adms adms 3.3 modelling summary of model features
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ADMS
ADMS 3.3 Modelling
Summary of Model Features
ADMS
ADMS 3.3• CERC
– “New Generation” Model– Detailed description of atmosphere based on boundary
layer properties
• Features– Point, area, line, volume and jet sources– Multiple sources and pollutants– Buildings and Topography– Plume rise– Single condition or statistical meteorology– Odours, radioactivity, plume visibility– Deposition (Wet and Dry)– Statistics, long and short term, percentiles
ADMS
Factors Influencing Dispersion
– Meteorology• Wind Speed and direction• Atmospheric stability (Monin–Obukhov Length and Boundary Layer Height)
– Release point and conditions• Elevation• Velocity• Temperature• Ground roughness
– Buildings• If > 1/3 stack height
– Topography• If steeper than 1:10 slope
ADMS
Meteorology
• Older Models – Passive dispersion model
• Pasquill-Gifford Stability Classes (A – G)• Wind speed, direction
• ADMS– Boundary Layer Model
• Boundary layer height• Monin – Obukhov length• Wind speed, direction
ADMS
Meteorological Parameters
• Boundary Layer Height– Height at which surface effects influence dispersion– ADMS calculates boundary layer properties for
different heights based on meteorology
• Monin-Obukhov Length– Measure of height at which mechanical turbulence is
more significant than convection or stratification
– ADMS calculates M-O length based on meteorology and ground roughness
ADMS
Meteorology Options• Specific Data
• Wind speed, wind direction, date, time, latitude, boundary layer height, cloud cover
• Met Office Data• Statistical data (10 years)
– 2200 lines of data (medium run times)
• Hourly sequential data (1 – 5 years)– Can be used to identify specific conditions for known
dates and times– 8760 lines of data per year (long run times)– Use to compare releases against environmental
standards (preferred option by EA)
ADMS
Meteorology Effects• Typical atmospheric conditions within the UK.• Pasquill - Gifford Stability Classes as modelled in ADMS• No exact correlation between boundary layer parameters
Stability Class
Wind Speed (m/s)
Boundary Layer
Height (m)
Monin – Obukhov
Length (m)Conditions
A 1 1300 -2 Convective - Hot Still Day
B 2 900 -10 Convective
C 5 850 -100 Convective
D 5 800 ∞ Neutral - Normal UK Day
E 3 400 100 Stable
F 2 100 20 Stable - Still Night
G 1 100 5 Stable
ADMS
Example of A – G Conditions
• Stack Release– SO2,150 g/s– 50 m stack– 5 m diameter, – 20 m/s velocity– 15°C
ADMS
A – G conditionsCentre Line Ground Level Concentrations
ADMS
A1 Conditions Contour PlotConvective - Hot Still Day
0 200 400 600 800 1000 1200 1400 1600 1800 2000
M etres
SO2 Concentration (ug/m3)
-1000
-800
-600
-400
-200
0
200
400
600
800
1000
Met
res
100
200
300
400
500
600
ADMS
D5 Conditions Contour PlotNeutral - Normal UK Day
0 200 400 600 800 1000 1200 1400 1600 1800 2000
M etres
SO2 Concentration (ug/m3)
-1000
-800
-600
-400
-200
0
200
400
600
800
1000
Met
res
20
40
60
80
100
120
140
160
ADMS
F2 Conditions Contour PlotStable - Still Night
0 200 400 600 800 1000 1200 1400 1600 1800 2000
M etres
S02 Concentration (ug/m3)
-1000
-800
-600
-400
-200
0
200
400
600
800
1000
Met
res
3
4
5
6
7
8
9
10
ADMS
Buildings
• Can have significant effects– Entrain pollutants into leeward cavity of
building– Increased concentrations close to building– Decreased concentrations further away– Only relevant if >1/3 stack height– ADMS allows 10 buildings
ADMS
Building Effects – Tall Stack
• Tall Stack– Release of NOx from a 50 m
stack (3 m diameter, 5 m/s velocity, 30°C, 1 g/s NOx)
– Unstable weather conditions
– Stack is at the centre point of the building
– Building is 30 m high, 30 m wide, 67 m long
ADMS
Tall Stack – No Building
0 100 200 300 400 500 600 700 800 900 1000
M etres
NOx Concentration (ug/m 3)
-400
-300
-200
-100
0
100
200
300
400
Met
res
2
3
4
5
6
7
8
9
10
11
12
ADMS
Tall Stack – With Building
0 100 200 300 400 500 600 700 800 900 1000
M etres
NOx Concentration (ug/m 3)
-400
-300
-200
-100
0
100
200
300
400
Met
res
2
4
5
6
7
8
9
10
ADMS
Building Effects – Short Stack
• Short Stack– Release of NOx from a 35 m
stack (3 m diameter, 5 m/s velocity, 30°C, 1 g/s NOx)
– Unstable weather conditions
– Stack is at the centre point of the building
– Building is 30 m high, 30 m wide, 67 m long
ADMS
Short Stack - Without Building
0 100 200 300 400 500 600 700 800 900 1000
M etres
NOx Concentration (ug/m 3)
-400
-300
-200
-100
0
100
200
300
400
Met
res
23456789101112131415161718192021222324
ADMS
Short Stack - With Building
0 100 200 300 400 500 600 700 800 900 1000
M etres
NOx Concentration (ug/m 3)
-400
-300
-200
-100
0
100
200
300
400
Met
res
23456789101112131415161718192021222324
ADMS
Topography
• Can effect dispersion– Changes plume trajectory– May increase or decrease concentrations– Include if terrain exceeds 1:10 (maximum 1:3)– Terrain data available from Ordnance Survey
ADMS
Topography Example
– Release of NOx from a 65 m stack– 5 m diameter– 5.25 m3/s flowrate– 69°C, – 1 kg/s NOx– Neutral weather conditions
• 10 m/s wind• Boundary layer 1000 m
– Simple hill 2.6 km to the East and 1 km South of the release
ADMS
Without Hill
-2000 -1000 0 1000 2000 3000 4000
M etres
NOx Concentration (ug/m3)
-2000
-1000
0
1000
2000
3000
4000
Met
res
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
1500
1600
ADMS
With Hill
-2000 -1000 0 1000 2000 3000 4000
M etres
NOx Concentration (ug/m3)
-2000
-1000
0
1000
2000
3000
4000
Met
res
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
1500
1600
ADMS
3D Hill
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
1500
1600
ADMS
Statistical Meteorology
• 10 years statistical data• 1 – 5 years hourly sequential data• Can calculate
– Annual averages– Percentiles (worst case conditions)– No of exceedences/year– Areas affected
• Direct comparison with UK Legislation (NAQS, PPC)
ADMS
Statistical Results
442000 442200 442400 442600 442800 443000 443200 443400 443600 443800
M etres
Long Term SO2 Concentration
374200
374400
374600
374800
375000
375200
375400
375600
375800
376000M
etre
s
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
1.6
ADMS
Statistical + Topography
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
1.6
Reproduced from Ordnance Survey® Panorama Digital Data, by permission of Ordnance Survey® on behalf of the Controller of Her Majesty’s Stationary Office. © Copyright 1990. All rights reserved. Licence No. 100040193
ADMS
Digital Maps
• Available from Ordnance Survey
• 1:50000 or 1:10000
• Can overlay release contours onto maps
ADMS
Digital Map Example
Reproduced from Ordnance Survey® 1:10K Raster Data, by permission of Ordnance Survey® on behalf of the Controller of Her Majesty’s Stationary Office. © Copyright 1990. All rights reserved. Licence No. 100040193
ADMS
Digital Map + Topography + Concentrations
Reproduced from Ordnance Survey® Panorama Digital Data and1:10K Raster Data, by permission of Ordnance Survey® on behalf of the Controller of Her Majesty’s Stationary Office. © Copyright 1990. All rights reserved. Licence No. 100040193
ADMS
Odours
• Model as Odour Units– ou: Number of times the mixture must be
diluted at STP to reach detection limit of 1 ou.
– ouE: The mass of pollutant that when evaporated into 1m3 of gas at STP is 1 ou.
– Information on detection limit is required.
• ADMS– Input and output in terms of ou or ouE.
ADMS
Odour Example
• Release from landfill site– Odours in ouE
– Two area sources, one line source• Landfill 1: 100 m x 100 m, 10 ouE/m2/s• Landfill 2: 100 m x 100 m, 5 ouE/m2/s• Line 1: 200 m, 2 ouE/m/s
– Flat terrain, no buildings– Neutral conditions
• 10 m/s wind• Boundary layer 1000 m
– Short term hourly average concentration
ADMS
Odour Example - Sources
0 200 400 600 800 1000 1200 1400
Landfill Site
-600
-400
-200
0
200
400
600
LAND FILL1
LINE1
LAND FILL2
O utput grid
Area/line/volum e source
ADMS
Odour Example - Results
0 200 400 600 800 1000 1200 1400
M etres
Landfill Odour Release (ouE)
-600
-400
-200
0
200
400
600
Met
res
15101520253035404550556065707580859095100
ADMS
Time Varying Releases
• Release rates often vary with production• Time varying releases
– Hourly sequential meteorological data– Details of release for each hour of met data
• flow, temperature, concentration, velocity
• Results can differ considerably when compared to average releases
ADMS
Fluctuations
• Meteorology usually stable over 1 hour• Turbulence causes short duration fluctuations
• Interest in lower times for exposure – Odours
– NAQS (SO2, 15 minute mean)
• ADMS turbulence calculations– Percentiles– Probability distribution function– Toxic response
ADMS
Other Features
• Variable surface roughness
• Treatment of land sea internal boundary layer
• Puffs
• NOx Chemistry
• Radioactive decay
• Plume visibility (condensed plume)