10 Applications of the Inverse Problem of Pollution Propagation
345
the same coast. In early simulations using 10-day long trajectories (Soomere et al.
2010) the separation point of the opposite coasts was set at the mainland border
between Estonia and Russia at the River Narva mouth in the SE of the Gulf of
Finland (28 ◦ 2 E, 59 ◦ 27.5 N). In later simulations with the same model and 20
day long trajectories, the separation point was set at the mouth of the River Neva
(Soomere et al. 2011c).
The equiprobability line followed the gulf axis in the narrowest part of this water
body, deviated substantially to the north of it at the gulf entrance and in the widest
part of the gulf, and came quite close to the southern coast of the easternmost narrow
part of the gulf. While the latter feature evidently mirrors the flow of the voluminous
runoff from River Neva that merges with the overall cyclonic circulation in the gulf
in this area (Chap. 6), the two other deviations of the equiprobability line from the
centreline of the gulf apparently signify certain systematic anisotropic features of
the transport by surface currents.
10.6.2 Cross-Sections
Different cross-sections of the distributions of the probability, the particle age and
the quantity ˆ
p characterizing the probability of hitting the opposite coasts of the
Gulf of Finland reveal several important features of the underlying fields (Fig. 10.9).
For relatively narrow parts of the gulf all the fields have a clearly defined extremum
or zero-crossing. A deviation from these points by only a few km is associated with
a considerable change in the values of the underlying quantities (equivalently, in the
environmental risks). Interestingly, the exact locations for the optimum values (potential locations for the sailing line) not necessarily coincide for different measures
even in the narrowest part of the gulf.
While the zero-crossings of ˆ
p are usually located very close to the gulf axis,
the extrema of other fields may be substantially shifted to either side. The largest
deviations are shown by the locations for the longest particle age for a particular
longitude. The particularly large deviation of these locations for the two ways of
interpreting the fate of particles that drift out of the gulf demonstrates the sensibility
of the entire approach on the underlying value system.
Another significant feature of the cross-sections of relatively wide sections of the
gulf is the presence of a wide area of low cross-gulf gradients in which the values of
the underlying distributions reveal quite limited changes. This area can be naturally
identified as an area of reduced risk. In most occasions this area ends abruptly, and
relocation of a potentially dangerous activity closer to the coast is associated with a
rapid increase in the relevant risks. The presence of a well-defined bend in the crosssections in Fig. 10.9 indicates a possibility for systematically selecting a reasonable
distance from the coast for possible sources of environmental risks. This feature can
be particularly useful for the specification of the minimum acceptable distance from
the coast for tanker routes along open ocean coasts.
345
the same coast. In early simulations using 10-day long trajectories (Soomere et al.
2010) the separation point of the opposite coasts was set at the mainland border
between Estonia and Russia at the River Narva mouth in the SE of the Gulf of
Finland (28 ◦ 2 E, 59 ◦ 27.5 N). In later simulations with the same model and 20
day long trajectories, the separation point was set at the mouth of the River Neva
(Soomere et al. 2011c).
The equiprobability line followed the gulf axis in the narrowest part of this water
body, deviated substantially to the north of it at the gulf entrance and in the widest
part of the gulf, and came quite close to the southern coast of the easternmost narrow
part of the gulf. While the latter feature evidently mirrors the flow of the voluminous
runoff from River Neva that merges with the overall cyclonic circulation in the gulf
in this area (Chap. 6), the two other deviations of the equiprobability line from the
centreline of the gulf apparently signify certain systematic anisotropic features of
the transport by surface currents.
10.6.2 Cross-Sections
Different cross-sections of the distributions of the probability, the particle age and
the quantity ˆ
p characterizing the probability of hitting the opposite coasts of the
Gulf of Finland reveal several important features of the underlying fields (Fig. 10.9).
For relatively narrow parts of the gulf all the fields have a clearly defined extremum
or zero-crossing. A deviation from these points by only a few km is associated with
a considerable change in the values of the underlying quantities (equivalently, in the
environmental risks). Interestingly, the exact locations for the optimum values (potential locations for the sailing line) not necessarily coincide for different measures
even in the narrowest part of the gulf.
While the zero-crossings of ˆ
p are usually located very close to the gulf axis,
the extrema of other fields may be substantially shifted to either side. The largest
deviations are shown by the locations for the longest particle age for a particular
longitude. The particularly large deviation of these locations for the two ways of
interpreting the fate of particles that drift out of the gulf demonstrates the sensibility
of the entire approach on the underlying value system.
Another significant feature of the cross-sections of relatively wide sections of the
gulf is the presence of a wide area of low cross-gulf gradients in which the values of
the underlying distributions reveal quite limited changes. This area can be naturally
identified as an area of reduced risk. In most occasions this area ends abruptly, and
relocation of a potentially dangerous activity closer to the coast is associated with a
rapid increase in the relevant risks. The presence of a well-defined bend in the crosssections in Fig. 10.9 indicates a possibility for systematically selecting a reasonable
distance from the coast for possible sources of environmental risks. This feature can
be particularly useful for the specification of the minimum acceptable distance from
the coast for tanker routes along open ocean coasts.