||Impacts of oceanic mass variations on GRACE gravity field processing
Oceanic mass anomalies obtained from numerical simulations with the Ocean Model for Circulation and Tides (OMCT) are currently in use for de-aliasing purposes within the recent GRACE re-processing campaign. Here, a review of recent model developments is given with a view to additional three-dimensional dynamical components in the oceans, which are expected to have an impact on the gravity field recovery from GRACE observations. Exemplarily, the presentation concentrates, in particular, on three aspects:
Due to long-term variations of air density, atmospheric pressure tides and, consequently, the corresponding oceanic response show significant seasonal variations. The use of 3-hourly atmospheric forcing fields provided by forecasts from ECMWF allows to take into account the transient impact of semidiurnal and diurnal pressure tides, dispensing with any additional time-invariant a priori model. Secondly, freshwater fluxes from precipitation, evaporation and river discharge alter the overall oceanic mass. OMCT simulations are used to analyse their effects on short-period oceanic mass redistributions. The third example focusses on the treatment of gravitational ocean tides. The OMCT principally allows to simulate tidal dynamics caused by the complete lunisolar tidal potential, affording the opportunity to study nonlinear interactions between circulation and tides as well as to analyse the impact of partial tides not included in tidal reduction models used within the GRACE processing. First estimates of expected effects will be presented.