Emissions factors are another critical point that deserves deeper consideration in
particular to define PM components (e.g. BC, metal, UFP, wildfires) and allow to
compute the emission of other gaseous pollutants (VOC, SLCP, reactive nitrogen),
of HFC emissions from refrigeration and air conditioning equipment’s and NO 2
emissions from catalytic converters of cars, as well as those resulting from agricultural fertilizers. Another important improvement would be the splitting of
aggregated road traffic emission factors to account for the continuous changes and
evolutions of the real vehicle fleets at local, regional and higher levels.
4.3.3 State (Concentration Levels)
Key areas to be addressed by research and innovation in the STATE module refer to
both actual measurements and modelling tools.
From the point of view of measurements, we suggest to develop a stronger
integration of ground-based and remote-sensing monitoring methods, to assess the
“current” AQ situation at a wider scale as well as improve the understanding of the
composition of the various PM fractions.
As to models, in order to better assess the AQ state (and the associated health
impacts), research should be oriented to better represent AQ at a very detailed scale.
This could be done either through the use of Computational Fluid Dynamics
(CFD) to explicitly represent local and street levels or by developing sub-grid scale
models and parameterization within Chemical Transport Models. Concerning
meteorological models, a better use of urban modules in mesoscale models would
benefit to regional and more local studies, and help to link models at different
scales.
Modelling the urban or local scales requires the inclusion of specific small-scale
processes, but also to consider the influence of larger scale effects. This is a
challenge that still needs to be worked on because common practices are mainly
based on the application of mesoscale models to urban areas without the proper
urban parameterizations, and on Gaussian models that are still limited, even with
the latest developments.
The use of CFD models to simulate urban areas, forced by a mesoscale model, is a
current research area, still with strong limitations because of the high demand of
computer time. It is still impossible to simulate a full year period with this modelling
approach without several simplifying assumptions. In the future, these limitations
could be overcome and the development of the proper link between the mesoscale
and the CFD models should therefore be considered as a key research area.
This said, there are still some processes that require a better description within
the models. In general, air quality models tend to underestimate peak PM concentrations while exceedances for PM are often considered the most meaningful
index in terms of health impact. Further research is required to improve modules for
describing windblown dust, resuspension and the formation and fate of secondary
organic aerosols. Significant scientific uncertainties also remain regarding the
4 Strengths and Weaknesses of the Current EU Situation
75
particular to define PM components (e.g. BC, metal, UFP, wildfires) and allow to
compute the emission of other gaseous pollutants (VOC, SLCP, reactive nitrogen),
of HFC emissions from refrigeration and air conditioning equipment’s and NO 2
emissions from catalytic converters of cars, as well as those resulting from agricultural fertilizers. Another important improvement would be the splitting of
aggregated road traffic emission factors to account for the continuous changes and
evolutions of the real vehicle fleets at local, regional and higher levels.
4.3.3 State (Concentration Levels)
Key areas to be addressed by research and innovation in the STATE module refer to
both actual measurements and modelling tools.
From the point of view of measurements, we suggest to develop a stronger
integration of ground-based and remote-sensing monitoring methods, to assess the
“current” AQ situation at a wider scale as well as improve the understanding of the
composition of the various PM fractions.
As to models, in order to better assess the AQ state (and the associated health
impacts), research should be oriented to better represent AQ at a very detailed scale.
This could be done either through the use of Computational Fluid Dynamics
(CFD) to explicitly represent local and street levels or by developing sub-grid scale
models and parameterization within Chemical Transport Models. Concerning
meteorological models, a better use of urban modules in mesoscale models would
benefit to regional and more local studies, and help to link models at different
scales.
Modelling the urban or local scales requires the inclusion of specific small-scale
processes, but also to consider the influence of larger scale effects. This is a
challenge that still needs to be worked on because common practices are mainly
based on the application of mesoscale models to urban areas without the proper
urban parameterizations, and on Gaussian models that are still limited, even with
the latest developments.
The use of CFD models to simulate urban areas, forced by a mesoscale model, is a
current research area, still with strong limitations because of the high demand of
computer time. It is still impossible to simulate a full year period with this modelling
approach without several simplifying assumptions. In the future, these limitations
could be overcome and the development of the proper link between the mesoscale
and the CFD models should therefore be considered as a key research area.
This said, there are still some processes that require a better description within
the models. In general, air quality models tend to underestimate peak PM concentrations while exceedances for PM are often considered the most meaningful
index in terms of health impact. Further research is required to improve modules for
describing windblown dust, resuspension and the formation and fate of secondary
organic aerosols. Significant scientific uncertainties also remain regarding the
4 Strengths and Weaknesses of the Current EU Situation
75