Environmental Engineering Reference
In-Depth Information
5. Questions and Answers
Question 1:
Is it worthwhile to set up such a complicated model system, given the
little differences obtained with respect to the original model version? (Stefano
Galmarini, JRC)
Answer:
In cases of such complex model setups, it is indeed important to weigh
the prospective benefits with the effort expended to set up and process indivi-
dual application cases. Nevertheless, one of the features of our system is that
the setup effort is largely restricted to the initial configuration- and calibration
phase, which mainly consists of microscale simulations. Once the metamodel
library is prepared, the cost of running additional cases becomes minimal.
Furthermore, the observed differences with the original mesoscale fields do
reveal a strong modification of the flow field on the two lowest layers (see, e.g.
Fig. 2b),
which is expected to have a significant effect on pollutant dispersion
calculations within urban cells.
Question 2:
You have demonstrated micro and mesoscale coupling of the dynamics.
How do you expect the coupling to behave when one is trying to model air
quality, especially NO
2
or PM
10
? (Bernard Fisher, University of Greenwich School
of Earth and Environmental Sciences)
Answer:
Qualitatively, we can expect the modification of the mesoscale fields as
caused by the two-way coupling to influence dispersion calculations in two
significant ways: the first is an overall increase of the average pollutant con-
centrations in densely built areas, due to the reduced average wind speeds as
calculated in these areas. The second one is the amplification of turbulent mixing
in the first two computational layers resulting from the introduction of additional
shear and TKE production by the coupling process. A quantitative assessment
of both effects on the dispersion of various pollutants (including NO
2
and
PM
10
) is the subject of ongoing work.
