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General and Specific Characteristics for Model: CTDMPLUS General and Specific Characteristics for Model:
CTDMPLUS
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General Characteristics
1
Abstract of Model
Capabilities
The Complex Terrain Dispersion Model Plus Algorithms for Unstable Situations (CTDMPLUS) is a
refined air quality model for use in all stability conditions for complex terrain applications.
Improvements made to the CTDMPLUS code which is only for stable and neutral conditions
include: (1) the ability to model daytime, unstable conditions, and (2) a number of additional
capabilities for improved user friendliness. The code calculates on an hourly (or appropriate
steady averaging period) basis how the plume trajectory (and, in stable/neutral conditions, the
shape) is deformed by each hill. The computed concentration at each receptor is then derived
from the receptor position on the hill and the resultant plume position and shape.
2
Sponsor and/or
Developing
Organization
Atmospheric Sciences Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
3
Last Custodian/
Point of Contact
Atmospheric Sciences Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
4
Life-Cycle
CTDMPLUS for stable and neutral conditions.
CTDMPLUS can also model daytime, unstable conditions and has a number of additional
capabilities for improved user friendliness.
5
Model Description
Summary
The Complex Terrain Dispersion Model Plus Algorithms for Unstable Situations (CTDMPLUS) is a
refined air quality model for use in all stability conditions for complex terrain applications. It
contains, in its entirety, the technology of CTDMPLUS for stable and neutral conditions. However,
CTDMPLUS can also model daytime, unstable conditions, and has a number of additional
capabilities for improved user friendliness. Its use of meteorological data and terrain information
is different than current EPA models; considerable detail for both types of input data is required
and is supplied by preprocessors specifically designed for CTDMPLUS. CTDMPLUS requires the
parameterization of individual hill shapes using the terrain preprocessor and the association of
each model receptor with a particular hill (except for receptors in flat terrain which CTDMPLUS
can also model). In modeling stable to neutral conditions, a central feature of CTDMPLUS is its
use of a critical dividing-streamline height to separate the flow in the vicinity of a hill into two
separate layers. Flow in the upper layer has sufficient kinetic energy to pass over the top of the
hill, while streamlines in the lower layer are constrained to flow in a horizontal plane around the
hill. Two separate components of CTDMPLUS compute ground-level; concentrations resulting
from plume material in each of these flows:
In modeling unstable (convective) conditions, the model relies on a probability density function
description of the vertical velocities to estimate the vertical distribution of pollutant concentration.
Terrain distortions of plume parcel trajectories are accounted for, as are deflections of the daytime
mixed layer height.
6
Application Limitation
See No. 7.
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Strengths/
Limitations
Principal strength of the CTDMPLUS is its capability to model dispersion over complex terrain.
Lack of the ability to accommodate dense gas dispersion is a weakness.
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Model References
!
Users Guide to the Complex Terrain Dispersion Model Plus Algorithms for Unstable Situations
(CTDMPLUS): Vol. 1. Model Description and User Instructions, EPA/600/8-89/041 (March
1989).
!
Users Guide to the Complex Terrain Dispersion Model: Vol. 1, EPA-600/8-87-058a, (1987).
9
Input Data/Parameter
Requirements
There are five required input files and two optional input files for CTDMPLUS:
!
A general file of program specifications, which consist of program switches, source data,
meterological tower coordinates and hill surface roughness lengths;
!
A terrain data file which is obtained directly from the terrain preprocessor;
!
A file containing receptor names, locations, and the associated hill numbers;
!
A surface meterological data file which is obtained directly from the meteorological
preprocessor program;
!
A user-created meterological profile data file which contains conventional meterological data
measured by multiple levels;
!
An optional file of hourly emissions parameters;
!
An optional file containing upper air data from rawinsonde data General and Specific Characteristics for Model:
CTDMPLUS
A-84
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Output Summary
Input meteorological data;
!
Stack data for each source;
!
Meteorological variables at plume height;
!
Geometrical relationships between the source and the hill;
!
Plume characteristics at each receptor for stable hours; (1) distance in along-flow and cross-
flow directions; (2) effective plume-receptor height difference; (3) effective sigma y, sigma z
values, both for flat terrain and the hill-induced case; and (4) concentration components.
Plume characteristics at each receptor for unstable hours; (1) distance in along-flow and cross-
flow directions; (2) horizontal distribution function; (3) sigma y; and (4) crosswind integrated
concentration.
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Applications
N/A
2
User-Friendliness
Alphanumeric, command line interface.
The code is considered to be user friendly even though the meteorological and topological files
are the required inputs.
13
Hardware-Software
Interface Constraints/
Requirements
Operating system: IBM-PC
Disk space required: 640 K-bytes for menu driven and 360 K bytes for non-menu driven
Run execution time for typical problem (CPU or Real Time): 2-3 minutes
Programming language: FORTRAN 77
Interface with other codes: Requiring a math co-processor chip
Portability: Extremely portable
14
Operational
Parameters
Yes, several spread throughout the code.
15
Surety Considerations
All quality assurance documentation: NA
Benchmark runs: None
Validation calculations: NA
Verification with field experiments that has been performed with respect to this code:
16
Runtime
Characteristics
Set up time 5 or 10 minutes.
Specific Characteristics
Part A: Source Term Submodel Type
A1
Source Term
Algorithm?
YES
U
NO
Part B: Dispersion Submodel Type
B1
Gaussian

U
U
Straight-line plume Segmented plume Statistical plume Statistical puff
Part C: Transport Submodel Type
C2
Deterministic
Yes
C4
Frame of Reference

U
Eulerian
Lagrangian
Hybrid
Eulerian-Lagrangian
Part D: Fire Submodel Type (Not Applicable)
Part E: Energetic Events Submodel Type (Not Applicable)
Part F: Health Consequence Submodel Type
F1
For Chemical
Consequence
Assessment
Models
Health effects: fatalities
cancers
latent cancers
symptom onset
Health criteria
IDLH
STEL
TLV
TWA
ERPG
TEEL
AEGL
WHO
Zones with flammable limits: UFL
LFL
Blast overpressure regions:
Fire radiant energy zones:
Risk qualification:
Concentration:

U
single value
U
time-history
integrated dose
Probits:
Part G: Effects and Countermeasures Submodel Type (No Information Provided.) General and Specific Characteristics for Model:
CTDMPLUS
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Part H: Physical Features of Model
H2
Release Elevation

U
ground

U
roof
H4
Horizontal Plume
Meander
Accounted for by measurement of lateral turbulence intensity.
H6
Mixing Layer

U
trapping
lofting
reflection
U
penetration
inversion breakup fumigation temporal variability
H7
Cloud Buoyancy

U
neutral [passive]
dense [negative]

U
plume rise [positive]
H13
Temporally and
Spatially Variant
Mesoscale
Processes
Urban heat island:
Canopies:
Complex terrain (land) effects:
U
mountain-valley wind reversals
anabatic winds
katabaic winds
Complex terrain (land-water) effects: seabreeze airflow trajectory reversals
Thermally Induced Boundary Layer definition seabreeze fumigation
landbreeze fumigation
Thunderstorm outflow:
Temporally variant winds:
High velocity wind phenomena: tornado
hurricane supercane microburst
Part I: Model Input Requirements
I1
Radio(chemical)
and Weapon
Release
Parameters
Release rate:
U
U
Continuous Time dependent
Instantaneous
Release container characteristics: vapor temperature tank diameter
tank height
tank