United States
Environmental Protection
Agency
Environmental Sciences
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S8-84-013 May 1984
Project Summary
User's Guide to the MESOPUFF
II Model and Related Processor
Programs
J. S. Scire, F. W. Lurmann, A. Bass, and S. R. Hanna
A user's guide has been assembled to
describe the design and operation of the
MESOPUFF II regional-scale air quality
model. MESOPUFF II is a Lagrangian
variable-trajectory puff-superposition
model that has been designed to treat
transport, transformation, diffusion,
and removal processes of pollutants
emitted from multiple point and/or
area sources at transport distances
beyond the range of conventional
straight-line Gaussian models (i.e.,
beyond ~ 10-50 km).
The major features of this model and
enhancements over its predecessor,
MESOscale Puff (MESOPUFF), include
the use of hourly surface meteorologi-
cal data, twice-daily rawinsonde data,
and hourly precipitation data; separate
wind fields to represent flows within
and above the boundary layer; parame-
terization of vertical dispersion in terms
of micrometeorological turbulence
variables; transformation of sulfur diox-
ide (SO2) to sulfate (SO4) and nitrogen
oxides (NOx) to nitrate (NO!); a resis-
tance model for dry deposition; time-
and space-varying wet removal; and a
computationally efficient puff sampling
function. The scientific and operational
bases of the methods used in the model
are briefly discussed. Complete user
instructions and test-case input/output
are provided for each program.
This Project Summary was developed
by EPA's Environmental Sciences
Research Laboratory, Research
Triangle 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 order-
ing information at back).
Introduction
The regional and long-range transport
and transformation of sulfur oxides and
nitrogen oxides emitted from major point
sources have been of considerable
concern. There is a need for easily usable,
cost-efficient air-quality models that can
realistically treat the various physical
processes important on these scales. The
MESOscale Puff (MESOPUFF) model has
been extensively modified to revise and
more realistically treat the transort, verti-
cal dispersion, chemical transformation,
and dry and wet removal processes. The
new model, designated MESOPUFF II, is
one element of an integrated modeling
package that includes components for
preprocessing of meteorological data
(READ56, MESOPAC II) and for postpro-
cessing of predicted concentrations
(MESOFILE II).
Major Model Features
MESOPUFF II uses a puff-superposition
approach to represent continuous
plumes. The pollutant material in each
puff is transported independently of that
in other puffs and is also subjected to
dispersion, chemical transformation, and
removal processes. Some of the general
features of the MESOPUFF II modeling
system are as follows:
(1) Hourly surface meteorological data,
twice-daily rawinsonde data, and
hourly precipitation data are read
from magnetic tapes.
(2) Wind fields to represent the mean
flow in the boundary layer and
above the boundary layer are con-
structed, although several options
are given.
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(3) Boundary-layer structure is treated
in terms of micrometeorological
parameters that include the surface
friction velocity, mixing height,
convective velocity scale, and
Monin-Obhukov length.
(4) Space- and time-varying chemical
transformation can be performed
simultaneously for up to five pollut-
ant species, including sulfur
dioxide (SO2). sulfate (SO4=),
nitrogen oxides (NOX=NO+NO2),
nitric acid (HNO3), and nitrate
(NOi).
(5) Dry deposition is prescribed by a
resistance model in the surface-
depletion mode, and the source-
depletion method is optional.
(6) Space- and time-varying wet
removal is parameterized according
to precipitation rate and scavenging
coefficients.
The meteorological data inputs
required by the preprocessors consist of
the routine twice-daily upper air
soundings, hourly surface meteorological
observations, and hourly precipitation
measurements reported by the National
Weather Service. The preprocessor
programs have been designed to read the
standard-formatted meteorological data
tapes available from the National Climatic
Center in Asheville, NC.
Wind fields for MESOPUFF II are
constructed from the hourly surface wind
observations, as well as from the twice-
daily rawinsonde wind profile data. The
surface station network data allow better
temporal and spatial resolution than do
the upper air sounding data, which
involve much larger distances and less
frequent measurements. The wind fields
are constructed at two user-specified
levels-a lower level representing the
mean boundary-layer flow and an upper
level representing flow above the
boundary layer.
Boundary-layer structure is parame-
terized in terms of micrometeorological
variables computed from the surface
station data and information about
surface characteristics (land use, or
roughness lengths) provided by the user
for each grid point. The surface friction
velocity, u*, the convective velocity scale,
w*, the Monin-Obukhov length, L, and
the boundary-layer height zb are
computed.
Chemical transformation rate
expressions were developed from the
results of photochemical model simula-
tions over a wide range of environmental
conditions. The rate expressions Include
gas-phase NO, oxidation, gas- and
aqueous-phase components of SO2
oxidation, and the chemical equilibrium
of the nitric acid, ammonia, and ammonia
nitrate system. The parameterized
transformation rates depend on solar
radiation, background ozone concentra-
tion, and atmospheric stability. The SO2
oxidation rate is empirically increased at
high relative humidity to account for
aqueous-phase reactions. In the case of
NO,, the transformation rate also depends
on the NOx concentration.
The spatial and temporal variations of
dry deposition are treated by a resistance
model. The pollutant flux is proportional
to the inverse of a sum of resistances to
pollutant transfer through the
atmosphere to the surface. The resist-
ances depend on the characteristics of
the pollutant and the underlying surface
and atmospheric conditions. MESOPUFF
II contains options for the commonly used
source-depletion method or for more
realistic surface depletion, where pollut-
ants are removed only from a surface
layer in the three-layer model.
Precipitation scavenging can be the
dominant pollutant removal mechanism
during precipitation periods. MESOPUFF
II contains a scavenging-ratio
formulation for wet removal. The
scavenging ratio depends on the type and
rate of precipitation (derived from hourly
precipitation measurements, if available)
and the characteristics of the particular
pollutant.
In addition, improvements were made
in the method of summing the
contributions of individual puffs to the
total concentration at a receptor
location. The model uses an integrated
form of the puff-sampling function that
eliminates the problem of insufficient
puff overlap commonly encountered with
puff-superposition models. This
development allows continuous plumes
to be more accurately simulated with
fewer puffs, thereby saving computation-
al time and reducing computer storage
requirements.
MESOPUFF II Modeling System
The MESOPUFF II modeling package is
schematically illustrated in Figure 1. The
two meteorological preprocessor
routines are READ56 and MESOPAC II.
READ56 processes the rawinsonde data,
and MESOPAC II reads the output file
created by READ56 and the standard-
formatted hourly surface meteorological
data and precipitation data. A single
output file is produced that includes all
the time- and space-interpolated fields of
meteorological variables required by
MESOPUFF II. MESOFILE II is a
postprocessing program that performs a
variety of statistical and graphical
operations on the concentration file(s)
produced by MESOPUFF II.
The user's guide contains a brief
technical description of the methods and
equations. Input format specifications are
given, along with detailed instructions
about the use of the available options
Complete user instructions and a tesi
case with example input/output are
provided for each of these programs.
All source, receptor, and program
control information is input by formatted
card images. The control-paramete
inputs determine which options are use<
in the computations and what type o
output is produced.
Conclusions
A user's guide to the MESOPUFF I
modeling package has been prepared. >
companion report entitled "Developmer
of the MESOPUFF II Dispersion Model
describes the methods in detail an
compares the outputs from several modi
algorithms against experimental meas
urements.
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{ MESOPACII
I Control Parameter
I Inputs
I READ56 Control
I Parameter Inputs
Twice-Dai,
Rawinsonde
Data Files
(TDF5600
Format)
READ56 Upper Air
Preprocessor Program
Hourly
Precipitation
Data (TD9657
Format)
Formatted
Twice Daily
Rawinsonde
Data Files
MESOPACII Meteorological
Preprocessor Program
Hourly
eteorological
Variables
fMESOPUFFH
I Control Parameter
I Inputs
MESOPUFFII Dispersion Model
Concentration
Tables
Predicted
oncentration
fMESOFILEII
I Control Parameter
I Inputs
MESOFILE II
Postprocessor Program
^s
,
(Direct Acces
{Concentration}
Files for
Plotting
Figure 1. MESOPUFF II modeling package.
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J. S. Scire, F. W. Lurmann. A. Bass, and S. R. Hanna are with Environmental
Research and Technology. Inc.. Concord. MA 01742.
James M. Godowitch is the EPA Project Officer (see below).
The complete report, entitled "User's Guide to the Mesopuff II Model and Related
Processor Programs." (Order No. PB 84-181 775; Cost: $20.50, 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:
Environmental Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
if OS. GOVERNMENT PRINTING OFFICE: 1984 - 789-015/7690
United States
Environmental Protection
Agency
Center for Environmental Research
Information
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