Study of the seasonal gravity signal in superconducting gravimeter data

Thanks to their high sensitivity and their long-term stability, superconducting gravimeters (SG) are able to record surface gravity changes on a wide frequency band (periods from a few seconds to secular variations). We focus in this presentation on the seasonal gravity changes measured by about 20 worldwide SG. We model all well-known sources of long-term gravity changes, i.e. solid Earth tides, polar motion and length-of-day as well as global atmospheric, tidal and non-tidal ocean loading effects. These corrections lead to gravity residuals characterized by a strong seasonal signal with an amplitude of a few microgals. We compare these residuals with loading estimates from global hydrology (snow and soil-moisture) models. For more than half of the analysed SG, we are able to show a good correlation between the gravity residuals and the estimated continental water storage loading effects. For the other instruments, the discrepancies may be associated with local hydrology effects, which cannot be taken into account in global continental water storage models. (c) 2005 Elsevier Ltd. All rights reserved.