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)