Abstract's details
Performances of the new Copernicus Marine Service global ocean monitoring and forecasting real-time high-resolution system
CoAuthors
Event: 2022 Ocean Surface Topography Science Team Meeting
Session: Application development for Operations
Presentation type: Type Poster
Contribution: not provided
Abstract:
Since October 2016, and in the framework of Copernicus Marine Service, Mercator Ocean International delivers in real-time daily services (weekly analyses and daily 10-day forecasts) with a global 1/12° high resolution (eddy-resolving) system (Lellouche et al., 2018). Oceanic observations are assimilated in the model using a reduced-order Kalman filter method. Along track altimeter Sea Level Anomaly (SLA), satellite sea surface temperature (SST) and sea ice concentration, and in situ temperature and salinity vertical profiles are jointly assimilated to estimate the initial conditions for numerical ocean forecasting. A 3D-VAR scheme is also used to better control the slowly evolving large-scale biases in temperature and salinity.
A major release of this analysis and forecasting system will be available at the end of 2022 with the following changes and updates:
- A new version of NEMO ocean and sea ice models (new numerical schemes, coherent bulk formulation with the atmospheric forcing, multi-categories sea ice model);
- Higher spatial and temporal resolution (1/10° - 1 hour) atmospheric forcing from IFS ECMWF analyses and forecasts;
- A new assimilated SST observation (assimilation of L3 ODYSSEA SST high resolution product instead of L4 OSTIA gridded product);
- A new Mean Dynamic Topography for SLA assimilation;
- A different parametrization of the model error covariance with a new anomalies base deduced from the Mercator Ocean reanalysis at 1/12° (Lellouche et al., 2021);
- A 4D extension of the data assimilation scheme allowing a better spatiotemporal continuity of mesoscale structures;
- The assimilation of “super-observations” to filter out noisy data and scales that the model does not resolve;
- The use of satellite-based monthly estimates of the Global Mean Sea Level to better constrain the ocean mass and the steric height.
This presentation will show how some identified weaknesses present in the previous system have been improved. It will also highlight the new system’s performance in terms of analysis and forecast skills, of representation of mesoscale activity, of mass/steric distribution and of representation of the equatorial dynamics.
The new system is very close to SLA observations with a forecast RMS difference below 5 cm (best analysis is around 4 cm). The description of the ocean water masses is also very accurate and departure from in situ temperature and salinity observations are generally below 0.3 °C and 0.05 PSU. In addition, a global comparison with independent (not assimilated) velocity measurements shows that the location of the main currents is accurately represented.
A major release of this analysis and forecasting system will be available at the end of 2022 with the following changes and updates:
- A new version of NEMO ocean and sea ice models (new numerical schemes, coherent bulk formulation with the atmospheric forcing, multi-categories sea ice model);
- Higher spatial and temporal resolution (1/10° - 1 hour) atmospheric forcing from IFS ECMWF analyses and forecasts;
- A new assimilated SST observation (assimilation of L3 ODYSSEA SST high resolution product instead of L4 OSTIA gridded product);
- A new Mean Dynamic Topography for SLA assimilation;
- A different parametrization of the model error covariance with a new anomalies base deduced from the Mercator Ocean reanalysis at 1/12° (Lellouche et al., 2021);
- A 4D extension of the data assimilation scheme allowing a better spatiotemporal continuity of mesoscale structures;
- The assimilation of “super-observations” to filter out noisy data and scales that the model does not resolve;
- The use of satellite-based monthly estimates of the Global Mean Sea Level to better constrain the ocean mass and the steric height.
This presentation will show how some identified weaknesses present in the previous system have been improved. It will also highlight the new system’s performance in terms of analysis and forecast skills, of representation of mesoscale activity, of mass/steric distribution and of representation of the equatorial dynamics.
The new system is very close to SLA observations with a forecast RMS difference below 5 cm (best analysis is around 4 cm). The description of the ocean water masses is also very accurate and departure from in situ temperature and salinity observations are generally below 0.3 °C and 0.05 PSU. In addition, a global comparison with independent (not assimilated) velocity measurements shows that the location of the main currents is accurately represented.