Comparison of signal/noise content in the combined monthly gravity fields and secular/seasonal signal content in the deterministic signal model.

The deterministic GRACE signal model (bias, trend, annual and semi-anual variations) is fitted to the monthly means of all GRACE time-series contributing to COST-G GRACE RL02 in the time period 2004-2010. In the top plots the mean degree amplitudes of the monthly combined gravity fields (blue line) and the signal model evaluated at the mean epochs of the months (red line) are shown, either for geoid heights (left) or equivalent water heights (right). The differences are indicated in black. The time-variable signal content in the low degrees is well represented by the signal model, while in the medium to high degrees the differences between signal model and combined gravity fields indicate the noise content of the combined solutions.

The bottom plots are based on monthly grids of either the combined gravity fields (blue) or the signal model evaluated at the mean epochs of the months (red), both smoothed with a 400 km Gauss filter. They show the RMS of the variability over the oceans and the differences, which are used to characterize the noise content (black).

geoid height
equivalent water height
spectral secular/periodic signal content spectral secular/periodic signal content spectral secular/periodic signal content
secular/periodic signal content over oceans secular/periodic signal content over oceans secular/periodic signal content over oceans

Below, monthly plots of the combined gravity fields and the deterministic GRACE signal model evaluated at the corresponding epochs in either geoid heights or equivalent water heights are provided. All plots are smoothed by a 400 km Gauss filter. As a static reference field GOCO06S was subtracted.

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