MERCATOR OCEAN JOURNA: 
SEPTEMBER 2021 
% diff ensemble_da_3 minus ctri 201810* SLA:omb rms 
2732604 obs, mean -0.002 rms 0.061 
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igure &: Global sea level anomaly root-mean-square deviation (RMSD) compared with altimeter observations before their assimilation. The 
map shows the percentage change in the RMSD of the innovations of the hybrid DA ensemble mean compared with the standard 3DVar (blue 
implies the hybrid DA has lower RMSD) 
2. POST 2021 PERSPECTIVES 
The immediate priority beyond Copernicus 1 is operational 
‚Mplementation, expected by early 2022, of the upgrade to 
deliver ocean products from the coupled NWP system 
(currently in final testing). Several drivers exist for future 
jdevelopment and upgrades after that. These are particularly 
around enhancing the representation of processes in the 
surface ocean as this will both directly improve ocean 
product quality, and have most benefit for improving NWP 
performance (and therefore also atmospheric foreing) in 
the coupled system. Given the relatively low eddy- 
permitting 1/4° ocean resolution used at present there is a 
Clear encouragement to increase it toward an eddy- 
resolving resolution. This would enable: 
- more accurate feature representation for surface 
currents and sea surface temperatures, 
nore effective use of high-resolution satellite 
abservations, 
improved feedbacks between the oceanic and 
atmospheric boundary layers. 
An upgrade to 1/12° would allow the GLO-CPL system to 
benefit from work in the IMMERSE H2020 project to 
estimate forecast error covariance characteristics in 
ORCA12 and to improve HPC efficiency. 
Other user drivers include improved analyses and forecasts 
in Arctic regions, the ability to provide reliable probabilistic 
acean products based on an ensemble of ocean 
zonfigurations, and the provision of more accurate surface 
3cean predictions as a result of better representation of 
vertical mixing, tides and wave effects. Examples of likely 
Jevelopments to help address these requirements include 
3ssimilation of sea ice thickness data (within a new SI3 ice 
zonfiguration replacing CICE as used currently), and 
implementation of the ocean ensemble generation 
described above within the GLO-CPL system. Other 
jdevelopments include an upgrade to the NEMO 
configuration to use a z- type Arbitrary Lagrangian 
Eulerian vertical coordinate (to help reduce spurious 
numerical mixing associated with vertical motion; this 
would build on work within the RENUMERATE and IMMERSE 
projects). A wave component may also be added hut this is 
not an immediate priority. 
The system will also be funded and used for global weather 
prediction. Hence, there will be a whole range of other 
drivers and constraints on the development and evolution 
of the GLO-CPL system to ensure the atmospheric 
performance also continues to improve due to model. 
observation, assimilation and ensemble method upgrades.