The DMI ocean models calculate:

- hydro dynamics (sea current, sea temperature, salinity, sea ice)
- storm surge (sea level)
- waves
- drift and spreading of oil/dissolved substances or lost cargo
- marine ecology (nutrients, oxygen, ..)

Ocean models are forced by the weather forecast, as produced by a

- numerical weather prediction model

Marine ecology is a new field of work, not yet fully developed.

Focus areas are:

- North Sea - Baltic Sea
- Danish Waters
- Greenland Waters

In addition, DMI produces ocean forecasts for the Arctic, the Mediterranean, the Yellow Sea, the Red Sea, the Irish Sea, the Norwegian Coast and the North Atlantic.

DMI sets up local and regional models as required. Global metocean models are run at ECMWF, Reading, England.

Ocean forecasts are valid for the upcoming 2½-10 days, depending on model type and domain.

Publicised at DMI web sites (most in danish):

sea areas
farvandsuds igter
havprognoser
strandvejr
ocean.dmi.dk

You will find hourly maps of ocean conditions. The data is valid on grid points, separated by some kilometers. 2-dimensional parameters (sea level, sea ice, waves) are shown as surface maps. 3-dimensional parameters are mapped at a number of depth levels. Locations with some kind of recording equipment will have time series displayed.

Model output is stored on tape in GRIB (GRid In Binary) format.

The backbone of all ocean forecasting is a numerical weather prediction (nwp) model. The nwp provides the surface forcing - mechanic, thermodynamic and radiative - that sets the ocean in motion and changes its physical and chemical state.

DMI-Hirlam forecasts range 2½ days ahead. DMI-Hirlam covers the North Sea - Baltic Sea in 3km resolution, and a large part of the North Atlantic, including the Arctic Sea and the Mediterranean, in 15 km resolution. Other sub-domains cover the Caspian Sea, the Red Sea, and the Yellow Sea.

Global ECMWF forecast are valid 10 days ahead. They are produced at the european center in Reading, England. ECMWF forecasts supplement DMI-Hirlam where required, but the time/space resolution is coarser.

No weather forecast is perfect, and the errors are carried over into the ocean forecast. Given an ocean model, the best possible forecast is produced using analysed weather maps, where observed weather and weather model are combined to minimise the error. All weather forecasts start out with an analysis. Hirlam is re-analysed every 6 hours, ECMWF every 12 hours.

A hydro-dynamical model describes the motion of water bodies, represented by sea current and sea level. A complete hydrographic description include sea temperature, salinity, and sea ice.

DMI-BSHcmod is a nested 3-dimensional ocean model developed at the Bundesamt für Seeschiffahrt und Hydrographie, Hamburg, Germany. It has been used in Germany since 1995, at DMI since 2001. Originally constructed specifically for the North Sea - Baltic Sea, DMI-BSHcmod is today a general model, in principle applicable to any model region. Until now it has only been used in shallow-water, regional areas, e.g. the Northwest European Shelf Seas.

Hycom is a 3-dimensional ocean model developed in Miami/Los Alamos, USA. DMI has set up Hycom for the the North Atlantic north of 20°N, including the Arctic Sea and the Mediterranean. Hycom is well suited for large-scale modelling, with the possibility to zoom in on small domains.

Mog2D is a 2-dimensional ocean model developed in Toulouse, France. Mog2D is a finite element model, where an irregular grid provides large flexibility in horizontal resolution and coastline representation. Mog2D has no thermodynamics, and current velocity is independent of depth. The primary model output is sea level.

DMI uses the 3-dimensional model DMI-BSHcmod for sea level / storm surge predictions. The 2-dimensional model Mog2D served as back-up, only to be used if the main model breaks down. A storm surge model calculates the sea level. This can be done with a 3-dimensional hydro-dynamic model, or with a more simple 2-dimensional model. A 2-d model has only one vertical layer, so that the current velocity has no vertical structure. In some regions, e.g. the North Sea, this is close to reality. In strafied regions, e.g. the Transition Area, surface and bottom current may be very different. In such regions, a 3-d model gives better sea level predictions.

Both DMI models (2-d and 3-d) cover the entire North Sea - Baltic Sea. They calculate sea level variations along the Danish coast, with a durance up to about a week. These depend on the weather (strong wind events), and the Atlantic tide.

DMI-WAM is based on the spectral 3rd generation wave model WAM Cycle 4.5 developed in the late 1980'ies by the SWAMP modelling group. WAM calculates wind-generated waves in open waters, outside the breaker zone. It has been used at DMI since 1999. DMI-WAM covers the North Atlantic north of 30°N, with bordering seas

BSHdmod calculates drifting objects, spreading of dissolved substances, and oil drift and weathering. BSHdmod is an add-on module to the hydro-dynamical model DMI-BSHcmod, and was also developed at the Bundesamt für Seeschiffahrt und Hydrographie, Hamburg, Germany, specifically for the North Sea - Baltic Sea. DMI has generalised BSHdmod, to it may be combined with other ocean models, and used in other regions.

Hycom also comes with a drift module. It is used to calculate drift of fry in Greenland waters, icebergs, .. .

A coupled ERGOM/DMI-BSHcmod model is under development, in collaboration with the National Environmental Research Institute (NERI) and the Danish Fisheries Research Institute (DFRI). ERGOM is developed at Institut für Ostseeforschung in Warnemünde. It calculates the content of oxygen, nutrient and a number of plankton/algae types in sea water.