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CITY-DELTA European Modelling Exercise -
calculations with the THOR integrated air
pollution forecast and management system
Ruwim Berkowicz, Jørgen Brandt and Jesper H.
Christensen, National Environmental Research
Institute Department of Atmospheric Environment
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The THOR integrated model system
Global meteorological data from NCEP, USA
Numerical weather forecast model (Eta)
Emission and traffic models
Long range transport model (DEOM)
2000 visualizations and animations of weather
and air pollution, four times a day
Urban background model (UBM)
Street canyon model (OSPM)
Subset to decision makers, web site, the public,
etc.
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CityDelta modelling results are available for
Berlin
London
Copenhagen
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Urban emissions constitute a singularity
compared to regional emissions
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Berlin Emissions
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London Emissions
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Modelling results with 50km grid resolution
cannot reproduce the increased NOX levels within
the urban areas.
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In order to reproduce the increased NOX levels
within the urban areas the resolution of the
emission data must be at least 2km, or better.
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• Regional scale (European) scale modelling tools
  are not suitable for urban scale modelling (?)
• regional scale chemical transformations,
  depositions are important
• urban scale atmospheric dilution of local
  emissions is more important than chemical
  transformations and deposition

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Urban Background Model (BUM) - High resolution
dispersion modelling but simplified chemistry.
Applied only for the urban area.
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NO2 formation
Formation of the nitrogen dioxide due to
oxidation of NO by ozone is calculated using a
simple chemical model based on assumption of a
photochemical equilibrium on the time scale of
the pollution transport across the city area.
The rate of entrainment of fresh rural ozone is
governed by this time scale.
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Emissions
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Berlin
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Berlin
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London
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London
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Copenhagen - Methods
Traffic
Emissions
Vehicle emission factors
PM10Total traffic related emissions !!- based
on street measurements and OSPM modelling!
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Copenhagen - Methods
Time variation of emissions is defined for 8 day
classes. DC1 - Monday to Thursday DC2 -
Friday DC3 - Saturday DC4 - Sunday DC5 to DC8 the
same as above but for July (summer holidays in
Denmark)
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Results
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Jagtvej, Copenhagen
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Average diurnal variation of NOX, Berlin
Average diurnal variation of PM10, Berlin
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Average diurnal variation of O3, Berlin
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Model performance is better for hours with higher
mixing heights than for hours with limited
vertical dispersion. Prediction of hourly
variation of the mixing height is crucial for
model results.
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London NOX
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London NO2
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London O3
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London PM10
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London
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Copenhagen
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Copenhagen PM10
Measured urban backgroundMay -June 2002
Modelled urban background1999
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Copenhagen NOX
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Copenhagen NO2
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Copenhagen O3
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Copenhagen PM10