Model comparison between CALPUFF and AERMOD on Chlorine ...

<strong>Model</strong> <strong>comparison</strong> <strong>between</strong>
<strong>CALPUFF</strong> <strong>and</strong> <strong>AERMOD</strong> on
Chlorine Gas Explosion
Edmund Mc-Addy

Introduction
• Hypothetical accidental explosion of
liquid Chlorine on a highway leading to
intersections I81 <strong>and</strong> I690 close to the
(Centre of Excellence building in
Syracuse)

Coupled system processes
We live in a highly <strong>and</strong> non-linearly coupled Climate System
characterized by a range of spatial <strong>and</strong> temporal scales

ATMOSPHERE
Meso-scale Dynamics
Clouds &
Precipitation
Radiation
Aerosols &
Chemistry
Aermod
or
Calpuff
Precipitation
Radiation
Boundary Layer
LAND/OCEAN SURFACE
Surface Fluxes
Albedo
Biosphere
& Soils
Hydrology
& Lake
Ocean
Fluxes
Snow
& Sea Ice
Agriculture
River Runoff
Ecosystem

Generalized process for performing a refined air dispersion
modelling assessment
1-Emission Estimates
1. Type of Chemicals
2. Emission rate
3. Phase-Vapoir/Solid
2-Site Parameters
1. L<strong>and</strong> Use
2. Buildings
3. Source Location
4. Terrain
3-Met Data
1. Wind Speed
2. Wind Direction
3. Temperature
4. Mixing Height
Buildings Downwash
Terrain Processing
Source Inputs
1. Coordinates
2. Rlease Height
3. Exit Temp
4. Exit Velocity
5. Emission Rate
Receptor Definition
1. Grid
2. Discrete
3. Elevation
AIR DISPERSION MODEL
Met Processing
1. Stability Parameter
2. Micrometeorology Parameter
Analysis of results
1. Contouring/Plot
2. Percentiles
3. Thresholds

Terrain Data
• USGS DEM
• GTOPO30 DEM
• UK DTM
• UK NTF
• XYZ File
• AutoCAD DXF
Maps
• Bitmap
• USGS DLG
• USGS LULC
• AutoCAD DXF
• ESRI Shapefile
• JPEG
• TIFF

The <strong>AERMOD</strong> air dispersion modeling system
NWS
Surface
DEM
file
AERMAP
Surface
file
(1)
Upper Air
AERMET
(1)
<strong>AERMOD</strong>
Profile
File
On-Site
(1) From raw data files, AERMAP <strong>and</strong> AERMET generate, the
new file input to the model.

<strong>AERMOD</strong> Regulatory Status <strong>and</strong>
Applicability
• <strong>AERMOD</strong> is the EPA Guideline <strong>Model</strong>,
replacing ISCST3
• Applicable for distances up to 50 km
• Promulgated 9 Dec 2005

Source: Howard Balentine, CCM, PE Sara Head, QEP

Expect to Pay for <strong>AERMOD</strong> <strong>and</strong>
Training
http://www.epa.gov/ Free BEE Line
(BEEST Suite) $695 (1-Day) $1,255
Lakes Environmental
(ISC/<strong>AERMOD</strong>
View)
$950 (2-Day) $1,499
Trinity BREEZE
(<strong>AERMOD</strong>/ISC GIS
PRO)
$1,199 (2-Day) $1,995
Trinity BREEZE
(<strong>AERMOD</strong>/ISC PRO)
$1,199 (2-Day) $795

<strong>CALPUFF</strong> is an Integrated
<strong>Model</strong>ing System
• Meteorological model (CALMET)
• Observational data (surface <strong>and</strong> aloft)
• Prognostic models (MM5, ETA, RUC2, RAMS) Non-steady-state
Lagrangian puff dispersion model (<strong>CALPUFF</strong>)
• All distances out to 300 km
• EPA approved for distances 50 km to 300 km Pre- <strong>and</strong> postprocessing
modules
• Terrain elevation <strong>and</strong> l<strong>and</strong> use geophysical data
• • Surface <strong>and</strong> upper air meteorological data
• • Precipitation data
• • Cloud observations
• • Visibility <strong>and</strong> deposition flux calculations

• Known shortcomings of current gridded
modeling input <strong>and</strong> their impact…precip.
inconsistences, lack of calms (very few), etc.
– Precipitation inconsistences – should be crosschecked
when employing wet deposition
– Fewer calms -- results…steady-state models
(<strong>AERMOD</strong>) will use more hours to calculate
concentration estimates; could lead to higher design
concentrations

Results
• The <strong>AERMOD</strong> <strong>and</strong> <strong>CALPUFF</strong> dispersion
models performed very differently from
one another all two models grossly underestimated
the relative Chlorine gas
concentration calculated

Met data from NOAA
• RUC…20km to 13km (June 2005)
• WRF…initial storage by NCDC ~April,
2006
• MM5 storage by NCDC

Thank you