MODEL
INPUTS
Source parameters
include:
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source location data,
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road widths and canyon heights for road sources,
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stack heights, diameters, exit velocities etc
for industrial sources,
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grid dimensions for aggregated emissions data.
Once source data have been loaded into the model users
can use the GIS link to view the sources as the part of the input data
validation process. For example, the picture below shows all the sources
from an example modelling scenario: industrial points, roads, and aggregated
emissions, displayed using the ArcGIS link. Note the additional GIS
tools for use with ADMS-Urban. The point and road sources are being
modelled explicitly with all other emissions aggregated onto grid sources.
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For road sources, the user can enter hourly speed and traffic
flow data into the model and use
ADMS-Urban’s built-in emission factors or, alternatively, the
user can enter pre-calculated emissions data, for example, emissions
calculated within CERC’s Emissions Inventory Toolkit, EMIT
which includes many factors such as current and future factors for
Euro standard engines.
Modelling roads in urban areas is more complex than
just modelling the emissions from traffic as a line source. Both the
effect of street canyons, and traffic-induced
turbulence are included when roads are modelled in ADMS-Urban.
When modelling any local emissions, it is important to include the
background ambient concentrations
that are advected from outside the modelling area. In the UK, these
background data can be downloaded from the UK National Air Quality
Archive website (http://www.airquality.co.uk/archive/index.php)
and included directly in any ADMS-Urban modelling scenario. Background
ambient concentrations can be hourly values, or if these are not available,
constant values can be assumed.
In urban areas, it is also important to include the aggregated
emissions from sources that may
be too small to define explicitly, but whose aggregate emissions contribute
to overall pollution levels. For example, domestic emissions of NOx
from an individual household may not be known, but the aggregated
emissions could be calculated using area-wide figures for fuel consumption.
In ADMS-Urban, a grid source with up to 3000 grid cells can be included
in any run to represent these aggregated emissions.
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