EDS Newsletter #2

Regional Copernicus Ocean Circulation Models

Regional Copernicus Ocean Circulation Models

Global ocean circulationย models, such asย HYCOM,ย BlueLinkย and Copernicus,ย portray and predict the ocean state and its variability atย a largeย spatio-temporal scaleย (seeย EDS Newsletter #1).ย Despite the significant progressย in providing reliableย large-scale physical processes,ย coastal and shelf phenomena can be subject toย certain practical limitsย on theย horizontal resolution refinement, and process parameterization.ย This isย particularly trueย for regional seasย presenting aย complex geographic regionย such as sea straits, archipelagos, or semi-enclosed seas where the coastline, seamounts, and bottom topography are not well resolved.ย Consideringย thatย accurateย coastal circulation is essential for decision- andย policy-making,ย regional modelsย have beenย configuredย andย reproducedย with finer horizontal grid spacingย for particular delimited areas.

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Diverse methodologies are usedย inย order toย provideย regional modelling.ย One of the methodsย โ€“ downscaling โ€“ย involves transferring ofย large-scale information from the global model to the interior of the nested regional domainย in order toย adequately represent airโ€“sea and landโ€“sea interactions.ย An alternative approach consists of using unique unstructured grid models.ย ย 

In the framework of theย Europeanย Copernicus Marine Environment Monitoring Serviceย (CMEMS),ย seven Monitoring and Forecastingย Centersย (MFC)ย are responsible toย maintain operationallyย an inventory of regional oceanย modelsย acrossย allย theย regionalย European seas,ย providingย betterย comprehension of the coastal circulation. RPSย hasย integratedย into its Environmental Data Services (EDS),ย the different regional CMEMS operational forecasting datasets for the Mediterranean Sea, the Iberia-Biscay-Irelandย regional seas, theย Atlanticย European North West Shelf, the Baltic and the Black Seas, and the Arctic Ocean. Some of these Copernicus Regional models are using the Nucleus for European Modelling of the Ocean (NEMO v3.6), driven by high frequency meteorological and oceanographic forcing, and bathymetry derived from the General Bathymetric Chart of the Oceans (GEBCO). All these models also include data of temperature, salinity, sea level and satellite data of sea level, and assimilating in situ and satellite data.ย 

Copernicus Mediterranean Sea

The Mediterranean Sea operational forecastย modelย (MED MFC) lead by Fondazione CMCCย covers the entirety of the Mediterranean Sea and extends into the Atlantic Ocean, toย properlyย resolve theย complexย exchanges between the Atlantic and the Mediterranean at the Strait of Gibraltar. It is nested within the Global Ocean operational system (CMEMS GLO MFC), which provides its lateral open boundary conditions (temperature, salinity, velocities, and sea level). The model is forced by momentum, water and heat fluxes, and bathymetry generated from a filtered and modified version of the GEBCO 30arc-second grid. Data assimilation includes in-situ data of vertical profiles of temperature and salinity, and satellite data of Sea Level Anomaly (SLA) and Sea Surface Temperature (SST).ย ย 

Copernicus Black Sea

The Copernicus Black Seaย Operational Forecastย (BS MFC,ย ledย by IO BAS)ย is based on version 3.4 of the Nucleus for European Modelling of the Ocean (NEMO) ocean model. The bathymetry dataset used in the system is GEBCO, and the atmospheric fields for forcing the ocean model come from the European Centre for Medium-Range Weather Forecasts (ECMWF). A 3-hourly time resolution fields are used for the first three days, while 6-hourly fields are used for the remaining 7 days. The atmospheric forcing variables include zonal and meridional components of wind, total cloud cover, air temperature, dew point temperature, mean sea level pressure and precipitation. Data assimilation for theย modelingย includes in-situ data of vertical profiles of temperature and salinity, satellite data of sea level anomaly, and sea surface temperature.ย 

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Copernicus Iberia-Biscay-Ireland

The Iberia-Biscay-Ireland Regional Seasย ocean forecastย (IBI MFC)ย led byย Mercator Oceanย Internationalย is based on aย model application of theย Nucleus for European Modelling of the Ocean (NEMO v3.6), driven by high frequency meteorological and oceanographic forcing, and bathymetry derived from the General Bathymetric Chart of the Oceans.ย It provides a near-real-time short-term regional forecast of currents (and other oceanographic variables such as temperature, salinity, and sea level)ย for the European Atlanticย faรงade,ย interpolated from the CMEMS GLOBAL eddy resolving system,ย and includingย river discharge of the main 33 rivers, and assimilating in situ and satellite data.ย 

Copernicus Atlantic European Northwest Shelf

Theย Atlanticย European North West Shelfย (NWSย MFC)ย led by the UKย MetOfficeย maintainsย an operational forecasting system over the North Sea, the Irish Sea, and the English Channel.ย The model provides the forecast using the Nucleus for European Modelling of the Ocean (NEMO v3.6). The NEMOVAR 3D-Var First Guess Appropriate Time is used for data assimilation of sea surface height, vertical profiles of temperature and salinity, and sea level anomaly. The model is forced by tides, temperature, and salinity from the CMEMS Baltic MFC system at its boundary. River fluxes come from a climatology of daily discharge data for 279 rivers from the Global River Discharge Data Base and from data prepared by the Centre for Ecology and Hydrology. The bathymetry is generated from a modified version of the GEBCO 1arc-second grid.ย 

Copernicus Baltic Sea

The Copernicus Baltic Sea Forecastย (BAL MFC)ย led by the Danish Meteorological Instituteย (DMI)ย is based on HIROMB-BOOS Model (HBM) which is a three-dimensional, hydrostatic, free-surface, baroclinic ocean circulation and sea ice model. The HBM code was developed in the early 1990โ€™ies atย Bundesamtย fรผrย Seeschifffahrtย undย Hydrographieย (BSH, Germany)ย and then undergone extensive revision, in collaboration betweenย Danish DMIย and BSH. The bathymetry dataset used in the system is GEBCO (at 1-minute resolution); and the atmospheric fields for forcing the ocean model comes from the DMI-HARMONIE (2.5km resolution) and ECMWF. The DMI-HARMONIE system is used for the first 2.5 days and ECMWF forcing is leveraged for the remaining 3.5 days. The atmospheric forcing variables include wind speed and direction, mean sea level pressure, surface air temperature and humidity, and cloud cover. However, no data assimilation is used in this model application.ย 

Copernicus Arctic Ocean

The Copernicus Arctic Ocean operational Forecastย data productย (ARCย MFC)ย is led by Nansen Environmental and Remote Sensing Center (NERSC, Norway) in collaboration with Norwegian Meteorological Institute (MET Norway) and the Institute of Marine Research (IMR, Norway). TOPAZ4 data assimilation system is at the core of the Arctic Ocean forecast, which uses the latest version of the Hybrid Coordinate Ocean Model (HYCOM). TOPAZ4 also uses the Ensemble Kalman filter to assimilate remotely sensed sea level anomalies, sea surface temperature, sea ice concentration, sea ice thickness andย Lagrangianย sea ice velocities. The bathymetry dataset used in the system is GEBCO while the atmospheric fields for forcing the ocean model comes from ECMWF.ย 

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Dataset Model Parameters

Addingย theseย newย regionalย EUย datasetsย in EDS means thatย coastalย users canย use higher resolution dataย products andย run multipleย predictionย cases using differentย metoceanย inputย combinations.ย This consensus approach providesย aย greaterย confidence in the decisions made from the modelling results.ย In order toย help compare datasets,ย users can log into our EDS Viewerย (OceansMap)ย and check the spatial and temporal differences.ย ย 

The following table and figures show an example of this comparison across theseย regionalย current models.ย ย 

Table 1 โ€“ Parameters of regional Copernicus current forecast products on RPSโ€™ EDS

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Figure 1: Visual comparison of Copernicus IBI (red vectors) and Copernicus Atlantic NW Shelf (blue vectors) in European Waters.

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Figure 2: Visual comparison of Copernicus Med Sea (red vectors) and Copernicus IBI (blue vectors) in Spanish Waters offshore Sierra del Cabo (South East of Spain).

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