Temporal Gravity Variations in GOCE Gradiometric Data
The accuracy and spatial resolution expected from GOCE gravity gradiometry might deteriorate due to temporal gravity variations, which are mainly induced by mass redistributions in the System Earth. These mass redistributions occur in the atmosphere at various time scales, in the oceans as ocean tides and currents and on the continents as solid Earth tides, loading and hydrological effects. Opposite to GRACE, GOCE is developed to measure the static gravity field. Therefore, any time variable effects have to be removed from the measured data prior to further processing in a dealiasing step.
In this report the effects mentioned above are analysed by means of available models in order to investigate if they deliver significant contributions to the GOCE gradiometer measurements. Simulations of the different system parts (Atmosphere, Hydrosphere, Cryosphere and Solid Earth) are run. The gravitational effect of the simulated mass changes is expanded into spherical harmonics from which gravitational gradients are computed along a simulated GOCE orbit. The resulting gradients are compared with the specifications of the GOCE gradiometer. Furthermore, the residual (i.e. atmospheric and oceanic parts removed) time variable part of the gravity field as detected by GRACE is discussed with respect to its impact on GOCE gradiometry.
Keywordsgravity satellite mission GOCE GRACE gravity gradiometry global hydrological model temporal gravity field variations
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