Local Hydrological Effects on Gravity at Metsähovi, Finland: Implications for Comparing Observations by the Superconducting Gravimeter with Global Hydrological Models and with GRACE

We construct a model for the influence of variation in local water storage on the observations of the superconducting gravimeter (SG) T020 in Metsahovi, Finland. The following hydrological components are accounted for: (1) soil moisture and groundwater in sediments, (2) groundwater in the fractures of the crystalline bedrock, (3) snow on the ground, and (4) snow on the laboratory roof. We show that due to the geometry of the local storage, its gravity influence at the SG is only a fraction of the influence of the corresponding Bouguer sheet, and discuss the implications for comparing the SG with variation in gravity observed with GRACE. We compare the SG residuals with the variation in gravity predicted from the local model and two models of continental water storage. The general patterns are similar but there are differences in amplitude and phase. Further research is outlined.