236 Lennart Funkquist and Rans Dahlin
countries around the Baltic Sea. The idea is with common efforts to run a state of
the art operational oceanographic model for the Baltic Sea. The kemel of the
project is the ocean model and other ingredients are real-time exchange of data for
assimilation and validation, a post-processing system including presentation on a
WEB-page and regular workshop meetings.
Although tides have no significance in the Baltic area, sea level forecasts are
required for flood wamings, to maximize the loading of ships and for simplified
forecast models of currents in straits. Flood waming is a govemmental service to
protect people and property, while the other forecasts have shown to increase the
profit for cargo ships and ferries. There is an increasing need offorecasts and information of currents, mainly in connection with offshore construction but also for
regular shipping. The surf ace currents also form the basic module in the oil-drift
model, which is also used for sea-rescue operations.
The basic oceanographic model, HIROMB, is a modified version of the BSH
(Bundesamt fUr Seeschiffahrt und Hydrographie) operational model (Kleine, 1994)
with identical boundaries between the Atlantic and the North Sea. It is a primitive
equation model derived using the hydrostatic and Boussinesq approximations. The
model solves for water level, currents, salinity, temperature, ice-coverage and ice
concentration. The first operational runs started in mid 1995 and since then the
model has been run operationally.
The resolution of the model is mainly chosen as to fit into available computer
memory and CPU-time. This has resulted in a 12 nautical miles grid, covering the
whole North Sea and Baltic Sea region. East of 6° E, a 3 nautical miles grid (see
Fig. 12.3) for the Skagerrak, Kattegat, Belt Sea and Baltic Sea is nested in the
larger grid. In the vertical, there is a variable resolution starting at 4 ro for the
mixed layer and gradually increasing to 60 m for the deeper layers. The model code
has recently been parallelized to fit into a distributed memory computer (Wilhelmsson and Schiile, 1998) and the model is presently run in parallel on a CRAY T3E
computer. In connection with the transfer of the model to the more powerful computer the horizontal resolution has increased to 1 nautical mile for the area east of
9°E.
The model produces up to 48 hours forecast each day and is forced by the atmospheric model (HIRLAM), which gives 10 m wind, sea level pressure, 2 m temperature, 2 m humidity and total cloudiness. There is a further forcing applied to the
surf ace layer mixing and currents (Stoke's drift) from the wave model. Hydrological forcing is applied at about 80 river outlets as daily forecasted river runoff. The
forcing at the open boundary to the North Atlantic is accounted for by specifying
17 tidal constituents and sea level from a North Atlantic storm surge model. A further condition at the open boundary consists of monthly averages of salinity and
temperature profiles.
countries around the Baltic Sea. The idea is with common efforts to run a state of
the art operational oceanographic model for the Baltic Sea. The kemel of the
project is the ocean model and other ingredients are real-time exchange of data for
assimilation and validation, a post-processing system including presentation on a
WEB-page and regular workshop meetings.
Although tides have no significance in the Baltic area, sea level forecasts are
required for flood wamings, to maximize the loading of ships and for simplified
forecast models of currents in straits. Flood waming is a govemmental service to
protect people and property, while the other forecasts have shown to increase the
profit for cargo ships and ferries. There is an increasing need offorecasts and information of currents, mainly in connection with offshore construction but also for
regular shipping. The surf ace currents also form the basic module in the oil-drift
model, which is also used for sea-rescue operations.
The basic oceanographic model, HIROMB, is a modified version of the BSH
(Bundesamt fUr Seeschiffahrt und Hydrographie) operational model (Kleine, 1994)
with identical boundaries between the Atlantic and the North Sea. It is a primitive
equation model derived using the hydrostatic and Boussinesq approximations. The
model solves for water level, currents, salinity, temperature, ice-coverage and ice
concentration. The first operational runs started in mid 1995 and since then the
model has been run operationally.
The resolution of the model is mainly chosen as to fit into available computer
memory and CPU-time. This has resulted in a 12 nautical miles grid, covering the
whole North Sea and Baltic Sea region. East of 6° E, a 3 nautical miles grid (see
Fig. 12.3) for the Skagerrak, Kattegat, Belt Sea and Baltic Sea is nested in the
larger grid. In the vertical, there is a variable resolution starting at 4 ro for the
mixed layer and gradually increasing to 60 m for the deeper layers. The model code
has recently been parallelized to fit into a distributed memory computer (Wilhelmsson and Schiile, 1998) and the model is presently run in parallel on a CRAY T3E
computer. In connection with the transfer of the model to the more powerful computer the horizontal resolution has increased to 1 nautical mile for the area east of
9°E.
The model produces up to 48 hours forecast each day and is forced by the atmospheric model (HIRLAM), which gives 10 m wind, sea level pressure, 2 m temperature, 2 m humidity and total cloudiness. There is a further forcing applied to the
surf ace layer mixing and currents (Stoke's drift) from the wave model. Hydrological forcing is applied at about 80 river outlets as daily forecasted river runoff. The
forcing at the open boundary to the North Atlantic is accounted for by specifying
17 tidal constituents and sea level from a North Atlantic storm surge model. A further condition at the open boundary consists of monthly averages of salinity and
temperature profiles.