United States
Environmental Protection
Agency
Atmospheric Research and
Exposure Assessment Laboratory
Research Triangle Park NC 2771 1
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Research and Development
EPA/600/S3-89/044 Sept. 1989
&EPA Project Summary
Development of the Regional
Oxidant Model Version 2.1
Jeffrey 0. Young, Mourad Aissa, Trudy L. Boehm, Carlie J. Coats, Jr., Jeanne
R. Eichinger, Dianne J, Grimes, Susan W. Hallyburton, Warren E. Heilman,
Donald T. Olerud, Jr., Shawn J. Roselle, Allan R. Van Meter, Richard A.
Wayland, and Thomas E. Pierce
This report describes improve-
ments that were made to version 2.0
of the Regional Oxidant Model (ROM)
in order to create version 2.1. The
ROM is an Eulerian grid model that
calculates hourly concentrations of
ozone and other chemical species for
episodes up to about a month long.
The ROM's modeling domain, com-
posed of grid cells that are ap-
proximately 19 km on a side, encom-
passes an area on the order of 1000
km by 1000 km. The physical proc-
esses that the ROM simulates include
photochemistry, nocturnal jets and
temperature inversions, spatially- and
temporally-varying wind fields, terrain
effects, dry deposition, and emis-
sions of biogenic and anthropogenic
ozone precursors. Major technical
improvements include upgrading the
Carbon Bond Mechanism to version
4.2, improving the biogenic emissions
processing system (which now
includes a canopy model), updating
the wind fields processor, and ex-
panding the use of buoy data for de-
termining meteorological data fields
over water. Also, ROM 2.1 can be
adapted more easily than version 2.0
to various modeling domains in
eastern North America. In addition,
the computer software has been re-
designed to facilitate ROM's eventual
application by outside users.
This Project Summary was devel-
oped by EPA's Atmospheric Research
and Exposure Assessment Laboratory,
Research Triangle Park, NC, to an-
nounce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
Field studies have shown that ozone
and its precursors can be transported
more than 100 km from their point of
origin. This indicates that the high ozone
concentrations in many areas of the
Northeast—particularly in areas of low
emissions density—may be due in signi-
ficant part to the influx of these species
from outside sources. Thus, urban-scale
models may be inadequate for evaluating
ozone-reduction emissions scenarios
because these models cannot accurately
treat long-range transport of ozone and
its precursors. The regional character of
the ozone problem led the EPA to begin
work on the first version of the Regional
Oxidant Model (ROM) in the mid-1970s.
The ROM is a sophisticated regional-
scale model that predicts hourly ozone
concentrations for episodes extending up
to about a month in duration; each
episode is modeled as a series of three-
day executions. The model domain,
divided into a set of grid cells approx-
imately 19 km by 19 km each,
encompasses an area on the order of
1000 km by 1000 km. For much of
eastern North America, the ROM can
model the regional variability of the
chemical and physical processes that
affect photochemically-produced ozone
concentrations on a regional scale.
The ROM system is composed of a
core model, which solves the sets of
-------
equations that describe the above proc-
esses, and a series of over 30 processors
that prepare the input data needed by the
core model. ROM 1.0, the first version of
the ROM, emerged in 1984 and was used
for a limited set of applications for the
Northeast Corridor Regional Modeling
Project. ROM 2.0 became operational in
1987. To create it from ROM 1.0, several
features were changed or added: (1) The
Demerjian chemical mechanism was
replaced with version 4.0 of the Carbon
Bond Mechanism (CBM 4.0), which
simulates some 70 reactions among 28
chemical species. (2) Biogenic hydro-
carbon emissions were added to the list
of emission types modeled; ROM 1.0
modeled only anthropogenic emissions.
(3) The code was modified to allow
atmospheric layer thicknesses to vary
over space and time; in ROM 1.0, these
thicknesses remained constant. (4) The
ability to simulate the effects of nocturnal
jets and nighttime inversions was added.
Application requirements for EPA's Re-
gional Ozone Modeling for Northeast
Transport (ROMNET) project have
prompted us to upgrade ROM 2.0 to pro-
duce ROM 2.1. For the ROMNET appli-
cation, we have expanded the model's
domain in the northeastern U.S. from 60
by 42 cells to 64 by 52 cells in order to
include major urban emitters in Ohio and
Virginia. As a result, the design of ROM
2.1 allows the user to increase or reduce
the numbers of columns and rows in the
grid more easily than before. ROM 2.1
also can be adapted more easily to other
modeling domains in eastern North
America. Some of the other modifications
include an updated biogenic hydrocarbon
processor; an improved wind fields pro-
cessor; an upgraded Carbon Bond Mech-
anism (CBM 4.2) in the ROM's chemistry
solver; expanded use of buoy data and
the use of mobile-source emissions data;
and changes that allow the ROM system
to use computer resources more
efficiently. We have also added features
that should allow future outside users to
apply the ROM more easily when it is
released to them.
Overview of the Regional
Oxidant Model
The ROM is an Eulerian, episodic grid
model that simulates the hourly concen-
trations of chemical species in a rec-
tangular domain that is on the order of
1000 km on a side. The domain is rep-
resented by a grid of cells that are
approximately 19 km on a side; the
coordinate system that delineates the
columns and rows of cells is based on
the latitude-longitude system, so cell size
varies somewhat over the domain. Col-
umns are the north-south components of
the grid (marked off in degrees longitude)
and rows are the east-west components
(marked off in degrees latitude). To date,
the model has been adapted for three
different regions: the Northeast Regional
Oxidant Study (NEROS) region, con-
sisting of 60 columns by 42 rows (2520
cells per atmospheric layer); the South-
east Regional Oxidant Study (SEROS)
region (60 columns by 42 rows); and the
Regional Ozone Modeling for Northeast
Transport (ROMNET) region (64 columns
by 52 rows, or 3328 cells per layer).
Figure 1 shows the ROMNET region.
The ROM has three and one-half
vertical layers—termed layers 0, 1, 2, and
3—whose thicknesses vary dynamically
in space and time in response to
meteorological phenomena. We say there
are three and one-half layers rather than
four because in layers 1, 2, and 3 the
concentrations of chemical species are
treated prognostically, while in layer 0
they are treated diagnostically.
For each model layer, the ROM system
combines observational data and the-
oretical formulations of the governing
chemical and physical processes to pro-
duce predicted species concentrations.
The main component of the system, the
core model, is a set of algorithms that
calculate the solutions to computer-
solvable analogues of the differential
equations that describe the governing
processes. The core model outputs con-
centrations for all species for every cell in
every layer, for each model time step.
The basic model time step, called the ad-
vection time step, is one-half hour. Within
each advection time step, the vertical
fluxes and chemical kinetics are modeled
using smaller time steps. A single core
model run can simulate episodes up to
72 hours (144 advection time steps) in
length; this limit is imposed because of
file-size restrictions. Episodes of longer
than three days are run as a series of 72-
hour executions; simulations usually are
limited to the length of an ozone episode
(approximately two weeks).
The core model requires five types of
input data: air quality, meteorology,
emissions, land use, and topography. We
acquire these rawdata from various
sources and process them through data
extraction and quality assurance routines.
This process produces data that are then
prepared for the core model by a network
of over 30 processors, which range in
function from simple data reformatting
routines to programs that generate th<
complex wind fields that drive the at
mospheric transport. The processors an
organized into nine distinct stages tha
reflect the sequence of program exe
cution. Processors at the same stag<
may execute simultaneously, but eacl
processor must wait to execute until a
the lower-stage processors in its dati
path have finished running.
Most of the processors in the networl
produce either processor files (PFs) o
model files (MFs). PFs, generally writtei
by lower-stage processors, contain dat
used by higher-stage processors. MF
also provide input to some higher-stagi
processors, but they primarily contain thi
parameter fields that are transformed int<
the data elements required by the con
model governing equations. The proces
sor network ultimately produces severe
large data files for the core model, whicl
contain initial-condition and boundary
condition concentrations as well as thi
data used to model all physical an>
chemical processes affecting specie
concentrations in a given episode. Thes
files combined contain tens of millions c
core model input values; simulating on
day, for example, requires nearly 100 bi
lion computations with these millions c
values.
Figure 2 is a schematic of the R0^
system. By structuring the ROM in thi
modular fashion, we can change th
method used to generate values of
particular independent variable withoi
having to overhaul the entire ROM sys
tern. Thus, to create ROM 2.1 from ROI
2.0, we have been able to modify and irr
prove some components without havin
to rewrite the code for all the others
Figure 3 shows the resulting ROM 2.
processor network. It consists of thre
interrelated parts: the initial-condition an
boundary-condition (IC/BC) processor:
the meteorology processors, whic
process topography and land use data i
addition to meteorology data; and th
emissions processors. The network trans
forms the raw data input files into the foi
core model input files shown on the righ
ICON (initial-condition concentratic
data), BCON (boundary-condition coi
centration data), BTRK [diffusivity ar
backtrack (advection transport) inform:
tion], and BMAT (parameterization fi
vertical fluxes, meteorological paramete
necessary for chemistry rate constant ai
justments, and parameterized emissioi
source strengths). Table 1 summarize
the functions of all the processors in tf
ROM 2.1 network.
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Figure 1 The gridded ROMNET region (64 columns by 52 rows); dots represent grid cell corners.
The modular structure is also advanta-
geous because it facilitates implementing
quality assurance (QA) procedures. All
programs in the system are operated and
maintained in strict conformance with a
set of QA procedures that involve both
machine and human checks of the com-
puter code, the input and output data
streams of each submodule, and the
overall behavior of the model.
The ROM system has been pro-
grammed using the American National
Standards Institute (ANSI) FORTRAN-77
full language specification, except for the
Biogenic Emissions Inventory System
(BEIS), an emissions processing system
written in SAS*. Development of the
system began on the EPA's Sperry
UNIVAC® 1100 mainframe computer. It
was then shifted to a VAX'" 11/780 mini-
computer in May 1983. Currently, we are
running the core model on the EPA-
NCC's IBM* 3090 and the processor net-
work on the EPA-NCC VAX cluster, con-
sisting of two VAX 8650s and one VAX
11/785. Running the model system
requires a significant amount of CPU
time; for example, for one three-day exe-
cution the ROM 2.0 core model required
about 6 h of IBM 3090 CPU time and the
ROM 2.0 processor network used about
12 h of VAX 8600 CPU time.
Summary of the Differences
Between ROM 2.0 and ROM 2.1
This section briefly lists the major dif-
ferences between the 2.0 and 2.1 ver-
sions of the ROM.
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Raw Input Data
r
1 (^ Air Quality ^
i
i ^^__-
' (^Meteorology^) —
i
[ Q~ Emissions J)
i ~~ •
•
J (" Land Use ~~^) —
i , ,
[ (^ Topography ^) —
L_
1
I
. J
Core Model
Processor
Network
i r
PF/MFFile
Database
\
H
fc 7~i
A
i
L* Vet
And
Kinetic
L_
n
arizonta/
'ansport
Igorithm
i
•tkalFlux
Chemical
S Algorithms
^
Predicted
^ Species
Concentrations
V
Run On The EPA-NCC Run On The
VAX Cluster EPANCC IBM 3090
Figure 2. General structure of the ROM system, from input data through final output concentrations.
" HP3*G}
|P*1G| [P36G1
|P13Q|
STAGED
[P16GJ !
P15G>
STAGE 1 STAGE!
STAGES STAGE 4 STAGES STAGEG STAGE 7 STAGES
F/gure 3. Structure and output files of the ROM 2.1 input processor network.
-------
Table 1.
Processor
P01G
P02G
P03G
P04G
P05G
P06G
P07G
P08G
P09G
P10G
P11G
P12G
P13G
P14G
P15G
P16G
P17G
P19G
P21G
P22G
P23G
P24G
P25G
P26G
P29G
P31G
P32G
P33G
P34G
P36G
Functional Descriptions of the ROM 2. 1 Input Processors
Stage Function in ROM 2. 1
2
1
1
2
2
0
3
4
5
7
5
6
0
2
6
1
5
1
0
2
1
1
0
1
6
0
5
6
0
0
Interpolates profiles of upper-air meteorological parameters at intervals of 50 m from hourly rawinsonde vertical profiles
Writes to the file ICON the gridded initial-condition concentrations for each layer and species simulated by the core model,
using P2lG's clean-air concentrations as initial-condition concentrations
Prepares surface meteorology data (e.g., mixing ratio, virtual temperature, and wind speed) for use in higher-stage
processors
Computes gridded surface roughness, and hourly gridded Monin-Obukhov length, surface heat flux, friction velocity,
surface temperature, surface relative humidity, and surface wind speed
Uses surface observations to compute hourly gridded values for the fraction of sky covered by cumulus clouds, and also
calculates cumulus cloud-top heights
Computes the smoothed terrain elevation for each 10' lat. by 15' long. ROM domain grid cell, and also for a larger domain
that extends three grid cells beyond the ROM domain. In addition, it computes average terrain elevations in a finer-
resolution domain (cells 5' lat. by 5' long.) for the terrain penetration calculation. Finally, it computes the north-south and
east-west components of the terrain elevation gradient (slope)
Computes hourly gridded wind fields in the cold layer, hourly gridded terrain penetration fractions, hourly gridded cold
layer growth rates, and hourly gridded thicknesses for layers 0 and 1
Computers hourly gridded cell thicknesses for layers 2 and 3, and various parameters used to specify volume fluxes
between these two layers
Computes hourly gridded atmospheric density, temperature, cloud cover, solar zenith angle, and water vapor concentration
Computes hourly gridded emissions source functions in layers 0, 1, and 2 for combined anthropogenic and biogenic
sources, and a/so computes the plume volume fraction in layer 0
Computes hourly gridded horizontal winds for each layer, using rawinsonde vertical profiles and surface-station wind
observations
Computes hourly gridded volume fluxes through all model layer boundaries, and cumulus cloud vertical flux parameters
Computes the total length of all line emissions sources (highways and railroads) within each grid cell
Prepares files containing hourly emissions values and stack descriptions for all major point sources, and combined hourly
gridded emissions values for minor point sources, area sources, and mobile sources
Computes hourly gridded effective deposition velocities for a set of representative species
Interpolates between rawinsonde observations to produce hourly upper-air profiles at 25-mb resolution
Computes hourly gridded elevations (above MSL) for the tops of layers 0, 1,2, and 3, and local time derivatives of these
elevations
Computes hourly gridded values of fractional sky coverage at the terrain surface for all cloud types combined
Computes daytime and nighttime tropospheric background (clean-air) concentrations in each layer for each chemical
species
Computes and writes to the file BCON the gridded boundary-condition concentrations for each species, layer, and
advection time step simulated by the core model, for the north, south, east, and west boundaries
Computes hourly gridded upper-boundary-condition concentrations (C-infinity) for a set of representative species
Equilibrates background concentrations of all modeled chemical species with averaged observed ozone concentrations on
the north, south, east, and west boundaries, for both daytime and nighttime conditions in each layer
Computes the fraction of each grid cell in each land use category recognized by the model
Computes hourly gridded mobile-source VOC, NOX, and CO emissions parameters, adjusted for daily average temperature
Computes hourly gridded 30-min backtrack (advection) cell locations and horizontal diffusivities for each layer simulated by
the core model
Allocates annual point-source emissions data between a weekday-emissions file, a Saturday-emissions file, and a Sunday-
emissions file
Calculates hourly gridded horizontal eddy diffusivities for layers 1, 2, and 3, and also produces parameter fields needed to
compute interfacial volume fluxes across layer boundaries
Generates hourly gridded locations and strengths of constant-source emitters for a tracer emissions species
Converts all point-, area-, and mobile-source data files from GMT to LST
Applies A/0X a^d WC emission controls at the county level for area- and mobile-source emissions data
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Table 1. (Continued)
Processor Stage
Function in ROM 2.1
P38G 7 Reads the backtrack and diffusivity hourly gridded MF files and computes the BTRK file parameters for each advection t
step simulated by the core model
P39G 7 Reads all meteorology hourly gridded MF files except the backtrack and diffusivity files read by P38G and computes the
intermediate meteorology (IMET) file parameters for each advection time step simulated by the core model
P40G 8 Reads the intermediate meteorology (IMET) file and the emissions sources hourly gridded MF files and computes the SA
parameters for each advection time step simulated by the core model
P41G 0 Applies NOX and VOC emission controls to point-source emissions data, at a state, county, point, or individual-boiler lev*
BBS" 6 Prepares hourly gridded biogenic emission rates for isoprene, paraffin, olefin, high molecular weight aldehydes (RCHO,
R>H), nonreactive hydrocarbons, NO and NO2, based on a canopy model
"All processors (PnnG) are written in FORTRAN, but the Biogenic Emissions Inventory System (8EIS) is written in SAS. Because of the differen
the BEIS is not given a PnnG name.
Changes Made to the Core
Model and Its Input Files
ROM Chemistry Solver Changes
The first two changes listed below have
increased the computation time for a core
model run by about 54%, for a NEROS
domain three-day execution on the IBM
3090.
• We implemented a more recent ver-
sion of the Carbon Bond Mechanism,
CBM 4.2; ROM 2.0 used CBM 4.0.
CBM 4.2 includes a different chemical
species list, a different list of chemical
reactions and their rate constants, and
it uses an additional variable, water
vapor concentration, to adjust some of
the reaction rate constants.
• Partly as a result of implementing
CBM 4.2, we have altered the FRAX
mechanism, which chooses the
lengths of the model's chemistry time
steps and controls the degree of
solution accuracy for the chemical
kinetics equations. Overall, the
changes cause the model to choose
shorter time steps more often than in
ROM 2.0, resulting in increased com-
putation time. However, we have offset
this increase by changing the mini-
mum allowable time step length from
10s to 20s.
• We have added methanol to the list of
model species (in addition to the other
species list changes caused by imple-
menting CBM 4.2), so that ROM 2.1
can be used to evaluate ozone-
reduction strategies involving choices
between automotive fuels.
Core Model I/O Modifications to
Improve Efficiency
• We have split the ROM 2.0 B-matrix
(BMAT) file into two files. BTRK and
the new BMAT. The BTRK file
contains the backtrack and diffusivity
information used by the core model's
BIGGAM module; the new BMAT file
contains the parameterization for
vertical fluxes, the meteorological
parameters necessary for chemistry
rate constant adjustment, and param-
eterized emissions source strengths,
all needed by the core model's
LILGAM module. We also designed
the new BMAT file to be a multiple
BMAT file that can be distributed over
many disks.
• We eliminated the row-windowing fea-
ture, which was included in ROM 2.0
because of memory limits on older
computers.
Changes That Should Allow
Future Outside Users to Apply
the Core Model
• Eventually, we plan to release the core
model to outside users so that they
can perform their own emission
control strategy evaluations. To assist
these users, we have designed the
ROM 2.1 processor network to pro-
duce one large file from stages 0
through 7 of the meteorology network,
called the IMET file (see Figure 3). For
each three-day episode outside users
want to model, we will run the
meteorology portion of the network
and provide them with the resulting
IMET file; the users will run the
emissions portion of the processor
network themselves to produce the
final emissions MF files, and then
combine these with our IMET file to
produce their own BMAT file. We will
also give them the other three files
needed to run the core model (ICON,
BCON, and BTRK) for each episode.
In addition to the changes listed in the
three subsections above, we also im-
proved the core model by (1) reversing
the vertical-layer-then-column order of
BIGGAM's computations, (2) improv
reporting to the run-time log file,
standardizing the code so that it is ea:
to read and to maintain, and (4) simpl
ing and standardizing the structure of
file headers that give information on
contents of each core model file.
Changes Made to the Input
Processor Network
ROM 2.0 Processors Deleted
from the Network During the
Upgrade
Overall, in converting from ROM 2.(
ROM 2.1, we deleted the following
ROM 2.0 processors from the netw
P18G and P20G, which we have
corporated as subroutines into the R
2.1 version of P11G; P27G, which
been transformed into the ROM 2.1 I
genie Emissions Inventory Syst
(BEIS); P28G whose functions are f
formed in ROM 2.1 by process
P38G.P39G, and P40G; and P3!
whose functions are performed by
ROM 2.1 processors P36G and P41G.
ROM 2.1 Processors Added tc
the Network During the Upgra
We also added seven new process
and the new BEIS to the network
upgrading the ROM to version 2.1. S<
of these perform functions that were
eluded in ROM 2.0 processors we ri
deleted from the network (see abo
and some perform functions not inclu
in ROM 2.0's processor network at
Refer to Table I for descriptions of
seven new processors: P21G, P2
P36G, P38G, P39G, P40G, and PA
The other addition, BEIS, performs
combined functions of ROM 2.0's Bl
and P27G. Because the BEIS is very
ferent from the ROM 2.0 biogenic ei
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sions processing system, we have aug-
lented the Table 1 BEIS information by
sting other major differences below:
• In computing biogenic hydrocarbon
emission rates, the BEIS uses broad
vegetation classes instead of indi-
vidual species.
• It includes a canopy model that allows
it to compute more accurately the
temperature and solar intensity pro-
files within a tree canopy.
• It calculates emission rates for iso-
prene, a-pinene, monoterpene, and
unknown species (instead of for nine
roughly-defined hydrocarbon classes),
and then converts these into emission
rates for the CBM 4.2 species iso-
prene, paraffin, olefin, high molecular
weight aldehydes (RCHO, R > H),
and nonreactive hydrocarbons.
• It calculates NO and N02 emission
rates for grasslands; P27G in ROM 2.0
did not output these species at all.
ROM 2.0 Processors that are
Included in the ROM 2.1
Network
Twenty-seven of the ROM 2.0 proces-
sors are also included in the ROM 2.1
processor network. Some are essentially
unmodified, but all have been changed in
linor or major ways. In addition to the
Changes listed below, the code for all
processors has been standardized so that
it is easier to read and to maintain. Also,
we have completed enhancements to the
network that allow us to model domains
with dimensions other than 60 columns
by 42 rows, and that allow us to apply the
network more easily to different geo-
graphic regions.
We have modified the PF/MF database
directory file, which controls the proces-
sors' access to the PFs and MFs, to re-
flect the changes we have made to the
processor network for ROM 2.1. We have
also upgraded the PF/MF database soft-
ware by incorporating better error
checking procedures.
In addition to upgrading processors, we
have also created a set of raw data
processing routines that preprocess the
emissions data before they reach the
emissions portion of the network. These
routines reduce file sizes, and therefore
computation time, by eliminating un-
necessary parameters.
ROM 2.0 Processors that Did
Not Change for ROM 2.1-
There were eight ROM 2.0 processors
at we did not modify in converting to
r(OM 2.1, except in the general ways
mentioned in the previous paragraph:
P01G, P06G, P13G, P17G, P19G, P25G,
P29G and P32G. Table 1 describes their
functions.
ROM 2.0 Processors Altered for
ROM 2.1-
We made minor or major modifications
to 19 of the ROM 2.0 processors during
the upgrade to ROM 2.1, in addition to
the general changes we made to all
processors. The items listed below are all
differences between ROM 2.0 and ROM
2.1 versions of the processors.
• P02G processes the CBM 4.2 species
instead of the CBM 4.0 species, and
also writes the ICON file header in the
new format required by the ROM 2.1
core model.
• P03G can now estimate the occurrence
of nighttime inversions on a local (grid
cell by grid cell) basis.
• P04G now writes hourly gridded files of
surface temperature, surface relative
humidity, and surface wind speed. We
have also added new procedures that
use buoy data to estimate meteoro-
logical parameters.
• P05G can accept surface meteorology
station identification codes in either
WBAN or call-letter format.
• We eliminated a coding error in P07G
that caused the magnitudes of the
computed cold-layer winds to be in
error by about 20%.
• P08G no longer computes gridded
layer 1, 2, and 3 divergence fields used
in wind fields processing; we trans-
ferred this function to P11G. Also,
P08G now grids the top of layer 2 with
respect to ground level instead of sea
level. Also, if the top of layer 2 in the
morning is higher than 800 m, it is
reset to 800 m exactly. Finally, P08G
can accept surface meteorology station
identification codes in either WBAN or
call-letter format.
• P09G uses an improved gridding meth-
od, and also outputs water vapor
concentration values.
• P10G makes better use of terrain
penetration factors to compute cell
volumes and source strengths, and
also includes methanol in the list of
species it can process. In addition, we
eliminated the option to include haz-
ardous waste TSDF input data.
• We made substantial changes to P11G:
—P11G now uses a height-dependent
weighting scheme to compute aver-
ages for layers 2 and 3 from raw-
insonde profiles.
—It includes scaling factors in shear
transformations in order to model
the variations in both wind speed
and direction with altitude.
—It now computes divergence fields
for layers 1, 2, and 3; P08G per-
formed this function in ROM 2.0.
Also, the algorithm for layer 1 diver-
gences now incorporates surface
data, in addition to the vertical-
profile rawinsonde data used by the
older P08G version of the algorithm.
—We have incorporated the ROM 2.0
processors P18G and P20G into
P11G as subroutines.
—We corrected three errors in the
ROM 2.0 version; overall, these cor-
rections resulted in winds having less
of a westerly component and having
somewhat higher energy.
• Because we changed the gridded in-
version indicator file read by P12G, we
had to change the processor's mech-
anism for deciding which of two volume
flux schemes to use. Also, we sub-
stantially improved and optimized
P12G's code so that it runs noticeably
faster than before.
• P14G now allows mobile-source and
area-source data to be input as
separate files; it also includes methanol
in the list of species it can process.
• P15G includes improved parameteriza-
tions for species-dependent deposition
resistances, and models ten repre-
sentative species instead of seven.
• To produce its upper-air profiles, P16G
now uses an improved smoothing
method that does not oversmooth the
data. We have also eliminated the
option to read in data for nonstandard
rawinsonde launch times, and have
modified P16G to accept surface mete-
orology station identification codes in
either WBAN or call-letter format.
• P22G can now process the CBM 4.2
species. It also reads in four sets of
boundary conditions instead of one,
and writes the BCON file header in the
new format required by the 2.1 core
model.
• P23G now processes the CBM 4.2
species, and includes the GPRIME set
of algorithms that is based on the CBM
4.2 ROM chemistry solver mechanism.
In addition, P23G equilibrates back-
ground concentrations with an ozone
level representative of the top bound-
ary of the model. It also models 12 re-
presentative species instead of 13, and
calculates the values for these 12
species a different way.
• Like P23G, P24G now processes the
CBM 4.2 species and includes the
GPRIME set of algorithms. It also pro-
duces four different sets of boundary
conditions instead of just one.
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• P31G no longer windows the annual
point-source data for a particular
season, and it no longer writes the data
file containing the major point-source
stack parameters; the new raw emiss-
ions data preprocessing routines per-
form both these functions. Also, P31G
now includes methanol in the list of
species it can process.
• P33G can now process the species
methanol.
• P34G now includes mobile-source
emissions in its time-shifting process,
and it includes methanol in the list of
species it can process.
Jeffrey O. Young, Mourad Aissa, Trudy L Boehm, Carlie J. Coats, Jr., Jeanne R.
Eichinger, Dianne J, Grimes, Susan W. Hallyburton, Warren E. Heilman, Donald T.
Olerud, Jr., Shawn J. Rose/to, Allan R. Van Meter, Richard A. Wayland are with
Computer Sciences Corporation, Research Triangle Park, NC 27709; the EPA
author, Thomas £ Pierce (also the EPA Project Officer, see below), is with the
Atmospheric Research and Exposure Assessment Laboratory, Research Triangle
Park, NC 27711
The complete report, entitled "Development of the Regional Oxidant Model Version
2.1," (Order No. PB 89-194 252/AS; Cost: $15.95, subject to change) will be
available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Atmospheric Research and Exposure Assessment 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/S3-89/044
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