United States
                   Environmental Protection
                   Agency
Atmospheric Sciences
Research Laboratory
Research Triangle Park NC 27711
                   Research and Development
EPA/600/S9-86/026 Dec. 1986
v>EPA         Project  Summary
                   A  Workshop  Report  on  the
                   Complex Terrain   Model
                   Development  Project
                   (February  4-6,  1986)

                   Thomas F. Lavery, David G. Strimaitis, and Bruce A. Egan
                     In early October 1985 an initial ver-
                   sion of the Complex Terrain Dispersion
                   Model (CTDM) was delivered to EPA. A
                   final version will be delivered in August
                   1987. Over the next several months,
                   CTDM will  be modified  and will
                   undergo extensive evaluation. A major
                   step in the evaluation of CTDM and its
                   evolution toward becoming a regula-
                   tory model was a workshop that was
                   conducted in February 1986. The work-
                   shop was attended by the model devel-
                   opers, EPA, other regulatory agencies,
                   air quality consultants and university
                   scientists. Each participant was asked
                   to exercise the model to assess its over-
                   all effectiveness and validity. Each par-
                   ticipant also gave a 1/2-hour presenta-
                   tion of  his findings. After the
                   presentations, the participants were
                   partitioned into three workgroups to
                   discuss:

                     • CTDM algorithms,
                     • applications and practical consider-
                      ations of the model, and
                     • evaluation of the model.

                   The full report discusses the recom-
                   mendations of the workshop partici-
                   pants.

                     This Project Summary was devel-
                   oped for 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 Complex Terrain Model Develop-
ment (CTMD) project is being spon-
sored by the U.S Environmental Protec-
tion Agency (EPA) to develop, evaluate
and refine practical models for calculat-
ing  ground-level  air pollutant concen-
trations in mountainous terrain. The
emphasis of the  project is  to develop
models with known accuracy and limi-
tations for simulating 1-hour concentra-
tions during stable conditions. To sup-
port the model development activities,
four major tracer and flow visualization
field experiments have been conducted
since September 1980. The resulting
data bases and data from towing tank
and wind tunnel studies, conducted at
the EPA Fluid Modeling Facility, and our
understanding of the physical proc-
esses have been used to develop the
Complex Terrain Dispersion  Model
(CTDM).
  The delivery of the final  model will
include estimates of the accuracy and
precision of the model and an  assess-
ment of its overall limitations.
  A workshop was conducted in Febru-
ary 1986 as a major step in evaluating
CTDM and its evolution toward  becom-
ing a regulatory model. The workshop
was attended by the model developers,
EPA, other regulatory agencies, air
quality consultants  and university sci-
entists. Each participant was provided a
diskette or tape of  the CTDM code, a
draft User's  Guide and the Fifth
Milestone Report (DiCristofaro, et al
1986, EPA Document Number EPA/600/

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3-85/069) and was asked to exercise the
model to assess its overall effectiveness
and validity in whichever way they
choose.  For example, some of the par-
ticipants evaluated the model using SO2
and meteorological data collected
around electric generating plants, some
performed sensitivity studies, and some
compared  model assumptions to theo-
retical and numerical  model calcula-
tions. Each participant gave a 1/2-hour
presentation of his findings. After the
presentations, the participants were
partitioned into three workgroups to
discuss:
  • CTDM algorithms,
  • applications and practical consider-
    ations of the model, and
  • evaluation of the model.
The full report discusses the recom-
mendations of the workshop partici-
pants.

Recommendations
  The key recommendations  of the
three workgroups are:

CTDM Algorithm Workgroup
1. The CTDM-formula for 
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flows); other information can come
by efforts of recommendation (3),
above.
Finally, the workgroup  recom-
mended that sensitivity studies be
performed to examine the effect of
input errors on predicted peak con-
centrations. Inputs identified for
evaluation in decreasing order of im-
portance are: wind direction, vertical
diffusion, shape and  orientation of
hill from source, dividing streamline
height, plume rise, potential temper-
ature gradient and  horizontal diffu-
sion.
Thomas F. Lavery and David G. Strimaitis are with Sigma Research Corporation,
  Lexington, MA 02173; B. Egan is with Environmental Research & Technology,
  Inc.. Concord, MA 01742.
Peter Finkelstein is the EPA Project Officer (see below).
The complete report entitled "A Workshop Report on the Complex Terrain Model
  Development Project (February 4-6. 1986)," (Order No. PB 87-100 681/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

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Environmental Protection
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EPA/600/S9-86/026
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