United States
Environmental Protection
Agency
Atmospheric Sciences
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S9-86/017 Dec, 1986
SER& Project Summary
U.S. EPA Workshop to
Develop a Simple Model for
Acid Deposition—Final Report
Harvey E. Jeffries
The Acid Deposition Planning Staff in
the Office of Acid Deposition/U.S. EPA
requested that the Atmospheric Sci-
ences Research Laboratory (ASRL) de-
velop a low-computational-demanding
model suitable for educational use in
understanding the linear or non-linear
nature of the acid deposition process
and that could assist in constructing a
"what if" analysis for a particular situa-
tion. In response, ASRL held a work-
shop, attended by EPA and non-EPA
scientists, to discuss the design of such
a model. In addition, a five person
working committee of non-EPA scien-
tists was established to write a state-
ment of work for the construction of
such a model.
The full report describes the planning
activities that occurred before the
workshop, the two-day discussion at
the workshop, the three days of work-
ing committee meetings after the
workshop; it also includes the resulting
Statement of Work for the creation of a
Comprehensive Chemistry Acid Deposi-
tion Model (CCADM).
This Project Summary was devel-
oped by EPA's Atmospheric Sciences
Research Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title {see Project Report ordering infor-
mation at back).
Introduction
The Acid Precipitation Act of 1980
(P.L. 96-294) calls for a comprehensive
and coordinated program to identify
causes and effects of acid precipitation,
as well as actions needed to control
harmful effects. Under the guidance of
an Interagency Task Force on Acid Pre-
cipitation, U.S. EPA's Atmospheric Sci-
ences Research Laboratory (ASRL) un-
dertook to develop a relatively simple
nomogram-type chemical mechanistic
model which, complementing other
more sophisticated models, would as-
sist in further understanding the relative
roles of the various precursors in the
acid precipitation phenomenon. More
specifically, the intended use of this
Comprehensive Chemistry Acid Deposi-
tion Model (CCADM) was to compute
changes in acid deposition from
changes in precursor emissions for a
given, fixed set of meteorological vari-
ables. It was also desirable that the
CCADM use the most advanced gas and
aqueous phase chemical mechanisms
and have relative low computer re-
source requirements.
The subject workshop was designed
to first focus on the EPA needs in the
acid deposition modeling area, on util-
ity of existing or under development
models, and on the desired utility of the
new model. Next, the attendees dis-
cussed various technical approaches
and problems in development of the
requisite model. In the third and final
stage of the workshop effort, a commit-
tee of workshop attendees selected an
approach and developed a Scope of
Work statement, detailing the technical
approach and specific objectives of a
one year, $240K contractual effort to-
ward development of the requisite
model.
Conclusions and Recommenda-
tions
1. The primary use of CCADM should
be that of an educational tool and not
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to perform assessments in competi-
tion with other, more complex re-
gional scale Euierian models (such
as the Regional Acid Deposition
Model) or their "engineering" ver-
sions.
2. For CCADM to be acceptable, it must
represent in the best possible way
the gas-phase chemistry, aqueous
phase chemistry, and cloud physics
processes attendant to the acid de-
position phenomenon.
3. As a compromise between model
comprehensiveness and computer
resource requirements, the CCADM
framework should be equivalent to
that of a one-cell Langrangian model
treating emission dispersion, dilu-
tion and entrainment associated with
diurnal variation of box height
(boundary layer), cloud processes on
top of box, cloud processes within
the box, gas-phase and aqueous
phase chemistries, and dry and wet
deposition processes. Model inputs
should be chemical mechanism
modules, meteorology related in-
puts, time-varying emission data,
and control inputs. Model outputs
should include displays of concen-
tration and of deposition of selected
species over the box/column path-
way, as well as displays illustrating
the importance of processes at se-
lected times.
4. A Scope-of-Work (SOW) statement
was developed and recommended
for use in procuring a contractual ef-
fort to develop the CCAPM. The req-
uisite work was structured in terms
of 8 tasks: Development of Work
Plan, Development and Testing of
Major Model Components, Integra-
tion of Model Components and De-
velopment of Input Processor, Exer-
cising the Model for Limited
Sensitivity Analysis and for Explor-
ing the Linearity Issue, Assessment
of Feasibility of Deriving Long Term
Deposition Estimates, Development
of Display Techniques, Proposing
Procedures for Testing and Evaluat-
ing the Model, and Documentation
of the Model.
Harvey E. Jeffries is with the University of North Carolina, Chapel Hill, NC27514.
Basil Dimitriades is the EPA Project Officer (see below).
The complete report, entitled "U.S. EPA Workshop to Develop a Simple Model for
Acid Deposition: Final Report." (Order No. PB 86-242 856/AS; Cost: $11.95,
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, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S9-86/017
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REGION 5 LIBRARY
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