United States
Environmental Protection
Agency
Atmospheric Sciences
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S3-85/069 Apr. 1986
Project Summary
EPA Complex Terrain Model
Development: Fifth Milestone
Report- 1985
Donald C. DiCristofaro, David G. Strimaitis, Benjamin R. Greene, Robert J.
Yamartino, Akula Venkatram, Daniel A. Godden, Thomas F. Lavery, and
Bruce A. Egan
The Fifth Milestone Report docu-
ments work accomplished on the EPA
Complex Terrain Model Development
project from June 1984 through May
1985, and describes in detail the August
1984 Full Scale Plume Study (FSPS), in-
cluding its setting, the experimental de-
sign, and the resulting data base. The
FSPS produced a 128-hour data set of
SF6 and CF3Br concentrations, ground-
based and airborne lidar measure-
ments, photographs, 8-mm movies,
videotapes, and extensive meteorologi-
cal data. The highest ten SF6 and CF3Br
concentrations and a modeling analysis
of 14 hours are discussed in the mile-
stone report.
The milestone report presents a vari-
ety of modeling and analyses using the
Cinder Cone Butte (CCB), Hogback
Ridge (HBR), and FSPS data bases. For
example, the HBR data have been used
to show that the path of the oil-fog
plume centerline was predicted well by
assuming the layer of air below the di-
viding streamline was "dead" and by
incorporating the effects of tempera-
ture stratification. Boundary layer simi-
larity relationships were shown to sim-
ulate satisfactorily the winds and
temperature measured at CCB and HBR
up to an altitude of about 10L (ten times
the Monin-Obukov length). The report
also discusses the highest ground-level
tracer concentrations measured at the
CCB, HBR, and FSPS sites. The meteor-
ological characteristics of the concen-
tration events and the differences
among the sites are discussed.
The further development of the Com-
plex Terrain Dispersion Model (CTDM)
is described, and mathematical descrip-
tions of the modifications to the model
are presented. The latest version of the
model has been tested using a subset
of impingement hours from the CCB,
HBR, and FSPS data bases. The initial
14-hour FSPS data base was also used
to test four existing complex terrain
models—COMPLEX I and II, Valley, and
RTDM.
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 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 plume models for
calculating ground-level air pollutant
concentrations that would result from
emission sources located in hilly or
mountainous terrain. The primary ob-
jective of the project is to develop mod-
els to simulate 1-hour average concen-
trations during stable atmospheric
conditions.
The CTMD project was begun in June
1980. Four major field experiments
have been completed during the last
five years to collect data for develop-
ment and evaluation of various model-
ing approaches.
The first field experiment, Small Hill
Impaction Study No. 1 (SHIS #1), was
conducted during the fall of 1980 at Cin-
der Cone Butte (CCB), Idaho. CCB is a
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roughly axisymmetric, isolated 100-m
tall hill located in the broad Snake River
Basin near Boise, Idaho. SHIS #2 was
performed during October 1982 at the
Hogback Ridge (HER) near Farmington,
New Mexico. HBR is a long, 90-m tall
ridge located on the Colorado Plateau
near the western slopes of the San Juan
Mountains. Both small hill studies con-
sisted of flow visualization and tracer
experiments conducted during stable
flow conditions with supporting mete-
orological, lidar, and photographic
measurements. At these sites the tracer
gases were released from mobile
cranes or a tower.
The third and fourth field experiments
were conducted at the Tracy Power
Plant (TPP) located next to the Truckee
River east of Reno, Nevada. The third
experiment, performed in November
1983, was undertaken as a feasibility
and design study for the Full Scale
Plume Study (FSPS). It was cospon-
sored by the Electric Power Research In-
stitute (EPRI). The November experi-
ment not only demonstrated the
feasibility of conducting the FSPS at the
TPP, but with the expanded scope made
possible by EPRI's participation, it also
produced a data base that is useful for
modeling purposes. The FSPS was per-
formed at Tracy in August 1984.
The data bases compiled from the
CCB, HBR, and November Tracy experi-
ments are available from the EPA Pro-
ject Officer. The FSPS data base will be
available in late 1985. The data bases
compiled from each of the experiments
include the following components:
• Source information: emission rates,
locations, and heights of SF6, CF3Br,
and oil-fog releases
• Meteorological data: measure-
ments of the approach flow as well
as information on flow and disper-
sion near the terrain
• Tracer gas concentrations: data
from more than 50,000 individual
samples collected during the exper-
iments from as many as 100 sam-
pler locations in each experiment
• Lidar data: sections across the
plume characterizing the trajectory
and growth of the plume upwind of,
interacting with, and sometimes in,
the lee of key terrain features
• Photographic data: still photo-
graphs taken from fixed locations,
aerial photographs taken at CCB
and Tracy from an aircraft flying
overhead, and (occasional) 16-mm
and 8-mm movies and videotapes
During the course of the CTMD proj-
ect, four Milestone Reports (Lavery et al.
1982; Strimaitis et al. 1983; Lavery et al.
1983; and Strimaitis et al. 1984) have
been published. These reports (EPA-
600/3-82-03G, EPA-600/3-83-015, EPA-
600/3-83-101, and EPA-600/3-84-110),
which are available from EPA, describe
the progress in developing and evaluat-
ing complex terrain models using the
CCB and HBR data bases. They also de-
scribe in detail the two small hill stud-
ies, the November Tracy study, and a
series of towing tank and wind tunnel
studies performed at the EPA Fluid
Modeling Facility in support of the mod-
eling.
This current phase of the CTMD proj-
ect will end in December 1986. An ini-
tial, partially validated model, will be
delivered to the Project Officer by Octo-
ber 1, 1985. A workshop will be held in
early 1986 to present results from the
field experiments, model development
activities, and related work conducted
both within and outside the CTMD pro-
ject to the scientific community. The
final stable plume impingement mod-
el(s) will be delivered in late 1986. A
project report will be published in De-
cember 1986.
Principal Accomplishments
Refinement of the HBR Meteor-
ological Data Base
The refinement of the meteorological
data collected during SHIS #2, which
involved the filtering and flagging of the
raw 1 -s counts data to reduce the effects
of noise on the calculated measure-
ments, is now complete. Corrections
were also made on the basis of the audit
results and the cosine response charac-
teristics of the fixed propeller
anemometers. Five-minute and one-
hour averaged values of meteorological
measures were calculated from the cor-
rected and flagged 1-s data. The success
of the refinement efforts is demon-
strated by the improvement in consis-
tency between collocated measure-
ments.
HBR Streamline Analysis
Lidar data collected at HBR have been
used to compare streamline heights up-
wind and over the crest of HBR to calcu-
lations from potential flow theory and
from a linearized perturbation analysis.
The comparisons suggest that for re-
leases above the dividing streamline
height (Hc) at HBR a substantial portion
of the streamline deflection near the
crest can be explained by potential flow
of the air above Hc over a cylinder. This
approach assumes the terrain is "cut-
off" below Hc. The perturbation analysis
shows some improvement in the simu-
lation of the streamline height when
stratification is included in the calcula-
tions.
Representativeness of Stable
Boundary Layer Similarity
Theory
Modeling the dispersion of an ele-
vated plume requires meteorological
data representative of plume height.
Since this information is not always
available, it is useful to consider if near-
surface measurements can be used to
infer information at plume elevations.
This issue was addressed by using sta-
ble boundary layer similarity relation-
ships to predict wind and temperature
data at 40 m and 150 m from data ob-
tained to 10 m and 2 m. The predictions
were compared to measurements taken
at CCB and HBR. The results indicate
that the similarity relationships repro-
duce the observations fairly well to ele-
vations less than about 10 L. Above 10L
the predictions have little reliability.
Since L is typically a few meters during
stable conditions, near-surface mea-
surements will not be useful for estimat-
ing meteorological conditions above
about 50 m. Most major sources gener-
ate plumes the equilibrium heights of
which are well above 50 m. Therefore,
proper modeling of these sources will
require meteorological data collected
on tall towers or via acoustic sodar.
Investigations of Vertical
Plume Growth
CTDM uses the expression
1 +
to simulate the vertical diffusion of an
elevated plume, where crw is the stand-
ard deviation of vertical velocity fluctua-
tions, t is the travel time, and TL is the
Lagrangian time scale. Hourly-average
lidar data from 14 FSPS impingement
hours were used to perform an initial
evaluation of the expression for
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vicinity of the stack, once the plume had
leveled. Typically, o-^ was measured at
a distance of 700 m from the stack. The
lidar scans taken downwind of this dis-
tance were then used to evaluate the
subsequent growth of
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Once the modifications to the model
are complete, CTDM will undergo a sys-
tematic series of sensitivity studies.
These will help identify the conditions in
which the terrain effects contained in
CTDM have the greatest and least im-
pact on the magnitude of the ground-
level concentrations. The effects of un-
certainties of the model input data on
concentrations will also be analyzed.
These will include direct input (wind
speed, etc.), the various terrain parame-
ters, and the location of the meteorolog-
ical tower.
An analysis of the FSPS data will be
undertaken to provide a description of
the observed flow throughout the ex-
periment area. The behavior of the visi-
ble plume from the Tracy stack and the
corresponding tracer-gas concentra-
tions measured at the ground will be
characterized as a function of area-wide
meteorological measurements. This
analysis will serve to identify the roles
of the upper-level flow and the local
drainafft|i$w in determining the char-
actef'^jjjjjjjjl'ow and turbulence in the
valley. *i. :?
Development of FSPS Meteoro-
logical Data Base
Because the height of the SFe/oil-fog
plume at Tracy was often greater than
150 m, and because the flow in the
Truckee Valley was sheared at these ele-
vations in very stable conditions^mete"
orological data reJevartfto the p
will have to be detwed for many.
from measurements madeTpy. tet
sonde, Doppler sodar, and rabals.
different characteristics of the-measu
ment systems and the representatj
ness of the data imply that the'-dev
ment of a Modeler's Data Archive for
FSPS will be somewhat more complex
than those for CCB and HBR.
The audit of the meteorological tower
systems indicated that the quality of
data from these instruments is excellent
and no major noise problems have been
discovered. The principal effort in the
refinement of these data will be the cor-
rection of the averaged speeds and di-
rections from UVW propellers for non-
cosine response.
Donald C. DiCristofaro, David G. Strimaitis. Benjamin R. Greene. Robert J.
Yamartino, Akula Venkatram, Daniel A. Godden, Thomas F. Lavery, and Bruce
A. Egan are with Environmental Research & Technology, Inc., Concord, MA
0/742.
P. L. Finkelstein is the EPA Project Officer (see below).
The complete report, entitled "EPA Complex Terrain Model Development: Fifth
Milestone Report—1985," (Order No. PB86-1'67'350/AS; Cost: $28.95, 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/S3-85/069
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