Preprints
https://doi.org/10.5194/egusphere-2024-756
https://doi.org/10.5194/egusphere-2024-756
26 Mar 2024
 | 26 Mar 2024
Status: this preprint is open for discussion.

Assessing the impact of future altimeter constellations in the Met Office global ocean forecasting system

Robert R. King, Matthew J. Martin, Lucile Gaultier, Jennifer Waters, Clément Ubelmann, and Craig Donlon

Abstract. Satellite altimeter measurements of Sea Level Anomaly (SLA) are a crucial component of current operational ocean forecasting systems. The launch of the SWOT wide-swath altimeter mission is bringing a step change in our observing capacity with 2-dimensional mesoscale structures now able to be observed over the global ocean. Proposals are now being considered for the make-up of the future altimeter constellation. In this study we use Observing System Simulation Experiments (OSSEs) to compare the impact of additional altimeter observations from two proposed future satellite constellations. We focus on the expected impact on the Met Office operational ocean analysis and forecasting system of assimilating an observation network including either 12 nadir altimeters or 2 wide-swath altimeters.

Here we show that an altimeter constellation of 12 nadir altimeters produces greater reductions in the errors for SSH, surface currents, temperature and salinity fields compared to a constellation of 2 wide-swath altimeters. The impact is greatest in the dynamic Western Boundary Current regions where the nadir altimeters can reduce the SSH RMS error by half, while the wide-swath altimeter only reduces this by one-quarter. A comparison of the spatial scales resolved in daily SSH fields also highlights the superiority of the nadir constellation in our forecasting system. We also highlight the detrimental impact spatially-correlated errors could have on the immediate use of wide-swath altimeter observations. However, we still achieve promising impacts from the assimilation of wide-swath altimetry and work is ongoing to develop improved methods to account for spatially-correlated observation errors within our data assimilation scheme.

Robert R. King, Matthew J. Martin, Lucile Gaultier, Jennifer Waters, Clément Ubelmann, and Craig Donlon

Status: open (until 21 May 2024)

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Robert R. King, Matthew J. Martin, Lucile Gaultier, Jennifer Waters, Clément Ubelmann, and Craig Donlon
Robert R. King, Matthew J. Martin, Lucile Gaultier, Jennifer Waters, Clément Ubelmann, and Craig Donlon

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Short summary
We use simulations of our ocean forecasting system to compare the impact of additional altimeter observations from two proposed future satellite constellations. We found that in our system an altimeter constellation of 12 nadir altimeters produces improved predictions of sea surface height, surface currents, temperature and salinity compared to a constellation of 2 wide-swath altimeters.