Can GPS-Derived Surface Loading Bridge a GRACE Mission Gap?

Jens.Schroeter [ at ]


We investigated two ‘gap-filler’ methods based on GPS-derived low-degree surface loading variations (GPS-I and GPS-C) and a more simple method (REF-S) which extends a seasonal harmonic variation into the expected Gravity Recovery and Climate Experiment (GRACE) mission gap. We simulated two mission gaps in a reference solution (REF), which is derived from a joint inversion of GRACE (RL05) data, GPS-derived surface loading and simulated ocean bottom pressure. The GPS-I and GPS-C methods both have a new type of constraint applied to mitigate the lack of GPS station network coverage over the ocean. To obtain the GPS-C solution, the GPS-I method is adjusted such that it fits the reference solution better in a 1.5 year overlapping period outside of the gap. As can be expected, the GPS-I and GPS-C solutions contain larger errors compared to the reference solution, which is heavily constrained by GRACE. Within the simulated gaps, the GPS-C solution generally fits the reference solution better compared to the GPS-I method, both in terms of spherical harmonic loading coefficients and in terms of selected basin-averaged hydrological mass variations. Depending on the basin, the RMS-error of the water storage variations (scaled for leakage effects) ranges between 1.6 cm (Yukon) and 15.3 cm (Orinoco). In terms of noise level, the seasonal gap-filler method (REF-S) even outperforms the GPS-I and GPS-C methods, which are still affected by spatial aliasing problems. However, it must be noted that the REF-S method cannot be used beyond the study of simple harmonic seasonal variations.

Item Type
Primary Division
Primary Topic
Research Networks
Publication Status
Eprint ID
DOI 10.1007/s10712-013-9276-5

Cite as
Rietbroek, R. , Fritsche, M. , Dahle, C. , Brunnabend, S. E. , Behnisch, M. , Kusche, J. , Flechtner, F. , Schroeter, J. and Dietrich, R. (2014): Can GPS-Derived Surface Loading Bridge a GRACE Mission Gap? , Surveys in Geophysics, pp. 1-17 . doi: 10.1007/s10712-013-9276-5

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