Comparing Vertical Surface Displacements Using GRACE and GPS over Shanxi Province

Hydrological processes cause variation in gravitational potential and surface deformations,both of which are detectable using space geodetic techniques. We computed surface vertical displacements due to inland water storage changes using GRACE time-variable gravity field for GORS sites in Shanxi province, during from May 2009 to Dec. 2010, and compared the results with GPS height residuals during the same period. The results demonstrate that variations of hydrological surface deformation derived from GRACE and GPS height residual time series, for most CORS sites, are both about ±6.0 mm. The average amplitudes of annual signal extracted from GRACE and GPS are both about 2.5 mm, however, the phase discrepency is large. Since no corrections were applied for diurnal and semi-diurnal atmospheric loading, high order ionosphere, and non-tidal ocean loading, which would propagate into site coordinates time series and affect GPS annual signals. Therefor, we believe that the disagreement between GRACE and GPS is more due to errors in the GPS data processing.