EDS Newsletter #2: Regional Copernicus Ocean Circulation Models
Global ocean circulation models, such as HYCOM, BlueLink and Copernicus, portray and predict the ocean state and its variability at a large spatio-temporal scale (EDS Newsletter #1). Despite the significant progress in providing reliable large-scale physical processes, coastal and shelf phenomena can be subject to certain practical limits on the horizontal resolution refinement, and process parameterization. This is particularly true for regional seas presenting a complex geographic region such as sea straits, archipelagos, or semi-enclosed seas where the coastline, seamounts, and bottom topography are not well resolved. Considering that accurate coastal circulation is essential for decision- and policy-making, regional models have been configured and reproduced with finer horizontal grid spacing for particular delimited areas. Diverse methodologies are used in order to provide regional modelling. One of the methods – downscaling – involves transferring of large-scale information from the global model to the interior of the nested regional domain in order to adequately represent air–sea and land–sea interactions. An alternative approach consists of using unique unstructured grid models.
27 October 2021 | 5 min read
Copernicus Mediterranean Sea
The Mediterranean Sea operational forecast model (MED MFC) lead by Fondazione CMCC covers the entirety of the Mediterranean Sea and extends into the Atlantic Ocean, to properly resolve the complex 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).
The Iberia-Biscay-Ireland Regional Seas ocean forecast (IBI MFC) led by Mercator Ocean International is based on a model application of 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. It provides a near-real-time short-term regional forecast of currents (and other oceanographic variables such as temperature, salinity, and sea level) for the European Atlantic façade, interpolated from the CMEMS GLOBAL eddy resolving system, and including river discharge of the main 33 rivers, and assimilating in situ and satellite data.
Copernicus Atlantic European Northwest Shelf
The Atlantic European North West Shelf (NWS MFC) led by the UK MetOffice maintains an operational forecasting system over the North Sea, the Irish Sea, and the English Channel. 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.
Copernicus Baltic Sea
The Copernicus Baltic Sea Forecast (BAL MFC) led by the Danish Meteorological Institute (DMI) 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 1990’ies at Bundesamt für Seeschifffahrt und Hydrographie (BSH, Germany) and then undergone extensive revision, in collaboration between Danish DMI 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.