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GOCE gravity gradients for time-variable applications (GOCE4TV-APPs)



The gravity gradients of the highly successful ESA Earth Explorer mission GOCE (Gravity field and steady-state ocean circulation explorer), which have been reprocessed by applying enhanced calibration strategies in the frame of the ESA project GOCE High-level Processing Facility (HPF), have reached a very high quality level, especially in the long-wavelength spectral range where the main time-variable gravity field signals occur. In the frame of this project, it shall be investigated if time-variable gravity field signals can be extracted from these newly processed gravity gradient data. Due to their direct relation to mass and mass change, temporal variations reflect mass transport processes in the Earth system, which by themselves are subtle indicators of climate change. Therefore, the GOCE gradients shall be analysed for and used in dedicated time-variable geophysical applications, such as the detection of earthquakes reflecting pre-, co-, and post-seismic mass movement, land hydrology reflecting changes in the total water storage of large hydrological catchments, and ice mass balance trends such as ice mass melting in Greenland and Antarctica.
For this purpose, existing processing strategies based on spherical harmonic modelling of the gravity field, as well as promising contemporary processing and parameterization strategies, among them a so-called Mascon approach, shall be applied. The latter is routinely used in temporal gravity modelling based on data of the inter-satellite ranging mission GRACE (Gravity Recovery And Climate Experiment), but has never been applied to GOCE data yet, and will be developed and adapted for GOCE data assimilation and data exploitation.
The main outcome will be gradiometry-only regional and global data sets of identified gravity changes, giving information about the amplitude, seasonal/periodic and drift behavior of the changes. The results will be validated against GRACE temporal gravity models. Especially, it will be evaluated if by means of GOCE gradients the spatial resolution of recoverable time-variable gravity signals can be increased. The data sets shall be provided in common and easy to use data formats in order to be used within relevant related fields of applications.


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