10 Applications of the Inverse Problem of Pollution Propagation
353
The provided statistical estimates of the gain from the systematic use of an optimum sailing line (almost halving the probability for coastal hits or buying almost
four days to combat the pollution in the open sea) are obviously considerably overestimated. Such a high benefit is evidently not possible in realistic conditions because
a large part of the ship traffic uses anyway deep offshore areas that have relatively
low probabilities for coastal hits and high values of the particle age (Andrejev et al.
2011).
10.7.2 Critically Questioning the Recommendations
The computed 2D maps inevitably contain some noise. Given also the intrinsic uncertainties of the technology, it is obvious that the presented solutions are just approximations for the best ones. The above has also shown that they may substantially
differ when based on different criteria used in building the maps and may depend
on the details and options of the technique. The results for their use in engineering
applications, however, have to be robust: new achievements (e.g., an increase in the
resolution of the ocean model) may perhaps add more details but should in no way
override the principal outcome of the first approximation.
The constructed fairways represent approximations of the climatologically valid
solution as they are based on a multi-year average of the underlying fields of probability and particle age from which the potential seasonal effects evidently have
been filtered out. Substantial seasonal variations in net and bulk transport patterns
calculated using a similar technology (Soomere et al. 2011d), similar variations in
the basin-average values of wind stress (Andrejev et al. 2011), significant seasonal
patterns of the predominant wind direction (Soomere and Keevallik 2003) and distributions of upwelling regions (Lehmann and Myrberg 2008) suggest that properties of surface transport (and, consequently, the location of the optimum fairway)
apparently show extensive seasonal and possibly also interannual variations in the
Gulf of Finland. Some of the variations in the dynamical regimes corresponding to
the inflow and outflow conditions in the SW Baltic Sea have been addressed in Lu
et al. (2012). A much longer time period has to be covered by simulations in order to establish the presence and extension of the related variations in the optimum
solutions.
The quality of the recommendations for the location of stationary activities can
be roughly estimated as the level of invariance of (the extrema of) the maps of
probability, particle age and ˆ
p with respect to different options (Fig. 10.7). There
exists, however, no single measure to characterize the quality of the solutions for the
optimum fairway. Technically, the robustness of the outcome of the presented approach can be quantified as the typical root-mean-square deviation (rmsd) between
the optimum fairways. The difference between various optimum sailing lines can be
interpreted as a measure of the uncertainty of the entire approach (Soomere et al.
2010). Uncertainty has not necessarily a negative meaning here: strictly following
the optimum path is not always the best solution as ships do need some freedom
353
The provided statistical estimates of the gain from the systematic use of an optimum sailing line (almost halving the probability for coastal hits or buying almost
four days to combat the pollution in the open sea) are obviously considerably overestimated. Such a high benefit is evidently not possible in realistic conditions because
a large part of the ship traffic uses anyway deep offshore areas that have relatively
low probabilities for coastal hits and high values of the particle age (Andrejev et al.
2011).
10.7.2 Critically Questioning the Recommendations
The computed 2D maps inevitably contain some noise. Given also the intrinsic uncertainties of the technology, it is obvious that the presented solutions are just approximations for the best ones. The above has also shown that they may substantially
differ when based on different criteria used in building the maps and may depend
on the details and options of the technique. The results for their use in engineering
applications, however, have to be robust: new achievements (e.g., an increase in the
resolution of the ocean model) may perhaps add more details but should in no way
override the principal outcome of the first approximation.
The constructed fairways represent approximations of the climatologically valid
solution as they are based on a multi-year average of the underlying fields of probability and particle age from which the potential seasonal effects evidently have
been filtered out. Substantial seasonal variations in net and bulk transport patterns
calculated using a similar technology (Soomere et al. 2011d), similar variations in
the basin-average values of wind stress (Andrejev et al. 2011), significant seasonal
patterns of the predominant wind direction (Soomere and Keevallik 2003) and distributions of upwelling regions (Lehmann and Myrberg 2008) suggest that properties of surface transport (and, consequently, the location of the optimum fairway)
apparently show extensive seasonal and possibly also interannual variations in the
Gulf of Finland. Some of the variations in the dynamical regimes corresponding to
the inflow and outflow conditions in the SW Baltic Sea have been addressed in Lu
et al. (2012). A much longer time period has to be covered by simulations in order to establish the presence and extension of the related variations in the optimum
solutions.
The quality of the recommendations for the location of stationary activities can
be roughly estimated as the level of invariance of (the extrema of) the maps of
probability, particle age and ˆ
p with respect to different options (Fig. 10.7). There
exists, however, no single measure to characterize the quality of the solutions for the
optimum fairway. Technically, the robustness of the outcome of the presented approach can be quantified as the typical root-mean-square deviation (rmsd) between
the optimum fairways. The difference between various optimum sailing lines can be
interpreted as a measure of the uncertainty of the entire approach (Soomere et al.
2010). Uncertainty has not necessarily a negative meaning here: strictly following
the optimum path is not always the best solution as ships do need some freedom