7°
such a simulation, the contributions which are delivered by the in-
dividual rivers (represented by the number of the particles sub-
mitted) are weighted in accordance with the following schedule:
Rhine/Meuse
Elbe —
Weser/Jade
Tyne
5Schelde
Firth of Forth
Seine
Humber
Ems
Thames
DHI-Model
52
L3
5.
6.
5
6
4
37
2%
ä %
IfMH-Model
5f &
21 z
7%
71%
3%
Rn 7
Tab. 1: Weighted river inputs, as used in the model simulations
The weightings used in the DHI model were taken from the data pub-
lished in "Gütezustand der Nordsee” (DHI, 1984) concerning the total
load of pollutants over the individual rivers. Owing to the fact
that the data for each indivudual pollutant temporally very consi-
derably, the concentrations in the North Sea thus calculated produce
only an estimate of the pollution load. The IfMH model works with a
8lightly varying weighting of the sources.
The results of the simulations with the IfMH model and the DHI-model
are shown in Fig. 9 und Fig. 10.
Both models calculate very similar distributions. Accordingly, the
Netherlands, German, and Danish coastal regions - in other words,
the eastern part of the North Sea - are constantly burdened with a-
round au order of magnitude higher pollution concentrations than the
western part of the North Sea, The unfavourable position and situa-
tion in the German Bight is further elucidated by the concentration
near the bottom (Fig. 10b) of the DEI model.
The irregular distribution of the concentrations is worthy of note,
about which will be gone into in Chapter 4.2 in more detail. Al-
though the models differ in some fundamental pre-requisites, never-
theless the results are very similar.
Both models neglect different part of the current variability
present in nature, The DHI model leaves out the long periodical
variability of the circulation caused by the atmospheric forcing
deviation of the wind, the IfMH model neglects the mixing effect of
the tidal current.
The reason for the, in the main, similar results, is the aforemen-
tioned prominent significance of the mean circulation for the prob-
lems dealt with here. The results of the 3-dimensional DHI spreading
