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Computer simulations of dispersion processes in the ocean have been gaining
in importance over the past few years. Applications include modelling of
the dispersion of pollutants and computations of the drift paths of shipwrecked
persons. The BSH operates two models serving different purposes. Both dispersion
models are based on the
current
predictions provided by the Operational Circulation
Model.
Lagrangian Dispersion Model
To simulate the drift and dispersion of a substance in the Lagrangian Model,
the substance is represented by a particle cloud drifting with the current.
Substances floating on the surface are additionally driven by a certain
percentage of wind velocity. In simulations of oil dispersion, the physical
behaviour of different oil types on the water surface and in the water column
is taken into account as well.
The Lagrangian Model is used primarily to support search and rescue operations
and to assist the coast guard in cases of marine environmental pollution.
Among the applications of the model are drift forecasts for shipwrecked persons
and floating objects (boats, lost cargo etc), as well as drift and dispersion
computations for oil and water-soluble chemicals. The model is frequently
used to trace back harmful substances to their sources and constitutes a
valuable tool in the identification of environmental polluters.
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Simulated oil distribution after stranding of "Pallas" (black: oil at the
water surface; blue: dispersed oil; red: oil deposited on the seafloor and
shores)
Eulerian Dispersion Model
The Eulerian dispersion model simulates the temporal development of concentration
distributions. With the transport algorithm used, it is capable of modelling
strong concentration differences (fronts).
Therefore, the Eulerian dispersion model is preferably used to study the
dispersion of water-soluble substances and to monitor water quality in the
North Sea and Baltic Sea. For example, it may help to answer questions concerning
riverine inputs of harmful substances and their dispersion in the marine
environment.
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