variations in mass distribution on and within Earth. The analysis process involves integrating satellite orbits then estimating changes in mass on mass concentration elements (known as "mascons") to provide a best-fitting set of parameters to match the observations of position, velocity and range acceleration between the two satellites.

What's different about the ANU space gravity solutions?

There are two fundamental differences in our analysis approach that make our solutions unique:

Range acceleration

We use the time derivative of the range rate observations as the principal inter-satellite observation in our analysis. The use of the range acceleration enhances the spatial localisation of the mass change signals (Allgeyer et al., 2022).

Irregularly shaped mascons

Rather than estimating spherical harmonic coefficients to represent the temporal gravity field, we estimate directly the changes in mass - expressed as a height of equivalent water - on each mascon. We use 12755 primary mascons, each comprised of ~100 smaller ternary mascons. Each ternary mascon is roughly 18x18 km and we add them together to form the primary mascons (Tregoning et al., 2022).

The deliberate ad hoc approach to constructing our primary mascons means that we can form irregularly shaped primary mascons, which means that boundaries of the primary mascons can follow coastlines and/or drainage boundaries. This helps to reduce the leakage of signals across ocean/continent boundaries as well as across drainage basins (McGirr et al., 2023).

External members

Analysis/Methods of processing space gravity data

  • McGirr, R., P. Tregoning, S. Allgeyer,  H. McQueen and A.P. Purcell, Interplay of altitude, ground track coverage and noise on the spatial resolution of GRACE gravity field models, Journal of Geophysical Research,  https://doi.org/10.1029/2022JB024330, 2023.

  • Tregoning, P., R. McGirr, J. Pfeffer, A.P. Purcell, H. McQueen, S. Allgeyer and S.C. McClusky, ANU GRACE data analysis: Characteristics and benefits of using irregularly shaped mascons, Journal of Geophysical Research, https://doi.org/10.1029/2021JB022412, 2022.

  • Allgeyer, S., P Tregoning, H. McQueen, S.C. McClusky, E.-K. Potter, J. Pfeffer, R. McGirr, A.P. Purcell, T.A. Herring and J.-P. Montillet, ANU GRACE data analysis: Orbit modelling, regularisation and inter-satellite range acceleration observations, Journal of Geophysical Research, https://doi.org/10.1029/2021JB022489, 2022.

  • McGirr, R., P Tregoning, S. Allgeyer, H. McQueen and A.P. Purcell, Mitigation of thermal noise in GRACE accelerometer observations, Advances in Space Research, https://doi.org/10.1016/j.asr.2021.10.05, 2022.

 

Applications using space gravity data

  • McGirr, R., P. Tregoning, S. Allgeyer, A.P. Purcell and H. McQueen, Significant local sea level variations caused by continental hydrology signals, Authorea preprint, https://doi.org/10.22541/au.170709016.67679707/v1, 2024.

  • Razeghi, M., P. Tregoning, M. Shirzaei, K. Ghobadi-Far, S. McClusky and L. Renzullo, Characterization of changes in groundwater storage in the Lachlan Catchment, Australia, derived from observations of surface deformation and groundwater level data, Journal of Geophysical Research, http://doi.org/10.1029/2022JB024669, 2022.

  • Ghobadi-Far, K., S.-C. Han, S. Allgeyer, P Tregoning, J. Sauber-Rosenberg, S. Behzadpour, T. Mayer-Gurr, N. Sneeuw and S. Okal , GRACE gravitational measurements of tsunamis after the 2004, 2010, and 2011 great earthquakes, J. Geodesy, 94, 65, https://doi.org/10.1007/s00190-020-01395-3, 2020.

  • Tian, S., L. Renzullo, A. van Dijk, P Tregoning, and J Walker, Global joint assimilation of GRACE and SMOS for improved estimation of root-zone soil moisture and vegetation response, Hydrology and Earth System Sciences, 23, 1067-1081, 2019

  • Tian, S., A.I.J.M van Dijk, Tregoning, P. and L.J. Renzullo, Forecasting dryland vegetation condition months in advance through satellite data assimilation, Nature Comm., 10, 469, 2019.

  • Tian,S.,  P. Tregoning, L.J. Renzullo, A.I.J.M. van Dijk, J.P. Walker, V.R.N. Pauwels and S. Allgeyer, Improved water balance component estimates through joint assimilation of GRACE water storage and SMOS soil moisture observations, 2016 Water Resourc. Res., 53, 1820-1840, doi:10.1002/2016WR019641, 2017

  • van Dijk, AIJM, Renzullo, LJ, Wada, Y and P. Tregoning, 2013, A global water cycle reanalysis (2003-2012) reconciling satellite gravimetry and altimetry observations with a hydrological model ensemble, HESS, 10, 15475-15523, 2013.

  • N. Darbeheshti, L. Zhou, P. Tregoning and S.C. McClusky, 2013, The ANU GRACE visualisation web portal, Computers and Geoscience, 52, 227-233, 2013.

  • Purcell, T., A. Dehecq, Tregoning, P., K. Lambeck, E-K Potter and S. McClusky 2011. Relationship between the Glacial Isostatic Adjustement and gravity perturbation observed by GRACE, Geophys. Res. Lett., 38, L18305,

  • Tregoning, P., C. Watson, G. Ramillien, H. McQueen and J. Zhang, 2009. Detecting hydrologic deformation using GRACE and GPS, Geophys. Res. Lett. 36, L15401, doi:10.1029/2009GL038718.

  • Tregoning, P., G. Ramillien, H. McQueen and D. Zwartz 2009. Glacial isostatic adjustment and non-stationary signals observed by GRACE, J. Geophys. Res.114 B06406, doi:10.1029/2008JB006161

  • Leblanc, 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.

  • Tregoning, P., K. Lambeck and G. Ramillien , 2008. GRACE estimates of sea surface height anomalies in the Gulf of Carpentaria, Australia, Earth Planet. Sci. Lett., 271, 241-244, doi:10.1016/j.epsl.2008.04.018

Contacts

Rebecca McGirr
rebecca.mcgirr@anu.edu.au