In this study we compared weekly
gnss position time series with modelled values of crustal deformations on the basis of Gravity Recovery and Climate Experiment (
grace) data. The Global Navigation Satellite Systems (
gnss) time series were taken from homogeneously reprocessed global network solutions within the International
gnss Service (
igs) Reprocessing 1 project and from regional solutions performed by Warsaw University of Technology (
wut) European Permanent Network (
epn) Local Analysis Center (
lac) within the
epn reprocessing project. Eight
gnss sites from the territory of Poland with observation timespans between 2.5 and 13 years were selected for this study. The Total Water Equivalent (
twe) estimation from
grace data was used to compute deformations using the Green’s function formalism. High frequency components were removed from
grace data to avoid aliasing problems. Since
grace observes mainly the mass transport in continental storage of water, we also compared
grace deformations and the
gnss position time series, with the deformations computed on the basis of a hydrosphere model. We used the output of WaterGAP Hydrology Model (
wghm) to compute deformations in the same manner as for the
grace data. The
wghm gave slightly larger amplitudes than
gnss and
grace. The atmospheric non-tidal loading effect was removed from
gnss position time series before comparing them with modelled deformations. The results confirmed that the major part of observed seasonal variations for
gnss vertical components can be attributed to the hydrosphere loading. The results for these components agree very well both in the amplitude and phase. The decrease in standard deviation of the residual
gnss position time series for vertical components corrected for the hydrosphere loading reached maximally 36% and occurred for all but one stations for both global and regional solutions.For horizontal components the amplitudes are about three times smaller than for vertical components therefore the comparison is much more complicated and the conclusions are ambiguous.