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Currents, water levels, water temperatures, salinities, and ice coverage
for the North Sea and Baltic Sea are computed in nightly routine runs on
interactively coupled grids. Grid spacing in the German Bight and western
Baltic is 1.8 km, and 10 km in the other North and Baltic Sea areas. The
model also simulates the flooding and falling dry of tidal flats, allowing
the complex processes in the highly structured German coastal waters (tidal
flats, sandbanks, tidal channels, barrier islands) to be modelled realistically.
The circulation model is three-dimensional and takes into account meteorological
forecasts for the North Sea and Baltic Sea provided by the
German Weather Service (DWD), tides
and external surges entering the North Sea from the Atlantic, as well as
river runoff from the major rivers. The forecasts for the sea computed by
the operational circulation model cover 48 hours.
The meteorological forecast data needed to drive the BSH model are computed
by an atmospheric model of the German Weather Service in Offenbach and are
transmitted to the BSH on a daily basis. To compute the heat fluxes between
air and water, the BSH model uses wind and atmospheric pressure forecasts
and, additionally, measurements of air temperatures, clouds, and specific
humidity above the sea. The tidal boundary values at the open model boundaries
of the North Sea are computed from the harmonic constants of 14 tidal
constituents. External surges entering the North Sea are computed using a
model of the northeast Atlantic. This two-dimensional model has a grid spacing
of about 40 kilometers and is also forced by meteorological data from the
DWD
Click for a larger version
In the circulation model, both the influence of wave action on the
currents
and water levels
as well as density driven currents determined by current temperature and
salinity distribution are taken into account. Density driven currents play
an important role, especially in the Baltic Sea. For a realistic computation
of the density distribution, a transport algorithm has been developed at
the BSH which allows strong temperature and salinity gradients (fronts).
As the hydrodynamic conditions are also influenced by ice development in
the North and Baltic Seas, an ice model has been coupled to the circulation
model which simulates the formation, melting, and drift of sea ice.
Data of the
North Sea heat content,
based on model results, are released monthly.
The chart below shows predicted currents in the area of the Jade and Weser
estuaries. Click on the chart for a larger version.
Click for a larger version | 
