United States
Environmental Protection
Agency
Atmospheric Sciences
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S8-87/046 Dec. 1987
Project Summary
User's Guide for RAM-
Second Edition
Joseph A. Catalano, D. Bruce Turner, and Joan H. Novak
RAM is an air quality model based
on the Gaussian-plume simplification
of the diffusion equation which
assumes time independence in the
input meteorology and concentration.
The model is primarily used to deter-
mine short-term (one hour to one day)
concentrations from point and area
sources. A maximum of 250 point
sources and 100 area sources can be
considereed to yield pollutant concen-
trations at a maximum of 180 recep-
tors. The simulation is done using
hourly meteorological data for periods
ranging from one hour to one year. A
default option is available in the model
for regulatory applications. Use of this
option automatically sets certain
parameters to preassigned values for
consistency with the ' 'Guideline on Air
Quality Models (Revised)" (EPA,
1986).
This Project Summary was devel-
oped by EPA's Atmospheric Sciences
Research Laboratory. Research Trian-
gle Park, NC. to announce key findings
of the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
The RAM algorithm is a Gaussian-
plume dispersion model that calculates
short-term pollutant concentrations from
multiple point and/or area sources at a
user-specified receptor grid in level or
gently rolling terrain. Pollutants consi-
dered are relatively non-reactive, such as
sulfur dioxide and suspended particu-
lates. Both urban and rural situations can
be simulated. In the rural mode, the
model uses the Pasquill-Gifford disper-
sion parameters; in the urban mode.
those proposed by Briggs based on the
work of Pooler-McElroy are used. Plume
rise is calculated following the methods
of Briggs and both buoyancy rise and
momentum rise are included. For point
sources, concentrations are determined
using distance crosswind and distance
upwind from the receptor to each source.
For area sources, the narrow plume
simplification of Gifford and Hanna is
used with the modification that the area
sources are not at ground level, but have
an effective height.
Inputs to the model are a set of options
selected by the user, source parameters,
meteorological data, and receptor infor-
mation. Using the hourly meteorology,
concentrations are calculated for recep-
tor locations either specified by the user
or generated by the program. Emissions
and source parameters for point or area
sources are required inputs. The meteo-
rological data base, and hence the
simulation, can vary from one hour to
one year. Concentrations for 5 averaging
periods can be computed. For long-term
runs such as a year, a high-five tabu-
lation can be obtained to determine the
highest and second highest concentra-
tions at each receptor for each of five
averaging periods. Receptors can be
specified by the user or they can be
generated by the program. If they are
input by the user, receptor name as well
as coordinates may be provided on input.
For model execution, the user specifies
parameters and options needed for the
application. Requried parameters are
type of pollutant, number of sources,
averaging periods), power-law wind-
profile exponents, and whether the urban
or rural mode is to be used. Options are
included for the treatment of stack-tip
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downwash, gradual plume rise, and
buoyancy-induced dispersion. The user
also specifies types of sources and those
that are significant, receptor configura-
tion, characteristics of emission sources,
and meteorological inputs. Whether the
run is part of a segmented run, outputs
desired, and use of the default feature
are also specified by the user. The default
feature sets parameters and options for
regulatory application; final plume rise
and momentum plume rise are used as
are buoyancy-induced dispersion and
stack-tip downwash. Calm wind condi-
tions are treated following the "Calms
Processor (CALMPRO) User's Guide."
Both point and area sources are
considered by the model. Their particu-
lars can be included in the run stream
or they can be read from disk or tape
files. Source coordinates and parameters
must be given, as well as emisison rates.
A total of 250 point sources and 100 area
sources are permitted. Of these, up to
25 point sources and 10 area sources
can be labeled significant to obtain their
contribution at a receptor separately.
As with the data on emissions, the
meteorology can be read as part of the
input stream, from a file processed by
the program RAMMET, or from a file
having the format of RAMMET. Surface
parameters and mixing height must be
present for each simulation hour; the
meteorological file is of a variable length
from one hour to one year.
Receptors can be specified by the user
or they can be generated by the model.
If they are input by the user, receptor
name as well as coordinates may be
provided. If generated by the program,
the user selects whether a polar coor-
dinate grid of 180 receptors (36 radials
by 5 distances) or a honeycomb receptor
configuration is desired. Also, when
significant sources are specified, the
model selects two receptors downwind
of each source where maxima are likely
to occur. A total of 180 receptors are
permitted.
On output, the model produces printed
and disk or tape files. The printed output
lists the options and source information
including a ranking according to source
height; those selected by the user as
significant are properly identified. Recep-
tors are next listed with their appropriate
coordinates. This is followed by the
meteorological parameters as input by
the user. Model-calculated concentra-
tions are tabulated by receptor. Various
other output files can be obtained.
Joseph Catalano is with Aerocomp, Inc.. Costa Mesa, CA 92626; the EPA authors
Bruce Turner (also the EPA Project Officer, see below) and Joan Novak
are with the Atmospheric Sciences Research Laboratory, Research Triangle
Park, NC 27711.
The complete report, entitled "User's Guide for RAM—Second Edition," fOrder
No. PB 88-113 261/AS; Cost: $25.95. subject to change) will be available
only from: _^
National Technical Information Service ', '-
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Atmospheric Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park. NC27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S8-87/046
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