A»^V
United States
Environmental Protection
Agency
Region 3
6th and Walnut Streets
Philadelphia, PA 19106
EPA 903/9-82-005
February 1982
&EPA
Improving Performance of the
Maryland Air Management Administration
Ozone Model (OZIPM)
U.S. Envlrmma^&J Prstecfiea Agtocy
favjn III te'c-fifiaUon ae»ar«t
f;iC:'«tiwt Street
a, PA
EPA Report Collection
Intormatipn Resource Center
D. US ERA Region 3
Philadelphia, PA 19107
P«flinn III I ihrarv
Ewlrinmentat Protect«»
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FINAL REPORT
EPA Contract No. 68-02-3511
Work Assignment No. 18
PES Project No. 566
IMPROVING PERFORMANCE OF THE MARYLAND
AIR MANAGEMENT ADMINISTRATION OZONE MODEL
(OZIPM)
U.S. Environment^ PrstocSoa
Prepared by: Lowell G. Wayne k ';von HI information Resource
Joseph A. Cassmassi C^ULT (CPM52)
PI Chestea! S*f«i
Prepared for:
U.S. ENVIRONMENTAL PROTECTION AGENCY
Region III
6th and Walnut Streets
Philadelphia, Pennsylvania 19106
Edward A. Vollberg, Project Officer
February 1982
PACIFIC ENVIRONMENTAL SERVICES, INC.
1930 14th Street
Santa Monica, CA 90404
(213) 450-1800
IH library
Envfronmenial Protection
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This report is issued by the Environmental Protection Agency to report
technical data of interest to a limited number of readers. Copies are
available - in limited quantities - from the Library Services Office
(MC-35), U.S. Environmental Protection Agency, Research Triangle
Park, North Carolina 27711; or, for a fee, from the National Tech-
nical Information Service, 5285 Port Royal Road, Springfield,
Virginia 22161.
Publication No. EPA-903/9-82-005
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ACKNOWLEDGMENT
This report was prepared under contract by Pacific Environmental
Services, Inc. (Contract No. 68-02-3511). Edward A. Vollberg served
as Project Officer for the performance of the work described and the
preparation of the report.
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EXECUTIVE SUMMARY
In response to a work assignment, PES studied the functioning
of a photochemical air quality simulation model, OZIPM, which had
been found by the Air Management Administration of the State of
Maryland to yield unsatisfactory ozone isopleth curves in a test
application in which a complex chemical kinetic mechanism was
utilized. PES was assigned to determine the cause of the problem
and recommend means to overcome it.
A major cause of the problem was found to consist in a
discrepancy between the Users Manual directions and the actual
structure of the OZIPM program. This discrepancy hinged on the
distinction between molar and carbon-based units for the expression
of concentrations of hydrocarbons; that is, between parts per
million by volume (ppmV) and parts per million as carbon (ppmC). A
method of correcting the discrepancy is recommended in this report,
and alternative measures which involve slight revisions to the
instructions in the Manual, but with no alteration to the existing
program, are also described and discussed.
In a separate line of inquiry, the possibility that the
chemical mechanism used in Maryland's application might be at fault
was investigated. Results from a chamber simulation study done at
the University of North Carolina were made available, prior to
publication, by the Air Management Technology Branch, Office of Air
Quality Programs and Standards, U.S. EPA. These results showed that
isopleth curves based on the mechanism (CIT, devised by
investigators at the California Institute of Technology) which was
used by Maryland were similar in character to those based on other
complex chemical mechanisms which have been provided for the same
purpose. Although some of the reaction rate factors taken by the
UNC investigators differed from those used by Maryland, it was
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concluded that the CIT mechanism was not at fault in yielding
isopleths of the type found in the Maryland application.
Study of the OZIPM output furnished by Maryland indicated that
the isopleths were consistent with the proper functioning of the CIT
mechanism and that the program itself functioned properly, except
for the discrepancy already noted. Isopleth diagrams which
represent simulations with no assumed hydrocarbons in air aloft,
when interpreted three-dimensionally, may be expected to exhibit a
ridge of ozone maxima, diagonally directed toward the plot origin.
The lack of such a ridge in the Maryland isopleth diagram is a
consequence of the conditions assumed in the program input, together
with the program discrepancy noted.
In the Maryland application, a substantial level of
hydrocarbons was assumed to be transported from aloft. At the same
time, NOx was assumed to be absent from the transported air mass.
Further, the effect of these transported hydrocarbons was magnified
by an assumed large increase in mixing height during the day, which
results in the final mixture consisting of nearly 90 percent air
from aloft. Acting in the same direction, the program discrepancy
erroneously multiplied the hydrocarbon concentrations in the air
aloft by a factor of about 5. The net result of these circumstances
was to displace the expected ozone ridge completely beyond the
boundaries of the diagram produced by the computer.
In analogous circumstances in the atmosphere, the extent of
reaction in the photochemical system would be severely limited by
the availability of NOx and the quenching effect of excess
hydrocarbons. Maryland's isopleth diagram correctly reflects these
conditions, showing a large sensitivity of the ozone peak to initial
NOx, but a low sensitivity to initial hydrocarbons.
A search was also made for possible errors in Maryland's
version of OZIPM, which might have been introduced in the course of
modifying OZIPM to accept the CIT mechanism. The program code as
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applied by Maryland was compared in detail with that of an OZIPM
program supplied by AMTB. A total of 43 revisions were identified,
affecting 12 segments of the program. These revisions appeared to
reflect two main purposes: to provide dimensions needed for the CIT
mechanism, and to adjust internal parameters to minimize the
occurrence of underflows. However, many of the changes were
evidently directed toward reducing redundancy and improving the
logic flow of the basic program.
None of these changes appeared inappropriate or likely to cause
program malfunctions. It is concluded that, with manual and program
corrections as suggested in this report, Maryland's OZIPM should
operate as intended.
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TABLE OF CONTENTS
Section Page
1.0 INTRODUCTION 1-1
2.0 CORRECTIONS TO OZIPM 2-1
3.0 REASONS FOR SHAPE OF ISOPLETH CURVES 3-1
4.0 REVIEW OF OZIPM CODING 4-1
5.0 CONCLUSIONS AND RECOMMENDATIONS 5-1
APPENDIX A - DISCREPANCIES IN REACTION RATE FACTORS FOR CIT
MECHANISM A-l
APPENDIX B - SUGGESTED MODIFICATION TO OZIPM B-l
APPENDIX C - SUMMARY OF CHANGES MADE TO OZIPM BY JAMES
TILDEN (CALIFORNIA INSTITUTE OF TECHNOLOGY) AND
BY MARYLAND AIR MANAGEMENT ADMINISTRATION C-l
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1.0 INTRODUCTION
Pacific Environmental Services, Inc. (PIS) was directed by Work
Assignment No. 18 under EPA Contract No. 68-02-3511 to examine the
ozone model, OZIPM, being used by the Maryland Air Management
Administration as an aid in developing a control strategy for
atmospheric ozone, in order to locate the cause of poor performance
by the model in the isopleth generation mode, and to modify the
model as necessary to bring its performance to an acceptable level.
This report describes findings by PES in response to Work
Assignment No. 18. PES discussed the program, OZIPM, with personnel
of the Maryland agency, most especially Mr. Mario Jorquera, and
reviewed samples of OZIPM input and output as furnished by the
Maryland agency, as well as the detailed coding of both Maryland's
OZIPM computer program and a closely related program, also known as
OZIPM, which has been under study by Mr. Gerald Gipson of the Air
Management Technology Branch, Office of Air Quality Programs and
Standards, U.S. Environmental Protection Agency.
Initial examination and discussion revealed an apparent flaw in
the Users Manual for Maryland's OZIPM, in that it was ambiguous in
regard to units to be used in specifying hydrocarbon concentrations
in program input. At the suggestion of PES, Maryland undertook
additional computer runs to test the effect of suggested changes in
input. Based on verbal reports of the results of these exercises,
PES arrived at a conclusion as to the cause and correction of the
problem perceived by Maryland.
In a separate line of inquiry, PES reviewed the possibility
that the apparent malfunction might be a consequence of the use, in
Maryland's OZIPM, of a chemical kinetic mechanism known as CIT,
devised by investigators at the California Institute of Technology
for simulating the reactions which occur in photochemical air
pollution. From AMTB, PES learned that investigators at the
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University of North Carolina had recently compared the ability of
several chemical kinetic mechanisms, including CIT, to simulate
reactions in artificial smog systems, irradiated in an environmental
chamber. PES requested and received from AMTB relevant excerpts of
a draft report from UNC, dealing with these comparisons. From a
review of these excerpts, PES concluded that the CIT mechanism, when
applied using the parameters described in the draft report, produces
isopleth curves which are comparable in shape and sensitivity to
those obtained with other mechanisms.
In order to determine whether the reaction rate factors used by
the UNC investigators in simulating photochemical ozone production
by the CIT mechanism were consistent with those supplied to
Maryland, PES compared them with those listed in the UNC draft
report. Numerous differences were found, the largest representing a
factor of about 5 in the rate factor applied for one of the 58
reactions in the mechanism. PES concluded, however, that the
discrepancies encountered could not be mainly responsible for the
problem of OZIPM performance as perceived by Maryland. (Appendix A
presents a comparison of the factors used by Maryland and by UNC.)
Following sections of this report present more detailed
discussion of PES findings and conclusions. The diagnosis of a
relevant program flaw in OZIPM is described and discussed in Section
2.0, and a recommended program modification is shown in Appendix B.
In Section 3.0, we review the perceived defects in the isopleth
diagram produced by Maryland's OZIPM, and show how the program flaw
diagnosed in the previous section, together with conditions assumed
by Maryland as input to the program, accounts for the general
character and sensitivity of the ozone isopleth curves.
In Section 4.0, we review the differences in coding between
OZIPM as used by Maryland and OZIPM as presently being studied by
AMTB. A detailed comparison is presented in Appendix C.
Conclusions and recommendations are presented in Section 5.0.
1-2
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2.0 CORRECTIONS TO OZIPM
By reviewing the computer printout provided by the Maryland Air
Management Administration in conjunction with the Users Manuals for
both Maryland and EPA versions of OZIPM, PES has located an
inconsistency between the actual functioning of OZIPM and the
instructions provided in the manuals. PES believes that this
inconsistency has been largely responsible for the difficulties
encountered by Maryland.
The inconsistency is as follows. In describing input values
for the TRAN card and its successors (which are used to specify the
concentrations and composition of contaminants in ambient air at the
start of simulations and of air aloft which will enter the system as
the inversion rises), the Maryland manual fails to specify the units
to be used. The manual for EPA's OZIPM specifies that
concentrations are to be entered as ppmC. Further, both manuals
instruct the user to enter a "fraction vector" on the same card; one
such card is to be used for the initial background hydrocarbons and
another for the hydrocarbons in the air aloft. However, in the case
of air aloft, the program i s designed to perform calculations using
concentrations in ppmV (not ppmC) and a "fraction vector" based on
such concentrations; consequently, when the instructions are
followed, the results will be wrong.
To correct this condition, various options are available.
Without changing the program, correct results can be obtained by
revising the instructions in either of two ways:
1. instruct the user to enter hydrocarbon concentrations (in
air aloft) in terms of ppmV, and "fraction vectors" in
terms of volume fractions, or
2. instruct the user to enter hydrocarbon concentrations in
terms of ppmC; then, instead of a "fraction vector," to
apply (for air aloft only) a composite vector, where each
term is the product of the carbon-based fraction (for a
given hydrocarbon) times the reciprocal of the carbon
number.
2-1
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Alternatively, the program can be modified to accept and act
correctly on concentrations and fraction vectors specified in terms
of ppmC, so that the instructions as given in the EPA manual would
be correct. This can be done by inserting a statement in the main
program which would retrieve the necessary carbon-number values from
the previously read input and apply them to the corresponding
specific hydrocarbons in the necessary manner. A recommended
modification is shown in Appendix B.
It appears to us that this defect exists not only in Maryland's
version of OZIPM, but also in EPA's version. Therefore, we believe,
both versions should be modified by one or another of the methods
described above.
The fact that OZIPM yields satisfactory results when run in a
"default" mode might suggest that our recommended change is
unnecessary, or even undesirable. To determine why the default mode
might give reasonable results despite the existence of the
inconsistencies described above, we studied the default data, which
are embedded in the program. We found that, when the default mode
is selected, the values which the program supplies to the array
which accepts the user's "fraction vector" do not in fact constitute
a fraction vector, but rather form a composite vector of exactly the
type described in option 2, above. Thus it appears that the OZIPM
program, in either the Maryland version or the EPA version, has been
adjusted in such a manner that it works correctly in the default
mode (using the Dodge mechanism), but not when an alternate
mechanism is inserted.
2-2
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3.0 REASONS FOR SHAPE OF ISOPLETH CURVES
Study of the OZIPM output forwarded to PES by M. Jorquera of
the Maryland Air Management Administration indicates to us that the
isopleths produced by the computer in this instance are consistent
with the proper functioning of both OZIPM and the Caltech mechanism,
except for the mistake in OZIPM which we have discussed above.
Isopleth diagrams produced by the OZIPM default mechanism, and
by other mechanisms used with similar assumptions, often yield sets
of curves which, when interpreted three-dimensionally, exhibit a
ridge of ozone maxima, diagonally directed toward the origin. The
isopleth diagram derived from Maryland's trial of OZIPM exhibits no
such ridge. We conclude, however, that the absence of the ridge
reflects no defect in the Caltech mechanism, but rather is a
consequence of the conditions assumed in the program input, together
with the program inconsistency discussed above.
In the application of OZIPM in the default mode, the Dodge
mechanism is used and the assumption is made that no pollutants are
transported into the atmospheric mixing layer from aloft. When this
is done, the resulting isopleth chart displays a ridge of peak ozone
values corresponding roughly to an initial ratio (of hydrocarbons,
ppmC, to NOx, ppm) of 7 to 10. This is, in effect, a ratio of these
contaminants in the irradiated air which, according to the Dodge
mechanism, should give higher ozone maxima than any other ratio, so
long as the concentration of hydrocarbons and NOx are assumed not to
increase simultaneously.
When CIT or some other mechanism is taken, rather than the
Dodge mechanism, it is to be expected that a similar ridge will
exist, although it may occur at some other ratio than that found
with the Dodge mechanism. However, even with the Dodge mechanism,
the ratio of HC to NOx for highest ozone peaks is altered if
contaminant transport is taken into account. If the transported
3-1
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contaminants contain hydrocarbons without NOx, the ratio in the
simulated air is increased, but the axes of the isopleth diagram do
not reflect this increase. As a result, the ozone ridge is
displaced toward higher initial NOx values, and corresponds (in the
diagram) to lower ratios of initial HC to NOx.
In the Maryland application, unlike the OZIPM default case, a
substantial level of hydrocarbons transported from aloft was
assumed; at the same time, NOx was assumed not to be present in the
transported air. Thus, for any set of initial concentrations, the
ratio (HC/NOx) in the simulated air during the hours following
initiation would increase as hydrocarbons from aloft were added to
the mixing layer. This would result in the displacement of the
ozone ridge on the isopleth chart toward higher initial NOx values;
we believe that, in the Maryland application, this displacement was
great enough to shove the expected ridge completely off the diagram.
This rather large displacement of the ozone ridge in the
Maryland application is caused by a combination of three
circumstances, which all reinforce the effect. First, Maryland
assumed rather high concentrations of hydrocarbons transported
aloft; the total hydrocarbon aloft was taken as 0.7 ppmC, which was
52 percent of the total (1.36 ppmC) of initial emitted hydrocarbons
and initial background hydrocarbons present in the air at the start
of simulation.
Second, the effect of the transported hydrocarbons was
magnified by the large quantity of air aloft which was assumed to be
incorporated in the mixing layer during the day. From an initial
mixing height of 225 meters, the rising inversion was assumed to
lift to 1,925 meters, at which point almost 90 percent of the air in
the mixing layer would have originated in the contaminated,
transported air aloft.
Third, the concentration of hydrocarbons specified in the air
aloft was erroneously treated by the program as if it had been given
3-2
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in ppmV rather than in ppmC. The result of this was that the
program interpreted the entry 0.7 to represent ppmV and took it to
be equivalent to almost five times as many ppmC as Maryland intended.
The effect of these circumstances on the ratio of HC to NOx was
to cause a drastic increase within a short time after the start of
simulation. Examination of the Maryland OZIPM output shows that
HC/NOx was about 9 at the start of simulation, but increased to 75
after one hour, 750 after 2 hours, and much higher values still as
the NOx provided in the initial ground-based layer of air was
depleted by reaction as well as dilution.
Under these circumstances, the extent of reaction in the
photochemical system would be severely limited by the availability
of NOx and the quenching effect of excess hydrocarbons. The
isopleth diagram obtained by Maryland correctly reflects these
conditions, showing a large sensitivity of the ozone peak to the
initial NOx, but a low sensitivity to initial hydrocarbons, which
represent only a minor fraction of the hydrocarbons available in the
system.
PES believes that isopleth diagrams representing the same
assumptions but with the use of other mechanisms (such as Dodge)
would show the same general character as the one obtained by
Maryland using the CIT mechanism. Isopleth diagrams have been
generated by investigators at the University of North Carolina to
simulate reactions in a photochemical irradiation chamber, in which
atmospheric transport is not a factor, and these show the expected
ozone ridges for the Caltech mechanism as well as for the Dodge
mechanism and two other mechanisms which involve several classes of
hydrocarbons. We therefore conclude that the Caltech mechanism is
not at fault in the Maryland application of OZIPM.
3-3
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4.0 REVIEW OF OZIPM CODING
A comparison of the computer coding of OZIPM as applied by
Maryland with that under study by EPA has been completed. A total
of 43 differences have been identified. We assume that the Maryland
version was generated by modifying a program originally identical to
the EPA version of OZIPM.
The modifications affect 12 segments of the program. In our
judgment, they reflect two main purposes: to allow for larger
dimensions needed to accommodate the CIT mechanism, and to adjust
certain internal parameters in the hope of minimizing underflows and
similar operational impediments during execution. However, many of
the observed changes were apparently undertaken mainly to reduce
redundancy and improve the logic of the underlying program.
PES found no changes that appeared inappropriate or likely to
cause malfunctioning of the program. It is our opinion that the
Maryland version of OZIPM, including slight alterations inserted by
the Maryland agency staff as well as those made before delivery to
Maryland, should be expected to execute properly and to yield
isopleth curves which correctly reflect consequences of the Caltech
mechanism.
A review of the specific modifications detected by our study is
given in Appendix C.
4-1
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5.0 CONCLUSIONS AND RECOMMENDATIONS
PES concludes that the ozone isopleths obtained by the Maryland
Air Management Agency are erroneous because of a discrepancy between
the actual functioning of the OZIPM program and the input
instructions given in the Users Manual, which Maryland followed.
This discrepancy can be easily corrected; measures for correcting it
are discussed in Section 2.0.
PES further concludes that the CIT mechanism is not
inappropriate for the type of simulation embodied in OZIPM, although
the reaction rate factors which have been used in the CIT mechanism
as applied by Maryland may not constitute an optimum set.
Finally, PES concludes that the changes made in the OZIPM
computer program to accommodate the CIT mechanism and to facilitate
operation on Maryland's computer system are not such as to impair
the operation of the program or to cause disorder in the generation
of ozone isopleth diagrams when the program is used in the ISOPLETH
mode.
Recommendations resulting from this study are the following:
1. The OZIPM program and Users Manual should be revised as
specified as In Appendix C. Alternatively, without
modifying the program, either of two options specified in
Section 2.0 may be used. These are considered less
desirable than the procedure given in Appendix C because,
unless carefully understood and applied, they could confuse
the user and lead to other errors.
2. The selection of reaction rate factors embodied in the CIT
mechanism, as given in the Users Manual, should be reviewed
and, where necessary, updated.
5-1
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APPENDIX A
DISCREPANCIES IN REACTION RATE FACTORS FOR CIT MECHANISM
Reaction
HN04 = H02 + N02
OLE + OH = R02
OLE + 0 = R02 + RC03
RO = H02 + HCHO(RCHO)C
N20s = N02 + N03
03 + H02 = OH
OLE + 03 = products^
Number
14
28
29
39
50
53
30 to
Maryland9
Factor
21.8
89,100
22,100
360,000
8.85
3.48
35 0.136
Number
17
35
36
42
10
25
37, 38
UNCb
Factor
4.37
59,500
39,300
200,000
6.85
1.50
0.103
aSource: OZIPM output provided by Maryland Air Management Administration.
^Source: Excerpts from draft report of University of North Carolina project,
provided by Air Management Technology Branch, Office of Air Quality Programs
and Standards, U.S. EPA.
CUNC assumes the product is RCHO.
dThe factors cited are totals of the rate factors for all reactions
attributed to the reactants, OLE and 03.
A-l
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APPENDIX B
SUGGESTED MODIFICATION TO OZIPM
The purpose of this modification is to correct an error in
program MAIN, which causes concentrations of hydrocarbons in air
aloft to be treated as if given in ppmV, whereas other
concentrations are read as ppmC. This change will allow the program
to deal correctly with all input data regarding hydrocarbon
concentrations when all such data are consistently entered as ppmC.
In program MAIN, follwoing Card No. 00002940, insert the
following two cards:
DO 171 I = 1, JAL 00002941
171 FALHC(I) = FALHC(I)/CARB(I) 00002942
In the Users Manual for OZIPM, two notes should be added, both
in connection with the TRANSPORT option in Table 1. These are as
follows:
1. The TRANSPORT option must not precede the MECHANISM option,
which must include the vector of carbon numbers for
hydrocarbon species (as already indicated in the Manual).
2. Total hydrocarbons entrained from aloft and total initial
background hydrocarbons, in the TRANSPORT option, must be
entered in terms of ppmC, not ppmV.
B-l
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APPENDIX C
SUMMARY OF CHANGES MADE TO OZIPM BY
JAMES TILDEN (CALIFORNIA INSTITUTE OF TECHNOLOGY)
AND BY MARYLAND AIR MANAGEMENT ADMINISTRATION
Sections modified:
MAIN
PHOT
RLINE
SIM
DRIVES
DIFFUN
LINER
CURVE
ISOPLT
BLOCK DATA
EMIS
EDGMX
Type of change:
1,
1,
3,
4,
6
3
2,
2,
2,
6,
2
3
1.
2.
3.
4.
5.
2, 4,
2, 4,
4, 5
5
3, 4,
4
5
1
Rest
Init
Rout
Omis
Rede
5
6
5
ru
ia
in
si
fi
Restructure data statements
Initialization and dimension
6.
Redefinition of programs or
program simplification
Addition of data/change of data
value
C-l
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HIGHLIGHTS
MAIN: 1.
2.
3.
4,
5.
6.
Data statements have been moved from main program to
block data statements.
Redefinition of PHOT - Large Core Memory (LCM)
variable: IPH(9) IPH(IO);
RFCT(8) RFCT(IO)
to include extra photolytic species
Addition of SNLT1 (LCM) defining XJ1 array
Use of MT2DNV subroutine to create/initialize XJ array
as transpose of XJ1
Option IDIL AMIX (1) = -3 is taken care of through Blk.
data default
Option IRDY changes made to the definition of variable
RTO(I) and XNLL(JK)
PHOT: 1. Data statements placed in Blk. data
2. Redefinition of CF(45,10) and P(15,10) arrays.
3. Inclusion of CONTINUE statement at end of loop.
RLINE 1. Change to equivalence statement made by Maryland
Equivalence (NR, NRTO), (RTO, R)
(NR, NRTO), (RTO, R(l))
2. Deletion of statement IFG = 0
3. Inclusion of 45-CONTINUE statement
4. Reformatting of calculation of HCG ((statement 60 to
65)) apparent assumption and simplification
5. Similar treatment of variable RHO (1, I) as in No. 4.
6. ((Statements 270 to 280)) Deletion of redefinition of
HCS = TOL * HCT(3)
7. Inclusion of CONTINUE statement at 280
8. Elimination of dummy variable OZS ((Statement 285))
C-2
-------
SIM: 1. Changes to data definitions
2. Deletion of TOIL = 0 from text
3. Statements 55 and 70,71 omitted (IF statements used to
redefine if data not in order)
4. Deletion of redefinition of variable TOT if
INX-NE-3. ((Between Statements 90 and 95)).
DRIVES: 1. Value of UROUND is changed from 7.5 E-9 to 8.0 E-7
DIFFUN: 1. Definition of I slightly modified.
2. Slight recalculating of DILU/DILUT
3. Definition of RT-R(IR) if I.EQ.O not addressed (i.e.,
changes to the DO 110 loop) not significant
LINER: 1. Changes made to the placement of variables in LCMs
/NEED/ XNLL:missing
/GEARC/ HCBP:missing
2. Value of array DUM1 expanded fro DUM1(274) to DUM1(294)
3. Deletion of initialization statement RPL (I, J) = -9
and loop
4. Deletion of several cards to print a new line if
condition OZP(LS).LT.OC(4)
5. Restructure statements 85 NR1 = NR and definition
clause NR1 = NR-1 that follows
6. Restructuring between statements 90 and 100 variables
changed include: UNDIFF
7. Omission of definition of U(K) = HCBP(I) and V(K) = 0.
((Statements between 150 and 151))
8. Deletion of several lines of code calling curve
production if U(IJ) and V(IJ)<0.0 code is used to
redefine parameters for plotting the curve.
C-3
-------
CURVE: 1. Exclusion of common statements with LCM /NEED/ and
associated variables
2. Deletion of statements preventing the calling of
subroutines VVLBLF and VVLBLC under variable USX or USY
out-of-bound conditions
ISOPLT: 1. Changes made to the dimensional sizes of variables DUM2
and DUM3
2. Deletion of statement included to prevent definition of
DUM(3), NR1 if (NPTO.NE.O)
BLOCK 1. Inclusion of value RONO (photolytic species name) in the
DATA SPEC array
2. Changes made to UROUND
3. Inclusion of equivalence statements defining
XJ1A to XJ1E
4. Restructuring the data specification in those arrays.
Also restructuring the SIGMA, PHI, and IW1 arrays.
EMIS:
Change size of variables dimensions
EM(15) to EM(ll)
EC(58) to EC(38)
IFLAG(15) to IFLAG(ll)
EDGMX:
Exclusion of escape clause in DO 5 loop if conditions
are not met
C-4
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
90319-82-005
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Improving Performance of the Maryland Air Management
Administration Ozone Model (OZIPM)
5. REPORT DATE
February 1982
6. PERFORMING ORGANIZATION CODE
7 AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
Lowell G. Wayne
Joseph C. Cassmassi
FR 566
. PERFORMING ORGANIZATION NAME AND ADDRESS
Pacific Environmental Services, Inc.
Western Operations Division
1930 Fourteenth St., Santa Monica, CA 90404
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
EPA 68-02-3511,
Assignment No. 18
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. EPA, Region III, Air Media and Energy Branch
Curtis Bldg., 6th and Walnut Sts, Philadelphia, PA 19106
Project Officer: Edward A. Vollberg
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16 ABSTRACT
The assignment was to study the functioning of a photochemical air quality simula-
tion model which, in a test application, appeared to yield unsatisfactory ozone
isopleth curves; to determine the cause of the problem and overcome it.
A major cause of the problem was found to consist in a discrepancy between the
instructions given in the Users Manual and the actual functioning of the OZIPM program.
A method of correcting the discrepancy is recommended, and alternative measures are
discussed.
In a separate line of inquiry the possibility that the chemical mechanism used
("Caltech" mechanism) might be at fault was investigated. Results showed that
isopleth curves based on the mechanism were similar in character to those based on
other complex chemical mechanisms.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATl } leld/Group
Ozone
Photochemical air pollution
Simulation model
Kinetic mechanism
OZIPM
18. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
20
20 SECURITY CLASS (Thispage}
Unclassified
22. PRICE
EPA Form 2220-1 (Rev. 4-77)
PREVIOUS EDITION IS OBSOLETE
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INSTRUCTIONS
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14. SPONSORING AGENCY CODE
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15. SUPPLEMENTARY NOTES
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To be published in. Supersedes, Supplements, etc.
16. ABSTRACT
include a brief (200 words or less) factual summary of the most significant information contained in the report. If the report contains a
significant bibliography or literature survey, mention it here.
17. KEY WORDS AND DOCUMENT ANALYSIS
(a) DESCRIPTORS - Select from the Thesaurus of Engineering and Scientific Terms the proper authorized terms that identify the major
concept of the research and are sufficiently specific and precise to be used as index entries for cataloging.
(b) IDENTIFIERS AND OPEN-ENDED TERMS - Use identifiers for project names, code names, equipment designators, etc. Use open-
ended terms written in descriptor form for those subjects for which no descriptor exists.
(c) COSAT1 FIELD GROUP - Field and group assignments are to be taken from the 1965 COSATI Subject Category List Since the ma-
jority of documents are multidisciplmar> in nature, the Primary Field/Group assignment(s) will be specific discipline, area of human
endeavor, or type of phjsical object. The application(s) will be cross-referenced with secondary Field/Group assignments that will follow
the primary postmg(s)
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EPA Form 2220-1 (Rev. 4-77) (R.veri.)
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