Setting the Standard: ADMS-2, The Multiple Source Air
Dispersion Model
System requirementsModel developmentValidationMeteorological InputBoundary Layer StructureDepositionSourcesDispersionPlume RiseBuildingsOutputComplex TerrainCoastlineFluctuations of concentration - OdoursRadioactivity
Output facilities offered include:
Comprehensive validation includes:
Comparisons with standard field, laboratory and numerical data sets
Participation in EU workshops on short range dispersion models
Comparision with archived LIDAR data in a study sponsored by HMIP
Flexible input allows use of basic data such as cloud cover,
time of day and day of year; or boundary layer data such as
Monin-Obukhov length or surface heat flux and boundary layer height
Worldwide data specifically for use in ADMS is available
from the UK Meteorological Office, or users may use their own data
ADMS is based on an up to date understanding of the
structure of the atmospheric boundary layer
This contrasts strongly with the surface layer approach
used by older models such as CALINE, ISC, and R91
Diffusion of gases and particulates and gravitational settling
of particulates to ground (dry deposition) is calculated by using
a dry deposition velocity which may be user defined or calculated
by the model.
Wet deposition of material is modelled by a washout coefficient
Comprehensive treatment of source types including:
Up to 50 sources, 10 particle sizes, 10 pollutant types
in a model run
Point, area, line and volume sources
Both continuous and discrete sources
The model allows for the skewed nature of turbulence within the
atmospheric boundary layer which for elevated sources (height greater
than about 25m) can bring material rapidly down to the surface in
unstable (daytime) conditions
Allowance for partial penetration by the pollutant of any
inversion at the top of the boundary layer
Takes account of the buoyancy and momentum of all
source types
Buildings have a profound effect on the concentration
distribution - changing the concentration sometimes by a
factor of ten
The model explicitly calculates changes in mean flow and
turbulence over the building and its effects on the
dispersion
Treats a recirculating region behind the building where
pollutant may be trapped and a main wake where pollutants
are brought down towards the surface
Comprehensive output includes:
Concentrations: means, percentiles, short term fluctuations
Wet and dry deposition fluxes or deposits
Plume geometry: dispersion coefficients and plume height
Numerical data
Contour and X-Y plots
Link to a GIS (Geographical Information System)
Complex terrain has a significant effect on the location
and value of the maximum surface concentration where there are
slopes, typically greater than 1:10
Treatment in ADMS is based upon CERC's advanced airflow
model, FLOWSTAR
Calculates the effect of the terrain on the air flow and
hence the dispersion
Allowance for changes in surface elevation and roughness,
and also for stability of the atmosphere
Terrain elevation data may be loaded automatically from
OS Landform Panorama (tm) digitised terrain data (1:50,000)
The model allows for the change in the structure of the
atmospheric boundary layer near coasts
Important for the prediction of odours
Calculates both the variance in the concentration, and
the probability that a particular concentration is exceeded
for a range of times
Based on a comprehensive database of isotopes and their
decay chains
Calculates the decay and hence concentration and, if
required, the deposition of up to 50 isotopes
Allows calculation of gamma radiation beneath the plume
centreline
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