Assessing the ITRF2005 Earth Orientation Series with EOP Measurements and Global Geophysical Fluid Models

Unlike previous realizations of the terrestrial reference frame, the ITRF2005 realization was constructed by simultaneously combining time series of station positions and Earth orientation parameters. So, besides site positions and velocities, the set of ITRF2005 products also includes a series of combined Earth orientation parameters. Here, the ITRF2005 Earth orientation series is assessed by comparing it with other combined EOP series and with models of surface geophysical fluids. Ideally, assessments of EOP series should be done with independent data. However, since all available combined EOP series, including the ITRF2005, IERS, and JPL series used here, are constructed from the same basic set of SLR, VLBI, and GPS measurements, they are not completely independent of each other. But because Earth orientation variations on subdaily to interannual time scales are known to be predominantly caused by atmospheric, oceanic, and hydrospheric effects, and because models of these effects are independent of Earth orientation measurements, it may be possible to use models of global geophysical fluids to independently assess the ITRF2005 Earth orientation series. This possibility is explored here by comparing the ITRF2005, IERS, and JPL length-of-day and polar motion excitation series, from which tidal effects have been removed, to daily averaged atmospheric angular momentum from the NCEP/NCAR reanalysis project, daily averaged oceanic angular momentum from the ECCO/JPL data assimilating ocean model, and monthly averaged hydrospheric angular momentum from the Land Dynamics (LaD) model. In addition, mass conservation of the global geophysical fluids is imposed when using them to assess the EOP series. The results of this assessment will be presented.