Improving altimetry's non-tidal high-frequency ocean de-aliasing correction through the inclusion of daily GRACE updates
- (University Of South Florida, Tampa)
The ~10 day repeat pattern of Topex/Poseidon and Jason 1-3 means that ocean signal moving faster than one cycle per 20 days cannot be well resolved and will alias into much longer periods. To correct for this, the altimetry community applies a non-tidal de-aliasing model constructed of the inverted barometer (IB) response and the Mog2D ocean model. However, Mog2D, like many global ocean models, is expected to have relatively high errors in some parts of the ocean, particularly the southern ocean. Previous research has shown that a GRACE-based daily series can provide improvements over similar ocean models at higher latitudes, based on a comparison to altimetry itself.
We therefore propose an experiment to improve the quality of future altimetry data by accomplishing three goals. First, to create modern daily or near-daily high spatial resolution GRACE gravity time series with relatively low expected errors. This would build on the existing infrastructure at the Center for Space Research that developed high resolution monthly GRACE gravity fields. Second, to determine whether this modern near-daily GRACE time series provides an improvement in accuracy over the current altimetry de-aliasing model, in some or all parts of the ocean, at periods between 1-20 days. And third, to create a new de-aliasing model which includes GRACE data over the locations and frequency bands where it is more accurate than the current model. Assuming we are successful, the final improved product would mean altimetry data with more of the high-frequency aliased signal removed, leading to less trackiness and a more accurate view of global oceanography.