United States
Environmental Protection
Agency
Atmospheric Sciences Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S8-86/021 Sept. 1986
Project Summary
Addendum to the User's
Guide for MPTER
Thomas Chico and Joseph A. Catalano
MPTER (Multiple Point source model
with TERrain adjustment) was devel-
oped by the U.S. Environmental Protec-
tion Agency (EPA) in 1979 to estimate
air quality concentrations of relatively
non-reactive pollutants from multiple
sources with adjustments made for
slight terrain differences. The model
was first released as part of the User's
Network for Applied Modeling of Air
Pollution (UNAMAP) Version 4 and re-
released with minor modifications in
UNAMAP Version 5. This addendum
provides a complete description of the
MPTER revisions and outlines the mod-
ifications required for updating the
user's guide and the earlier versions of
the FORTRAN source code to result in
the code included in UNAMAP (Ver-
sion 6).
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).
Summary of Modifications
Important features added to the
MPTER model are as follows:
• Urban and rural modes, for wind-
profile exponents and dispersion
parameters,
• Treatment of calm conditions ac-
cording to methods developed by
EPA (1984)», and a
• Default option, primarily for regula-
tory application.
These features were designed to satisfy
the requirements outlined in "Guideline
on Air Quality Models (Revised)." The
default option feature is designed as a
convenience for the user to avoid inad-
vertent errors in setting the appropriate
options for regulatory applications. The
reader is cautioned to refer to the cur-
rent regulatory guidance contained in
EPA's "Guideline on Air Quality Mod-
els'* and to confer with the appropriate
regional meteorologist when this model
is being used to satisfy regulatory re-
quirements. With the addition of the
above features, the model is acceptable
for regulatory applications and is con-
sidered a guideline model by the EPA.
The revisions are discussed in greater
detail next; user's guide and computer
code modifications follow the revisions.
The numerical values in the original
test case output remain unchanged.
Urban and Rural Modes
Separate urban and rural default
wind-profile exponents were added to
MPTER and are presented in Table 1.
These exponents are used by the model
when the user exercises the default op-
tion. The rural exponents correspond to
a surface roughness of about 0.1
meters; the urban exponents result
from a roughness of about 1 meter (plus
urban heat release influences).
An urban dispersion algorithm has
been added to the rural scheme in the
original MPTER. The urban dispersion
parameter values are those recom-
mended by Briggs.
The urban or rural setting is indicated
by the user by input variable MUOR on
card 4.
Treatment of Calm Conditions
When the default option is exercised,
calm conditions are handled according
to methods developed by the EPA
(1984) which are summarized here. A
calm hour is indicated by an hour with a
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Table 1. Default Urban and Rural Wind-Profile Exponents
Stability class
Mode
Urban
Rural
0.15
0.07
0.15
0.07
0.20
0.10
0.25
0.15
0.30
0.35
0.30
0.55
wind speed of 1.0 m/sec and a wind di-
rection equal to that of the previous
hour. When a calm is detected in the
meteorological data, the concentrations
at all receptors are set to zero, and the
number of hours being averaged is re-
duced by one, except that the divisor
used in calculating the average is never
less than 75 per cent of the averaging
time. For any simulation, this results in
the following:
• 3-hour averages are determined by
dividing the sum of the hourly con-
tributions by 3;
• 8-hour averages are calculated by
dividing the sum of the hourly con-
tributions by the number of non-
calm hours or 6, whichever is
greater;
• 24-hour averages are determined
by dividing the sum of the hourly
contributions by the number of
non-calm hours or 18, whichever is
greater; and
• Period of record averages, regard-
less of length, are calculated by di-
viding the sum of all the hourly
contributions by the number of
non-calm hours during the period
of record. This is the only exception
to the 75 per cent rule.
This calms procedure is not available
in MPTER outside of the default option.
The user can employ this procedure,
however, through the use of the CALM-
PRO postprocessor program (EPA,
1984). CALMPRO is available as part of
UNAMAP Version 6.
Default Option
An option has been added to the
model to facilitate compliance with reg-
ulatory requirements. Exercising the de-
fault option (i.e., IOPT (25) = 1) over-
rides other user-input selections and
results in the following:
• Final plume rise is used (gradual or
transitional plume rise is not exer-
cised for plume height but is used
to calculate the magnitude of the
buoyancy induced dispersion),
• Buoyancy induced dispersion is ex-
ercised,
• Terrain adjustment factors are set
to zero for all stabilities,
Stack tip downwash is considered,
Default urban or rural wind profile
exponents are used (see Table 1),
and
Calms are treated according to
methods developed by the EPA
(1984) as noted previously.
Decay half-life is set to 4.0 hours for
S02 for the urban option, and in-
finite half-life (no decay) for all
other cases.
Other Features
There are additional regulatory fea-
tures that are inherent in the UNAMAP
Version 5 and later versions of MPTER.
These are summarized below.
(1) Momentum plume rise is always
considered.
(2) Terrain adjustments are used for
receptors below stack base eleva-
tion in the same manner as ele-
vated receptors. The difference,
defined as the receptor ground
level elevation minus source
ground level elevation, is com-
puted and subtracted from the ef-
fective plume height. This has the
effect of raising the plume at re-
ceptors below the source ground
level elevation and lowering the
plume at receptors above the
source ground level elevation.
(3) Mixing height is compared with
the final plume height without re-
gard to plume height changes due
to terrain.
(4) Exponential decay (half-life) is
available if required by the simu-
lation.
Thomas Chico and Joseph Catalano are with Aerocomp, Inc., Costa Mesa, CA
92626.
D. Bruce Turner is the EPA Project Officer (see below).
The complete report, entitled "Addendum to the User's Guide for MPTER, "(Order
No. PB 86-217 163/AS; Cost: $11.95, subject to change) will be available only
from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 221'61
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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Official Business
Penalty for Private Use $300
EPA/600/S8-86/021
U.G.GFF
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