AirWare:
COMPREHENSIVE AIR
QUALITY MODEL
WITH EXTENSIONS
VERSION 4.30, PBM
DDr. Kurt Fedra
Environmental Software & Services GmbH
A-2352 Gumpoldskirchen AUSTRIA
info@ess.co.at http://www.ess.co.at/AIRWARE
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CAMx
CAMx simulates the emission,
dispersion, chemical reaction,
and removal of pollutants in the
troposphere by solving the
pollutant continuity equation for
each chemical species (l) on a
system of nested threedimensional grids.
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CAMx
The Eulerian continuity equation
describes the time dependency
of the average species
concentration (cl) within each
grid cell volume as a sum of all
of the physical and chemical
processes operating on that
volume.
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CAMx basic structure:
Where:
Cl
= concentration of chemical species l
VH
= horizontal wind vector

= net vertical entrainment rate

= atmospheric density
K
= turbulent diffusion
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CAMx (simple version)
• Regular terrain-following 3D
grid, supports nesting;
• Describes conservative
substances, particulates and
aerosols, various alternative
chemistry mechanisms
including complete
photochemistry (ozone).
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CAMx model grid:
2 level nesting:
• 1 km master
domain (240*180)
• up to 9 subdomains (city level,
12-30 km at 250m)
• 8 vertical layers.
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CAMx Performance
• Performance independent of the
number of (gridded) sources;
• Depends on: horizontal and vertical
extent and resolution of the model
domain, run duration
• 24 hours Cyprus (240*180*8, 9 subdomains of 20*20 km 250m)
conservative
 3 hours
• 24 hours Cyprus, ozone (CBM IV, no subdomain nesting
 10 hours.
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CAMx
The Eulerian continuity equation
describes the time dependency
of the average species
concentration (cl) within each
grid cell volume as a sum of all
of the physical and chemical
processes operating on that
volume.
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CAMx implementation
Used for scheduled runs:
• Daily 24 hour forecasts (SO2,
NOx, PM10)
• Hourly now-casts (waiting for
real-time data assimilation,
nudging the initial conditions
with monitoring data.
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AirWare R5.3
PBM
photochemical
box model
DDr. Kurt Fedra
Environmental Software & Services GmbH
A-2352 Gumpoldskirchen AUSTRIA
info@ess.co.at http://www.ess.co.at/AIRWARE
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PBM photochemical box model
• Simple, fast and efficient numerical model for urban
scale (10-100 km) photochemical smog.
• Initial and boundary conditions can be taken from
the daily regional ozone forecasts by CAMx.
• Input data include:
– Meteorology (temperature, wind speed, mixing height,
insolation/cloud cover) can be taken from the MM5
weather forecasts;
– Dynamic (hourly) emission data of NOx and VOC are
taken from the city domain level emission scenarios
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PBM photochemical box model
Simple representation:
• Variable volume (vertical movement of the
mixing layer), well mixed reactive cell (box);
• Transport and dispersion of pollutants
through the cell;
• Dynamic emission of primary precursor
species;
• Chemical transformations into intermediate
and secondary products.
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PBM photochemical box model
Simulation runs:
Daily forecast runs for the period from
– 05:00 LST (at/around/before sunrise)
– 23:00 LST (after sunset
Hourly model output.
Speed/efficiency of the model makes it ideal
for stochastic/ensemble simulations:
probability of exceedances of daily/next day
ozone warning and alert levels.
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PBM data requirements:
Meteorology (hourly):
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•
•
Date, location
Wind speed
Mixing height (can be simulated)
Ambient air temperature
Solar radiation or UV radiation (can be
simulated if cloud cover is known)
• Cloud cover, amount and (optional) height
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PBM data requirements:
Air Quality data:
• Initial conditions (concentrations)
• Boundary conditions/concentrations:
upwind monitoring station ?
• Observed concentrations (optional)
• Hydrocarbon speciation factors for
– Initial concentrations
– Boundary conditions
– Observed concentrations
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PBM reactivity classes:
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•
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•
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•
Non-reactives (NONR)
Ethylene (ETH)
Olefins/alkenes, minus ethylene (OLE)
Paraffins/alkanes, minus methane (PAR)
Formaldehyde (FOR)
Other aldehyde species (ALD)
Toluene (TOL)
Other aromatic species (ARO)
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PBM data requirements:
Emissions (hourly):
• CO (area, point sources)
• NOx (area, line, point sources)
• THC (total hydrocarbon) emissions
• NMHC (non-Methane compounds)
• NO2/NOx ratio in emissions (0.1)
• CH4/THC ratio in emissions
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PBM model dynamics:
• Mixing height growth: option to interpolate
between minimum and maximum;
• Photolytica rate constants: diurnal variation
of photolytica rate constants based on
theoretical clear-sky insolation and
attenuation based on cloud cover or
oberserved insolation;
• Chemical kinetics: 63 reactions and 41
chemical species in 8 hydrocarbon classes
(Demerjian generalized chemical kinetics)
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PBM model governing equation:
ci
ci z ci Qi
u

  Rci ,......, cn 
t
x t z z
where :
ci  mean concentrat ion of species
i
u  mean wind speed
Qi  source emission flux
R i  reaction (productio n/destruct ion) rate
x, z , t  length (horizonta l, vertical) , time
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PBM major assumptions:
1. Well mixed box, no significant spatial variation
inside the box/surface;
2. Low wind to near stagnant conditions (< 2m/s)
3. Emission sources are homogeneously distributed
within the domain;
4. Entrainment/exchange
1. laterally by advective transport
2. Vertically by rising mixing layer
5. Molecular and turbulent diffusion neglected
(well mixed…)
6. Horizontal and vertical wind shear neglected.
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