TROPOSPHERIC ULTRAVIOLET RADIATION
Assessment of Existing Data and Effect on Ozone Formation
by
M. W. Gery
R. D. Edmond
G. Z. Whitten
Systems Applications, Inc.
101 Lucas Valley Road
San Rafael, CA 94903
Interagency Agreement DW 14931805
U.S. Department of Interior
National Park Service
Denver, CO 80225
Project Officer
Bruce W. Gay, Jr.
Atmospheric Chemistry and Physics Division
Atmospheric Sciences Research Laboratory
Research Triangle Park, NC 27711
ATMOSPHERIC SCIENCES RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NC 27711
/\1 8 1 0 8 7 1 2 3 y-
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NOTICE
The information in this document has been funded by the United States
Environmetal Protection Agency under Interagency Agreement, DW1493L805.
Don Henderson supervised the agreement for the National Park Service.
It has been subjected to the Agency's peer and administrative review, and
it has been approved for publication as an EPA document. Mention of trade
names or commercial products does not constitute endorsement or
recommendation for use.
67123r 1
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Abstract
This study was performed to determine the impact that potential changes in
stratospheric ozone concentrations and surface temperatures might have on
the chemical processes that create tropospheric ozone and cloud acidifica-
tion precursors. The investigation consisted of two distinct parts.
First, an assessment was performed of the ultraviolet radiation informa-
tion and molecular absorption cross section and quantum yield data cur-
rently used in air quality simulation. This assessment addressed both the
quality of existing data and approaches available for utilizing these data
to determine chemical photolysis rates in the troposphere. Particular
attention was paid to the photolysis reactions of ozone, formaldehyde, and
acetaldehyde because these species absorb light in the spectral region
where surface ultraviolet irradiance could increase due to decreased
stratospheric absorption by ozone.
The algorithms and data resulting from this assessment were used in the
second portion of the study to determine photolysis rates that might occur
in the troposphere under future conditions of decreased stratospheric
ozone. The sensitivity of photochemical dynamic processes was tested for
a large number of urban airshed data sets under conditions of decreased
stratospheric ozone and increased surface temperatures. The predicted
surface ozone and hydrogen peroxide concentrations resulting from incre-
mental changes in the assumed future stratospheric ozone and temperature
parameters were analyzed for each city and for specific groups of
cities. Instances of greater future oxidant forming potential were most
common for cities with already high hydrocarbon control requirements. The
increased energy input during future scenarios provided more rapid ozone
formation in all cases, indicating the possible exposure of a larger por-
tion of the urban population to higher ozone concentrations nearer to the
center of the urban plume.
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CONTENTS
Abstract iii
List of Figures vi
List of Tables xi
1 INTRODUCTION 1
2 ASSESSMENT OF ULTRAVIOLET SPECTRAL DATA AND CALCULATION
OF TROPOSPHERIC PHOTOLYSIS RATES 5
3 SIMULATION OF URBAN PHOTOCHEMISTRY UNDER CONDITIONS OF
FUTURE GLOBAL CHANGE 57
4 DISCUSSION OF URBAN SIMULATION RESULTS 122
5 CONCLUSIONS AND RECOMMENDATIONS 154
References 161
Appendix A: INPUT DATA USED FOR THE OZIPM/EKMA SIMULATION 165
Appendix B: PHOTOLYSIS RATE RATIOS (to jN02) AS A FUNCTION
OF ZENITH ANGLE FOR A NUMBER OF TEST CITIES 176
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FIGURES
1-1 A simple representation of the coupling of atmospheric
chemical and physical processes that could result in
increased ultraviolet penetration to the troposphere 3
2-1 Ozone absorption cross section 7
2-2 Simplified representations of extraterrestrial flux
and solar irradiance of 0 and 30 km above the earth's
surface 8
2-3 Extraterrestrial flux distributions of the World
Radiation Center 12
2-4 Extraterrestrial flux distributions of the World
Radiation Center and the World Meteorological
Organization 13
2-5 Extraterrestrial flux distributions of the World
Radiation Center for the middle ultraviolet region 15
2-6 Extraterrestrial flux distributions of the World
Radiation Center and the world Meteorological
Organization for the middle ultraviolet region 16
2-7 Comparison of Braslau and Dave model results
with Schippnick and Green calculations for
similar conditions 19
2-8 Comparison of Braslau and Dave model results
with Schippnick and Green calculations for similar
conditions at different zenith angles 21
2-9 Surface irradiance data for zenith angles of
approximately 20, 65, and 80 degrees measured
at ground level in rural North Carolina 28
871Z 3f 1
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2-10 Actinic flux for 20 and 60 degree solar zenith
angles in bin sizes of 1 and 5 nm 30
2-11 Photoaction spectra for NO2 using 1 and 5 nm bins 34
2-12 Comparison of absorption cross sections for
formaldehyde 41
2-13 Photoaction spectra for formaldehyde to stable
products and formaldehyde to radicals 42
2-14 Photoaction spectra for acetaldehyde using 1 and
5 nm bins 44
2-15 Comparison of relative j-value curve shapes with
respect to solar zenith angle for the five major
photolytic species 45
2-16 Comparison of photoaction spectra for and
JqIq for 20 and 60 degree solar zenith angles 46
2-17 Comparison of 1 nm photoaction spectra for
jhCHOr spectra calculated with 10, 5,
and 1 nm bins 48
2-18 Comparison of 1 nm photoactio spectra for
jHCH0s w1^ spectra calculated with 10, 5,
and 1 nm bins 49
2-19 Comparison of measured and calculated j'q^q values 54
3-1 Single-day urban modeling data-set selection
process protocol 73
3-2 Calculated zenith angles for Seattle, Washington
and Los Angeles, California for 1 August 76
3-3 Calculated j'03 values for Seattle, Washington and
Los Angeles, California for 1 August at 0.300 and
0.200 cm-atm overhead ozone column 77
3-4 Results of 0ZIPM future sensitivity tests for
the simulation of 26 June 1974, Los Angeles,
California 101
87 1 2 3|- 1
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3-5 Results of OZIPM future sensitivity tests for
the simulation of 24 June 1980, New York 102
3-6 Results of OZIPM future sensitivity tests for
the simulation of 13 July 1979, Philadelphia,
Pennsylvania 103
3-7 Results of OZIPM future sensitivity tests for
the simulation of 7 August 1980, Wahsington, DC 104
3-8 Results of OZIPM future sensitivity tests for
the simulation of 24 June 1980, Philadelphia,
Pennsylvania 105
3-9 Results of OZIPM future sensitivity tests for
the simulation of 14 September 1984, Phoenix,
Arizona 106
3-10 Results of OZIPM future sensitivity tests for
the simulation of 1 July 1981, Tulsa, Oklahoma 107
3-11 Results of OZIPM future sensitivity tests for
the simulation of 21 July 1980, Washington, DC 108
3-12 Results of OZIPM future sensitivity tests for
the simulation of 5 July 1984, Phoenix, Arizona 109
3-13 Results of OZIPM future sensitivity tests for
the simulation of 10 August 1980, Nashville,
Tennessee 110
3-14 Results of OZIPM future sensitivity tests for
the simulation of 10 August 1980, Nashville,
Tennessee Ill
3-15 Results of OZIPM future sensitivity tests for
the simulation of 31 August 1984, Phoenix,
Arizona 112
3-16 Results of OZIPM future sensitivity tests for
the simulation of 6 August 1982, Tulsa, Oklahoma 113
3-17 Results of OZIPM future sensitivity tests for
the simulation of 11 August 1981, Seattle,
Washington 114
87 12 3r 1 viii
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3-18 Results of OZIPM future sensitivity tests for
the simulation of 7 August 1981, Seattle,
Washington 115
3-19 Results of OZIPM future sensitivity tests for
the multi-day simulation of 26-27 June 1974,
Los Angeles, California 116
3-20 Results of OZIPM future sensitivity tests for
the multi-day simulation of an 02one NAAQS
attainment scenario for Pheonix, Arizona 117
4-1 Ozone, NO2, ^2, and PAN plots for extreme
scenarios in the future sensitivity tests-
simulation of 13 July 1979, Philadelphia,
Pennsylvania 124
4-2 Ozone, NOg, H2O2, and PAN plots for extreme
scenarios in the future sensitivity tests-
simulation of 21 July 1980, Washington, DC 125
4-3 Ozone, NO2, ^2, and PAN plots for extreme
scenarios in the future sensitivity tests-
simulation of 1 July 1981, Tulsa, Oklahoma 126
4-4 Ozone, N02, ^2, and PAN plots for extreme
scenarios in the future sensitivity tests—
simulation of 31 August 1984, Phoenix, Arizona 128
4-5 Ozone, NO2, ^2, and PAN plots for extreme
scenarios in the future sensitivity tests-
simulation of 11 August 1981, Seattle, Washington 131
4-6 Ozone, N02» NO, and HNO-j plots for extreme
scenarios in the future sensitivity tests-
simulation of 24 June 1980, Philadelphia,
Pennsylvania 134
4-7 Percent increase in predicted ozone over the
future base case for two temperature increments
and three test groups 137
4-8 Percent increase in predicted ozone over the
future base case for two ozone column density
decrements and three test groups 141
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4-9 Ozone, NC^, and PAN plots for extreme
scenarios in the future sensitivity tests--
multi-day simulation of an ozone NAAQS attainment
scenario for Phoenix, Arizona 149
4-10 Ozone, NO2, ^2, and PAN plots for extreme
scenarios in the future sensitivity tests--
multi-day simulation of 26-27 June 1974,
Los Angeles, California • 151
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TABLES
2-1 Values of optical thickness for moelcular and
aerosol scattering, and aerosol extinction 24
2-2 Absorption cross sections and quantum yields
for N02 photolysis 31
2-3 Results of calculations 33
2-4 Absorption cross sections and quantum yields
for formaldehyde photolysis to radical product 36
2-5 Absorption cross sections and quantum yields
for formaldehyde photolysis to stable products 37
2-6 Absorption cross sections and quantum yields
for ozone photolysis to 0(*D) 38
2-7 Absorption cross sections and quantum yields
for acetaldehyde photolysis to radical products 39
2-8 SAI and UNC j-value calculations for actinic
flux corrected to 640 m and slightly
different albedos 40
2-9 J-values calculated for formaldehyde photolysis
at different bin sizes 50
2-10 Results of j-value calculations WRC extraterrestrial
flux and Schippnick and Greene actinic flux
formulation 51
3-1 0ZIPM-3 listing of the CBM-X mechanism 60
3-2 0ZIPM-3 listing of the CALL mechanism 65
3-3 Initial single-day data sets in the 0ZIPM/EKMA
investigation 74
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3-4 Design values and model results for BASE CASE
simulations 81
3-5 Data sets used in future scenario tests 64
3-6 Maximum hourly concentrations and percentage
changes for ozone, and PAH for the future
sensitivity tests for the simulation of 26 June
1974, Los Angeles, California - 86
3-7 Maximum hourly concentrations and percentage
charges for ozone, and PAN for the future
sensitivity tests for the simulation of 24 June
1980, New York 87
3-8 Maximum hourly concentrations and percentage
changes for ozone, and PAH for the future
sensitivity tests for the simulation of 13 July
1979, Philadelphia, Pennsylvania 88
3-9 Maximum hourly concentrations and percentage
changes for ozone* HjC^, and PAH far the future
sensitivity tests For the simulation of 7 August
1980, Washington, OC 89
3-10 Maximum hourly concentrations and percentage
changes for ozone, and PAH for the future
sensitivity tests for the simulation of 24 Jurte
1980, Philadelphia, Pennsylvania 90
3-11 Maximum hourly concentrations and percentage
changes for ozone, and PAH for the future
sensitivity tests for the simulation of 14 September
1974, Phoenix, Arizona 91
3-12 Maximum hourly concentrations and percentage
changes for ozone, H^, and PAN for the future
sensitivity tests for the simulation of 1 July
1981, Tulsa, Oklahoma 92
3-13 Maximum hourly concentrations and percentage
changes for ozone, ard PAN far the future
sensitivity tests for the simulation of 21 July
1980, Washington, DC........ 93
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3-14 Maximum hourly concentrations and percentage
changes for ozone, and PAN for the future
sensitivity tests for the simulation of 5 July
1984, Phoenix, Arizona 94
3-15 Maximum hourly concentrations and percentage
changes for ozone, H2O2, and PAN for the future
sensitivity tests for the simulation of 10 August
1980, Nashville, Tennessee (trajectory number 1) 95
3-16 Maximum hourly concentrations and percentage
changes for ozone, H2O2, and PAN for the future
sensitivity tests for the simulation of 10 August
1980, Nashville, Tennessee (trajectory number 2) 96
3-17 Maximum hourly concentrations and percentage
changes for ozone, H202, and PAN for the future
sensitivity tests for the simulation of 31 August
1984, Phoenix, Arizona 97
3-18 Maximum hourly concentrations and percentage
changes for ozone, H202, and PAN for the future
sensitivity tests for the simulation of 6 August
1982, Tulsa, Oklahoma 98
3-19 Maximum hourly concentrations and percentage
changes for ozone, ^2, and PAN for the future
sensitivity tests for the simulation of 11 August
1981, Seattle, Washington 99
3-20 Maximum hourly concentrations and percentage
changes for ozone, ^2, and PAN for the future
sensitivity tests for the simulation of 7 August
1981, Seattle, Washington 100
3-21 Maximum hourly concentrations and percentage
changes for ozone, ^2, and PAN for the future
sensitivity tests for the multi-day simulation
of 26-27 June 1974, Los angeles, California 118
3-22 Maximum hourly concentrations and percentage
changes for ozone, ^2, and PAN for the future
sensitivity tests for the multi-day simulation
of attainment of the NAAQS in Phoenix, Arizona,
using a modified data set from 5 July 1984 119
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3-23 Maximum hourly concentrations and percentage
changes for ozone, ^2, and PAN for the future
sensitivity tests for the simulation of 5 July
1984, Phoenix, Arizona, with the CALL mechanism 120
3-24 Maximum hourly concentrations and percentage
changes for ozone, H2O2, and PAN for the future
sensitivity tests for the simulation of 13 July
1979, Philadelphia, Pennsylvania, with the CALL
mechanism 121
4-1 Rates of increases in maximum hourly ozone
concentrations with increases in temperature and
decreases in overhead ozone column 139
4-2 "Disbenefit" to future base case maximum hourly
H2O2 concentrations caused by increases in
temperature and decreases in overhead ozone column 143
4-3 Comparisons of future scenario maximum hourly
H2O2 concentrations versus original base case H2O2 144
4-4 Group averaged ozone responses to moderate and
extreme changes to future scenario conditions 148
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SECTION 1
INTRODUCTION
PURPOSE AND METHOD
This study was carried out to elucidate the impacts that potential future
changes in stratospheric ozone concentrations and surface temperatures
might have on tropospheric chemical processes resulting in formation of
tropospheric ozone and cloud acidification precursors. The investigation
was divided into two distinct, successive tasks. We first performed an
assessment of the ultraviolet radiation information currently used in air
quality simulation models for the determination of chemical photolysis
rates. This assessment included both the quality of existing data and
approaches available for utilizing these data to determine chemical photo-
lysis rates in the atmosphere. The resulting algorithms and data were
then used in the second task to determine photolysis rates that might
occur in the troposphere under future conditions of decreased strato-
spheric ozone. This second task involved testing the sensitivity of
chemical dynamic processes for a large number of urban data sets under
conditions of decreased stratospheric ozone and increased surface tempera-
tures.
The remainder of this section provides background information concerning
the relevance of this study to current air quality issues and concerns.
Section 2 describes our investigation of photolysis rate calculation
methods and data, and the actinic flux algorithm, data, and results used
in the second task. Sections 3 and 4 discuss the photochemical dynamic
sensitivity of the data sets to potential changes to global surface tem-
peratures and stratospheric ozone concentrations: the former describes
models, mechanisms, and input data from various city-specific data sets;
the latter discusses simulation results, with particular emphasis on
photochemical dynamics and the impacts of various degrees of change on
specific data sets. Conclusions and recommendations are presented in Sec-
tion 5. Appendixes contain city-specific input data used in the sensi-
tivity tests.
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BACKGROUND
In recent years scientists have become increasingly aware that potential
chemical modification of the the upper atmosphere by trace gases may pro-
duce an overall global warming by blocking the escape of thermal infrared
radiation. This phenomenon is commonly referred to as the Greenhouse
effect (Dickinson and Cicerone, 1986; Ramanathan et al., 1985; Wang et
al., 1986). Several climatic and atmospheric modeling studies have also
predicted that the chemical reactions of halocarbons (Cicerone et al.,
1983; Prather et al., 1984), methane (Craig and Chou, 1982) and ^0
(Weiss, 1981) will cause future decreases in overall stratospheric ozone
levels. One consequence of this decrease in stratospheric ozone levels
would be an increase in the penetration of ultraviolet radiation to the
troposphere, since stratospheric ozone is the principal attenuator of
radiation in this spectral region. In addition to resulting in a probable
increase in the incidence of skin cancer, a greater transmission of ultra-
violet radiation would augment a principal energy source responsible for
photochemical reactions in the troposphere. This, in turn, would cause an
increase in the rates of a number of photochemical reactions critical to
smog formation. The combination of possible temperature increases with an
increase in ultraviolet radiant energy might alter the energy balance of
the atmosphere in such a way that anthropogenic impacts on the strato-
sphere might again manifest in the troposphere because of stronger physi-
cal coupling between both regions (see Figure 1-1).
These potential increases in specific photochemical reaction rates,
resulting from potential increases in thermal and radiant energy, have
been largely ignored in studies of future chemical changes within the
planetary boundary layer. Enhanced photochemical reactivity could
increase the prevalence and magnitude of regional and urban ozone forma-
tion, and augment the urban contribution of acid precursors by increasing
the production capacity of oxidized species. This study involved an
initial analysis of the possible impacts of these changes. Because the
effects of projected global changes on near-surface photochemistry will
vary with the characteristics of each airshed tested, we chose to analyze
a large number of different test sets. Large numbers of data sets are
currently available only for urban areas whose compliance with the air
quality standards for ozone must be verified. Since urban photochemical
systems are the most studied, and probably the best understood, and since
their precursor loading could make them the most sensitive to potential
global changes, we chose to investigate global impacts on this type of
system first.
In such a sensitivity study, it is also necessary to formulate some under-
standing of the possible ranges of projected surface temperature and stra-
tospheric ozone changes anticipated. Our methodology was to analyze
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OJ
TJ
EXTRATERRESTRIAL
SOLAR IRRADIATION
(constant)
STRATOSPHERIC OZONE
(decreasing with CFC impact)
. 20km
2 km
1 km
UNFILTERED ULTRAVIOLET
IRRADIATION (increasing with
decreased stratospheric
ozone absorption)
PHOTOCHEMICAL SMOG ill
(Ozone increase with
higher ultraviolet
intensity)
m
FIGURE 1-1. A simple representation of the coupling of atmospheric chemical and
physical processes that could result in increased ultraviolet penetration to the
troposphere.
871 2 3
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available information, and then to devise two sets of values representing
moderate and extreme future conditions. The moderate values were selected
to be midway between future projections for the period 2010 to 2030, while
the extreme values represented high but possible conditions, especially
for later decades.
It is beyond the scope of this discussion to consider the complex pertur-
bations that may alter future surface temperatures. However, recent
efforts in global climate modeling (Dickinson and Cicerone, 1986; Wang
et al., 1986; Ramanathan et al., 1985) indicate that global warming could
increase the average temperature as much as 1 to 3 K by the year 2030.
Therefore, in the scenarios considered in this work, we used present sur-
face temperature data, and incremented those values by 2 and 5 K to
generate future case data sets.
Because a complex set of chemical and physical dynamic processes are
involved in potential future changes to mid-latitude ozone column density,
projections of concentration changes into the next century are extremely
uncertain. On the basis of chemical modeling of chlorocarbon and bromo-
carbon chemistry, Prather and coworkers (1984) projected a potential
decrease in ozone column density of more than 15 percent by the middle of
the next century. These projections appear to be supported by measure-
ments of solar-backscattering ultraviolet radiation from the Nimbus 7
satellite. In recent years, decreases of about 0.5 percent/year have been
measured, but comparisons between the Nimbus 7 and earth-based instruments
render those numbers somewhat uncertain (Kerr, 1987). For our investiga-
tion, we chose a base-case ozone column of 0.300 cm-atm for all simula-
tions. This represents approximately the monthly average at North Ameri-
can latitudes for the July and August period when most measurements in the
test data sets were performed (Iqbal, 1983). Daily weather conditions
specific to each data set are assumed to be contained in the simulation of
each base case data set. At any rate, the perturbations caused by strato-
spheric ozone depletion are dominant since over 90 percent of atmospheric
ozone is at upper levels. The moderate and extreme overhead ozone column
conditions chosen in this study were 0.25 and 0.20 cm-atm, representing
16.7 and 33.3 percent decreases in ozone for the future test period.
8 7 1 2 3 8
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SECTION 2
ASSESSMENT OF ULTRAVIOLET SPECTRAL DATA AND CALCULATION
OF TROPOSPHERIC PHOTOLYSIS RATES
This section describes the processes, methods of calculation, and uncer-
tainties associated with determination of photochemical impacts in the
lower troposphere caused by depletion of stratospheric ozone.
PHYSICAL AND CHEMICAL PROCESSES AFFECTED BY
FUTURE DEPLETION OF STRATOSPHERIC OZONE
The most direct way that depletion of stratospheric ozone could induce
greater photochemical reactivity in the lower troposphere (and possibly
cause tropospheric ozone concentrations to rise) would be through an
alteration in the magnitude of radiant energy transfer processes, i.e., a
physical-chemical coupling of the stratosphere and troposphere, as opposed
to mixing resulting from atmospheric motion. This linkage of two
generally isolated atmospheric regions (Figure 1-1) is often ignored and
we briefly describe this process next.
The light that is incident on the uppermost part of the atmosphere due to
radiant energy from the sun is referred to as extraterrestrial flux. The
calculation of all other radiant energy values for all atmospheric condi-
tions is derived from this extraterrestrial flux value. Although the
energy output of the sun is fairly constant and well known (see Iqbal,
1983), the spectral distribution of the solar constant is less well deter-
mined. As photons penetrate the atmosphere, various processes affect the
transmission of radiation to the earth's surface. The most important of
these are absorption (and re-radiation) by gases, aerosol absorption and
scattering, and Rayleigh (molecular) scattering. In this report, we
address two types of processes that affect radiative transfer:
(1) Alteration of the global temperature balance by increases in the
concentrations of trace gases that absorb and reradiate energy
at longer wavelengths.
87123f 2
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(2) Depletion of stratospheric ozone by some trace gases, allowing
greater transmission of ultraviolet energy that would have
originally been absorbed by the ozone to penetrate more deeply
into the atmosphere.
The first process has been discussed in Section 1. The second is addres-
sed in the remainder of this section.
As shown in Figure 2-1, ozone absorbs light in a number of spectral
regions (Calvert and Pitts, 1966). Of particular interest are the bands
of Huggins that occur between 300 to 350 nm. Because the ability of ozone
to absorb light increases with decreasing wavelength, ozone in the upper
atmosphere limits the transmission of ultraviolet radiation to the earth's
surface. Below 300 nm, the ability of ozone to absorb radiation increases
dramatically into the Hartley bands (200 to 300 nm), resulting in the cut-
off of short wavelength ultraviolet transmission to the earth's surface.
This cutoff is depicted as line b in Figure 2-2 (adapted from Bahe et al,
1979a). Note also that at an arbitrary point 30 km above the surface
(line c), where a large percentage of the atmosphere is below the viewer,
the ultraviolet cutoff is shifted to the shorter wavelengths. In addi-
tion, a "window" opens around 210 nm (area d), allowing extremely high-
energy light to penetrate that region. The higher wavelength side of this
"window" is defined by the falloff of ozone absorption in the Hartley
bands (Figure 2-1); the lower wavelength side results from the increased
absorption of molecular oxygen (which increases dramatically around 190
nm).
Although the depletion of stratospheric ozone needed to cause the degree
of surface solar irradiance shown in Figure 2-2 would have to be very
extreme, the figure does indicate the spectral region in which an increase
in ultraviolet irradiance due to diminished stratospheric ozone absorption
would occur. This increase in ultraviolet surface irradiation should be
manifest in the shifting of the ultraviolet cutoff a small number of nm
toward the blue end of the visible spectrum. The increase is confined to
a rather small region between 310 and 280 nm because the change depends
completely on the absorption characteristics of ozone, which is a much
poorer absorber of radiation above 310 nm. However, though the range of
the increase is small, a number of key tropospheric trace species photo-
lyze to very reactive products only upon absorption of radiation at the
edge of the ultraviolet cutoff. Therefore, even though the change in
total available radiant energy may be relatively small, because of the
highly localized nature of the absorption, the increase in certain tropo-
spheric photolysis rates would be much larger.
Photolysis of stable molecules is the major source of new radicals in
tropospheric gas-phase chemistry. In atmospheres capable of sustaining
87123f 2
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Wavelenth, A
8000
FIGURE 2-1. Ozone absorption cross section (10A = lnm). Source: Calvert
and Pitts (1966).
87095
7
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10
15
rn—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—r
«.o,A
10
13
10
12
10
11
d. "stratospheric
window" of
ultraviolet
1rradlance at
30 km above
the earth's
surface
a. Extraterrestrial
flux
b. Spectral
_ 1rradlance
at the earth's
surface
c. Spectral
irradlance
at 30 km
above the
earth's surface
I I I I I I L
150 170 190 210 230 250 270 290 310 330 350 370
Wavelength (nm)
FIGURE 2-2. Simplified representations of extraterrestrial flux and solar
1rradlance of 0 and 30 km above the earth's surface. (Adapted from Bahe
et al.t 1979a).
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even a moderate rate of photochemical reactivity, a greater production
rate for new radicals would tend to increase the initial and continued
oxidation of organic compounds, resulting in additional thermochemical
radical generation and sustained production of additional stable species
capable of more photolysis. Therefore, the increased radical mass flux
that would result from potential enhancement of some photolysis reactions
could translate into more reactive tropospheric photochemistry. The
result could be increased production of those oxidized species now regu-
lated as photochemical oxidants (urban ozone), or of other compounds
(peroxides) critical to the formation of acidic precipitation after trans-
port out of an urban area.
With this in mind, it is obvious that accurate determination of key photo-
lysis rates, especially for periods when the "radical pool" is limited
(early in the day), is critical if proper representation of the radical
balance is to be achieved in a photochemical kinetics model. As we dis-
cuss next, the most significantly affected tropospheric photolysis rates
should be those of ozone [to produce 0(*D)] and aldehydes, both well-
characterized pollutants generated during episodes of photochemical smog.
The formaldehyde emitted from automobiles and stationary sources is usu-
ally a product of incomplete combustion. Formaldehyde is also produced
chemically in the troposphere, since it is a major oxidation product of
virtually all organic molecules. The two formaldehyde photolysis reac-
tions that could be enhanced by increased ultraviolet radiation due to
depleted stratospheric ozone are
and
HCHO —- 2H- + CO ,
HCHO ^ H2 + CO .
(1)
(2)
Obviously, reaction 1 is of greater concern here because it forms highly
reactive radical products. In the atmosphere, H* reacts almost exclusiv-
ely with oxygen molecules to form the hydroperoxy radical:
H- + 02 —> H02* (3)
H02* can contribute to radical oxidation reactions in a number of signifi-
cant ways, e.g.,
H02* + NO —> N02 + 'OH , (4)
87123r 2
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which not only oxidizes NO to N02, but also produces a hydroxyl radical
that can then react with almost all organic and inorganic trace species in
the troposphere. Whitten (1983) has shown that reaction 1 is often the
main source of radicals responsible for the photochemical chain reactions
leading to urban smog. In addition, reaction 1 is more sensitive to
changes in ultraviolet radiation in the spectral region of potential
increases than is reaction 2. Hence, we consider the potential effects on
this process in some detail.
The tropospheric photolysis of ozone to electronically excited oxygen
atoms is thought to be the second most important source of the radicals
that drive smog formation:
03 —- 0(1D) + 02 . (5)
The 0(*D) radical is extremely reactive and almost always reacts in the
troposphere through one of two paths:
0(1D) + M —> 0(3P) + M , (6)
where M is 02 or N2, and
0(1D) + H20 —> 2 -OH , (7)
again producing hydroxyl radicals.
In reactive, oxidizing atmospheres, however, the role of ozone photolysis
differs from that of formaldehyde. At low levels of oxidation potential,
the excited oxygen atoms tend to accelerate smog reactions, making the
atmospheric chemistry more efficient in generating ozone from minimal pre-
cursor emissions. However, at the highest or most severe ozone levels,
the excess radicals can partially supress the ozone peak, making the pre-
cursors seem less efficient in generating ozone. Hence, the chemical
effects on specific photochemical systems could differ for formaldehyde
and ozone since these species can occur at different times during an epi-
sode of photochemical smog and produce different photochemical impacts.
In addition, because we are considering the effect of greater ultraviolet
transmission to the troposphere due to a decrease stratospheric ozone, the
resulting enhancement of irradiation to the surface should occur precisely
at the wavelengths that are optimum for tropospheric ozone absorption.
Therefore, the relative increase in photolysis rate for this process
should be larger than that for formaldehyde.
8 7 1 2 3 f 2
10
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ASSESSMENT OF EXISTING DATA, RADIATION MODELS, AND UNCERTAINTIES
IN THE CALCULATION OF TROPOSPHERIC PHOTOLYSIS RATES
Extraterrestrial Flux Data
Tropospheric photochemical kinetics models used to predict the chemical
impact of stratospheric ozone depletion require as input a measure of the
ultraviolet radiant energy in the atmosphere near the surface so that the
photolysis rates of various chemical species can be determined. The rela-
tive intensity and spectral distribution of surface radiation is affected
by numerous atmospheric radiative transfer processes throughout the day
for each location and elevation. Because the number of measurements
needed to provide such a multi-dimensional distribution of information is
prohibitive, analytical characterizations of physical radiative transfer
processes are utilized to determine these flux values for each set of
atmospheric conditions. In all cases, an extraterrestrial flux distribu-
tion is used as the initial boundary condition or energy source.
The spectral region from about 280 nm to 800 nm is of interest in the cal-
culation of atmospheric photolysis rates for photochemically active trace
species. The values for solar irradiance, especially at the high energy
end of this region, are still somewhat uncertain, though improvements have
been made to the entire data set over the last decade. The solar constant
distribution is compiled at the mean earth-sun distance, which occurs in
April and October. During other times of the year, the extraterrestrial
flux changes by as much as 3.4 percent (Demerjian et al., 1980). The work
by Demerjian and coworkers is one of the most quoted sources of extrater-
restrial flux used by tropospheric photochemists. They considered six
sources of solar irradiance measurements and eventually utilized the then
most recent values of DeLuisi (1975) in the critical region of 300 nm to
400 nm, noting a disagreement of up to ten percent for specific intervals
among the different data sets considered. These values are in 5 nm bins
at shorter wavelengths, and 10 and 20 nm bins at longer wavelengths and
are shown in Figure 2-3.
Additional information has recently become available in the form of sum-
maries by Iqbal (1983) and the World Meteorological Organization (WM0)
(1985). The pricipal differences betweem these summaries and earlier work
reside in the high energy end of the spectra; rocket-borne measurements
contributed to the earlier data and reexamination of instrument variation
now provides a somewhat different interpretation of previous results. The
recommended WM0 spectrum is shown in Figure 2-4. Bin sizes are 5 nm, with
the exception of slightly smaller bins near 280 nm. Both Figure 2-3 and
2-4 contain data from Iqbal (1983), which is based on work done at the
World Radiation Center (WRC) by Frohlich and Brusa (1981). These results
8 7 1 2 3 p 2
11
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I I I I l I I I l I I I ' I I I I I I 1 I 1 1 1 1 1 1 1 1 1 1 1 L
300 320 340 360 3S0 4O0 420 440 460 480 600 620 640 6A0 680 600 620 640 660 680 70
8
WAVELENGTH (nm)
FIGURE 2-3. Extraterrestrial flux distributions of the World Radiation
Center (Iqbal, 1983) and Demerjlan et al. (1980).
-------
CD
lO
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M
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a
o
A
A
B
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3
0 300 320 340 360 380 400 420 440 460 460 BOO S20 640 660 680 600 620 640 660 660 70S
WAVELENGTH (am)
FIGURE 2-4. Extraterrestrial flux distributions of the World Radiation
Center (Iqbal, 1983) and the World Meteorological Organization (1985).
-------
are compiled into 2 nm bins; since many of the data sets used by WMO were
similarly considered by the WRC, the data in Figure 2-4 agree quite clos-
ely. Comparison with the Demerjian distribution (Figure 2-3) indicates
that the more recent WRC and WMO values are slightly lower for wavelengths
of 300 to 400 nm, but higher for wavelengths greater that 500 nm. How-
ever, the values are generally within the stated uncertainties of about
10 percent.
For our purposes, the significant portion of the solar irradiance spectrum
is the middle ultraviolet region (approximately 280 to 340 nm). There are
two reasons for this: First, the ultraviolet region in which upper atmo-
spheric ozone causes the the short wavelength cutoff of surface irradia-
tion (depicted in Figure 2-2) will be most affected by depletion of stra-
tospheric ozone because greater transmission of short wavelength radiation
to the surface will occur. Second, the photochemical result of additional
radiant energy in the ultraviolet region is enhancement of the photolysis
reactions that produce more photochemically reactive products, generally
the radical species that contribute to the reactivity of trace gases in
the troposphere.
The extraterrestrial flux data of Demerjian et al. (1980), WRC (Iqbal,
1983) and WMO (1985) are shown for the middle ultraviolet spectral region
in Figures 2-5 and 2-6. The most important differences among these data
occur between 300 and 330 nm. The photoaction spectra of ozone [forming
0(*D)] and formaldehyde (forming 2 H* plus CO) occur in this region, with
maximums for ozone between 305 and 310 nm and for formaldehyde between 310
and 325 nm. Unfortunately, comparison of the values shown in Figures 2-5
and 2-6 shows that the area between 305 and 315 nm can vary among data
sets up to nearly 25 percent for specific intervals. As we discuss later,
the WRC data (Iqbal, 1983) was chosen for the calculations to be used in
the final simulations of our photochemical kinetics models. We felt that
the inclusion of more recent measurements would provide a more complete
basis than would be provided by the earlier summary of Demerjian and co-
workers (1980). In addition, since the correspondence between the WRC and
WMO data was usually good, we selected the WRC data for our calculations
because it was available at a higher resolution. However, we will also
utilize the Demerjian extraterrestrial flux data in a number of subsequent
calculations because comparisons with previous calculations using those
data will be useful. Both sets of data have been interpolated with a
cubic spline routine to yield 1 nm bins, preserving the original bin
energies in all cases.
Radiative Transfer Models and Actinic Flux Calculations
While irradiance generally refers to the flux (e.g., extraterrestrial)
that is incident on a flat, horizontal surface, actinic flux refers to the
87123f 2
14
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WAVELENCTH (am)
FIGURE 2-5. Extraterrestrial flux distributions of the World Radiation
Center (Iqbal, 1983) and Oemerjlan et al. (1980) for the middle
ultraviolet region.
-------
WAVELENGTH (am)
FIGURE 2-6. Extraterrestrial flux distributions of the World Radiation
Center (Iqbal, 1983) and the World Meteorological Organization (1985) for
the middle ultraviolet region.
-------
flux incident on a spherical surface. This is the "correct" flux for the
calculation of photolysis rates in the atmosphere because radiation, which
induces the photolysis of a molecule, can come from any direction. Radia-
tive transfer models determine the amount of direct (at the angle of the
solar disc) and diffuse (incident at various other angles due to scatter-
ing, reflection, and emission) radiation, and combine these data to cal-
culate actinic flux at various locations and conditions in the atmo-
sphere. As noted, the initial energy source of these calculations is the
extraterrestrial flux.
The most complex radiative transfer model to date was developed by Dave
(1972). The complete model and six simulations are described by Braslau
and Dave (1973a and b). The original version of this model was capable of
addressing ozone absorption, molecular scattering, and aerosol absorption
and scattering, and was later modified to include oxygen, water vapor, and
carbon dioxide absorption. The atmosphere was divided into 160 layers and
contained an arbitrary set of ozone and aerosol distributions. Calcula-
tions, particularly the aerosol optical calculations, were extremely time-
consuming but resulted in spectrally integrated flux values stated to be
accurate to within 0.5 percent. Subsequent uses of this complex model
have followed two paths: Peterson (1977) and Demerjian et al. (1980) used
a version of the model with 40 layers to calculate actinic flux values at
various altitudes from the earth's surface for different atmospheric con-
ditions and solar elevations. Adopting a different approach, Green et al.
(1980) and Schippnick and Green (1982) used the model results as a basis
for development of a simpler analytical characterization for middle ultra-
violet sky light.
Both approaches have yielded information and methods useful in the calcu-
lation of photolysis rates in the troposphere. The results of Demerjian
et al. (1980) and Peterson (1977), however, are in the form of tabulated
actinic fluxes for a fixed ozone column density (0.295 cm-atm), but a
variable aerosol distribution and surface albedo. Therefore, though these
results provide very useful actinic flux conditions for simulating aver-
age, present-day ozone column scenarios, Investigation of the effects of
future ozone depletion requires similar calculations at different ozone
column densities. Such calculations have not yet been performed. Also,
better and more highly resolved measurements of extraterrestrial flux and
absorption cross sections and quantum yields have now become available.
Hence, new calculations would be extremely useful in future work because
they could be done at a somewhat higher resolution than the earlier work
and would have the credibility associated with calculations performed
directly by the Dave model (as opposed to the analytical characterizations
to be discussed next).
8 7 1 2 3)- 2
17
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Characterization of upward and downward diffuse spectral irradiance by
Green et al. (1980) and Schippnick and Green (1982) allows calculation of
actinic flux in the middle ultraviolet region for a number of conditions
that are necessarily variable in the study of future stratospheric ozone
and climate change. However, it is limited because it is a characteriza-
tion of the results of a rigorous model and not of the model itself.
Therefore, the range over which it is well characterized cannot exceed the
range of the orignal model results without some loss of certainty. Fortu-
nately, the formulation was not a mere curve-fitting exercise, but
directly accounted for the effects of physical processes, as in the model
of Braslau and Dave. This approach increases confidence in its applica-
tion outside the range of the Braslau and Dave results since the descrip-
tions of the processes, as well as the results, are actually characteri-
zed.
The Schippnick and Green (1982) formulation allows calculation of downward
diffuse, direct, and upward diffuse radiation. These fluxes can be
determined at variable wavelengths (280 to 380 nm), solar zenith angles
(0 to 86 degrees), altitudes (0 to 5 km), and albedos. The calculations
depend on vertically resolved distributions of ozone and aerosol to deter-
mine optical depths for ozone absorption, molecular scattering, and aero-
sol absorption and scattering. An excellent technical explanation of the
empirical fitting parameter is found in the works of Green et al. (1980)
and Schippnick and Green (1982); we refer the reader to those publications
for further detail.
A key difference among the future scenarios investigated in this study is
the magnitude of the increase in actinic flux resulting from depletion of
stratospheric ozone. Because the Schippnick and Green model (1982) can
rapidly perform a large set of calculations, we chose it for the calcula-
tion of tropospheric actinic flux in our future scenarios of different
ozone column values. We were convinced that their formulation could
account for perturbations in the spectral actinic flux due to changes in
the ozone column in a rigorous manner, but we wanted assurance that the
absolute values of actinic flux did not deviate from the Braslau and Dave
predictions for the conditions under which these comparisons were pos-
sible. Unfortunately, not all comparisons can be this complete since the
Braslau and Dave model calculations were performed many years ago at bin
sizes larger than those currently used. However, we have obtained
unpublished, altitude-dependent flux output from the Braslau and Dave
model (Schere, 1986) as run by Peterson (1977) and Demerjian and coworkers
(1980; 40 layers) to facilitate such comparisons. Figure 2-7 compares
these flux values with those predicted by the Schippnick and Green formu-
lation for four different solar zenith angles (0, 20 50 and 78 degrees)
over the middle ultraviolet range using the standard input conditions of
8 7 1 2 3r 2
18
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Braalau & Dave
0 degrees
290 Zfifl 300 306 310 315 320 32ft 330 336 340 348 350 350 360 306 370 3TB 300 306 360 396 400 405 4LO *IB 430
WAVELENGTH BIN (nm)
FIGURE 2-7. Comparison of Braslau and Dave inodel results with Schippnick and Green calculations
for similar conditions.
-------
Demerjian et al. (1980), an ozone column density of 0.295 cm-atm, and an
albedo of 0.05. The analytical formulation duplicates the Braslau and
Dave values for the short wavelength end of the spectrum; however, a dif-
ference exists above approximately 330 nm.
Because the Schippnick and Green formulation is designed to operate only
within the spectral region bounded by 280 and 380 nm, its upper limit
occurs below the long wavelength end of the NO2 photoaction spectrum
(approximately 410 nm). Therefore, even if the Schippnick and Green for-
mulation had fit the Braslau and Dave results at the upper end of the
middle ultraviolet range, calculation of some photolysis rates, such as
JNQ2' woj^ n°t Possible. However, at the lower wavelengths the for-
mulation appears to be quite accurate in predicting absolute actinic flux
(Figure 2-8). Fortunately, this region is precisely where the effect of
stratospheric ozone depletion is expected to be prominant (Figure 2-2).
We therefore utilized the Schippnick and Green formulation to calculate
the variations in short wavelength actinic flux resulting from a changing
ozone column. However, since many other species (including NO^, NO-j
and HONO) have photoaction spectra too far into the red range for their
calculated j-values to be affected by the localized change in ultraviolet
flux due to stratospheric ozone depletion, we used the original Braslau
and Dave model as formulated by Peterson (1977) and Demerjian et al.
(1980), and recently evaluated by Jeffries and Sexton (1987) to determine
the absolute photolysis rates of these species. The Schippnick and Green
formulation could be used to determine relative changes in the longer
wavelength absorbers due to ozone column variation, but it is known in
advance of these calculations that the relative variation for even the
most sensitive species is no more than approximately 2 percent.
We noted earlier the dirth of actinic flux measurements at known condi-
tions and the resulting lack of data for verification of these actinic
flux formulations. Nonetheless, other types of data in the form of direct
measurements of specific photolysis rates are available and can be used to
test our calculations. In fact, these data provide the ultimate compari-
son, since they are measurements of precisely the values we are attempting
to calculate. We utilize these data to evaluate our radiation and
photolysis rate calculations in a following section. First, however, we
briefly discuss the additional parameters and uncertainties associated
with the actinic flux models, followed by consideration of the method and
uncertainties involved in the calculation of specific photolysis rates
from these models.
Data Requirements and Uncertainties
We have already described the available extraterrestrial flux data and the
associated uncertainty. However, these models also require information
87123r 2
20
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WAVELENGTH BIN (sm)
FIGURE 2-8. Comparison of Braslau and Dave model results with Sch'ippnick and Green calculations
for similar conditions at different zenith angles.
-------
describing processes affecting radiation transfer at different altitudes
of the atmosphere and at the earth's surface. In addition to our main
variable, the ozone column density, consideration must be given to surface
albedo, aerosol distribution, Rayleigh (molecular) scattering, and even
cloud cover. Obviously, we could not vary all of these parameters during
the present study. In addition, though these variables have been shown to
affect calculated j-values, we have no reason to assume that there will be
significant changes between present and future cases. Therefore, we
briefly discuss the variables and their effects, and provide the values
we utilized in subsequent calculations.
Surface Albedo
The albedo can be simply defined as the fraction of incident radiation
that is reflected from a surface. This definition includes the effects of
aerosol and gas molecules between the viewer and the ground. Therefore,
if one looks down from a location well above the ground, most of the
reflected radiation is actually from the gas and aerosol below the view-
point and only partly from the generally low reflection from the ground
below (Jeffries and Sexton, 1987). This is generally referred to as the
regional albedo. It should not be confused with local albedo, which is
calculated inches or feet above a surface. The difference in measurement
points may explain discrepancies between the large values determined from
satellite observations and generally smaller surface values. In their
calculations of spectral actinic flux, Demerjian et al. (1980) used a
"best estimate" surface albedo of 0.05 (290 to 400 nm), 0.06 (400 to 450
nm), 0.08 (450 to 500 nm), 0.10 (500 to 550 nm) and 0.11 (550 to 660 nm).
Their work showed that slight variations in albedo could provide small
differences in actinic flux calculations, since their calculations indi-
cate about a 2 percent increase in actinic flux for a 1 percent increase
in albedo through the short wavelength region. We used a value of 0.05
and a larger integrated average of 0.08 for the entire region when compar-
ing our results with those of Jeffries and Sexton (1987). However, local
albedo is extremely variable and dependent on land use. We used location-
specific, monthly average ground albedo (Iqbal, 1983) during the modeling
portion of this study to better define this parameter.
Aerosol Distribution
Perhaps the most difficult variables to describe are the aerosol distribu-
tion and resulting scattering and absorption optical thicknesses. The
diurnal and location-specific variations in atmospheric aerosol properties
are difficult to establish and are certainly poorly described by use of
8 7 1 2 3r 2
22
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only one average. Nevertheless, because such data are sparse we are
forced to assume a standard distribution. However, some constraints limit
the uncertainty in our application. First, the simulations performed in
this study are primarily of cities that have air pollution problems and
can thus be expected to have elevated aerosol loading due to anthropogenic
impacts. To address this condition in our calculations, we chose optical
thickness functions more typical of urban environments. In addition,
because certain optical thickness functions have already been developed to
describe different types of aerosol conditions for similar models [first
by Braslau and Dave (1973), and later by Demerjian et al. (1980) and
Schippnick and Green (1982)], we felt that these established data should
be used when possible in our present work. Therefore, we used aerosol
optical depths for Los Angeles, but from an area to the west of the hazi-
est sections of the city (Demerjian et al, 1980). Data for both areosol
scattering and extinction are shown in Table 2-1.
Molecular Scattering
Also shown in Table 2-1 are spectral data for molecular (Rayleigh)-scat-
tering normal optical thickness. These values were used by Demerjian et
al. (1980) and Green et al. (1980), and were originally derived from Penn-
dorf (1957). The treatment of sky cover in this and other models is dif-
ficult because the phenomenon is not easily or completely described.
There are no provisions for inclusion of this variable in actinic flux or
most photochemical kinetics simulation models. In application, the least
sky cover, or the minimal attenuation of solar irradiance, is generally
associated with high rates of ozone formation that occur on the episode
days that we investigated. Therefore, we assumed clear-sky conditions in
all simulations.
Altitude
Both Peterson (1977) and Demerjian et al. (1980) addressed the issue of
altitude in their calculations using the modified (40-layer) model of
Braslau and Dave (1973a and b). Schere (1986) provided copies of these
results in 10 nm bins for 10 zenith angles and 10 altitude levels from
0 to 4210 m above sea level. It is clear from these data that an accurate
assesment of the observation point is necessary to provide an accurate
basis for actinic flux calculations. Our calculations are to be utilized
in a two-cell model with the top of the lower cell defined by the mixing
height. We assume an average afternoon mixing height of 1280 m above the
surface. Therefore, our actinic flux (and j-value) calculations were per-
formed for an altitude 640 m above the local surface. Hence, slightly
87123r 2
23
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TABLE 2-1. Values of Optical Thickness for Molecular and Aerosol
Scattering, and Aerosol Extinction. Source: Demerjian et al. (1980)
Wavelength
Interval
Scattering
Aerosol
(nm)
Molecular
Aerosol
Extincti
280-285
1.590
0.201
0.236
285-290
1.470
0.202
0.237
290-295
1.361
0.203
0.238
295-300
1.265
0.204
0.239
300-305
1.178
0.205
0.239
305-310
1.098
0.206
0.240
310-315
1.025
0.206
0.240
315-320
0.958
0.207
0.241
320-325
0.896
0.209
0.242
325-330
0.839
0.210
0.242
330-335
0.788
0.211
0.243
335-340
0.739
0.211
0.243
340-345
0.694
0.212
0.244
345-350
0.653
0.213
0.244
350-355
0.617
0.214
0.245
355-360
0.582
0.215
0.245
360-365
0.548
0.216
0.246
365-370
0.517
0.217
0.247
370-375
0.489
0.217
0.247
375-380
0.462
0.218
0.248
380-385
0.438
0.219
0.248
385-390
0.415
0.219
0.248
390-395
0.393
0.220
0.249
395-400
0.373
0.221
0.249
87095 W
24
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different j-values were determined for each city, depending on the local
elevation and other factors such as local albedo. These values are dis-
cussed in a subsequent section.
Ozone Column Density
The absorption of solar irradiance by atmospheric ozone is the main vari-
able in this study. Ozone column density is defined as the thickness of a
layer that would result if all ozone directly between the surface and the
top of the atmosphere were compressed to 1 atmosphere pressure at 273 K.
In North America, a typical suirener value is 0.300 cm-atm. These data are
also given in Dobson Units (DU), which are milli-cm-atm. Therefore, the
same typical value would be 300 DU. The effect of atmospheric ozone
absorption is described by Beer's Law,
I/Iq = e"^°^3)XT(®3)/C0S(9) 1 (8)
where I/I0 is the fraction of irradiance reaching the observer, o(03) is
the ozone absorption coefficient (described next), and T(03)/cos(e) is the
"effective" ozone column density. The effective ozone column density
approximates the actual mass of ozone that sunlight passes through by
increasing the overhead ozone column (1(03)) by a factor of l/cos(e) to
account for the zenith angle (e) of the sun. We will demonstrate that
this measure of effective ozone column density can be used to unify vari-
ous measurements of irradiance or actinometry performed in different loca-
tions, as long as the overhead column and zenith angle are known. We
describe this process in greater detail and present our ozone absorption
cross-section data in a subsequent section.
CALCULATION OF PHOTOLYSIS RATES
We have shown that the Schippnick and Green (1982) characterization pro-
vides a method of calculating actinic flux that adequately represents cal-
culations of the more rigorous Braslau and Dave model. However, we must
also demonstrate that these results, regardless of which model they come
from, can be used to accurately predict atmospheric measurements. As we
have noted, the principal variable input for our photochemical kinetics
model scenarios will be the spectral actinic flux. Unfortunately, there
are very few direct measurements of spectral actinic flux at different
altitudes or locations. Often, only the downward-looking fraction is mea-
sured and little information relative to local and regional albedo, aero-
sol optical depths, or even ozone column density is given. Such measure-
ments are only now becomming available at the resolution necessary to
characterize the conditional dependencies of actinic flux and calculate
87 1 23r 2
25
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local photolysis rates. Collection of this type of data should be encour-
aged since it will provide the basic information needed to directly verify
and improve the calculations of large models (Braslau and Dave) and anal-
ytical characterizations (Schippnick and Greene).
The process of chemical actinometry is a direct measurement of the effects
of actinic flux. In such an experiment the photolysis rate of a chemical
species (photolyzing through a specific channel) is determined by direct
measurement of changes in concentrations of the initial reactant or of
products formed through photolysis. For our purposes, such measurements
(given accurate characterization of the measurement environment) are
extremely useful since our ultimate goal is to be able to calculate these
j-values for varying ozone column conditions. Therefore, where possible,
we have compared these measured j-values with our calculated photolysis
rates. The calculated rates are based on the actinic flux predicted for
the specific conditions at the time of the actinometry experiment. As
background to a comparison of our results with measured j-values, we
briefly discuss calculation methods and associated data uncertainties.
Calculation of J-values and Associated Uncertainties
The photolysis rate (j-value) of a specific molecular process is defined
at any given time by the integral of the triple product, Ia$, over the
wavelength interval of interest,
xmax
j = I(x)o(x)®(x)dx (9)
x .
mm
where I is the actinic flux, a is the molecular absorption cross section
and 9 is the quantum yield for a specific photolysis process (n). From
this simple formulation, it is apparent that uncertainties in j-value cal-
culations result from two sources: (1) the measure of spectral actinic
flux and its variation with time and conditions, and (2) the uncertainties
associated with the experimental determination of the absorption cross
section and quantum yields. The irradiance calculations have been dis-
cussed; we now concern ourselves with the remaining uncertainties inherent
in the j-value calculations.
In the application of most photochemical kinetics models to the tropo-
sphere, the rate of NO2 photolysis (Jn02^ *
no2 NO + 0 , (10)
8 7 1 2 3 j" 2
26
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is used as an indicator of the amount of light energy available at the
time of day and conditions simulated. However, N0£ absorbs light and
photolyzes at longer wavelengths compared to the photoreceptors (ozone and
aldehydes) considered significant in this investigation. It is well known
that the spectral distribution of surface actinic flux changes with solar
elevation; therefore, the photolysis rates of the species that absorb pri-
marily at shorter wavelengths will not linearly follow the jNQ2 value.
The reason for this is apparent from Figure 2-9, which shows surface mea-
surements of spectral irradiance in North Carolina (Jeffries, 1986) for
zenith angles of approximately 80, 65 and 20 degrees. Two points can be
made from these plots. First, the magnitude of these three traces
increases by more than a factor of 10 between each curve as spectra from
zenith angle decrease. Second, at larger zenith angles and increasing
atmospheric optical thickness, the effect of increased ozone absorption
(compare with Figure 2-1) is seen in the selective depletion of radiation
at the ultraviolet cutoff (below 300 nm) and the Bands of Chappuis (cen-
tered at 600 nm). Therefore, though the jNQ2 value can be used to track
the relative amount of energy available for photolysis throughout the day,
a second function representing the changing spectral distribution is also
included so that the absolute amount of energy available to species that
absorb in other spectral regions can be determined. For this function, we
use the zenith angle of the solar disk as a variable indicator. In prac-
tical applications of this method, nonlinear sets of ratios are multiplied
by the experimental j^ value for a given time of day to determine the
absolute j-values of other species at that time of day and zenith angle.
In this study, we are also interested in the effect of decreased strato-
spheric ozone (increased ultraviolet actinic flux) on the j-values that
depend on shorter wavelength radiation. Thus, another variable is intro-
duced, that of ozone column density. Consideration of this variable
results in a set of zenith-angle-dependent j-values for each different
column density. Fortunately, as discussed earlier, the region of radia-
tion change is confined to a small interval in the middle ultraviolet
range (Figure 2-2), causing changes to only the j-values based on short
wavelength ultraviolet radiation. The jNQ2 va1ue» f°r instance, is very
similar for all ozone columns considered in this study.
The following discussion addresses uncertainties associated with the cal-
culation of j-values to assess the associated error in j-value determina-
tions. We first investigate uncertainties in conditions used in our pre-
sent-day base-case scenarios (0.295 and 0.300 cm-atm ozone column density)
using the results of a recent evaluation by Jeffries and Sexton (1987) to
provide a set of independent calculations for comparison. We have inten-
tionally attempted to use the identical actinic flux data of Jeffries and
Sexton [who used values from Peterson (1977)] to focus our investigation
87 1 2 3r 2
27
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CD
O
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U1
WAVELENGTH (am)
FIGURE 2-9. Surface irradiance data for zenith angles of approximately
20, 65, and 80 degrees measured at ground level in rural North Carolina.
(Source: Jeffries, 1986).
-------
on the remaining quantum yield and absorption cross-section variables.
Later in this section, we briefly investigate the effect of bin size on
calculations, and provide our best estimate of present-day and future
j-values based on results obtained with the WRC (Iqbal, 1983) extraterres-
trial flux data, the Schippnick and Greene (1982) actinic flux formula-
tion, and varying ozone column conditions.
Specific j-values are usually calculated using a standard set of actinic
flux distributions for a range of zenith angles. In this comparison, both
sets of calculations use the clear-sky, ground-level actinic flux values
calculated by Peterson (1977), with altitude corrections to 640 m as pre-
scribed by Demerjian, Schere, and Peterson (1980). In most of their cal-
culations, Jeffries and Sexton (1987) instituted an albedo correction,
resulting in an integral albedo of 0.08. We use the aerosol distribution,
surface albedo (0.05), and ozone column density (0.295 cm-atm) of
Demerjian and coworkers (1980). Therefore, the values of actinic flux and
the resulting j-values will vary slightly between investigations because
Jeffries and Sexton usually corrected to an integral albedo of 0.08 and
performed their numerical integration of j-values with 5 and 10 nm bins.
It has been our practice to use either 1 or 2 nm bin sizes in all j-value
calculations. Later in this section we present results using the WRC
extraterrestrial flux data (Iqbal, 1983), which are available in 2 nm bin
sizes. To utilize the actinic flux of Demerjian and coworkers (1980), we
have interpolated the 5 and 10 nm bins to 1 nm values, verifying at all
times that the sum of the energy within five 1 nm bins is equal to the
energy in the original 5 nm bin. The spectral distributions at two zenith
angles (20 and 60 degrees) for 1 nm and 5 nm bins are shown in Figure
2-10.
NO? photolysis rates were calculated using the absorption cross sections
and quantum yields listed in Table 2-2. In this case (only), Jeffries and
Sexton present calculations for a surface actinic flux data set with an
albedo of 0.05, the value of our calculations. A comparison of results is
given in Table 2-3*.
* Jeffries and Sexton values are designated UNC for University of North
Carolina.
87 1 2 31" 2
29
-------
Aclinic Flux for 20 and 60 Degree ZAs
(Sauncv. Q«m»r(fan ti, 1960)
WM(«rgH) (wnj
FIGURE 2-10. Actinic f]ux for 20 and 60 degree solar zenith angles in bin
sizes of 1 and 5 nm. Areas under curves are equal. (Source: Demerjian
et al., 1980).
30
-------
Table 2-2. Absorption cross sections and quantum yields for N02
photolysis:
N02 ----+ NO + 0
Cross Section
Cross Section
Wavelength
(cm2/molec.)
Quantum
Wavelength
(cm2/molec.)
Quantum
(nm)
(x l.E+20)
Yield
(nm)
(x l.E+20)
Yield
280
5.54
0.984
315
22.50
0.968
281
5.58
0.984
316
21.31
0.967
282
5.36
0.984
317
23.29
0.966
283
5.36
0.984
318
24.81
0.966
284
6.25
0.984
319
23.14
0.965
285
6.99
0.984
320
25.37
0.964
286
7.29
0.984
321
26.53
0.963
287
7.37
0.984
322
26.49
0.962
288
7.66
0.984
323
27.68
0.962
289
7.89
0.984
324
26.75
0.961
290
8.18
0.984
325
27.86
0.960
291
9.90
0.984
326
28.79
0.959
292
9.37
0.984
327
29.09
0.958
293
9.75
0.984
328
30.77
0.958
294
9.48
0.984
329
29.98
0.957
295
9.68
0.984
330
29.87
0.956
296
9.30
0.983
331
30.50
0.955
297
12.17
0.982
332
30.05
0.954
298
11.72
0.982
333
37.27
0.954
299
12.57
0.981
334
29.80
0.953
300
11.72
0.980
335
34.52
0.952
301
12.28
0.980
336
35.08
0.951
302
13.87
0.978
337
34.63
0.950
303
15.92
0.978
338
34.78
0.950
304
15.96
0.977
339
39.88
0.949
305
16.56
0.976
340
38.80
0.948
306
15.81
0.975
341
41.66
0.947
307
16.33
0.974
342
38.32
0.946
308
16.18
0.973
343
35.45
0.946
309
18.38
0.973
344
40.21
0.945
310
17.56
0.972
345
40.70
0.944
311
18.78
0.971
346
42.93
0.943
312
19.61
0.970
347
42.78
0.942
313
20.35
0.970
348
48.21
0.942
314
19.42
0.969
349
46.12
0.941
(Continued)
31
-------
Table 2-2 (Concluded)
N02 NO + 0
Wavelength
(nm)
Cross Section
(cm2/molec.)
(x l.E+20)
Quantum
Yield
Wavelength
(nm)
Cross Section
(cm2/molec.)
(x l.E+20)
Quantum
Yield
350
40.99
0.940
385
59.41
0.770
351
45.20
0.939
386
53.20
0.840
352
44.38
0.938
387
56.02
0.750
353
39.88
0.938
388
59.78
0.810
354
50.40
0.937
389
60.23
0.780
355
51.30
0.936
390
60.01
0.800
356
46.05
0.935
391
58.29
0.880
357
55.80
0.934
392
60.49
0.840
358
50.37
0.934
393
54.54
0.900
359
45.53
0.933
394
55.42
0.900
360
45.13
0.932
395
58.89
0.840
361
53.87
0.931
396
61.45
0.830
362
50.40
0.930
397
56.65
0.820
363
51.23
0.930
398
64.06
0.770
364
48.74
0.929
399
56.03
0.780
365
57.81
0.928
•400
67.59
0.680
366
53.98
0.912
401
65.25
0.650
367
51.86
0.896
402
57.10
0.620
368
53.42
0.881
403
51.04
0.570
369
51.82
0.865
404
60.67
0.420
370
54.20
0.849
405
63.17
0.320
371
52.12
0.833
406
53.90
0.330
372
59.81
0.817
407
47.28
0.250
373
55.02
0.802
408
62.61
0.200
374
52.12
0.786
409
59.00
0.190
375
53.53
0.770
410
57.73
0.150
376
62.35
0.780
411
58.78
0.100
377
56.69
0.920
412
53.65
0.090
378
51.74
0.820
413
70.04
0.080
379
54.68
0.870
414
59.41
0.080
380
59.86
0.900
415
60.41
0.070
381
56.62
0.810
416
48.47
0.060
382
56.36
0.700
417
53.12
0.050
383
53.72
0.680
418
55.17
0.040
384
59.67
0.700
419
52.79
0.030
420
57.72
0.020
32
-------
TABLE 2-3. Results of jNq2
Calculations (min ).
Zenith
Angle
(deq)
Albedo
= 0.05
SAI
UNC
0
0.485
0.503
10
0.481
0.499
20
0.469
0.487
30
0.448
0.464
40
0.415
0.430
50
0.366
0.379
60
0.295
0.306
70
0.194
0.202
78
0.095
0.099
86
0.020
0.019
Our results are 2 to 4 percent lower than those of UNC. In both cases,
the data were taken from the NASA (DeMore, 1985) review; however, the UNC
calculations are based on 5 nm bin averages of quantum yield and cross
section, whereas our calculations were performed at 1 nm. The resulting
photoaction spectra (the product, lot, versus wavelength) are shown in
Figure 2-11 for a 20° zenith angle. Our calculations using 1 nm and 5 nm
bins show that the variation in methodologies causes these minor dif-
ferences. Such differences in jNQ2 are not significant and are certainly
bounded by the uncertainty of the experimental quantum yield and absorp-
tion cross-section data. On the other hand, this variation does indicate
that some error due to lack of resolution can develop, even for a rather
wide and relatively featureless photoaction spectrum such as that of
N02. As we will see later in this section, uncertainties associated with
bin size can grow if conditions are less favorable.
Because the photoaction spectra for formaldehyde, acetaldehyde, and ozone
[to 0(^)1 occur at short wavelengths, where the actinic flux can be
enhanced by decreases in stratospheric ozone, we focus on the following
four processes:
JHCH0r:
HCHO 2H- + CO (1)
87 1 2 3r 2
33
-------
Photoaction Spectra for N02
(at Zanftti Angt* of 20 dagiMi}
WMtoigth (nm)
FIGURE 2-11. Photoactlon spectra for NO2 using 1 and 5 nm bins.
34
-------
JHCHOs:
HCHO —- H2 + CO
(2)
CH3CHO
H- + CO + CH300-
(11)
%D:
0
3
0(1D) + 02
(5)
The absorption cross sections and quantum yields used for formaldehyde,
acetaldehyde (ALD2), and ozone are presented in Tables 2-4 through 2-7.
The absolute, zenith-angle-dependent photolysis rates (calculated as
above) and the UNC values (calculated with A=0.08) are compared in Table
2-8 for Peterson's (1977) actinic flux corrected to 640 m (Demerjian et
al., 1980).
A comparison of the formaldehyde photolysis rates given in Table 2-8 with
those determined by UNC indicates the degree of uncertainty in many of the
published absorption cross-section and quantum yield data (and also points
out the need for atmospheric chemical actinometry and smog chamber model-
ing to verify the chosen rates). Calculations indicate that our j'ncHOr
and j'hchOs rates are approximately 85 and 65 percent of the UNC-determined
values, and that a significant portion of these differences is due to the
choice of quantum yield and absorption cross-section data. Our quantum
yield data for both formaldehyde photolysis channels are 1 nm values that
were fit by Calvert (1980) using his data and that of Moortgat and co-
workers (1978, 1979). Ten nm averages of these data are approximately
0 to 10 percent lower than the 10 nm values used by UNC.
Our two major sources of absorption cross-section data for formaldehyde
are Bass (1980) and Moortgat (1986). We have communicated with these
researchers and obtained their data. As shown in Figure 2-12, their
results differ by more than 30 percent, especially at the longer wave-
length region. After considering both data sets, we used the 0.05 nm
resolved data of Bass to derive 1 nm bin averages. UNC utilized 10 nm bin
values given by NASA (DeMore, 1985), which were determined by averaging
the two sets of absorption cross-section data. Figure 2-13 shows the
photoaction spectra for both formaldehyde photolysis channels using our
1 nm values, the UNC 10 nm bins, and a 5 nm light source (the amount of
light was equal for both photoaction spectra). The differences in
j-values noted above result almost completely from the differences in
8 7 1 2 3 Y~ 2
35
-------
e 2
:len<
nm)
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
Absorption cross sections and quantum yields for formaldehyde
photolysis to radical products:
HCH0 2H- + CO
Cross Section
(cm2/molec.)
(x l.E+20)
Quantum
Yield
Wavelength
(nm)
Cross Section
(cm2/molec.)
(x l.E+20)
Quantum
Yield
2.34
0.560
310
1.03
0.760
1.65
0.580
311
0.81
0.750
0.76
0.600
312
1.49
0.740
0.46
0.620
313
1.55
0.730
3.93
0.630
314
3.99
0.720
3.46
0.650
315
2.88
0.700
2.32
0.670
316
2.79
0.690
0.95
0.680
317
3.59
0.670
2.32
0.700
318
1.65
0.650
2.50
0.710
319
0.73
0.630
1.43
0.720
320
1.71
0.610
1.32
0.730
321
1.32
0.590
0.66
0.750
322
0.43
0.570
5.22
0.760
323
0.60
0.540
4.30
0.760
324
0.75
0.510
3.21
0.770
325
2.19
0.490
1.59
0.780
326
3.44
0.460
1.96
0.790
327
1.75
0.430
3.66
0.790
328
1.01
0.390
1.55
0.790
329
3.03
0.360
0.72
0.800
330
1.96
0.330
1.51
0.800
331
0.79
0.290
0.74
0.800
332
0.32
0.250
4.35
0.800
333
0.15
0.210
4.79
0.800
334
0.17
0.170
4.94
0.790
335
0.02
0.130
3.02
0.790
336
0.17
0.083
1.16
0.790
337
0.32
0.038
2.18
0.780
338
1.93
0.000
2.25
0.770
339
2.15
0.000
340
1.07
0.000
36
-------
e 2-
lenc
nm)
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
Absorption cross sections and quantum yields for formaldehyde
photolysis to stable products:
HCH0 CO + H2
Cross Section Cross Section
(cm2/molec.) Quantum Wavelength (cm2/molec.) Quantum
(x l.E+20)
Yield
(nm)
(x l.E+20)
Yield
2.34
0.440
320
1.71
0.390
1.65
0.420
321
1.32
0.410
0.76
0.400
322
0.43
0.430
0.46
0.380
323
0.60
0.460
3.93
0.370
324
0.75
0.490
3.46
0.350
325
2.19
0.510
2.32
0.330
326
3.44
0.540
0.95
0.320
327
1.75
0.550
2.32
0.300
328
1.01
0.570
2.50
0.290
329
3.03
0.580
1.43
0.280
330
1.96
0.590
1.32
0.270
331
0.79
0.600
0.66
0.250
332
0.32
0.610
5.22
0.240
333
0.15
0.620
4.30
0.240
334
0.17
0.620
3.21
0.230
335
0.02
0.620
1.59
0.220
336
0.17
0.620
1.96
0.210
337
0.32
0.620
3.66
0.210
338
1.93
0.610
1.55
0.210
339
2.15
0.610
0.72
0.200
340
1.07
0.600
1.51
0.200
341
0.31
0.590
0.74
0.200
342
0.94
0.570
4.35
0.200
343
1.37
0.560
4.79
0.200
344
0.57
0.540
4.94
0.210
345
0.12
0.520
3.02
0.210
346
0.04
0.500
1.16
0.210
347
0.04
0.470
2.18
0.220
348
0.07
0.450
2.25
0.230
349
0.03
0.420
1.03
0.240
350
0.03
0.390
0.81
0.250
351
0.09
0.360
1.49
0.260
352
0.90
0.330
1.55
0.270
353
1.17
0.300
3.99
0.280
354
0.72
0.260
2.88
0.300
355
0.26
0.230
2.79
0.310
356
0.05
0.200
3.59
0.330
357
0.03
0.160
1.65
0.350
358
0.04
0.130
0.73
0.370
359
0.03
0.100
37
-------
e 2
lerv
nm)
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
Absorption cross sections and quantum yields for ozone
photolysis to 0(iD):
03 O^D) + 02
Cross Section Cross Section
(cm2/molec.) Quantum Wavelength (cm2/molec.) Quantum
(x l.E+20)
Yield
(nm)
(x l.E+20)
Yield
397.00
0.900
300
39.20
0.900
360.00
0.900
301
34.40
0.900
324.00
0.900
302
30.30
0.900
301.00
0.900
303
26.30
0.900
273.00
0.900
304
23.50
0.900
244.00
0.900
305
20.20
0.884
221.00
0.900
306
18.00
0.848
201.00
0.900
307
15.60
0.800
176.00
0.900
308
13.60
0.740
158.00
0.900
309
12.30
0.660
141.00
0.900
310
10.30
0.560
126.00
0.900
311
9.27
0.450
110.00
0.900
312
8.00
0.340
98.90
0.900
313
6.92
0.250
86.20
0.900
314
6.29
0.180
76.70
0.900
315
5.22
0.120
66.40
0.900
316
4.78
0.080
58.80
0.900
317
4.04
0.050
51.00
0.900
318
3.72
0.020
45.20
0.900
319
2.91
0.000
38
-------
e 2-
lenc
nm)
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
Absorption cross sections and quantum yields for acetaldehyde
photolysis to radical products:
ALD2 H- + CO + CH3
Cross Section Cross Section
(cm2/molec.) Quantum Wavelength (cm2/molec.) Quantum
(x l.E+20)
Yield
(nm)
(x l.E+20)
Yield
4.50
0.580
305
3.40
0.370
4.54
0.575
306
3.27
0.350
4.58
0.570
307
3.14
0.330
4.62
0.565
308
3.01
0.310
4.66
0.560
309
2.88
0.290
4.70
0.555
310
2.75
0.270
4.74
0.550
311
2.62
0.250
4.78
0.545
312
2.49
0.230
4.82
0.540
313
2.36
0.210
4.86
0.535
314
2.23
0.190
4.90
0.530
315
2.10
0.170
4.82
0.520
316
2.04
0.156
4.74
0.510
317
1.98
0.142
4.66
0.500
318
1.92
0.128
4.58
0.490
319
1.86
0.114
4.50
0.480
320
1.80
0.100
4.46
0.470
321
1.66
0.088
4.42
0.460
322
1.52
0.076
4.38
0.450
323
1.38
0.064
4.34
0.440
324
1.24
0.052
4.30
0.430
325
1.10
0.040
4.12
0.418
326
1.18
0.032
3.94
0.406
327
0.94
0.024
3.76
0.394
328
0.85
0.016
3.58
0.382
329
0.77
0.008
330
0.69
0.000
39
-------
Table 2-8.
SAI and UNC j-value calculations for Peterson (1977) actinic flux
corrected to 640 m (Demerjlan et al., 1980) and slightly different albedos.
Zenith
Angle
SAI absolute photolysis rates
(xlOOO, min , albedo = 0.05)
UNC absolute photolysis rates
(xlOOO, min , albedo = 0.08)
(deg)
HCHOr
HCHOs
01D
ALD2
HCHOr
HCHOs
01D
ALD2
0
1.811
2.164
2.770
0.398
2.179
3.391
2.715
0.347
10
1.785
2.138
2.691
0.390
2.141
3.353
2.620
0.338
20
1.705
2.055
2.440
0.365
2.036
3.237
2.362
0.314
30
1.556
1.929
2.023
0.322
1.858
3.032
1.962
0.275
40
1.339
1.730
1.532
0.260
1.599
2.724
1.463
0.222
50
1.062
1.457
1.011
0.192
1.272
2.304
0.944
0.161
60
0.722
1.095
0.503
0.117
0.873
1.732
0.462
0.096
70
0.366
0.644
0.156
0.050
0.448
1.034
0.140
0.041
78
0.138
0.284
0.036
0.016
0.172
0.466
0.030
0.012
86
0.020
0.055
0.003
0.002
0.043
0.127
0.003
0.002
87095 5
-------
TiT
Wovfltngtr* nm
*700 MOO *900 3000 3100 MOO 3300 1 3400
WAVELENGTH, A
FIGURE 2-12. Comparison of absorption cross sections for formaldehyde
Moortgat (top) and Bass (bottom).
41
-------
Phoioaclion Speciro HCHOs
tw)
Photoaction Spectra HCHOr
* in >*
FIGURE 2-13, Photoaction spectra for formaldehyde to stable
products (top) and formaldehyde to radicals (bottom) using the
10 rim bins of NASA (DeWore, 1985) and the 1 rim bins of Bass (1980).
42
-------
quantum yield and absorption cross-section data, though a slight error can
also be attributed to the larger bin size used by UNC. Also, since the
significant differences between the Bass (1980) and Moortgat (1986) cross-
section data are found mainly in the longer wavelength regions, larger
variation for j^cHOs occur because that is a longer wavelength process.
Our determination of Jqjq is approximately 5 percent higher than that of
UNC, again resulting from the use of slightly different data sources. Our
absorption cross-section data were calculated by obtaining 1 nm averages
of high-resolution data provided by Dr. Arnold Bass of the National Bureau
of Standards (1986). Quantum yield data were obtained from Atkinson and
Lloyd (1984). The j'q^q photoaction spectra occur over a smaller region
and have fewer features than do the formaldehyde spectra. Also, there is
less uncertainty currently associated with these cross-section data. This
is reflected in the better correlation between j'qjq values shown in Table
2-8. On the other hand, acetaldehyde j-values differ significantly from
those of UNC (our values are approximately 20 percent larger). This again
indicates the range of variability in data sets. Our JALD2r va1ues were
derived from the quantum yields and absorption cross sections reported in
the latest CODATA review (Baulch et al., 1984). UNC used values from Car-
ter (1986), who utilized the quantum yields from Atkinson and Lloyd (1984)
and absorption cross sections from Calvert and Pitts (1966). Figure 2-14
shows the differences in photoaction spectra resulting from these dif-
ferent values.
These photolysis rates, namely JncHOr' J'HCHOs* J'oiD and JALD2* represent
the important short-wavelength tropospheric photolysis reactions. Each
process responds somewhat differently to diurnal changes in solar spectra
(as represented by changes in zenith angle), depending on the proximity of
their photoaction spectra to the more highly attenuated blue side of the
solar spectrum. Recalling the differences in solar irradiance shown in
Figure 2-9, Figure 2-15 shows the differences in the relationship of these
short wavelength j-values to at varying zenith angles. Figure 2-16
shows photoaction spectra calculated for jqjq and j^02* at so^ar zenith
angles of 20 and 60 degrees (for the solar spectra shown in Figure
2-10). While jNQ2 diminishes by only 37 percent, jg^ decreases by over
80 percent because a large fraction of the higher energy radiation needed
for O^D) production (below 300 nm) is not available at zenith angles of
60 degrees due to the increases in atmospheric optical thickness and
effective ozone column density with zenith angle.
In addition to the determination of these values, we undertook a brief
investigation of the bin width needed to accurately determine the j-value
through numerical integration methods. The appropriate bin width is
usually determined by the presence of fine structure in one or more of the
functions whose product is being integrated. For the species considered
87123p 2
43
-------
Photoaction Specira ALD2r
(at Zenttti Angle of 20 dagnm)
Wavelength (nm)
FIGURE 2-14. Photoaction spectra for acetaldehyde using 1 and 5 nm bins.
44
-------
Relative j-value Curves
(Lorgast |—wlu* (ZA"0) Equal to 1.0)
~ N02
HCHOr
Z«nHh Anal* (i
0 HCHOs
01D
ALD2
FIGURE 2-15. Comparison of realative j-value curve shapes with respect to
solar zenith angle for the five major photolytic species.
45
-------
Photoaction Spectra for 03 and N02
(at ZA-20 aid ZA-60)
280 300 320 540 MO
Wavelength (iwn)
380
400
420
FIGURE 2-16. Comparison of photoactlon spectra for jNQ2 and JoiD ^or
and 60 degree solar zenith angles.
45
-------
here, the finest structure occurs in the absorption cross-section data,
though some structure is also seen in the actinic flux data. Both the
quantum yield and actinic flux data, however, have been less highly
resolved than the cross sections (which are usually available in fractions
of nm bins), though it is assumed that their functions should be somewhat
smoother. Of the photoaction spectra shown thus far, the formaldehyde
curves had more distinct features, occurring irregularly at approximately
4 or 5 nm intervals. The lack of resolution of these features during
multiplication by the actinic flux and quantum yield data in each specific
bin may result in averaging errors during the numerical integration. The
j'oid» JALD2' an<* JN02 calculations should be less prone to this type of
error because their absorption cross sections are somewhat smoother func-
tions. Therefore, we will consider the formaldehyde calculations here as
an estimate of the largest potential error. Figures 2-17 and 2-18 compare
the photoaction spectra of 1 nm with that of other bin sizes for both
formaldehyde photolysis channels. The actinic flux used was that shown
for a 20° zenith angle in Figure 2-10. The calculated values of both
formaldehyde photolysis rates are shown in Table 2-9 for various bin sizes
and 20 and 60 degree zenith angles.
As we discussed previously, our calculations of j-values for photochemical
kinetics modeling of various urban areas (addressed later in this report)
were performed using the more resolved extraterrestrial flux data of WRC
(Iqbal, 1983). In addition, the Schippnick and Green (1982) algorithm was
used to calculate spectral actinic flux for the different urban locations
and altitudes (ground-level plus 640 m). The optical depth data given in
Table 2-1 were used for the different extinction coefficients. Because
these conditions differ somewhat from those used in the comparison and
error assessment, Table 2-10 presents results for ozone column densities
of 0.300, 0.250, and 0.200 cm-atm for a location at sea level.
The uncertainty in these values and other values calculated for locations
of higher elevation develops primarily because of uncertainty in the three
variables needed to determine photolysis rates, namely, actinic flux,
absorption cross section, and quantum yield. For ozone photolysis to
O^D), the absorption cross-section data appear to be within about 10 per-
cent agreement (Baulch et al., 1984), while the quantum yield data are
well-characterized but lacking for some critical regions. The uncertainty
could be as high as 20 percent in a few specific areas. The greatest
uncertainty associated with the calculation of j'qiq is the variability of
actinic flux in the narrow, high-energy region of the surface solar spec-
trum where the ozone photoaction spectrum exists. We discussed previously
an uncertainty in the extraterrestrial flux data of as high as 25 percent
in some bins within this region. Because it is located at the surface
ultraviolet cutoff, this j-value is also the most sensitive to changes in
87123y 2
47
-------
Photooction Spectra HCHOr
fr-0
Photooction Spectra HCHOr
Pt*o4ooctlon Spectra HCHOr
FIGURE 2-17. Comparison of 1 nm photoaction spectra for j^gr
spectra calculated with 10 (top), 5 (middle), and 1 nm (bottom) bins.
43
-------
Photoaction Spectre HCHOs
«* »—* *#.¦><• **—)
Ma
Photoaction Spectra HCHOs
(* tagh o» TO *»<*•)
Photoaction Spectra HCHOs
8709S
FIGURE 2-18. Comparison of 1 nm photoaction spectra for JHCHOs w1th
spectra calculated with 10 (top), 5 (middle), and 1 nm (bottom) bins.
49
-------
TABLE 2-9. J-values (xlOOO, min ) calculated for
formaldehyde phototlysis at different bin sizes (albedo
= 0.05, altitude=0, ozone column = 0.300 cm-atm).
Bin Zenith Angle = 20 Zenith Angle = 60
JHCHOr JHCHOs JHCHOr JHCHOs
1
1.470
1.803
0.592
0.905
2
1.471
1.801
0.592
0.903
5
1.475
1.872
0.601
0.947
10
1.555
1.700
0.632
0.842
Relative
Error (percent):
1
0.000
0.000
0.000
0.000
2
0.052
-0.110
0.039
-0.121
5
0.354
3.828
1.471
4.645
10
5.810
-5.719
6.830
-6.970
87095
50
-------
Table 2-10. Results of j-value calculations WRC extraterrestrial flux (Iqbal, 1983) and Schippnlck
and Greene actinic flux formulation. Albedo 1s 0.08 and altitude 1s 640 m.
Absolute photolysis rates at 640 m
(xlOOO, m1n , albedo = 0.08)
Zenith
0.300 i
cm-atm
0.250 <
cm-atm
0.200 i
cm-atm
Angle
(deg)
HCHOr
HCHOs
01D
ALD2
HCHOr
HCHOs
01D
ALD2
HCHOr
HCHOs
01D
ALD2
0
2.06
2.54
2.45
0.448
2.22
2.61
3.25
0.521
2.43
2.68
4.49
0.621
10
2.02
2.51
2.37
0.437
2.19
2.58
3.14
0.509
2.39
2.65
4.35
0.608
20
1.94
2.44
2.14
0.410
2.10
2.51
2.86
0.481
2.30
2.58
3.97
0.573
30
1.78
2.30
1.78
0.364
1.93
2.37
2.39
0.427
2.12
2.44
3.36
0.512
40
1.56
2.10
1.33
0.303
1.70
2.16
1.82
0.356
1.87
2.23
2.58
0.430
50
1.28
1.82
0.860
0.228
1.40
1.88
1.20
0.272
1.55
1.94
1.75
0.331
60
0.920
1.42
0.432
0.146
1.01
1.47
0.625
0.176
1.13
1.52
0.947
0.217
70
0.506
0.888
0.139
0.067
0.562
0.920
0.213
0.083
0.633
0.956
0.344
0.105
78
0.202
0.409
0.033
0.023
0.227
0.425
0.053
0.028
0.258
0.444
0.090
0.037
86
0.028
0.071
0.003
0.003
0.032
0.074
0.005
0.003
0.036
0.077
0.009
0.004
87095 6
-------
diurnal variables that depend on zenith angle (and atmospheric optical
thickness). Therefore, assuming 10, 15 and 20 percent associated overall
errors, respectively, for cross section, quantum yield, and actinic flux
data, the root mean square error is slightly greater than 50 percent, with
higher values occurring at very large zenith angles because of the
increasing uncertainty of actinic flux calculations for this region.
Calculation of formaldehyde j-values benefits from the fact that these two
processes occur at longer wavelengths than does the 0(*D)-forming channel
of ozone photolysis. This provides more certain extraterrestrial and
actinic flux values, and the j-values are less sensitive to changes in
zenith angle. Unfortunately, because they have been investigated less
thoroughly, the other variables are not as certain as the ozone varia-
bles. We have discussed the error associated with absorption cross-sec-
tion and quantum yield data. Our calculations show that the use of dif-
ferent, equally acceptable quantum yield data with typical actinic flux
and cross section data gives results that differ by about 10 percent. In
addition, the available absorption cross-section data differ by 30 percent
over large spectral regions. If we assign an arbitrary actinic flux error
of 10 percent and assume that calculations are performed in small enough
bins to minimize averaging error (see below), the root mean square error
is about 60 percent.
Acetaldehyde and higher formaldehydes have less fine structure in their
absorption cross sections, but the acetaldehyde absorption cross sections
are far less certain than the formaldehyde and ozone values. In addition,
the quantum yield data are sparse and the photoaction spectrum occurs in
the same region as that of ozone (forming 0(*D)), leading to greater
uncertainty than occurs in similar formaldehyde calculations. Because of
these conditions, it is difficult to place a numerical value on the error
bands of • We arbitrarily assume an associated error 100 percent for
calculation of j/\|_Q2 f°r diurnal conditions, though less error should
be associated with values calculated at lower zenith angles. Fortunately,
the rate of acetaldehyde photolysis is significantly slower than that of
formaldehyde, and far less acetaldehyde is produced during photochemical
reactions in the atmosphere.
There is also a smaller error associated with the methodology utilized in
the calculation of j-values. It is our suggestion that 10 nm bins not be
used in the calculation of j-values unless absolutely necessary because of
minimal data availability. The resolution of extraterrestrial flux in 2
nm bins, combined with absorption cross-section data of even finer resolu-
tion, necessitates the calculation of j-values at intervals of that size
or smaller. We have shown that calculations in 5 nm bins for formaldehyde
(which has a distinct fine structure at a peak width of about 2 nm) lose
17 1 2 3r 2
52
-------
accuracy when compared with 2 nm calculations. Therefore, we recommend
the calculation of photolysis rates at 2 nm intervals or less to ensure
that averaging of higher resolution data does not produce errors.
Comparison of Model Calculations with Direct Measurements
The simulations discussed in Section 3 (modeling) attempt to ascertain the
relative changes in urban photochemical conditions due to depletion of
ozone column densities by a fixed amount. We chose 0.300 cm-atm as a
general present-day base case, and reduced that column twice by 0.050 cm-
atm (16.67 percent) to provide the two future scenarios of 0.250 and 0.200
cm-atm. Before utilizing the j-values calculated from the modeled actinic
fluxes, however, it was necessary to verify that these calculations were
realistic for the conditions simulated. We compared our calculated rates
to chemical actinometry measurements at different ozone column densities
and solar zenith angles. This is a very useful test because the measured
actinometry value 1s the j-value, a real rate that can be directly com-
pared to the results of model calculations. In addition, because the
effective ozone column value accounts for increasing atmospheric thickness
with decreasing solar elevation, this value is always larger than the
overhead column. Hence, there are only a few future effective ozone
column conditions for very high solar elevations and low overhead column
densities that have not had comparable measurements performed under pre-
sent conditions of similar effective ozone column densities (from a some-
what different combination of zenith angles and overhead column densi-
ties). In addition, the future values outside the present range should be
extrapolations of the present relationship between effective ozone column
and j-values. In the following discussion, we compare measured j-values
and effective ozone column pairs with predicted pairs for a range of over-
head columns.
Over the previous decade, actinometry measurements for the 0(*D)-forming
channel of ozone photolysis have become increasingly rigorous. Unfortu-
nately, many of the earlier jq^q studies and the few available aldehyde
studies did not measure ozone column density and solar zenith angle;
therefore, they are not useful in assessing the ability of our model to
accurately predict changes in j-values caused by changes in these varia-
bles. However, the more recent actinometry data are sufficiently
complete for verifying that the model values of actinic flux are correctly
calculated in the shorter wavelelength regions. Therefore, we concentrate
our evaluation efforts on comparisons with these data sets.
The earliest data sets of are ground-level measurements performed by
Bahe et al. (1979b) and Dickerson et al. (1982). These data are shown at
the top of Figure 2-19, with the results of Bahe and coworkers appearing
87123r 2
53
-------
Measurements from Bahe
et al. (1979b) (squares)
and Dickerson et al. (1982)
(sol id circles).
in
o
ro
o
•r-j
"~o
cn
O
Measurements from Blackburn
(1984).
-i—i—i—r
0*0 ¦
0 TO ;
¦ h D
~ ,
~
0.20 -
0 10 -
-0 00 -
.o io -
-OJO -
~
Q
_J
I 00
0*0
0 to
-0 00
-0 10
-0 30
-0 30
Effective Ozone Column Densities
Model calculations for sea
level (squares) and 1840 m
(solid circles).
ro3/cose(xlO-1® cm"2)
FIGURE 2-19. Comparison of measured and calculated Jqid va1ues«
-------
as squares. As Dickerson and coworkers (1982) point out, the locations in
which these two sets of measurements were made differ significantly and
probably caused some differences in the results. The measurements of Bahe
et al. were done in the heavily industrialized Ruhr-Rhine Valley of West
Germany, where air pollution episodes are common; some decrease in surface
j-values could be expected due to this influence. The data of Dickerson
et al. (1982) were collected in Boulder, Colorado, an area of limited
clouds, high summer temperatures, relatively clean air and, most impor-
tant, an elevation of about 1800 m. An estimate* of the relative
difference in actinic flux for the 305 to 315 nm bin at 40 degree zenith
angle indicates an expected increase of about 50 percent at the higher
elevation. This translates into a difference of about 0.2 on the log j^g
scale of Figure 2-19, and Indicates that the somewhat higher j-values mea-
sured by Dickerson et al. (L982) compare quite well with those of Bahe et
al. (1979b) once environmental conditions are considered.
A far more complete set of surface Jq^q measurements, including ozone
column density and aerosol optical depths, was compiled by Blackburn
(1984). These data were collected at the University of Michigan for 75
days between May and July. The results of these measurements are also
shown in Figure 2-19. The main sequence of points is in a region similar
to that of Bahe et al. and is slightly lower than the numbers of Dickerson
and coworkers. This coincides with the foregoing argument, since the
Michigan elevation is also lower than the measurement site in Colorado.
The six outlying points are measurements at either low aerosol loading or
very high zenith angles (Blackburn, 1984).
The results of our model predictions for jQ,n at 0.300, 0.250 and 0.200
cm-atm are shown at the bottom of Figure 2-19. Squares represent near-
sea-level values and circles were calculated at 1840 m elevation to
facilitate comparison with the data of Dickerson et al. (1982). Our two
sets of values are not precisely linear because the l/cos(e) correction is
not exact (see Blackburn, 1984). Our predictions compare favorably with
the data of both Blackburn (1984) and Bahe et al. (1979b) for the near-
sea-level predictions, and Dickerson et al. (1982) for the 1800 m
values. As noted, our predictions extend to lower effective ozone column
values and larger j-values due to the inclusion of potential decrease in
future overhead ozone columns. We also include results beginning at
zenith angles of 20 degrees and less, whereas the measurements of most
researchers rarely exceeded 30 degrees. Therefore, extrapolation of these
measurements must be performed to verify our predictions of future, low,
effective ozone column conditions.
* Based on the model results of Demerjian et al, (Schere, 1986)
67123r 2
55
-------
We feel that, in all cases, these comparisons are favorable. Although
there are no similar chemical actinometry data for the formaldehyde and
acetaldehyde photolysis reactions, this evaluation indicates that our cal-
culation method for the prediction of future actinic flux is valid; there-
fore, the errors associated with the calculation of j-values for these
aldehydes should be mainly based on the uncertainties of their experimen-
tally determined absorption cross-section and quantum yield data, as
described earlier.
87 1 2 3r 2
56
-------
SECTION 3
SIMULATION OF URBAN PHOTOCHEMISTRY UNDER CONDITIONS
OF FUTURE GLOBAL CHANGE
The goal of this phase of the study was to Investigate the potential
changes in urban oxidant formation caused by possible future alterations
in global climate. More specifically, we were interested in (1) addi-
tional photochemical reactivity and (2) the amount of oxidant formation
that could occur as a result of future increases in surface temperature
and decreases in stratospheric ozone (increases in surface ultraviolet
irradiance and photolysis rates). Most photochemical kinetics modeling
performed in this phase involved the simulation of at least six urban tra-
jectories, covering as wide a range of locations and pollution precursor
conditions as possible; the primary objective was to provide information
on potential changes in urban ozone production due to future changes in
stratospheric ozone concentrations and surface temperature ranges.
Three different ozone column densities and temperature ranges were used in
the future scenario calculations. The results of photochemical kinetics
models were used to elucidate important dynamic processes that might occur
with changing conditions. It was envisioned that, in addition to changes
in ozone production, other indicators such as concentrations of hydrogen
peroxide, hydroxyl radicals, and various nitrogen-containing species would
also provide key information on possible alterations to urban atmospheric
chemical dynamics. In addition to the single-day city scenarios, we
studied multi-day impacts for two cities—one that had attained the
National Ambient Air Quality Standard (NAAQS) for ozone, and one in non-
attainment status. A second photochemical kinetics mechanism was used in
one set of simulations to verify that the results were not mechanism-
specific.
In this investigation of future urban impacts, we felt it appropriate to
use the OZIPM photochemical trajectory model since, when combined with the
EKMA procedure, that model is most often employed to determine the amount
of non-methane organic caron (NMOC) reduction needed to achieve compliance
with the ozone NAAQS of 0.12 ppm. EKMA calculations can also aid in
providing estimates of atmospheric and emission conditions expected in
future scenarios. Therefore, we have used OZIPM/EKMA and available input
87123r 3
57
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data from different State Implementation Plans (SIPs) to directly address
the regulatory impact of these anticipated global changes. The models and
chemical mechanisms used are briefly described next, followed by a
discussion of the modeling protocol, input data, and results.
DESCRIPTION OF MODELS AND MECHANISMS USED
The air quality simulation model used in this study was the OZIPM-3 tra-
jectory model described in Hogo and Whitten (1985). This model, in com-
bination with the Empirical Kinetic Modeling Approach (EKMA), has been
extensively used in Level-Ill, city-specific ozone modeling for SIPs. It
employs the CHEMK routine (Whitten and Hogo, 1980) for solution of the
partial differential equations representing the chemical species and
mechanism for each simulation. This routine is based on the higher order,
predictor-corrector method of Gear (1971) and is a very accurate solution
scheme for modeling stiff atmospheric chemistry systems. With OZIPM-3,
different chemical kinetic mechanisms can be easily input, eliminating the
need for complex coding of a second mechanism.
The OZIPM-3 model allows input of most key variables that affect the
chemistry of urban simulations. Of particular importance for this study,
hourly temperature values and variable photolysis rates (with zenith angle
and ozone column density), the key parameters for testing sensitivity, can
be input. Such parameters as initial concentrations, transported concen-
trations, aloft concentrations, inversion height profile, organic
reactivity, emissions, and photolytic effects due to location of a
specific city are also variable. These variables allow the simulation of
different city-specific scenarios such as the ones available to us from
past SIPs.
In the preceding section, we described the basis, procedure, and uncer-
tainties for our calculation of middle ultraviolet surface spectral
irradiance. These calculations were based on the method of Schippnick and
Green (1982) and the extraterrestrial flux data of the World Radiation
Center (WRC) [Iqbal, 1983]. From these calculations, we determined the
appropriate j-values for all photolytic species (and thus, the OZIPM-3
input values) needed to simulate the effects of different ultraviolet
intensities for three different future ozone column densities. Since
these values are necessarily zenith-angle-dependent, such calculations
were performed for each study location because each city has a different
longitude, latitude, and elevation. As described in Section 1, the selec-
ted ozone column densities were 0.300 (base case), 0.250, and 0.200 cm-
atm.
8 7 1 2 33
58
-------
The primary photochemical kinetics mechanism used in this study was the
CBM-X developed by Whitten et al. (1985) and implemented in the OZIPM-3 by
Hogo and Whitten (1985). A listing of this mechanism is provided in Table
3-1; the reader is referred to the referenced works for a complete model
description we initially envisioned the alternate mechanism as that of
Atkinson et al. (1982). However, since the newer CALL (Lurman et al.,
1987) and CBM-IV mechanisms (Gery et al., 1987) have recently become
available for OZIPM-type models, we selected one of these instead.
Although the CBM-IV is very different from the CBM-X mechanism, we chose
the CALL mechanism to ensure that we had selected an obviously unrelated
mechanism for this test. That mechanism is listed in Table 3-2; the
reader is referred to Lurman et al. (1987) and the references therein for
a more complete description of the mechanism. The listing in Table 3-2
contains a few updates from the referenced report. We advise all those
attempting to use a chemical kinetics mechanism, whether it be the CBM-X,
ALW, CALL, CBM-IV, or another, to contact the developer or project officer
to obtain the most recent and error-free source possible at the outset of
a study.
From the listings given in Tables 3-1 and 3-2, it is apparent that these
mechanisms are condensed versions of more explicit chemical mechanisms.
Both were developed from nearly the same fundemental data bases of basic
kinetic and stoichiometric data, and were evaluated and further developed
on the basis of smog chamber simulations. The primary focus in the
development of both mechanisms has been the prediction of oxidant forma-
tion in urban-type scenarios. The CBM-X and CALL mechanisms are not, how-
ever, duplicates of one another. In addition to the use of somewhat dif-
ferent assumptions concerning inorganic reactions, two different metho-
dologies have been used to describe the highly complex organic portions of
each mechanism. The CBM-X "lumps" structural groups, whereas the CALL
lumps molecular entities. Therefore, though these mechanisms represented
the state-of-the-science at the time that the mechanism comparison portion
of this study was performed, they use two different approaches and perfect
agreement between their predictions should not be expected. Conversely,
similar predictions in future trends by both mechanisms should be con-
sidered a strong argument for a good mechanistic description of the future
chemical dynamics as implemented in the test scenario in OZIPM-3.
MODELING PROTOCOL
There are a number of possible protocols for the use of existing urban
data sets to investigate potential future changes. The key procedure in
any such study is the method used to determine future conditions. That
is, a reasonable protocol requires a justifiable transition rationale for
87123r 3
59
-------
TABLE 3-1.
Reaction
Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
QZIPM-3 Listing of the CBM-X Mechanism.
Mechanism
N02
=
NO
+
0
0
=
03
03
+
NO
N02
0
+
ND2 =
NO
0
+
NO 2 =
N03
0
+
NO
N02
N02
+
03
N03
03
=
01D
03
=
0
01D
=
0
01D
=
2
OH
03
+
OH
H02
03
+
HO 2 =
OH
N03
+
NO
2
N02
N03
+
NO 2 =
NO
+
N02
N03
+
NO 2 =
N205
N205
-
2
HN03
N205
=
N03
+
N02
MO
+
N02 =
2
HN02
HN02
+
HN02 =
NO
+
NO 2
HN02
=
NO
+
OH
N02
+
OH
HN03
NO
+
OH
HN02
H02
+
NO
OH
+
NO 2
NO
+
NO
2
N02
87123 10
k298
(ppm'^in"^
1.000E 00
4.440E 06
2.660E 01
1.380E 04
2.320E 03
3.120E 03
4.740E-02
1.000E 00
4.200E-02
4.290E 10
6.520E 09
1.000E 02
3.000E 00
2.810E 04
5.900E-01
1.780E 03
3.800E-02
3.120E 00
3.200E-07
1.500E-05
1.800E-01
1.630E 04
9.770E 03
1.230E 04
1.520E-04
Activation
Energy
mi
O.OOOE-Ol
-6.900E 02
1.430E 03
O.OOOE-Ol
-6.000E 02
-4.110E 02
2.450E 03
O.OOOE-Ol
O.OOOE-Ol
-l.OOOE 02
O.OOOE-Ol
9.400E 02
5.800E 02
-2.500E 02
1.23 IE 03
6.000E 01
O.OOOE-Ol
1.084E 04
O.OOOE-Ol
O.OOOE-Ol
O.OOOE-Ol
-5.600E 02
-4.270E 02
-2.400E 02
-5.300E 02
-------
TABLE 3-1.
Reaction
Number
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
(continued).
Mechanism
H202
=
2 OH
OH
+
H202 =
H02
OH
+
HN02 =
N02
OH
+
HN03 =
N03
N03
=
0.85 N02
+
0.85 0
HO 2
+
H02 =
H202
H02
+
H02 =
H202
H02
+
N02 =
PNA
PNA
=
H02
+
N02
OH
+
CO
H02
FORM
+
H02 =
FROX
FORM
+
OH
H02
+
CO
FORM
=
2 H02
+
CO
FORM
=
CO
FORM
+
0
OH
+
H02
FORM
+
N03 =
HN03
+
H02
FROX
+
NO
N02
+
H02
FROX
=
FORM
+
HO 2
ALD2
+
0
C203
+
OH
ALD2
+
OH
C203
AL02
+
NO 3 =
C203
+
HN03
ALD2
=
ME02
+
HO 2
ALD2
+
H02 =
ME02
+
FORM
C203
+
NO
ME02
+
N02
C203
+
N02 =
PAN
87 123 10
c 293 Activation
+ 0.15 NO
+ CO
+ CO
CO
f ppm" "min""*)
Energy
(E/R)
l.OOOE
00
0.000E-01
2.520E
03
1.670E 02
9.770E
03
O.OOOE-Ol
1.920E
02
-7.780E 02
3.060E
01
O.OOOE-Ol
4.144E
03
-1.150E 03
4.360E
03
-5.800E 03
1.630E
03
-6.170E 02
5.120E
00
1.042E 04
4.000E
02
O.OOOE-Ol
1.480E
01
O.OOOE-Ol
1.500E
04
O.QOOE-Ol
l.OOOE
00
O.OOOE-Ol
l.OOOE
00
O.OOOE-Ol
2.370E
02
1.550E 03
9.300E-
-01
O.OOOE-Ol
1.040E
04
O.OOOE-Ol
9.000E
01
O.OOOE-Ol
6.360E
02
9.860E 02
2.400E
04
-2.500E 02
3.700E
00
O.OOOE-Ol
l.OOOE
00
O.OOOE-Ol
5.000E
00
O.OOOE-Ol
1.650E
04
-2.500E 02
9.000E
03
-2.500E 02
-------
TABLE 3-1. (continued)*
Reaction
Number
51
PAH
52
ME02
+
N02
53
MPNA
54
ME02
+
HO
55
MEO
+
NO
56
W EQ
+
MO
57
MEO
+
N02
58
MEO
59
MEN 3
+
OH
6Q
MNIT
+
OH
61
MNIT
62
HEQ2
+
MEO 2
63
ME02
+
C203
64
C203
+
C203
65
ME02
+
HO 2
66
C203
+
H02
67
AONE
68
AONE
+
OH
69
GLY
70
GLY
+
OH
71
MGLY
72
MGLY
+
OH
73
OH
74
PAR
+
OK
87123 10
C203
0-19 HO2
CO
0.13 H02 + 0.13 AL02
.067 X02N
k298
(ppfn"nm1n~M
2.220E-02
6.000E 03
9.200E 01
1.100E 04
4.440E 04
1.920E 03
Z-220E 04
3.940E 05
2.220E 03
2.370E 03
3.000E-01
5.030E 02
4.400E 03
3.700E 03
8.900E 03
9.600E 03
4.000E-05
5.8GOE 02
7.500E-03
1.500E 04
Z.000E-02
2.6QOE 04
2.100E 01
1.150E 03
Activation
Energy
LEZEL-.
1.400E 04
-7.350E 02
1.040E 04
-L.800E 02
-2.000E 02
O.OOOE-Ol
a.oooE-oi
1.313E 03
3.600E 02
3.400E 02
O.OOOE-Ol
-2.2Q0E 02
O.OOOE-Ol
O.OOOE-Ol
-1.300E 03
O.OOOE-Ol
O.OOOE-Ol
O.OOOE-Ol
O.OOOE-Ol
O.OOOE-Ol
O.OOOE-Ol
O.OOOE-Ol
O.OOOE-OL
O.OOOE-Ol
-------
TABLE 3-1. (continued).
Reaction
Number
Mechanism
o\
CO
75
ROR
+
N02 =
76
ROR
0.38
KET
+ 0.38
- 1.24
H02
PAR
77
ROR
ALD2
+
D
78
0
+
PAR *
X02
+
- 1.7
H02
PAR
79
D
+
KET *
C203
-
PAR
80
xoz
+
NO
H02
81
KET
C203
+
3
XO 2
PAR
82
0
+
OLE =
0.95
ALD2
+ 0.3
+ .05
H02
ME 02
83
OH
+
OLE =
MEG 2
+
AL02
84
03
OLE =
0.5
AL02
+0*516
+ .08
FORM
OH
85
M03
+
OLE =
0.91
X02
+ 0.91
H02
B6
0
+
ETH =
ME02
+
H02
87
OH
+
ETH =
0.78
ME02
+ 0.78
+ 0.22
FORM
H02
88
03
+
ETH =
FORM
+ 0.37
CRIG
89
CRIG
+
NO
FORM
+
N02
90
CRIG
N02 =
FORM
+
NO 3
91
CRIG
=
92
CRIG
+
FORM «
93
CRIG
+
ALD2 =
87123 10
k29S Activation
Energy
(ppro'^ln-*) (E/R)
2.200E 04 0.000E-01
0.62 AONE + 0.62 0 3.900E 05 0.000E-01
PAR 9.000E 04 7.000E 03
0.7 AONE + 0.3 ALD2 1.000E 04 O.OOOE-Ol
1.000E 04 0.000E-01
1.200E 04 0.000E-01
H02 + ALD2 3.0Q0E-04 O.OOOE-O1
0.15 XQ2 + 0.15 CO 5.920E 03 3.240E 02
.05 C203 - 0.35 PAR
PAR 4.200E 04 -5.370E 02
0.3 MCRG + 0.3 CRIG 1.800E-02 1.897E 03
,09 X02N 1.140E 01 O.OOOE-Ol
CO 1.080E 03 8.00QE 02
+ 0.22 XQ2 1.20CE 04 -3.820E 02
0.22 ALD2
0.37 CO + 0.13 H02 2.700E-03 2.840E 03
1.000E 04 O.GGOE-Ol
l.OOOE 03 O.OOOE-Ol
7.500E 03 O.OOOE-Ol
3.000E 01 O.OOOE-Ol
3.0aOE 01 O.QOOE-02
-------
TABLE 3-1. (concluded)
Reaction
Number
Mechanlsm
94
MCRG
+
NO
ALD2
+
N02
95
MCRG
+
HO 2 =
A.LD2
N03
96
MCRG
=
97
MCRG
+
FORM =
98
MCRG
+
ALD2 =
99
TOL
+
OH
H02
+
0.64
X02
+
0.36
PHEN
100
PHEN
+
NO 3 =
PHO
+
HN03
1D1
BZA
+
OH
BZ02
102
BZ02
+
NO 2 =
PBZN
103
BZQ2
+
NO
X02
+
PHO
104
PBZN
-
BZ02
+
N02
105
BZA
=
106
PHO
+
N02 =
107
XYL
+
OH
HO?
+
0.72
X02
+
0.28
PHEN
108
TLA
+
OH
X02
+
PHO
109
X02
+
HO 2 =
110
OH
=
H02
U1
X02N
+
NO
112
X02
+
C203 =
X02
+
H02
113
MR
=
NR
87]2 3r 1 C
k298
(ppnf
Activation
Energy
(E/R)
l.OOOE 04
O.OOOE-Q1
l.OOOE 03
0.000E-01
7.500E 03
0.000E-Q1
3.000E 01
O.OOOE-OI
3.000E 01
0.000E-01
GLY
+
0.56
MGLY
9.750E 03
O.OOOE-OI
PAR
+
.077
BZA
1.4Q0E 04
0.000E-Q1
2.000E 04
O.OOOE-Q1
2.500E 03
0.OOOE-Q1
CO
+
N02
3.700E 03
0.0Q0E-Q1
2.200E-02
1.400E 04
4.000E-03
0.000E-G1
2.0Q0E 04
O.OOOE-OI
GLY
+
1.33
MGLY
3.600E 04
0.000E-01
PAR
+
.06
TLA
PAR
2.000E 04
O.OOOE-OI
5.000E 03
-1.300E 01
8.S00E 01
O.OOOE-OI
l.OOOE 03
O.OOOE-01
FORM
2.400E 03
O.OOOE-OI
l.OOOE 00
O.OOOE-OI
-------
TABLE 3-2. 0ZIPM-3 Listing of the CALL Mechanism.
Reaction
Number
Mechanism
I
NQ2
=
NO
+
2
0
=
03
3
0
+
NO 2
NO
4
0
+
N02 =
N03
5
ID
T
03
NG2
6
H02
+
03
N03
7
NO
+
NO 3 =
2 N02
e
NO
+
HO
2 N02
9
N02
+
HO 3 =
N205
10
N205
=
N02
11
N20S
=
2 HN03
12
N02
+
NO 3 =
NO
+
13
N03
=
NO
14
N03
=
H02
+
15
03
=
0
16
03
=
0*SD
17
0*SQ
=
2 OH
IE
0*S5
=
0
19
HO
+
OH
HOMO
20
HGN0
=
UO
+
21
NO 2
=
HOHO
-
22
N02
+
OH
HN03
23
HH03
+
OH
N03
24
CO
+
OH
H02
25
03
+
OH
HO2
fil I 2 3 10
k298
Activation
Energy
(E/*)
Q
l.OOOE 00
0.00OE-01
4.650E 06
-L282E 03
1.370E 04
0.OOOE-01
3.300E 03
-8.940E 02
2.68GE 01
1.370E 03
4.520E-02
2.450E 03
2.7SCE 04
-2.520E 02
1.430E-04
-5.290E 02
1.710E 03
-2. 73DE 02
N03
2.080E 00
1.138E 04
3-000£-02
C-.OOOE-Ol
N02
5.980E-01
1.229E 03
l.OOOE 00
0.OOOE-01
0
1,OOOE 00
0.OOOE-01
l.OOOE 00
0.OOOE-01
l.OOOE 00
0.OOOE-01
6.54QE 09
0.OOOE-01
4.320E 10
O.OOOE-Ol
9.750E 03
-8.330E 02
OH
l.OOOE 00
0.00DE-01
NQ2 ¦+ HND3
1.170E-D4
0.OOOE-01
1.680E 04
-7.370E 02
1.890E 02
-7.780E 02
3.220E 02
0.OOOE-01
l.OOOE 02
9.420E 02
-------
TABLE 3-2.
Reaction
Number
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
(continued).
Mechanism
NO
+
H02 =
N02
+
N02
+
H02 =
HN04
HN04
=
N02
+
HN04
+
OH
N02
03
+
HO 2 =
OH
H02
+
HO 2 =
H202
H02
+
HO 2 =
H202
N03
+
H02 =
HN03
N03
+
HO 2 =
HN03
H202
=
2
OH
H202
+
OH
H02
R02
+
NO
NO
RC03
+
NO
NO
RC03
+
N02 =
N02
R02
+
H02 =
H02
RC03
+
H02 =
H02
ROOH
=
H02
+
R02
+
R02 =
R02
+
RC03 =
RC03
+
RC03 =
HCHO
=
2
H02
+
HCHO
-
CO
HCHO
+
OH
H02
+
HCHO
+
N03 =
HN03
+
HCHO
+
H02 =
R02R
+
87123 10
l<298 Activation
Energy
(ppnr'^min"^) (E/R)
OH
1.220E 04
-2.400E 02
2.020E 03
-7.730E 02
HO 2
4.930E 00
1.010E 04
5.910E 03
0.000E-01
2.960E 00
5.790E 02
4.460E 03
-7.710E 02
5.050E 03
-2.971E 03
4.460E 03
-7.710E 02
5.050E 03
-2.971E 03
l.OOOE 00
0.000E-01
2.450E 03
1.870E 02
1.140E 04
-1.800E 02
1.140E 04
-1.800E 02
7.570E 03
-1.800E 02
4.430E 03
0.000E-01
4.430E 03
0.000E-01
OH
l.OOOE 00
O.OOOE-Ol
1.480E 00
0.000E-01
4.430E 03
O.OOOE-Ol
3.690E 03
O.OOOE-Ol
CO
l.OOOE 00
O.OOOE-Ol
l.OOOE 00
O.OOOE-Ol
CO
1.330E 04
O.OOOE-Ol
H02 + CO
8.820E-01
2.060E 03
R02
1.480E 01
O.OOOE-Ol
-------
TABLE 3-2.
Reaction
Number
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
(continued).
Mechanism
ALD2
+
OH
MC03 +
ALD2
=
CO +
x
ALD2
+
N03 =
T
HN03 +
MC03
+
NO
N02 +
MC03
+
N02 =
PAN
MC03
+
H02 =
ROOH +
MC03
+
R02 =
0.5 H02 +
MC03
+
RC03 =
H02 +
PAN
=
MC03 +
RCHO
+
OH
RC03 +
RCHO
=
ALD2 +
RCHO
+
N03 =
T
HN03 +
PC03
+
NO
N02 +
PC03
+
N02 =
PPN
PC03
+
H02 =
ROOH +
PC03
+
R02 =
0.5 H02 +
PC03
+
RC03 =
H02 +
PPN
=
PC03 +
ACET
=
MC03 +
_1_
ACET
+
OH
MGLY +
MEK
=
MC03 +
+
87123 10
l<298 Activation
Energy
(ppm'Hmin"^) (E/R)
RC03
2.360E
04
-2.500E 02
HCHO
+
H02
+
R02R
l.OOOE
00
O.OOOE-Ol
R02
MC03
+
RC03
3.690E
00
1.427E 03
HCHO
+
R02R
+
R02
1.140E
04
-1.800E 02
7.570E
03
-1.800E 02
HCHO
4.430E
03
O.OOOE-Ol
HCHO
+
R02
4.430E
03
O.OOOE-Ol
HCHO
+
RC03
3.690E
03
O.OOOE-Ol
N02
+
RC03
2.210E-
-02
1.354E 04
PC03
2.930E
04
-2.520E 02
HO 2
+
CO
+
R02R
l.OOOE
00
O.OOOE-Ol
R02
PC03
+
RC03
3.690E
00
1.427E 03
ALD2
+
R02R
+
R02
1.140E
04
-1.800E 02
7.570E
03
-1.800E 02
ALD2
4.430E
03
O.OOOE-Ol
ALD2
+
R02
4.430E
03
O.OOOE-Ol
ALD2
+
RC03
3.690E
03
O.OOOE-Ol
N02
+
RC03
2.210E-
-02
1.354E 04
HCHO
+
RC03
+
R02R
l.OOOE
00
O.OOOE-Ol
R02
R02R
+
R02
3.390E
02
1.125E 03
ALD2
+
RC03
+
R02R
l.OOOE
00
O.OOOE-Ol
R02
-------
TABLE 3-2.
Reaction
Number
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
(continued).
Mechani sm
MEK
+
OH
1.5
R02R
+
1.5
R02
+
0.5
HCHO
GLYX
=
0.13
HCHO
+
1.87
CO
GLYX
+
OH
0.63
H02
+
1.26
CO
GLYX
+
N03 =
HN03
+
0.63
H02
+
0.37
RC03
GC03
+
N02 =
GPAN
GC03
+
NO
N02
+
H02
GPAN
=
GC03
+
NO 2
GC03
+
H02 =
ROOH
+
CO
GC03
+
R02 =
0.5
H02
+
CO
GC03
+
RC03 =
H02
+
CO
MGLY
=
MC03
+
H02
MGLY
+
OH
MC03
+
CO
MGLY
+
N03 =
HN03
+
MC03
ALK4
+
OH
0.19
HCHO
+
0.31
ALD2
+
1.6
R02
ALK7
+
OH
.02
HCHO
+
.03
ALD2
+
1.84
R02
ALKN
+
OH
N02
+
0.15
MEK
+
0.16
HCHO
R02N
+
NO
ALKN
R02N
+
H02 =
ROOH
+
MEK
R02N
+
R02 =
R02
+
0.5
HO 2
R02N
+
RC03 =
RC03
+
0.5
H02
8 7 12 3 10
0.5 MC03
0.5 PC03
0.37 GC03
1.26 CO
CO
RC03
R02
RC03
CO
RC03
CO
0.17 RCHO
0.25 RCHO
1. 5 RCHO
1.39 R202
MEK
MEK
l<29g Activation
Energy
(ppm~nniin-l) (E/R)
+ 0.5 ALD2 1.460E 03 7.450E 02
+ RC03
l.OOOE 00 0.000E-01
+ 0.37 RC03 1.700E 04 0.000E-01
+ 0.37 GC03 8.880E-01 2.058E 03
7.570E
03
-1.800E 02
1.140E
04
-1.800E 02
2.210E-
-02
1.354E 04
4.430E
03
0.000E-01
4.430E
03
0.000E-01
3.690E
03
0.000E-01
+
RC03
l.OOOE
00
0.000E-01
2.510E
04
0.000E-01
+
RC03
3.690E
00
1.427E 03
+
0.34
ACET
4.760E
03
3.530E 02
+
0.36
ACET
9.080E
03
2.890E 02
+
0.48
ALD2
2.980E
03
7.110E 02
+
1.39
R02
1.140E
04
-1.800E 02
4.430E
03
0.000E-01
1.480E
00
0.000E-01
4.430E
03
0.000E-01
-------
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
(continued).
k298
Mechanism (ppnT^in"*)
R202
+
NO
N02
1.140E
04
R202
+
H02 =
ROOH
4.430E
03
R202
+
R02 =
R02
1.480E
00
R202
+
RC03 =
RC03
4.430E
03
R02R
+
NO
N02
+
HO 2
1.140E
04
R02R
+
H02 =
ROOH
4.430E
03
R02R
+
R02 =
0.5
H02
+
R02
1.480E
00
R02R
+
RC03 =
0.5
H02
+
RC03
4.430E
03
ETHE
+
OH
R02R
+
R02
+
1.56
HCHO
+
0.22
ALD2
1.260E
04
ETHE
+
03
HCHO
+
0.12
HO 2
+
0.42
CO
2.570E-
-03
ETHE
+
0
HCHO
+
+
HO 2
R02
+
CO
+
R02R
1.080E
03
ETHE
+
N03 =
N02
+
2
HCHO
+
R202
+
R02
1.610E-
-01
PRPE
+
OH
R02R
+
HCHO
+
ALD2
+
R02
3.890E
04
PRPE
+
03
0.64
HCHO
+
0.5
ALD2
+
0.28
CO
+
.06
OH
1.670E-
-02
+
0.17
H02
+
0.13
R02R
+
0.13
R02
PRPE
+
0
0.6
ACET
+
0.4
HCHO
+
0.2
ALD2
+
0.2
HO 2
5.880E
03
+
0.6
R02R
+
0.4
CO
+
0.6
R02
PRPE
+
N03 =
N02
+
+
HCHO
R02
+
ALD2
+
R202
1.120E
01
TBUT
+
OH
R02R
+
2
ALD2
+
R02
9.420E
04
TBUT
+
03
ALD2
+
0.15
CO
+
0.27
R02R
+
0.12
OH
2.960E-
¦01
+
0.21
H02
+
0.27
R02
+
0.3
HCHO
TBUT
+
0
MEK
+
0.4
HO 2
3.450E
04
TBUT
+
N03 =
N02
+
2
ALD2
+
R202
+
R02
5.610E
02
-------
TABLE 3-2. (concluded)
Reaction
Number
k298
Mechanism
,-l>
Activation
Energy
112
TOLU
+
OH
0.16
CRES
+
0.16
H02
+ 0.84
R02R
+ 0.4
DIAL
9.080E
03
-3.200E 02
+
0.84
R02
+0.144
MGLY
+0.114
GLYX
113
DIAL
+
OH
PC03
+
RC03
4.430E
04
0.000E-01
114
DIAL
H02
+
CO
+
MC03
+
RC03
l.OOOE
00
0.000E-01
115
XYLE
+
OH
0.17
CRES
+
0.17
HO 2
+ 0.83
R02R
+ 0.83
R02
3.620E
04
-1.160E 02
+
0.65
DIAL
+0.316
MGLY
+ .095
GLYX
116
TMBZ
+
OH
0.17
CRES
+
0.17
HO 2
+ 0.83
R02R
+ 0.83
R02
9.160E
04
0.000E-01
+
0.49
DIAL
+ 0.86
MGLY
117
CRES
+
OH
0.2
MGLY
+
0.15
R02P
+ 0.85
R02R
+
R02
5.910E
04
0.000E-01
118
R02P
+
NO
NPHE
1.140E
04
-1.800E 02
119
R02P
+
H02 =
ROOH
4.430E
03
0.000E-01
120
R02P
+
R02 =
0.5
H02
+
R02
1.480E
00
0.000E-01
121
R02P
+
RC03 =
0.5
H02
+
RC03
4.430E
03
0.000E-01
122
CRES
+
N03
HN03
+
BZO
3.250E
04
0.000E-01
123
BZO
+
N02 =
NPHE
2.220E
04
0.000E-01
124
BZO
+
H02 =
PHEN
4.430E
03
0.000E-01
125
BZO
=
PHEN
6.000E-
-02
0.000E-01
126
PHEN
+
OH
0.2
MGLY
+
0.15
R02P
+ 0.85
R02R
+
R02
4.140E
04
0.000E-01
127
PHEN
+
N03 =
HN03
+
BZO
5.620E
03
0.000E-01
128
NPHE
+
N03 =
HN03
+
BZN2
5.620E
03
0.000E-01
129
BZN2
+
N02 =
2.220E
04
0.000E-01
130
BZN2
+
H02
NPHE
4.430E
03
0.000E-01
131
BZN2
=
NPHE
6.000E-
-02
0.000E-01
132
NRHC
=
NRHC
6.000E
01
0.000E-01
87 1 2 3j- 10
-------
calculating future conditions based on present data. Once a future
scenario is established, it is relatively simple to assess the effects of
parametric changes and their impacts within that scenario. In this study,
we feel that the mere resimulation of a present-day scenario using dif-
ferent photolysis rates or temperature values will not provide a reason-
able enough estimate of anticipated future urban conditions because man-
dated control requirements must necessarily alter present conditions.
Since the EKMA procedure is often used to determine the amount of NMOC
reduction that will ideally be implemented in the future, we utiilized this
direct link with the regulatory process to determine more realistic future
scenarios. Therefore, the present-day base-case data sets were imple-
mented in OZIPM-3, and standard EKMA calculations were performed to formu-
late scenarios of future attainment in each city based on the alleviation
of current smog scenarios. We felt that this approach would provide a
much better estimate of future base-case scenarios with which to assess
unanticipated (in the EKMA) perturbations due to changes in the two vari-
ables (temperature and ultraviolet radiation) of interest in this study.
Of course, this protocol assumes "ideal" performance in the EKMA calcula-
tion method and an "ideal" response of an urban atmosphere to EKMA-derived
emission controls. As we describe next, errors in the EKMA calculation
method can be minimized by selective application of only the best predic-
tions of present-day scenarios.
The principal strength of the EKMA procedure is its ability to compensate
for non-ideal simulation of the measured ozone maximum concentration using
the set of design conditions available for a specific day. This compensa-
tion is based on the expectation that the OZIPM photochemical mechanism
will accurately reproduce the nonlinear NMOC, N0X, and O3 relationships in
oxidant chemistry. In the current investigation, however, we actually
altered the chemical mechanism between the simulation of present and
future conditions by changing some future reaction rates through increases
in temperature and ultraviolet irradiance. This is a situation that the
EKMA procedure was not designed for. We therefore imposed additional con-
straints on our study that are not included in typical SIP calculations.
One key constraint is that the simulated ozone value and the design (mea-
sured) concentration should not vary excessively. That is, we require a
good fit between simulated ozone and measured ozone for the base-case
simulation. In this way, the EKMA program is not required to compensate
for a poor fit, but only to calculate the ratio of NMOC reduction needed
to "ideally" produce 0.12 ppm ozone. We use such EKMA calculations to
derive conditions of anticipated future NAAQS compliance for ozone. With
these scenarios, which we denote as future base cases, we assessed the
unanticipated impacts of changes to surface temperature and ultraviolet
irradiance.
8 7 1 2 31" 3
71
-------
The overall investigation protocol is depicted in Figure 3-1 for one of
the possible test cities. As shown, the number of simulations for each
city was reduced depending on the goodness-of-fit between measured and
simulated hourly maximum ozone concentrations for present base-case simu-
lations (all base-case runs were simulated with measured or calculated
temperature data and j-values for an ozone column of 0.300 cm-atm). EKMA
calculations were then performed to determine the "ideal" NAAQS compliance
conditions for each base-case data set. Occasionally, a few of these data
sets provided wildly variable EKMA results and were deemed unusable. In
addition, because some input data were rather uncertain, a few cities had
poor base-case simulations. All simulations from Chicago and Boston were
excluded from our base case pool. From the EKMA results, a future base-
case data set (still with of normal temperature and ozone column condi-
tions) was derived and simulated to verify that those conditions produced
ozone at the level of the NAAQS. Then, using this future base case as the
"ideal" anticipated result of prescribed NMOC reductions, we were able to
predict the extent of the photochemical changes caused by increased tem-
perature and ultraviolet irradiance. This was done by the incremental
increase of these values and the analysis of resulting changes in the con-
centrations of ozone and other chemical species.
As described in Section 1, the measured (or calculated) temperature dis-
tribution specific to each test day was used for all the base-case simula-
tions. In addition, since ozone column density data were not available
for these cities, we used a value of 0.300 cm-atm (300 DU) as the base-
case overhead ozone column density when calculating diurnally varying
j-values. Perturbations to these two parameters were made by simply
adding 2 and 5 K to the base-case temperatures, and by calculating j-
values for overhead ozone columns of 0.250 and 0.200 cm-atm. The j-values
were determined for an altitude 640 m above the surface elevation of each
city using monthly average surface albedoes for each location (Iqbal,
1983). The temperature and ozone column density changes were made
independently, and in combination, providing 9 future scenarios (including
the future base case) for each data set.
INPUT DATA
Our initial, single-day modeling data set consisted of atmospheric mea-
surements from 45 days in 10 cities. There were actually 57 initial base-
case simulations because some days were modeled with a multiple number of
trajectories. Table 3-3 provides a list of the cities studied, along with
the number of days and trajectory data sets initially simulated. The ele-
vation, location, regional albedo, temperature, and mixing height data
are given in Appendix A for each date and city in these simulations.
87 1 2 3r 3
72
-------
Days from 1
of 1 0 cities:
1
2 3
4
Data sets:
1
11
1 1
I 1
f:*v«v«V'
(•vyy:.
Good fits/present base cases
Good EKMA calculations:
Future base case
and sensitivity
cases:
u I r;r.'r;r:< i r* r; »-• « r'r/rjr** r«r»r"r»< r »rr.*r»ivr.u
|
[W--.-vy.-j [>vy.-y.-y.-j bv;>y-yii &v>v>»v3
I L.%.%.%.si [•¦••••••••••I l*s*s*s*si Li%i%is*%i Lis>%i%i%1
-Ahv-
Simulate each data set
(eliminate bad fits)
Perform EKMA calculation
to determine NMOC reduction
to future compliance (elimin-
ate unreasonable simulations)
Set up Future Base Case
Scenario
Perform sensitivity simu-
lations for AT and Ahv
FIGURE 3-1. Single-day urban modeling data-set selection process protocol.
67095
73
-------
Table 3-3. Initial single-day data sets in the
OZIPM/EKMA investigation.
City
Chicago, IL
Los Angeles, CA
Boston, MA
Nashville, TN
New York, NY
Philadelphia, PA
Phoenix, AZ
Seattle, WA
Tulsa, OK
Washington, DC
TOTAL
Number of
Days
3
1
7
6
1
6
4
3
9
5
45
Number of
Trajectories
3
1
7
9
2
7
5
8
10
5
57
87 1 23
74
-------
Individual NMOC, N0X, and design O3 values are discussed later. The
range of different city-specific input values in the test data sets is
large, but the effect of individual differences is not always discernable
because these changes are not isolated. In some particular cases, such as
in the multi-day tests, we have altered some values to directly address
individual parametric variations. However, in the single-day tests these
values were unchanged. Two important parameters that vary in the single-
day base-case data are the temperature and mixing height values (see
Appendix A). In most data sets, the base-case temperatures vary diurnally
from about 298 K to 305 K. Only in the case of Los Angeles, which has a
24-hour temperature field, does a more significant variation occur. As
noted in Appendix A, the Los Angeles temperature profile extends from 294
< (at night) to 317 K. It is difficult to judge the effect of this change
among different base-case simulations because Los Angeles also has one of
the lowest mixing height profiles. It is possible to discern the tempera-
ture effect in the future simulations, however, since that parameter is
individually varied.
Mixing height profiles appear to cover the range of variability expected
for different cities throughout the United States. Diurnal changes on the
west coast are generally small. For instance, the Los Angeles data varies
from about 80 to 540 m, while the variation in Seattle could be as small
as 250 to 670 m. This variation in mixing depth by a factor of less than
3, along with other conditions discussed next, creates a unique test set
for Seattle. The smaller mixing height changes on the west coast can be
compared to factors between 12 and 14 for some Phoenix, Tulsa, and
Washington days. The remaining mixing height profiles for individual days
fit between these data toward the higher values.
The photolysis rate ratios to jNQ2 that were used in the simulations are
given in Appendix B for ozone [to 0(0)I, formaldehyde, acetaldehyde, and
hydrogen peroxide. These values are shown as a function of zenith angle
and overhead ozone column. It can be seen from comparison of these values
for different cities that no significant variation occurs in the zenith-
angle dependency since regional albedo and elevation do not differ
significantly throughout our set of test cities. On the other hand,
because the latitude of a city affects the diurnal solar elevation func-
tion, areas located closer to the tropics will have lower zenith angles,
and therefore, higher j-values for a given time of day. In this study,
Seattle is located farthest north and Los Angeles and Phoenix are at the
lowest latitudes. Figure 3-2 shows the zenith angle functions calculated
for Seattle and Los Angeles for 1 August. The functions are slightly off-
set because of the differing longitudes of the cities, but the latitudinal
differences translate into about a 13.7 degree variation in solar eleva-
tion at local solar noon. Figure 3-3 shows the values calculated for
87 1 2 3r 3
75
-------
Zenith Angle Comparison
Las Angelas, CA vs. Seattle, WA
Time (mln.)
FIGURE 3-2. Calculated zenith angles for Seattle, Washington
and Los Angeles, California for 1 August.
76
-------
Comparison of Calculated j—Values
Las Angelas, CA vs. Seattle, WA
Time (mln.)
FIGURE 3-3. Calculated Jqj values for Seattle, Washington and
Los Angeles, California for 1 August at 0.300 and 0.200 cm-atm
overhead ozone column.
77
-------
both cities on that date as a function of time and overhead ozone
column. Integrating over the four-hour period centered on local solar
noon, we calculate the average Seattle JQ3 value to be 3.17 x 10~^ min"l
at a 0.300 cm-atm overhead ozone column, and that of Los Angeles to be
3.76 x 10"^ min . This represents a 20 percent difference in photolysis
rates at 0.300 cm-atm, with slightly less difference for the 0.200 cm-atm
ozone column calculations.
These variations demonstrate a localized difference in energy input
between two urban areas. Assuming all other factors are equal, areas with
additional radiant energy input would most likely be required to implement
more NM0C emission controls to attain the same air quality because that
additional energy input would make their urban atmospheric mixture of oxi-
dant precursors more reactive. Conversely, northern areas with lower
energy input might not require extra controls because the energy input is
low enough to render the photochemical production of oxidants less
efficient. However, as we discuss next, since these precursors are not
controlled, they will continue to exist downwind of the city. As condi-
tions change to future conditions of enhanced ultraviolet irradiance and
temperature, these uncontrolled precursors might achieve significantly
greater oxidant-forming potential within the city. Hence, one effect of
future increased ultraviolet irradiance is somewhat like moving a city to
lower latitudes, where conditions could produce more oxidant and oxidized
products.
Finally, since the city-specific data sets presented in the appendixes
span a wide range of urban oxidant production capacities, we have consoli-
dated the following discussion by creating three general group classifica-
tions:
Group 1: High ozone NAAQS exceedence days. In this group we include
all days with design values greater than 0.17 ppm. There are ten
such days in the 45 days simulated. These data sets are from Los
Angeles, Chicago, New York, Boston, Philadelphia, and Washington,
representing oxidant production episodes in regions where severe
ozone exceedences are common.
Group 2: Less extreme nonattainment days, often representing cities
that require moderate control (30 to 50 percent) of organic precur-
sors to achieve the ozone NAAQS. Hourly maximum ozone concentrations
are between 0.17 and 0.14 ppm in this group. Local meteorological
conditions can influence the magnitude of the ozone production in
many of these cases.
87 1 2 3
78
-------
Group 3: Days that are nearly in compliance with the NAAQS for
ozone. These data sets provide future sensitivity tests with current
ozone production at 0.13 ppm or below. The data are scattered
between a few test cities, including Boston, Nashville, and Tulsa.
We have used these groupings because common group characteristics facili-
tate later discussion of chemical dynamics. Although these data could be
considered typical of each individual city's ozone formation profile, we
will usually name specific cities only to identify the source of input
data for an example data set. One notable exception in the following dis-
cussion concerns the two data sets chosen from the Seattle data. As with
many data sets collected for use in the 1982 SIP process in smaller
cities, some measurements needed for OZIPM input parameters appear to be
rather uncertain. In this case, we refer to both the precursor concentra-
tions (which appear to be rather high) and the morning mixing height
(which may have been less than the 250-m values used in the SIP calcula-
tions). The calculated results for those days do not easily fit into any
of the grouping schemes. However, their results do demonstrate some
important atmospheric processes; so, though they are uncertain, we discuss
the conditions and predictions from those two tests to demonstrate certain
aspects of chemical dynamics. Therefore, our discussion focuses on the
three general groups, and a fourth test based on the Seattle data (denoted
as Group 4 in the following discussion). We feel that this grouping
scheme is as specific as the current data will allow. We stress that
though it is based on data from one city, even the Seattle data should be
considered a general test case since a much larger and better defined set
of city-specific measurements must be considered before the unique charac-
teristics of any individual city can actually be discussed.
In addition to the single-day tests, two multi-day data sets were used to
investigate the conditional variation of ozone and oxidized species with
potential future changes in surface temperature and ozone column density
previously described. One multi-day scenario was chosen to represent an
urban area in conditions of compliance with the ozone NAAQS. The second
was to represent a non-compliance day. For the non-compliance tests, we
utilized a two-day data set from Los Angeles for 26-27 June 1974. Since
the first day was used as our only Los Angeles simulation day, we had
already performed EKMA calculations and derived future base-case condi-
tions for that day (see Section 4). Therefore, we used those input data
to begin our multi-day tests. On the other hand, because we had no data
sets for NAAQS attainment conditions (since the sources of our data are
SIP simulations of non-compliance days), we selected one of the lower
ozone production Phoenix days (5 July 1980) and altered the data slightly
to produce conditions of approximately 0.1 ppm maximum predicted hourly
ozone concentrations. The alterations consisted of utilizing the Phoenix
mixing height data from the day with the largest change (dilution) and
87123p 3
79
-------
slightly lowering initial conditions and emissions. Since this day was
already nearly in compliance and these changes were rather small, we felt
that these initial conditions were realistic.
Finally, two sets of simulations were performed using the alternate chemi-
cal mechanism. We chose the (original) 5 July 1980 Phoenix test case to
represent Group 2, and the 13 July 1979 Philadelphia data to test the more
reactive Group 1. Except for mechanism changes, no alterations were made
to the original simulation input conditions.
RESULTS
In this section we first discuss the single-day simulation results for
both the base-case simulations and the future case results. Because the
multi-day simulations and the tests performed with the alternate mechanism
are based on the single-day simulations, only the future results will be
discussed here.
As noted in the protocol section, each single-day data set was simulated
with the best base-case information obtainable to ascertain the goodness-
of-fit of maximum hourly ozone concentration with those data. The NMOC,
N0X, NM0C/N0x ratios, and design O3 concentrations for each of the 57 data
sets are presented in Table 3-4, along with the predicted maximum hourly
ozone concentrations. From these simulations, we selected one to four
data sets from each city, depending on the similarity between predicted
maximum hourly ozone concentrations and measured values.
After the set of input files was thus reduced, we performed EKMA calcula-
tions to determine the potential future conditions of hydrocarbon control
resulting in attainment of the ozone NAAQS. In a few cases, the method
would not converge to an EKMA solution. In some other cases, the isopleth
shape was such that calculation of the necessary hydrocarbon changes could
not start from or near the original NMOC and N0X concentrations on the
NMHC/N0x line. Both types of data were set aside, leaving 15 future base-
case data sets with good base-case fits and reasonable EKMA calculations
starting from very near the original base-case NMOC and N0X concentra-
tions. These data sets, which are based on city-specific information from
8 different cities, are listed in Table 3-5 by the general categories dis-
cussed earlier. We feel that this process has eliminated much of the most
questionable data in an unbiased manner. The set of test data presented
in Table 3-5 should provide a basis for focusing on the photochemical
dynamic aspects of global climate change as it relates to urban atmo-
spheres. On the other hand, we repeat that these study data are not
extensive enough to allow conclusions regarding individual cities; hence,
the following discussion focuses on the generalized groups.
8 7 1 2 3f 3
80
-------
Table 3-4. Design values and model results for BASE CASE simulations.
Date*
Design Values
(ppm)
Simulated
NMOC
N0V Ratio
O3
O3
Pet.
BOSTON:
30 May 1978
0.312
0.034
9.4
0.240
0.143
-40.4
21 July 1978
0.231
0.033
7.0
0.150
0.109
-27.3
13 August 1978
0.310
0.034
9.4
0.125
0.140
12.0
15 August 1978
0.312
0.034
9.4
0.160
0.147
- 8.1
16 August 1978
0.231
0.033
7.0
0.140
0.113
-19.3
29 June 1979
0.191
0.023
8.3
0.125
0.148
18.4
10 July 1979
0.191
0.023
8.3
0.160
0.111
-30.6
CHICAGO:
10 July 1979
1.050
0.157
6.7
0.174
0.139
-20.1
11 July 1979
0.375
0.056
6.7
0.177
0.144
-18.6
26 August 1980
0.875
0.131
6.7
0.170
0.131
-22.9
LOS ANGELES:2
26 June 1974 0.168 0.027 6.2 0.490 0.447 - 8.8
NASHVILLE:
2
July 1980
0.256
0.054
4.7
0.130
0.087
-33.1
25
July 1980-1
0.168
0.036
4.7
0.130
0.085
-34.6
25
July 1980-2
0.196
0.043
4.6
0.130
0.097
-25.4
1
August 1980-1
0.176
0.037
4.8
0.130
0.076
-41.5
1
August 1980-2
0.203
0.044
4.6
0.130
0.089
-31.5
10
August 1980-1
0.412
0.088
4.7
0.130
0.121
- 6.9
10
August 1980-2
0.456
0.098
4.7
0.130
0.135
3.8
11
September 1981
0.336
0.070
4.8
0.156
0.094
-39.7
12
September 1981
0.238
0.052
4.6
0.127
0.087
-31.5
87123 4
81
-------
Table 3-4. (continued).
Design Values (ppm) Simulated
Date*
NMOC
_N0X
Ratio
O3
O3
Pet.
NEW YORK:
24 June 1980-1
2.03
0.122
16.6
0.253
0.226
-10.7
24 June 1980-2
2.03
0.122
16.6
0.234
0.235
0.4
PHILADELPHIA:
13 July 1979
0.916
0.125
7.3
0.200
0.237
18.5
19 July 1979
0.916
0.125
7.3
0.170
0.136
-20.0
24 June 1980
0.765
0.093
8.2
0.171
0.173
1.1
15 June 1981
0.916
0.125
7.3
0.206
0.171
-17.0
16 June 1981
0.883
0.148
6.0
0.161
0.233
44.7
19 August 1982
0.916
0.125
7.3
0.157
0.144
- 8.3
27 June 1983-1
0.916
0.125
7.3
0.156
0.209
34.0
27 June 1983-2
0.916
0.125
7.3
0.150
0.163
8.7
PHOENIX:
5 July 1984
0.397
0.026
15.3
0.140
0.143
2.1
29 August 1984
1.301
0.072
18.1
0.140
0.140
0.0
31 August 1984
1.004
0.094
10.7
0.130
0.133
2.3
14 September 1984-1
1.857
0.135
13.8
0.160
0.185
15.6
14 September 1984-2
1.857
0.135
13.8
0.140
0.164
17.1
SEATTLE:
7 August
1981-1
1.620
0.30
5.4
0.14
0.134
- 4.3
7 August
1981-2
1.620
0.30
5.4
0.13
0.136
4.6
10 August
1981-1
1.458
0.27
5.4
0.14
0.149
6.4
10 August
1981-2
1.458
0.27
5.4
0.15
0.150
0.0
10 August
1981-3
1.458
0.27
5.4
0.13
0.149
14.6
11 August
1981-1
1.404
0.26
5.4
0.14
0.131
- 6.4
11 August
1981-2
1.404
0.26
5.4
0.15
0.129
-14.0
11 August
1981-3
1.404
0.26
5.4
0.13
0.132
1.5
87 123 4
82
-------
Table 3-4. (concluded).
Design Values (ppm) Simulated
Date1 NMOC NOv Ratio 03 03_ Pet.
TULSA:
1 July 1981
1.589
0.0623
25.5
0.148
0.123
-16.
16 July 1981-1
1.589
0.0623
25.5
0.157
0.110
-29.
16 July 1981-2
1.589
0.0623
25.5
0.157
0.115
-26.
6 August 1981
1.589
0.0623
25.5
0.148
0.115
-22.
29 June 1982
1.589
0.0623
25.5
0.130
0.117
-10.
6 August 1982
1.589
0.0623
25.5
0.128
0.115
-10.
23 August 1982
1.589
0.0623
25.5
0.148
0.088
-40.
26 July 1983
1.589
0.0623
25.5
0.138
0.112
-18.
27 August 1983
1.589
0.0623
25.5
0.134
0.107
-20.
28 August 1983
1.589
0.0623
25.5
0.131
0.106
-19.
WASHINGTON:
16
July 1980
0.75
0.116
6.5
0.16
0.040
-75.
17
July 1980
0.76
0.076
10.0
0.20
0.112
-44.
21
July 1980
0.82
0.080
10.3
0.14
0.136
- 2.
7
August 1980
0.54
0.063
8.6
0.18
0.164
- 8.
29
August 1980
1.16
0.150
7.7
0.14
0.112
-20.
hyphenated dates refer to different trajectories used on the same day.
2
The Los Angeles simulation was a 1600 to 1600, 24 hour run; therefore,
the NMOC and NOx values are not 6-9 AM averages.
87 123 4
9
9
8
3
0
2
5
8
1
1
0
0
9
9
0
83
-------
Table 3-5. Data Sets Used in Future Scenario Tests*
Design Values
Simulation
EKMA
City
Date
NMOC
N0X
HC/N0X
°3
°3
% Dif.
Control
GROUP 1:
Los Angeles, CA
26
June 1974
0.1682
0.0272
6.22
0.490
0.447
- 8.8
84
New York, NY
24
June 1980
2.03
0.122
16.6
0.234
0.235
0.4
77
Philadelphia, PA
13
July 1979
0.916
0.125
7.3
0.200
0.237
18.5
56
Washington, DC
7
August 1980
0.54
0.063
8.6
0.18
0.164
- 8.7
24
Philadelphia, PA
24
June 1980
0.765
0.093
8.2
0.171
0.173
1.2
28
GROUP 2:
Phoenix, AZ
14
September 1984
1.857
0.135
13.8
0.16
0.185
15.6
47
Tulsa, OK
1
July 1981
1.589
0.062
25.5
0.148
0.123
-16.9
74
Washington, DC
21
July 1980
0.82
0.080
10.3
0.14
0.136
- 2.9
29
Phoenix, AZ
5
July 1984
0.397
0.026
15.3
0.14
0.143
2.1
34
GROUP 3:
Q
Nashville, TN
10
August 1980
(IK
0.412
0.088
4.7
0.13
0.121
- 6.9
50
Nashville, TN
10
August 1980
(2)
0.456
0.098
4.7
0.13
0.135
3.8
50
Phoenix, AZ
31
August 1984
1.004
0.094
10.7
0.13
0.133
2.3
18
Tulsa, OK
6
August 1982
1.589
0.062
25.5
0.128
0.115
-10.2
43
GROUP 4:
Seattle, WA
11
August 1981
1.404
0.26
5.4
0.15
0.129
-14.0
8
Seattle, WA
7
August 1981
1.620
0.30
5.4
0.13
0.136
4.6
3
Significant figures in table as given in data sources.
^Because the Los Angeles simulation was a 24-hour test, these values do not represent 6-9 AM NMOC
and N0V concentrations,
o x
Two trajectories were modeled for this day.
07123 4
-------
As described in the protocol discussion, nine future case scenarios were
performed for each set of future conditions. The future base case was
formulated from the EKMA-determined conditions for future compliance with
the ozone NAAQS. Perturbations due to either increases in temperature or
ultraviolet irradiance (or both) were made to this future base case to
derive eight other future climate change scenarios. The temperature was
increased from the measured profiles by adding 2 or 5 K to each hourly
data point, and the ultraviolet intensity was increased by changing calcu-
lated rate constants from their values at the base-case ozone column
(0.300 cm-atm or 300 Dobson) to values determined at 0.250 and 0.200 cm-
atm.
The maximum hourly ozone, hydrogen peroxide and PAN concentrations of the
nine individual future scenario calculations for the 15 single-day test
sets are tabulated in Tables 3-6 through 3-20. In this study we are
particularly interested in changes in urban oxidant-formation potential;
therefore, we also show the ozone and hydrogen peroxide results as bar
charts following each table (Figures 3-4 through 3-18). The order of
these results follows the listing of Table 3-5.
Two multi-day test sets were formulated from existing data--one represent-
ing ozone NAAQS attainment conditions and one representing non-attain-
ment. The non-attainment set was derived from the 26-27 June 1974 episode
in Los Angeles. We have already described the base-case results and EKMA
calculations for the 26 June 1974 simulation of the first day of this epi-
sode. The future base-case conditions from the single-day scenario were
used for the multi-day simulations. The other multi-day test set was for
a situation of initial attainment of the ozone NAAQS. The input data for
this test case were derived from available Phoenix data as described
earlier. No EKMA calculations were necessary because of the compliance
status for this test set, so future simulations were performed using the
original base-case input values. The results from the future scenario
tests for these two data sets are shown in Figures 3-19 and 3-20, and
recorded in Tables 3-21 and 3-22.
As noted earlier, we performed complete analyses of two data sets with the
CALL mechanism to verify that these results were not overly mechanism-
specific. The 13 July 1979 Philadelphia data set was selected to repre-
sent a Group 1 test, and the 5 July 1984 Phoenix data was selected to
represent Group 2. A complete reanalysis of each day, including base-case
simulation, EKMA calculation, and the nine future scenario calculations
were performed with the alternate mechanism. The results of the future
scenarios are reported in Tables 3-23 and 3-24.
87 1 2 3r 3
85
-------
TABLE 3-6. Maximum hourly concentrations and percentage changes for
ozone, H2O2, and PAN for the future sensitivity tests for the simulation
of 26 June 1974, Los Angeles, California.
OZONE
Concentration (ppm)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
0.112 0.113 0.114
0.126 0.129 0.131
0.157 0.162 0.165
Percent Change
(from base)
12.5
40.2
+2
0.9
15.2
44.6
+5
1.8
17.0
47.3
Concentration (ppb)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
0.01
0.01
0.03
0.01
0.01
0.04
0.01
0.01
0.05
H2O2
Percent Change
(from base)
0.0
200.0
+2
0.0
0.0
300.0
+5
0.0
0.0
400.0
PAN
Concentration (ppb)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
0.71
0.75
0.96
0.57
0.60
0.81
0.40
0.42
0.59
Percent Change
(from base)
5.6
35.2
+2
-19.7
-15.5
14.1
+5
-43.7
-40.9
-16.9
8 7 12 3 4
86
-------
TABLE 3-7. Maximum hourly concentrations and percentage changes for ozone,
HoOp, and PAN for the future sensitivity tests for the simulation of 24 June
1980, New York.
OZONE
Concentration (ppm)
Change in Temp (K) _0_ +2 +5
Dobson Number
Percent Change
(from base)
0
+2
+5
300
250
200
0.125 0.130 0.138
0.150 0.157 0.167
0.165 0.170 0.178
20.0
32.0
4.0
25.6
36.0
10.4
33.6
42.4
H2O2
Concentration (ppb)
Change in Temp (K) _0_ +2 +5
Dobson Number
Percent Change
(from base)
+2
+5
300
250
200
0.05
0.43
3.08
0.06
0.58
3.31
0.08
0.84
3.60
760.0
6060.0
20.0
1060.0
6520.0
60.0
1580.0
7100.0
PAN
Concentration (ppb)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
3.98
5.85
7.59
3.50
5.26
6.73
2.79
4.34
5.49
Percent Change
(from base)
47.0
90.7
+2
-12.1
32.2
69.1
+5
-29.9
9.1
37.9
87123 4
87
-------
TABLE 3-8. Maximum hourly concentrations and percentage changes for ozone,
H2O0, and PAN for the future sensitivity tests for the simulation of 13 July
1979, Philadelphia, Pennsylvania.
OZONE
Concentration (ppm)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
0.118 0.122 0.129
0.142 0.146 0.152
0.153 0.157 0.162
Percent Change
(from base)
20.3
29.7
+2
3.4
23.7
33.1
+5
9.3
28.8
37.3
Concentration (ppb)
Change in Temp (K) _0_ +2 +5
Oobson Number
300
250
200
0.07
0.86
3.80
0.09
0.99
3.90
0.13
1.19
4.01
H2O2
Percent Change
(from base)
1128.6
5328.6
+2
28.6
1314.3
5471.4
+5
85.7
1600.0
5628.6
PAN
Concentration (ppb)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
2.06
3.29
4.13
1.80
2.84
3.54
1.44
2.23
2.73
Percent Change
(from base)
0
59.7
100.5
+2
-12.6
37.9
71.8
+5
-30.1
8.3
32.5
8 7 12 3 4
88
-------
TABLE 3-9. Maximum hourly concentrations and percentage changes for ozone,
Ho02» and PAN for the future sensitivity tests for the simulation of 7 August
1980, Washington, DC.
OZONE
Concentration (ppm)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
0.119 0.125 0.134
0.142 0.150 0.163
0.171 0.178 0.188
Percent Change
(from base)
19.3
43.7
+2
5.0
26.1
49.6
+5
12.6
36.0
58.0
H2°2
Concentration (ppb)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
0.03
0.13
1.53
0.04
0.19
1.82
0.05
0.32
2.24
Percent Change
(from base)
+2
+5
333.3
5000.0
33.3
533.3
5966.7
66.7
966.7
7366.7
PAN
Concentration (ppb)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
3.42
5.00
7.64
3.08
4.63
6.87
2.58
4.04
5.76
Percent Change
(from base)
4.6
123.4
+2
- 9.9
35.4
100.9
+5
-24.6
18.1
68.4
87 123 t
39
-------
TABLE 3-10. Maximum hourly concentrations and percentage changes for ozone,
H0O2, and PAN for the future sensitivity tests for the simulation of 24 June
1980, Philadelphia, Pennsylvania.
OZONE
Concentration (ppm)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
0.119
0.144
0.156
0.124
0.150
0.160
0.132
0.158
0.167
Percent Change
(from base)
21.0
31.2
+2
4.2
26.1
34.5
+5
10.9
32.8
40.3
Concentration (ppb)
Change in Temp (K) _0[_ +2 +5
Dobson Number
300
250
200
0.06
0.57
2.87
0.08
0.73
3.07
0.12
0.97
3.28
H2O2
Percent Change
(from base)
+2
850.0
4683.3
+5
33.3
1116.7
5016.7
100.0
1516.7
5366.7
PAN
Change in Temp (K)
Dobson Number
300
250
200
Concentration (ppb)
0 +2 +5
2.50
3.86
5.11
2.18
3.40
4.46
1.76
2.74
3.60
Percent Change
(from base)
+2
+5
54.4
104.4
- 12.8
36.0
78.4
- 29.6
9.6
44.0
8 7 1 2 3 U
90
-------
TABLE 3-11. Maximum hourly concentrations and percentage changes for
ozone, H2O2, and PAN for the future sensitivity tests for the simulation
of 14 September 1974, Phoenix, Arizona.
OZONE
Concentration (ppm)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
0.120 0.124 0.129
0.129 0.132 0.136
0.133 0.136 0.139
Percent Change
(from base)
7.5
10.8
+2
3.3
10.0
13.3
+5
7.5
13.3
15.8
h2o2
Concentration (ppb)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
0.52
1.38
2.86
0.60
1.47
2.92
0.72
1.60
2.99
Percent Change
(from base)
165.4
450.0
+2
15.4
182.7
461.5
+5
38.5
207.7
475.0
PAN
Concentration (ppb)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
2.23
2.76
3.24
1.91
2.34
2.75
1.47
1.79
2.08
Percent Change
(from base)
0
23.8
45.3
+2
-14.4
4.9
23.3
+5
-34.1
-19.7
- 6.7
8 7 1 2 3 4
91
-------
TABLE 3-12. Maximum hourly concentrations and percentage changes for
ozone, and PAN for the future sensitivity tests for the simulation
of 1 July 1981, Tulsa, Oklahoma.
OZONE
Concentration (ppm)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
0.122
0.120
0.115
0.126
0.124
0.119
0.131
0.129
0.124
Percent Change
(from base)
-1.6
¦5.7
+2
3.3
1.6
-2.5
+5
7.4
5.7
1.6
Concentration (ppb)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
2.87
4.19
5.83
2.95
4.25
5.87
3.07
4.32
5.90
h2o2
Percent Change
(from base)
46.0
103.1
+2
2.8
48.1
104.5
+5
7.0
50.5
105.6
PAN
Percent Change
Concentration (ppb) (from base)
Change in Temp (K) _0_ +2 +5 0 +2 +5
Dobson Number
300 3.92 3.46 2.79 — -11.7 -28.8
250 4.24 3.79 3.13 8.2 - 3.3 -20.2
200 4.68 4.23 3.53 19.4 7.9 -10.0
8 7 12 3 4
92
-------
TABLE 3-13. Maximum hourly concentrations and percentage changes for ozone,
HoOo, and PAN for the future sensitivity tests for the simulation of 21 July
1980, Washington, DC.
OZONE
Concentration (ppm)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
0.120
0.124
0.126
0.124
0.127
0.129
0.128
0.131
0.134
Percent Change
(from base)
3.3
5.0
+2
3.3
5.8
7.5
+5
6.7
9.2
11.7
Concentration (ppb)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
0.91 1.02 1.18
2.16 2.26 2.39
3.88 3.94 4.05
Percent Change
(from base)
137.4
326.4
+2
12.1
148.4
333.0
+5
29.7
162.6
345.1
PAN
Concentration (ppb)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
3.14
3.66
4.31
2.77
3.21
3.83
2.22
2.60
3.14
Percent Change
(from base)
16.6
37.3
+2
-11.7
2.2
22.0
+5
-29.3
-17.2
0.0
87 123 4
93
-------
TABLE 3-14. Maximum hourly concentrations and percentage changes for ozone,
HoOo, and PAN for the future sensitivity tests for the simulation of 5 July
1984, Phoenix, Arizona.
OZONE
Concentration (ppm)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
0.119
0.121
0.121
0.122
0.124
0.124
0.125
0.127
0.127
Percent Change
(from base)
0
1.7
1.7
+2
2.5
4.2
4.2
+5
5.0
6.7
6.7
H2O2
Concentration (ppb)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
2.64
3.61
4.90
2.66
3.62
4.88
2.67
3.60
4.82
Percent Change
(from base)
36.7
85.6
+2
0.8
37.1
84.9
+5
1.1
36.4
82.6
PAN
Concentration (ppb)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
2.32
2.61
2.92
1.93
2.18
2.46
1.45
1.64
1.87
Percent Change
(from base)
0
12.5
25.9
+2
-16.8
- 6.0
6.0
+5
-37.5
-29.3
-19.4
87123 4
94
-------
TABLE 3-15. Maximum hourly concentrations and percentage changes for ozone,
HoOo, and PAN for the future sensitivity tests for the simulation of 10 August
1980, Nashville, Tennessee (trajectory number 1).
OZONE
Percent Change
Concentration (ppm) (from base)
Change in Temp (K) _0_ +2 +5 0 +2 +5
Dobson Number
300 0.119 0.120 0.122 -- 0.8 2.5
250 0.116 0.118 0.117 -2.5 -0.8 -1.7
200 0.111 0.112 0.112 -6.7 -5.9 -5.9
H2O2
Percent Change
Concentration (ppb) (from base)
Change in Temp (K) _0_ +2 +5 0 +2 +5
Dobson Number
300 3.01 3.02 3.03 — 0.3 0.7
250 4.40 4.39 4.38 46.2 45.9 45.5
200 5.70 5.71 5.63 89.4 89.7 87.0
PAN
Percent Change
Concentration (ppb) (from base)
Change in Temp (K) _0_ +2 +5 0 +2 +5
Dobson Number
300 1.75 1.47 1.11 — -16.0 -36.6
250 1.97 1.69 1.28 12.6 - 3.4 -26.9
200 2.30 1.96 1.52 31.4 12.0 -13.1
8 7 12 3 4
95
-------
TABLE 3-16. Maximum hourly concentrations and percentage changes for ozone,
H0O2, and PAN for the future sensitivity tests for the simulation of 10 August
1980, Nashville, Tennessee (trajectory number 2).
OZONE
Concentration (ppm)
Change in Temp (K) _0_ +2 +5
Dobson Number
Percent Change
(from base)
+2
+5
300
250
200
0.120
0.117
0.113
0.121
0.118
0.114
0.122
0.118
0.114
-2.5
-5.8
0.8
-1.7
-5.0
1.7
-1.7
-5.0
H2O2
Percent Change
Concentration (ppb) (from base)
Change in Temp (K) _0_ +2 +5 0 +2 +5
Dobson Number
300 3.06 3.07 3.08 — 0.3 0.7
250 4.47 4.46 4.41 46.1 45.8 44.1
200 5.83 5.80 5.73 90.5 89.5 87.3
PAN
Percent Change
Concentration (ppb) (from base)
Change in Temp (K) _0_ +2 +5 0 +2 +5
Dobson Number
300 1.77 1.48 1.10 — -16.4 -37.9
250 1.97 1.67 1.28 11.3 - 5.7 -27.7
200 2.27 1.94 1.49 28.3 9.6 -15.8
87 123 w
96
-------
TABLE 3-17. Maximum hourly concentrations and percentage changes for ozone,
HoOo, and PAN for the future sensitivity tests for the simulation of 31 August
1984, Phoenix, Arizona.
OZONE
Concentration (ppm)
Change in Temp (K) _0_ +2 +5
Oobson Number
300
250
200
0.122
0.124
0.124
0.126
0.127
0.128
0.134
0.134
0.133
Percent Change
(from base)
1.6
1.6
+2
3.3
4.1
4.9
+5
9.8
9.8
9.0
H2O2
Percent Change
Concentration (ppb) (from base)
Change in Temp (K) _0_ +2 +5 0 +2 +5
Dobson Number
300 1.29 1.39 1.61 - 7.8 24.8
250 2.15 2.22 2.43 66.7 72.1 88.4
200 3.36 3.45 3.57 160.5 167.4 176.7
PAN
Percent Change
Concentration (ppb) (from base)
Change in Temp (K) _0_ +2 +5 0 +2 +5
Dobson Number
300 4.12 3.71 3.11 — -10.0 -24.5
250 4.65 4.22 3.54 12.9 2.4 -14.1
200 5.41 4.96 4.25 31.3 20.4 3.2
87123 b
97
-------
TABLE 3-18. Maximum hourly concentrations and percentage changes for ozone,
H2O0, and PAN for the future sensitivity tests for the simulation of 6 August
1982, Tulsa, Oklahoma.
OZONE
Concentration (ppm)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
0.122
0.118
0.115
0.126
0.122
0.119
0.131
0.127
0.126
Percent Change
(from base)
-3.3
-5.7
+2
3.3
0.0
-2.5
+5
7.4
4.1
3.3
Concentration (ppb)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
5.01
5.90
7.06
5.03
5.92
7.11
H2O2
5.06
5.96
7.13
Percent Change
(from base)
17.8
40.9
+2
0.4
18.2
41.9
+5
1.0
20.0
42.3
PAN
Percent Change
Concentration (ppb) (from base)
Change in Temp (K) _0_ +2 +5 0 +2 +5
Dobson Number
300 4.90 4.36 3.66 — -11.0 -25.3
250 5.22 4.69 3.97 6.5 - 4.3 -19.0
200 5.68 5.17 4.47 15.9 5.5 - 8.8
8 7 12 3 4
98
-------
TABLE 3-19. Maximum hourly concentrations and percentage changes for ozone,
HoOo, and PAN for the future sensitivity tests for the simulation of 11 August
1981, Seattle, Washington.
OZONE
Concentration (ppm)
Change in Temp (K) 0 +2 +5
Dobson Number
300
250
200
0.116 0.123 0.130
0.136 0.145 0.156
0.170 0.182 0.198
Percent Change
(from base)
17.2
46.6
+2
6.0
25.0
56.9
+5
12.1
34.5
70.7
h2o2
Concentration (ppb)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
0.00
0.01
0.01
0.00
0.01
0.02
0.00
0.01
0.03
Percent Change
(from base)
+2
+5
PAN
Concentration (ppb)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
3.41 2.86 2.21
4.46 3.82 3.06
6.53 5.70 4.84
Percent Change
(from base)
30.8
91.5
+2
-16.1
12.0
67.2
+5
-35.2
-10.3
41.9
87 123 4
99
-------
TABLE 3-20. Maximum hourly concentrations and percentage changes for ozone,
HoOp, and PAN for the future sensitivity tests for the simulation of 7 August
1981, Seattle, Washington.
OZONE
Concentration (ppm)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
0.117
0.138
0.171
0.123
0.146
0.184
0.133
0.159
0.203
Percent Change
(from base)
18.0
46.2
+2
5.1
24.8
57.3
+5
13.7
35.9
73.5
h2o2
Concentration (ppm)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
0.01
0.01
0.03
0.01
0.01
0.04
0.01
0.02
0.06
Percent Change
(from base)
0
0.0
200.0
+2
0.0
0.0
300.0
+5
0.0
100.0
500.0
PAN
Concentration (ppm)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
4.12
5.44
7.93
3.60
4.86
7.34
2.89
4.02
6.48
Percent Change
(from base)
32.0
92.5
+2
•12.6
18.0
78.2
+5
-29.9
- 2.4
57.3
8 7 1 2 3
100
-------
OZONE
-i 1 r-
47 - to K
AT- + 2 K
4T> <5 K
0 160-
0 150-
E
a
0 140 —
0.130-
0.120l
P. 0,
Jo
0 » Q, o,
J0 *3 *0
0 010
« 000
871 2.3.
Los Angeles. June 26, 1974
FIGURE 3-4. Results of OZIPM future sensitivity tests for
the simulation of 26 June 1974, Los Angeles, California.
101
-------
OZONE
- 0 160
New York: June 24, 1980
4 ooo
3.500
3 ooo
2.500
2 000
1 500
1 000
0 500
0.000
"T 1
AT- 40 K
0 , 0, o,
Jo ss «b
H202
AT- +2 K
1 r
4T ¦ -t 5 K
c? > Oj O,
J0 5 *C)
O, o, 0,
-'o S5 eO
4 000
3 500
3.000
2 500
2 000
1 500
1 000
0 500
ooo
New York: June 24, 1980
FIGURE 3-5. Results of OZIPM future sensitivity tests for
the simulation of 24 June 1980, New York.
102
-------
OZONE
0 120
-------
OZONE
AT- 40 K
AT- +2 K
A 1 - +5 K
0 100 -
0 180
cs. 0 160 -
a
— C 160 q.
0 140 -
- 0 140
0 120L
c> > Oj, o
J0 %S eO
0 , 0-, 0
<5 «b
0 . 00J
*o
J-e 120
Washington August 7, 1980
H202
3 ooo
2 500
2 ooo
% 1.500
Q.
1 000
0 500
0 000
AT- 40 K
JUL
A T - +2 K
AT- +5k
0 t
*o «b
0 v Oj, p.
o, o. o.
J<2 ^5 *0
3 000
! 500
2 000
1 500 a
Q
1 000
0 500
eooo
Washington. August 7, 19S0
FIGURE 3-7. Results of OZIPM future sensitivity tests for
the simulation of 7 August 1980, Washington, DC.
8 712-3
104
-------
OZONE
air tOK
A T » +2 K
AT- +S K
J0 ^5
. n I.
J0 N5 ^0
Philadelphia: June 24, 1980
H202
4 000 r
3.500 -
—| 1 1 1 1 1
AT* +0 K AT- +2 K
AT- 1 5 K
4.000
3 500
3.000-
3 000
2.500-
2.500
2 000 ¦
2 000
1 500 -
1 500
1.000-
1 000
0 500 -
0 500
0 000L
ooo
Philadelphia' June 24, 1980
FIGURE 3-8. Results of OZIPM future sensitivity tests for
the simulation of 24 June 1980, Philadelphia, Pennsylvania.
105
-------
OZONE
i 1 r
A 7 » 4 0K
n 1 r
A 7 - -»2 K
\ t
A 1 ¦ 45 K
0 160-
- 0 160
0 160 -
0 160
0 140 ¦
0.120L
JH
0 » 0, Q-,
*3
0 140
- 120
3 500
3 000
2.500
2.000
1 500
1 000
0 500
0 000
Phoenix. September 14, 1984
H202
n r
AT" 40K
0 I °J> °J>
^0 *o
A 1 ¦ +2 K
i i r
A 7 - +5 K
0 i °J>
Jn
o > 0, o
3 500
3 000
2 500
2 000
1 500
1 000
0 500
e ooo
•Jn <"o
Phoenix- September 14, 1984
FIGURE 3-9. Results of OZIPM future sensitivity tests for
the simulation of 14 September 1984, Phoenix, Arizona.
106
-------
OZONE
A T - •+ 0
h —r
A T - 42 K
i I
AT ¦ +5 K
<>
¦S °*o
J0 •?¦$ <0
Tulscr July 1 , 1 981
H202
1 r
i T - +0 K
AT- +2 K
A T - <5«
°s> °) °J> °-J>
T ulsa. July 1, 1 981
*J£>
FIGURE 3-10. Results of OZIPM
the simulation of 1 July 1981,
107
future sensitivity tests for
Tulsa, Oklahoma.
-------
OZONE
h 1 1 1 1 r
0.180-
a 0 160 -
0 1^0 ¦
AT- +0 K
AT- t2 K
AT- -t 5 K
0 120L
Jo "\J '^o
n
o > O o
Jn »:*; °-
J0 ^6 <
Washington. July 21, 1980
H202
4 500 r
4 ooo -
AT- -tO K
AT. +2 K
AT- +5 K
4 500
4 000
3.500-
3 500
3.000 -
3 000
2 500-
2 500
2 000-
2 000
1.500-
1 500
1.000 -
1 000
0.500-
0.500
0 000L
<5 vO J0 <5 ^0
Washington. July 21. 19S0
^ooo
FIGURE 3-11. Results of OZIPM future sensitivity tests for
the simulation of 21 July 1980, Washington, DC.
108
87123
-------
OZONE
o leo -
0 160-
0.140 ¦
0 120L
A 7 * +0 K
01 °J> °J>
-------
OZONE
I I
A 1 - «0 K
-j 1 r
AT- +2 K
-1 1 1 1-
A T • 5 K
0 128 -
0 126
0.126 -
0 126
8
c
c
0 12-t ¦
0 12<
0 122 -
0 122
0 1 20l
0f 0, 0,
->0 Oj 0
Jo ^0
0 i °J>
«vs
3 000 C
- 2 000
1 000
i-eooo
Nashville' August 10, 1980
FIGURE 3-13. Results of OZIPM future sensitivity tests for
the simulation of 10 August 1980, Nashville, Tennessee
(trajectory number 1).
110
-------
OZONE
AT » 0 K
6 T • 42 K
AT- 45 K
0 126-
0 126-
0 124 -
0.122 -
0 120L
O i °J> °J>
J0
Of Q-> 0 J
Jo %s
Q > Q-> o,
°o *o *b
Nashville. August 10, 1980+
H202
i 1
AT- +2 K
6 000
1 I
AT- +5K
Nashville: August 10, I960*
FIGURE 3-14. Results of OZIPM future sensitivity tests for
the simulation of 10 August 1980, Nashville, Tennessee
(trajectory number 2).
Ill
-------
02 ONE
0 135 -
a 0 U0-
0 125-
-i r*
A 7 - 4 0 K
AT* 42 K
A T • 4$ *
0 1201-
* ^5
°i °*
J0 <5 ^0
Phoenix1 August 31, 1984
H202
4 OODr
i 1 r
AT- 40 K
A T • +2 K
AT *¦ +5 K
4,000
J 000-
a 2 D00 -
Cl
-\ ooo-
0 000L
Phoentx: August 31, 1954
FIGURE 3-15. Results of OZIPM future sensitivity tests for
the simulation of 31 August 1984, Phoenix, Ari2ona.
671 2 3
112
-------
OZONE
0 180-
0 180
0 1G0 -
0 160
0 140 -
0 140
0 120-
0 120
0 100L
Tulsa: August 6, 1982
H202
*o
*-e ioo
7.500
7.000
6.500
6 000
5.500
5 000
4 500
4.000
3.500
3.000
2.500
2.000
1.500
1 000
0 500
0 000
AT- +5 K
7 500
7.000
6 500
6 000
5 500
5 000
4 500
4 000
3.500
3 000
2 500
2 000
1 500
1 000
0 500
e ooo
Tulsa' August 6, 1982
FIGURE 3-16. Results of OZIPM future sensitivity tests for
the simulation of 6 August 1982, Tulsa, Oklahoma.
113
-------
OZONE
O 160
0 160
0 140
0.120
-| 1 1 1 1 1 1 r
11 • 40K 47 • (2 K
o, Oj o,
Jr> ¦?.<; «7
1
AT- •( 5 K
0 160
0 160
0 140
O, 0, o, o., o, o
6 120
[0 <5 *0 J0 ^0
Seattle: August 11, 1981
Jo '^s
H202
0 040r
~1 1 1-
»T - +0 K
-i r
A T • + 2 K
~I 1 r-
A T - 15k
0.040
0 030-
0 020-
0 010-
0 000L
O •> C , 0
_l I l_
Jo ^ 0 Jr, ^ "¦?,
- 0 030
- 0.020
- 0 010
0 „ 0, 0 0 > O, 0
ooo
ro
-------
OZONE
AT - 4 0 K
AT" +2 K
i r~
AT- +5 K
0 200 -
- 0 200
0 180 ¦
- 0 180
0 160 •
- 0 160
0 140 -
- 0.140
0 120L
Seattle: August 7, 1981
H202
120
0.060
o.oso
0 040
0 030
0.020
0 010
0 000
AT- tOK
AT- +2 K
AT- +5 K
0 060
0.050
0 040
0 030
0 020
0 010
e ooo
Seattle: August 7, 1981
FIGURE 3-18. Results of OZIPM future sensitivity tests for
the simulation of 7 August 1981, Seattle, Washington.
115
-------
OZONE
O 240
0 220
0 200
a 0.180
0 160
0 140
0 120
I I
AT- lOK
n 1 1 1 1 r
AT--»2K A 7 - ¦« 5 K
C 240
0 220
0 ?00
0 180 |
0 160
0.140
O, O, o,
Jo
-------
OZONE
AT- 40 K
AT- *2 K
AT- +5 K
Compliance Mechanism — Phoenix: July 5, 1984
0 124
0 123
0 122
0 121
0, O, O,
Jo eo
0, O 0.
°o "ss «b
^ 120
H202
4 ooo
3 000
a 2.000
Q
1 000
0 000
-| r-
A 1 • +0 K
AT" +2 K
AT- +5 K
4 000
- 3.000
2 000 d
a
- 1 000
*«000
Compliance Mechanism — Phoenix- July 5, 1984
FIGURE 3-20. Results of OZIPM future sensitivity tests for
the multi-day simulation of an ozone NAAQS attainment scenario
for Pheonix, Arizona.
117
-------
TABLE 3-21. Maximum hourly concentrations and percentage changes for
ozone, and PAN for the future sensitivity tests for the multi-day
simulation of 26-27 June 1974, Los Angeles, California.
OZONE
Concentration (ppm)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
0.115
0.146
0.212
0.119
0.152
0.219
0.119
0.155
0.229
Percent Change
(from base)
27.0
84.4
+2
3.5
32.2
90.4
+5
5
3 .8
99.1
Concentration (ppm)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
0.20
0.36
0.73
0.26
0.44
0.88
0.31
0.54
1.18
H2O2
Percent Change
(from base)
80.0
265.0
+2
30.0
120.0
340.0
+5
55.0
170.0
490.0
PAN
Change in Temp (K)
Dobson Number
300
250
200
Concentration (ppm)
0 +2 +5
1.12
2.10
4.10
1.43
2.56
4.56
1.76
3.18
5.16
Percent Change
(from base)
0
0.9
266.1
+2
27.7
128.6
307.1
+5
57.1
183.9
360.7
118
-------
TABLE 3-22. Maximum hourly concentrations and percentage changes for
ozone, H202» and PAN for the future sensitivity tests for the multi-day
simulation of attainment of the NAAQS in Phoenix, Arizona, using a
modified data set from 5 July 1984.
OZONE
Percent Change
Concentration (ppm) (from base)
Change in Temp (K) _0_ +2 +5 0 +2 +5
Dobson Number
300
.100
.104
.108
—
4.0
8.0
250
.114
.116
.119
14.0
16.0
19.0
200
.119
.121
.123
19.0
21.0
23.0
HoO
2U2
Concentration (ppm)
Change in Temp (K) _0_ -*-2 +5
Dobson Number
300
250
200
0.37
1.06
2.35
0.44
1.18
2.42
0.57
1.32
2.51
Percent Change
(from base)
186.5
535.1
+2
+5
18.9 54.1
218.9 256.8
554.1 578.4
PAN
Percent Change
Concentration (ppm) (from base)
Change in Temp (K) _0_ +2 +5 0 +2 +5
Dobson Number
300 1.83 1.67 1.37 — - 8.7 -25.1
250 2.12 1.83 1.39 15.8 0.0 -24.0
200 2.25 1.90 1.41 23.0 3.8 -23.0
119
-------
TABLE 3-23. Maximum hourly concentrations and percentage changes for
ozone, ^0?, and PAN for the future sensitivity tests for the simulation
of 5 July 1984, Phoenix, Arizona, with the CALL mechanism.
OZONE
Concentration (ppm)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
.118
.118
.115
.121
.121
.118
.124
.124
.122
Percent Change
(from base)
0.0
-2.5
+2
2.5
2.5
0.0
+5
5.1
5.1
3.4
H2O2
Change in Temp (K)
Dobson Number
300
250
200
Concentration (ppm)
0 +2 +5
2.70
3.42
4.31
2.72
3.45
4.33
2.74
3.44
4.34
Percent Change
(from base)
26.7
59.6
+2
0.7
27.8
60.4
+5
1.5
27.4
60.7
PAN
Concentration (ppm)
Percent Change
(from base)
Change in Temp (K)
0
+2
+5
0
+2
Dobson Number
300
2.24
1.88
1.42
-16.1
250
2.45
2.06
1.56
9.4
- 8.0
200
2.67
2.30
1.79
19.2
2.7
+5
-36.6
-30.4
-20.1
120
-------
TABLE 3-24. Maximum hourly concentrations and percentage changes for
ozone, H0O2. and PAN for the future sensitivity tests for the simulation
of 13 July 1979, Philadelphia, Pennsylvania, with the CALL mechanism.
OZONE
Concentration (ppm)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
.120
.140
.163
.126
.148
.170
.134
.160
.180
Percent Change
(from base)
16.7
35.8
+2
5.0
23.3
41.7
+5
11.7
33.3
50.0
H2O2
Concentration (ppm)
Change in Temp (K) _0_ +2 +5
Dobson Number
Percent Change
(from base)
+2
+5
300
250
200
0.03
0.12
1.69
0.03
0.19
2.07
0.05
0.32
2.57
300.0
5533.3
0.0
533.3
6800.0
66.7
966.7
8466.7
PAN
Concentration (ppm)
Change in Temp (K) _0_ +2 +5
Dobson Number
300
250
200
3.27
4.77
7.27
2.88
4.39
6.54
2.35
3.79
5.47
Percent Change
(from base)
45.9
122.3
+2
- 11.5
34.3
100.0
+5
28.1
15.9
67.3
121
-------
SECTION 4
DISCUSSION OF URBAN SIMULATION RESULTS
Our overall goal in this discussion is the extraction from the urban simu-
lation results of information related to the state of urban photochemical
reactivity under potential future conditions of increased surface tempera-
ture and ultraviolet radiation. Before presenting this information in its
necessarily condensed and tabulated form, we discuss the urban and photo-
chemical processes that act to produce such results by describing typical
simulations, focused by the grouping process previously described.
URBAN PHOTOCHEMICAL PROCESSES
Because we want to elucidate photochemical processes that pertain to urban
areas under the conditions of this study, we describe simulation results
from "typical" test sets representative of each group discussed in Section
3 (a complete discussion of all results from individual test sets would be
far too cumbersome for this report). Our discussions and the figures used
to show concentration changes will focus on extreme future conditions (+0
and +5 K, and 0.300 and 0.200 cm-atm overhead ozone column) to clearly
isolate the specific chemical processes and types of effects that occur.
Overall trends across the range of changes in the study are addressed in
our analysis of all results following this discussion of dynamic pro-
cesses.
Ozone
We begin our discussion of possible changes in urban photochemical pro-
cesses with the Group 1 test sets. These data sets represent non-attain-
ment days requiring substantial control of NMOC to comply with the ozone
NAAQS. All base-case simulations for Group 1 produced a maximum hourly
average ozone concentration of over 0.17 ppm. As a representative future
simulation set, we have chosen the 13 July 1979 tests for Philadelphia
(the Los Angeles simulations are discussed with the multi-day tests).
87 1 23f 6
122
-------
Figure 4-1 provides future simulation results for 0.300 and 0.200 cm-atm
overhead ozone columns at measured and +5 K temperature profiles. The
+0 K/0.300 cm-atm scenario is the future base case of ozone NAAQS attain-
ment. As with all simulation results shown, the ozone, NO2 and H2O2
traces are more distinctly separated for the ozone column changes than for
the assumed temperature changes. Therefore, the groupings found in most
figures for ozone and H2O2 show the 0.200 cm-atm results far above the
0.300 cm-atm results, and the +5 K simulations as slightly more reactive
than the +0 K runs. For NO2, an oxidant precursor that is eliminated more
rapidly in more reactive systems, these trends are reversed. In the case
of PAN, recall that peroxyacyl compounds exhibit some of the most extreme
temperature-dependent behavior of all atmospheric compounds. Hence, PAN
concentrations are lower for higher temperature simulations due to their
much higher decomposition rates (see Figure 4-1).
A key result that can be extracted from this plot and those to follow is
that an increase in ultraviolet irradiance tends to enhance short-term
reactivity in a photochemical system. This results in a more rapid ozone
formation rate early in the day because oxidant precursor species are
plentiful. However, since the afternoon maximum ozone concentrations
depend on afternoon precursors, which can be significantly depleted by
enhanced reactivity in the morning, the short-term trends cannot always be
equated with long-term reactivity measures such as maximum afternoon ozone
concentrations.
In the case of the Group 1 test data, N0X and NM0C emissions are high
enough throughout the day that the emissions reduction required to attain
the ozone NAAQS still allows sufficient precursors to exist (or accumu-
late) late in the afternoon during attainment conditions. Note also that
the ozone concentration is still increasing at the 1800 hour of the
attainment simulation, indicating additional oxidant-forming potential at
the end of the EKMA calculation period for those conditions. Increased
energy input to such a system (due to future changes in surface tempera-
ture or stratospheric ozone) provides increased reactivity, and therefore,
more efficient utilization of these precursors to form additional ozone
and oxidant products. This is evident in Figure 4-1, where more extreme
reactivity (from the 0.200 cm-atm overhead ozone column) consumed most of
the N02 faster, producing ozone and PAN more rapidly, and resulting in
enhanced H2O2 production. Higher PAN production can also affect continu-
ing reactivity since its decomposition near the end of the day contributes
acetyl peroxy radicals and NO2 back into the reactive mixture.
To represent simulations in the Group 2 cities, we selected the results of
the 21 July 1980 Washington DC and 1 July 1981 Tulsa simulations (Figures
4-2 and 4-3). Recall that these cities required moderate NM0C control
87 1 23j- 6
123
-------
Philadelphia, PA — 13 July 1979
t
t
c
6
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c
O
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A
£
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A.
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P
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a
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-P*
A
6.
A.
C
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c
n
0
0.20
cm-atmy
10
A
£L
A.
C
a
o
*
c
•
o
c
z
<
Simulation Hour
FIGURE 4-1
simulation of
Ozone, NO?, H2O?, and PAN plots for
13 July 1979, Philadelphia, Pennsyl
Simulation Hour
and PAN plots for extreme scenarios in the future sensitivity tests-
vania.
8712 3
-------
Washington, DC - 21 July 1980
E
ft
ft
c
0
1
c
•
o
c
6
U
•
c
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E
ft
a
w
s
%
*
t
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c
6
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8
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ro
ai
a
ft
s_<<
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i
r
•
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c
c
u
Tt
c
n
z
a
a.
ft
w
t
«
*
«
*
c
0
c
0
u
X
5
Simulation Hour
Stfnutattan Hour
FIGURE 4-2. Ozone, N02> an(* P^°^-s ^or extreme scenarios in the future sensitivity tests-
simulation of 21 July 1980, Washington, DC.
871 2 3
-------
Tulsa, OK - 1 July 1981
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FIGURE 4-3. Ozone, NOo, H202» and PAN plots for extreme scenarios in the future sensitivity tests--
simulation of 1 July 1981, Tulsa, Oklahoma.
871 2 3
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(except in the case of Tulsa, which had an NM0C/N0x ratio of 25.5) to
achieve the ozone NAAQS from measured concentrations of 0.17 to 0.14
ppm. We can describe the results by continuing the preceding Group 1 dis-
cussion. Analysis of Figures 4-2 and 4-3 shows that, even in the ozone
attainment simulations (+0 K and 0.200 cm-atm ovrhead ozone column), the
NO2 concentration approaches zero in the afternoon, with the result that
the rate of change in ozone concentration also tends to approach zero.
Comparison with the Group 1 simulation shown in Figure 4-1 indicates that
such a termination of oxidant-formation potential occurred only in the
more extreme (enhanced ultraviolet) future cases. Hence, it appears that
the moderate, Group 2 scenarios may have sufficiently low precursor load-
ing rates and more beneficial meteorological scenarios so that control of
NM0C to attain the ozone NAAQS diminishes the overall reactive potential
of the system to the point where large increases in afternoon ozone con-
centrations are not observed with additional energy input from increased
temperature or ultraviolet irradiance. However, as noted, these simula-
tions all predict enhanced short-term reactivity, resulting in more rapid
rates of ozone production earlier in the day (and possibly closer to more
densely populated areas).
In the case of the Tulsa simulation, this enhanced early reactivity due to
future diminished ozone column densities (0.200 cm-atm) serves to deplete
enough oxidant precursors to limit afternoon ozone production to levels
below those predicted for the base-case ozone column density (0.300 cm-
atm). Again, this result points out one of the key differences to be dis-
cerned from the predictions in this study; namely, that increases 1n
ultraviolet Irradiance tend to enhance short-term, midday reactivity in
ways that do not always result in greater overall ozone production because
(1) the greatest increases in ultraviolet irradiance occur at solar noon,
and (2) the results of these increases are enhanced photolysis rates and
formation of radical species (which are highly reactive and have very
short atmospheric half lives). On the other hand, increases in surface
temperature over the range studied provide generally higher yields of
oxidants and lower yields of PAN in all cases, for all periods during the
simulation, mainly because the future temperature increases were applied
evenly across the day.
To represent the group of test cases with design ozone concentrations
nearly in attainment of the ozone NAAQS (Group 3), we chose the Phoenix,
simulation of 31 August 1984. These results are shown in Figure 4-4.
Ideally, this group represents days on which moderate-to-low emissions are
combined with beneficial meteorological scenarios to yield less reactive
ozone production conditions. In the data shown, for instance, the effect
of large and rapid dilution is seen in the steep morning decline of the
NO2 curve. Results are similar to those for Group 2, where the rate of
87 1 2 3r 6
127
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Phoenix, AZ — 31 August 1984-
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FIGURE 4-4. Ozone, NO2, H0O2, and PAN plots for extreme scenarios in the future sensitivity tests--
simulation of 31 August 1934, Phoenix, Arizona.
871 2 3
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morning oxidant production is larger with more energetic future condi-
tions, but depletion of precursors by midday limits the overall amount of
ozone that can be produced. In fact, in cases where large dilution occurs
with morning mixing height rise, the effects of additional ultraviolet
radiation may be further countered since the increased rate of oxidant
formation will cause ozone production to occur earlier, during the period
of high morning dilution. This brings to light the fact that changes in
global climate due to Greenhouse warming will affect parameters other than
temperature at the surface. Some of these additional factors, which can
only be addressed here in a cursory manner, could be the rate of change in
mixing depth, amount of cloud cover, wind speeds, and water vapor concen-
trations.
In this discussion we have begun to touch on some interesting charac-
teristics of photochemical dynamics in possible future airsheds. As with
the present-day issue of urban ozone control, the magnitude of the poten-
tially harmful affects of photochemical smog formation can be related to
what is loosely described as the oxidan-forminq potential of the urban
system. This, in turn, is generally thought of as a function of meteoro-
logical conditions (mixing depth, temperature, etc.) and the efficiency
with which an individual urban atmospheric system can chemically convert
precursors to oxidant. This efficiency, sometimes also described as
reactivity, can differ due to the location of an urban area (i.e., the
variations in solar elevation at different latitudes) and will certainly
vary due to the changes in ultraviolet irradiance or surface temperatures
as studied in this investigation. We view this concept of reactivity as a
short-term measure of chemical rates (such as the rate of ozone formation,
rates of precursor decay or the mass flux through various radical reaction
paths), whereas oxidant-forming potential relates more closely to the
maximum concentration of oxidant that could be formed under various condi-
tions for a given level of precursors (depleting all or most precursors in
the process). The future scenarios always show increased reactivity with
more energy input (due to either enhanced ultraviolet irradiance or tem-
perature) but do not always Indicate additional oxidant-forming potential
when compared to the future base case.
In the Group 1 test sets we noted both increased reactivity (in the form
of more rapid precursor depletion and ozone formation) and increased oxi-
dant-forming potential as higher amounts of ozone are formed at the end of
the day. The Group 2 and 3 scenarios also indicated greater reactivity,
but showed far less oxidant-forming potential, and sometimes produced less
ozone for the future cases. This appears to be mainly because oxidant
precursors were already sufficiently depleted in the Group 2 and 3 future
base cases (+0 K and 0.300 cm-atm) to have achieved nearly the maximum
ozone-forming potential for those days. Additional energy input in the
non-base-case scenarios used the precursors more efficiently to produce
87123f 6
129
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ozone faster, but did not result in significantly higher ozone concentra-
tions. In the Group 1 tests, however, the future base-case scenarios were
created on the basis of control of ozone to 0.12 ppm at 1800 hours (the
EKMA completion point). At that point, sufficient precursor species and
emissions remained to result in a still-increasing ozone slope; indicating
that the full oxidant-forming potential of the system was not yet
realized. Therefore, the future Group 1 scenarios not only produced oxi-
dant more rapidly, but they utilized the precursors more efficiently to
generate higher concentrations of ozone in the time alloted. The differ-
ence here appears to be one of the range over which the original EKMA cal-
culations were made. Extension of the EKMA termination time past 1800
hours would probably yield higher NM0C control requirements, providing
less future sensitivity, because more of the oxidant-forming potential of
those days was actually accounted for. To provide an even more extreme
example, we now discuss the Group 4 data.
As stated in our earlier discussion of Group 4 data, we feel that the NM0C
and N0X measurements that contributed to the 0ZIPM input data are rather
uncertain for these simulations. The sampling period appears to have been
only one week for a very limited monitoring network. In addition, it is
not clear whether the morning inversion height was actually 250 m, or
whether that value was assumed. A lower morning layer would provide addi-
tional dilution around midday. On the other hand, since these precursor
and mixing height values were used in the Washington SIP and do present a
unique future scenario, we briefly discuss them here.
We use the results of the 11 August 1981 simulation for Seattle, (Figure
4-5) as our example of a Group 4 future sensitivity test. The interesting
aspect of these data is the persistance of high levels of N0X throughout
the simulation. As we saw with the Group 1 data, the availibility of oxi-
dant precursors near the end of the day in the future base-case scenario
can represent unused oxidant-formation potential. When additional radiant
or thermal energy is input to the system through future scenarios of
stratospheric ozone depletion or surface temperature increases, much
higher levels of oxidant and oxidized products are predicted to be
formed. We also see a similarity with the Group 1 tests in the fact that
the future base cases generated from EKMA control calculations do not
account for the overall oxidant-forming potential of the simulated chemis-
try, but only that up to 1800 hours. The control calculations for Groups
2 and 3 apparently accounted for a larger portion of their potential,
since most design ozone was formed before 1800 hours. Hence, the more
extreme Group 2 and 3 future scenarios produced ozone faster, but did not
yield significantly different amounts from the future base-case values
(0.12 ppm).
87123r 6
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Seattle, WA - 11 August 1981
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FIGURE 4-5. Ozone, NO2, H0O2, and PAN plots for extreme scenarios in the future sensitivity tests-
simulation of 11 August 1981, Seattle, Washington.
871 2 3
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The difference between the Group 1 and Group 4 test sets is that though
Seattle does not have a high precursor loading rate throughout the day
(such as in the Los Angeles Basin or the Northeast Corridor regions), a
combination of meteorological and emissions effects results in a high
sensitivity to future changes. As noted, these include the more northerly
location (lower light intensity), higher initial N0X concentrations, and
limited mixing height rise (providing a parcel with only about 40 percent
of the volume of a typical Group 1 simulation). The combined effect of
these factors was to initially yield only a small NMOC emission control
requirement from the EKMA calculation, because the lower light intensity
and high N0X concentrations limited ozone formation to a period later in
the day when solar energy input was diminishing. Therefore, under present
conditions, the Group 4 air parcels require little NMOC control to achieve
the ozone NAAQS (see Table 3-5). However, because these test cases are
precursor-rich and energy-limited, the future base case (NAAQS attainment
for ozone) scenarios appear to be near an energy "threshold" where addi-
tional energy (such as the enhanced ultraviolet irradiation caused by
stratospheric ozone depletion) could provide significant impetus for
increased afternoon reactivity by more efficiently utilizing the ozone
precursors. Therefore, though both the data and simulations must be veri-
fied, these results show sensitive future scenarios not completely like
the emissions-oriented Group 1 simulations. The Group 4 tests combine a
number of variable factors into a situation where, with the increased
energy of potential future global changes, a "threshold" may be crossed
and a rather dormant urban photochemical system can now achieve a large
fraction of its oxidant-forming potential.
Hydrogen Peroxide and Other Products
Up to now, we have only briefly described H2O2 concentrations and produc-
tion rates. We expand that description by discussing the overall chemical
dynamics of a typical system. A detailed explanation of the specific
photolytic and chemical processes that vary significantly with enhanced
ultraviolet irradiance has been provided in Section 2. Generally, the
enhanced ultraviolet irradiance expected to result from stratospheric
ozone depletion should increase surface photolysis rates in the tropo-
sphere, providing higher production rates (and therefore, higher concen-
trations) of radical species. The two key reactions to be enhanced appear
to involve the photolysis of ozone to 0(*D) and formaldehyde to radical
products (two H radicals per formaldehyde molecule). As we have already
noted, 0(D) provides two OH radicals upon reaction with water vapor, and
H radicals react rapidly with atmospheric 02 to form HO2 radicals. These
87123r 6
132
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two species are highly reactive and, therefore, occur at very low concen-
trations. In simulations of urban photochemistry, traces of their concen-
trations can be used as indicators of the extent of photochemical oxida-
tion processes.
Consider the results of future sensitivity simulations for the Philadel-
phia data set of 24 June 1980 provided in Table 3-6 and Figure 4-6. These
results are similar to the earlier Group 1 future scenario data in that
the 0.200 cm-atm case consumed N0X at a greater rate during the afternoon,
resulting in additional reactivity and greater ozone production. Also,
from these and the earlier data, it is apparent that ^2 production is
extremely sensitive to increases in ultraviolet irradiance. Referring to
Figure 4-6, this can be delineated in a simplified manner:
(1) Additional photolysis increases the source terms for OH and HO2
and, therefore, their concentrations,
(2) Higher concentrations of OH more rapidly deplete organic pre-
cursors, creating additional ozone in the radical chain oxida-
tion process of photochemical smog,
(3) Higher OH also removes NO2 more rapidly, forming HNO3,
(4) Higher OH and O3 diminish NO concentrations, eliminating a major
sink for HO2 and allowing it to Increase, and
(5) With little N0X remaining in the system, HO2 is lost through
radical-radical recombination reactions, forming such products
as H2O2.
The plots given in Figure 4-6 are all consistant with this description.
For instance, the NO2 and HNO3 traces are plotted on the same ordinate
scale to point out tnat the lost NO2 appears as HNO3 due to Increased
reaction of NO2 with OH at that time of day (OH reaches concentrations as
much as three times higher in the 0.200 cm-atm simulations). Also note
that the O3 and HNO3 traces generally track each other quite well, since
both are dependent on OH flux and N0X concentration changes. As for H2O2
sensitivity, consider the differences in the concentrations and timing of
the mid-afternoon OH peak, which influences the late-afternoon yields and
time offsets for H02 (though it is difficult to detect, NO at this time is
at least an order of magnitude lower in concentration for the 0.200 cm-atm
scenarios), and therefore, the end-of-the-day production rate of H202.
The result is the shapes and timing of the H2O2 curves shown in Figures
4-1 through 4-4. We did not plot H2O2 for the Group 4 case (Figure 4-5)
because enough NO remained in the air parcel at all times to hold down H02
concentrations and, thus, H2O2 production.
87123f 6
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Philadelphia, PA — 24 June 1980
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FIGURE 4-6. Ozone, NO?, NO, and HNO3 plots for extreme scenarios in the future sensitivity tests--
simulation of 24 June 1980, Philadelphia, Pennsylvania.
871 2 3
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Philadelphia,
Simulation Hour
FIGURE 4-6. Concluded.
871 2 3
Simulation Hour
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DISCUSSION OF SINGLE-DAY SCENARIO RESULTS
The previous discussion was intended to provide the reader with an under-
standing of the photochemical processes occurring at various periods in
the future sensitivity scenarios. We now present more complete results
from these sensitivity tests. Because the primary objective of this
research was to investigate potential impacts of global changes on urban
ozone formation, and because our future scenarios were based on control of
NMOC to attain the ozone NAAQS, we discuss the predicted responses of
ozone concentrations to these global changes in depth. Since urban pro-
duction of hydrogen peroxide might influence aqueous-phase acidification
in downwind areas, we also consider the effects of both future NMOC con-
trol and potential global changes on H2O2 concentrations. Whenever pos-
sible, the previous discussion and figures are referred to. For each
species, we first consider the effects of temperature increases, followed
by a discussion of the impacts of increased ultraviolet irradiance due to
decreases in stratospheric ozone levels. Following our presentation of
these data, we address the impacts of combined changes and discuss the
implications of future changes.
Ozone
The predicted effects of surface temperature increase for a 0.300 cm-atm
overhead ozone column are shown in Figure 4-7. These data represent the
percent increases predicted for maximum hourly ozone for +2 and +5 K
increases over the base-case temperature profiles. The divisions in the
figure represent the first three general test groups previously
described. We see from these plots that the average rate of predicted
ozone increase per degree Kelvin (over the +5-K range of this study) was
nearly linear in these groups. The resulting rates are given in Table 4-
1, averaged for each general test group. Rates of increase in that table
are calculated from the results of the +5-K simulations. In almost all
cases, the rates calculated from the +2-K simulations are statistically
indistinguishable from the +5-K simulations, indicating a linear increase
over the 5-K degree (9 Fahrenheit degree) range of this study.
It is also possible to estimate the effects of temperature increase for
the non-base-case overhead ozone columns (0.250 and 0.200 cm-atm) by
determining the relative percentage increase in the ozone maximum over the
normal temperature predictions for each ozone column. For instance,
though the Los Angeles simulations showed average hourly ozone increases
above the future base case of 40.2 percent, 44.6 percent, and 47.3 percent
87 1 2 3f 6
136
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1101
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(LA, JN2674; NY, JM?480;
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Group 2
(Phoenix, SE1484; Tulsa, JL0181;
Wash, JL2180; Phoenix, JL0584;
left to right)
Increase in Temperature (K)
FIGURE 4-7. Percent increase in predicted ozone over
the future base case (0.12 ppm) for two temperature
increments and three test groups.
137
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for +0 K, +2 K, and +5 K at a 0.200 cm-atm ozone column, the relative
increases over +0 K for that column were 3.2 and 5.1 percent for the +2 K
and +5 K scenarios. Performing similar calculations for all cities and
groups, we find that the 0.300 cm-atm linear factors hold quite well
through the 0.250 cm-atm calculations, and begin to diminish only slightly
for 0.200 cm-atm (see Table 3-21). As we see later, this is an indication
that the higher energy conditions present at 0.200 cm-atm tend to use a
large fraction of the oxidant-forming potential of these urban systems
(especially in the more reactive, Group 1 test cases), leading to
diminished ozone formation potential in the more extreme cases. Note also
that though the potential to form more ozone with increased temperature is
diminished, it is still a positive response.
As previously discussed, the Group 4 scenarios represent a somewhat unique
set of conditions compared to those of the other three general groups
because of their singular location, meteorological, and initial concentra-
tion conditions. As noted, these conditions cause significant differences
in future reactivity because of the greater sensitivity of the air parcels
to increased ultraviolet or thermal energies of the future conditions.
For the base-case ozone column simulations, a 2.6 percent/K- increase was
detected over the 5-K range of the study. Relative increases calculated
for the smaller ozone columns indicate an increasing ability to produce
ozone with decreasing ozone column (i.e., there is no evidence of
diminished ozone-forming potential over the ozone column range of this
study as there was in the other groups). We provide these results in
Table 4-1 and because of the unique character of these simulations, we
also list overall average results with and without the Group 4 data.
Predicted overall average increases in maximum hourly ozone due to
increased surface temperature are 1.6 percent/K (including the data from
Group 4), or 1.4 percent/K (2.5 percent/degree Fahrenheit) for only the
first three groups. The latter value decreases to 1.2 percent/K for the
0.200 cm-atm overhead ozone column simulations.
A comparison of the concentration traces used to represent each general
test group (Figures 4-1 through 4-6) indicates sensitivity to potential
increases in ultraviolet irradiation (ozone column depletion) in all
tests. However, these results also indicate that though the amount of
time required to produce concentrations near the NAAQS is clearly
shortened, the maximum predicted ozone does not always increase signifi-
cantly. Therefore, we focus next on the predicted effects of ozone column
depletion on maximum hourly ozone concentrations, as shown in Figure 3-26
for the first three general test groups. Recall that the Group 1 and 4
future base case scenarios showed increasing ozone concentrations at the
1800 hour termination of EKMA and individual scenario calculations, indi-
cating that those systems had not yet reached their individual oxidant-
forming potential. Additional input of thermal or radiant energy into
87123f 6
138
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Table 4-1. Rates of Increases in Maximum Hourly Ozone Concentrations with
Increases in Temperature and Decreases in Overhaed Ozone Column*
Average O3 Increase (percent/Kelvin)
Ozone Column: 0.30 cm-atm 0.25 cm-atm 0.20 cm-atm
Test Group
1 1.8 1.9 1.4
2 1.3 1.2 1.2
3 1.1 0.9 0.9
4 (2.6) (3.0) (3.5)
Total (1,2,3) 1.4 1.4 1.2
Total (all) 1.6 1.6 1.5
Average O3 Increase (pet./pet, decrease in 03 column)
Temperature: base base + 2 K base + 5 K
Test Group
1 1.1 1.1 1.0
2 0.1 0.1 0.1
3 -0.1 -0.1 -0.1
4 (1.4) (1.5) (1.6)
Total (1,2,3) 0.4 0.4 0.4
Total (all) 0.5 0.5 0.5
^¦Percent increases are increases over the future base case value of
0.12 ppm.
87 1 2 3 it
139
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these systems due to future global changes was predicted to enhance reac-
tivity and result in greater production of ozone and other oxidation pro-
ducts prior to 1800 hours. These results are summarized in Table 4-1 and
indicate that approximately a 1.0 percent increase in surface ozone maxi-
mum concentration was predicted for each percent decrease in overhead
ozone column. For Group 4, this value was about 1.4 percent; as with the
temperature data, this rate increased with additional depletion of the
column. The less reactive groups (2 and 3) yield only a 0.1 and -0.1 per-
cent change in ozone for a percent change in overhead column (note the
ordinate scale change in Figure 4-8), indicating that most or all of the
future scenario oxidant-forming potential had already been achieved in the
base-case simulations. The results for these groups (and Group 1) were
generally linear over the 0.10 cm-atm range of study, though slightly
higher rates of change were found in the 0.30 to 0.25 cm-atm comparisons
than in those from 0.25 to 0.20 cm-atm. Therefore, in almost all cases,
additional energy input from the future scenarios produced ozone at or
above the ozone NAAQS (the future base case), and always produced ozone
and other oxidized products faster (sometimes hours faster) than the base
case simulations.
Hydrogen Peroxide and Other Products
The hydrogen perixide results are not easily described for two reasons:
First, as noted in the photochemical dynamics discussion, ^2 production
rates and concentrations are extremely sensitive to variations in radical
flux. In addition, since radical flux is a function of ultraviolet
irradiance, the increases in H2O2 are linked to decreases in stratospheric
ozone. This is especially obvious when contrasted with ozone changes
since, unlike ozone, H2O2 does not have a significant photolysis loss
reaction. Therefore, once chemical conditions are such that H2O2 buildup
begins in the afternoon, there are only minor ^0? loss reactions to
suppress concentration increases (which are usually only halted at sunset
when radical concentrations drop substantially).
The second reason why the predicted impact of future global changes on
urban H2O2 concentrations is less easily described is that there is no
simple standard reference concentration on which to base a reasonable com-
parison. The individual simulation results given in Tables 3-6 through
3-20 present percentage increases of predicted future values over those of
the future base case (+0 K/0.300 cm-atm) simulation. For ozone, such
comparisons are very pertinent because of the federal mandate to achieve
future base case conditions (0.12 ppm), which is the basis of the protocol
that directs this study. There is, however, no such common basis for
8 7 1 2 3 f 6
140
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I
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Group 2
(Phoenix, SE1484; Tulsa, JL0181;
Hash, JL2180; Phoenix, JL0564;
left to right)
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(Nash, AU1080-1; Nash. AU1080-2;
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Future Ozone Column Density (cm-atm)
FIGURE 4-8. Percent increase in predicted ozone over
the future base case (0.12 ppm) for two ozone column
density decrements and three test groups.
141
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hydrogen peroxide comparisons. In addition, because the NMOC emission
controls used in our EKMA calculations to derive future base-case
conditions appear to be very effective in the limitation of hydrogen
peroxide formation, relative comparisons of increases in H2O2
concentration over the future base-case values (Tables 3-6 through 3-20)
can yield huge percentages. These numbers are derived from photochemical
kinetics model predictions indicating that the effect of NMOC controls
should tend to limit the photochemical reactivity in an air parcel,
shifting the oxidant-formation period to later in the afternoon when the
solar irradiance is diminishing. Hence, the oxidant-formation potential
is not completely reached, N0X is not as completely consumed; and a
signifi"'-* un ^^nk (NO) still remains to hold the concentration (the
Because there is currently no hydrogen peroxide NAAQS and the future base-
case concentrations provided in Tables 3-6 through 3-20 are not fixed con-
centrations (but rather very low values resulting from the large benefit
of NMOC emission control), we briefly summarize the predicted increases in
H2O2 concentrations above these future base-case concentrations. In
effect, this is an estimate of the potential "disbenefit" resulting from
future global changes) after control of NMOC to attain the ozone NAAQS.
In addition to this measure, however, we also compare the predicted future
case H2O2 concentrations against the original (pre-NMOC-control) base-case
H202 prediction for the conditions of each data set. In this way, we can
at least describe the relative changes from present to future conditions,
by combining expected future NMOC controls and potential future global
changes.
As we have shown in our discussion of urban photochemical processes, the
changes in maximum hydrogen peroxide concentrations due to increases in
surface temperature are rather insignificant compared to the effects pre-
dicted as a result of increases in ultraviolet intensity. Table 4-2 indi-
cates that the relative rates of increase over the ^2 concentrations
attained with NMOC control (to meet the NAAQS for ozone) are moderate com-
pared to the relative ^2 increases resulting from a one percent decrease
in ozone column. This comparison becomes even more exaggerated if we
roughly estimate that the likelihood of a +2-K increase is approximately
similar to a 10 percent decrease in the ozone column. This indicates that
loss of the benefit of NMOC controls will probably only occur with future
increases in radiant energy.
A comparison of the predicted ^2 concentrations to the original base-
case concentrations, however, more clearly points out the initial benefits
of future NMOC control, and the resulting "disbenefit" caused by these
changes in future conditions. Table 4-3 shows the relative differences
source
check
87 1 23r 6
142
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Table 4-2. "Disbenefit" to Future
Concentrations Caused by Increases
Overhaed Ozone Column .
Base Case Maximum Hourly H202
in Temperature and Decreases in
Average Increase (percent/Kelvin)
Ozone Column: 0.30 cm-atm 0.25 cm-atm 0.20 cm-atm
Test Group
1
15.6
17.5
6.0
2
3.8
1.5
0.4
3
1.4
0.6
0.2
Total
6.9
6.5
2.5
Average HgOg Increase (pet./pet, decrease in O3 column)
Temperature: base base + 2 K base + 5 K
Test Group
1 158.0 133.8 108.0
2 7.2 6.4 5.5
3 2.9 2.8 2.5
Total 56.1 47.7 38.7
Percent increases shown are increases over the HgOg concentration after
NMOC control to achieve the ozone NAAQS. Typically, these base
values are very low indicating a significant benefit from NMOC
control. Los Angeles and Seattle base case HgOg data were less than
0.01 ppb. Percentage increases over these concentrations were not
included in these calculations.
87 123 4
143
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Table 4-3. Comparisons of Future Scenario Maximum Hourly ^2
Concentrations versus Original Base Case
HgOg Difference / Original HgOg at base Temperature
Ozone Column: 0.30 cm-atm 0.25 cm-atm 0.20 cm-atm
Test Group
1 - 95.6 - 57.4 123.8
2 - 60.4 - 30.4 12.4
3 - 30.5 - 2.4 28.8
Total - 62.2 - 30.1 55.0
HgOg Difference / Original HgOg at base Temperature +2 Kelvin
Ozone Column: 0.30 cm-atm 0.25 cm-atm 0.20 cm-atm
Test Group
1 - 94.3 - 47.4 139.6
2 - 58.3 - 28.4 13.5
3 - 29.5 - 1.9 29.6
Total - 60.7 - 25.9 60.9
HgOg Difference / Original HqOq at base Temperature +5 Kelvin
Ozone Column: 0.30 cm-atm 0.25 cm-atm 0.20 cm-atm
Test Group
1 - 91.7 - 31.2 158.9
2 - 55.2 - 25.9 14.9
3 - 27.5 - 0.4 29.8
Total - 58.1 - 19.2 67.8
87 123 4
144
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between predicted future and original ^2 concentrations. Three sets
of data representing the changes due to decreases in the ozone column for
different temperature profiles are shown. As noted, these data sets are
very similar, indicating the relative insensitivity to temperature
increases. The main point to be drawn from these data is that until the
ozone column decreases to 0.25 cm-atm (a 16.7 percent decrease), the NMOC
control applied to derive the future base case of ozone compliance is pre-
dicted to also control ^2 to below its original level. In all cases,
however, the positive values in Table 4-3 for the 0.20 cm-atm simulations
indicate that these test air parcels have significant potential to produce
greater amounts of ^2 than predicted for the original air parcel using
original, uncontrolled NMOC emissions. As noted, this is caused by the
additional radiant energy input, which causes higher radical fluxes and
more rapid depletion of N0X, providing afternoon conditions more inducive
to hydrogen peroxide formation.
Synergistic Effects
This discussion has so far attempted to delineate isolated impacts on
future urban air parcels resulting from global changes. We can also
analyze the available data for an indication of whether synergistic
effects are predicted to occur. On the basis of the generally linear
decreasing rates of impact resulting from increases in ultraviolet
intensity and surface temperatures, we conclude that the combined effect
of increases in these parameters appears to be sometimes additive, but not
synergistic within the range of conditions simulated. Such a finding is
entirely consistent with our description of urban photochemical processes,
assuming that there is a limit to the oxidizing potential of a polluted
air mass. Thus, even though the short-term production rate of ozone and
other oxidized species is often enhanced by both an Increase in tempera-
ture and ultraviolet intensity, the long-term effect of combining these
two energy sources is, at best, additive because there are only limited
amounts of oxidant precursors available.
Summary of Single-Day Results
In summarizing city-specific simulation results, we recall that our origi-
nal intent in selecting the non-base-case, future temperature and overhead
ozone column values was to investigate whether unanticipated changes in
surface temperature or stratospheric ozone levels could cause additional
ozone production in urban areas that had achieved the NAAQS for ozone
through NMOC emission control. We selected two different ranges of change
for both the temperature and ultraviolet irradiation levels, and analyzed
87123r 6
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model results for different combinations of these parameters. Tempera-
tures that were 2 K above the base-case temperature profiles and an over-
head ozone column of 0.250 cm-atm were selected as a moderate or probable
(based on the best estimates available in the literature) future
scenario. More extreme conditions of +5 K and 0.200 cm-atm were also
selected to provide large, but not unrealistic, changes. We provide the
average group changes for predicted maximum hourly ozone concentration
under these conditions in Table 4-4 as a general summary of these
results.
As we have stated throughout the previous discussion, the highly reactive
air parcels from the Group 1 cities do not appear to be able to easily
sustain the ozone NAAQS level of 0.120 ppm under any conditions of
increased future energy input. Much of this sensitivity stems from the
fact that the EKMA calculations (and therefore, our future scenario base
cases), which are used to determine the amount of necessary NM0C reduc-
tions, end at 1800 hours when the ozone concentration is still increas-
ing. This provides increased oxidant-formation potential in the form of
extra, "allowed" NM0C emissions, which are more effectively used in the
future scenarios because those conditions are more reactive. For moderate
changes in the future temperature and ozone column parameters, an
unanticipated extra ozone production of 0.024 ppm, or 23.3 percent is pre-
dicted, on the average, for these very reactive days. More extreme con-
ditions could result in additional ozone formation, with an average Group
1 ozone concentration of 0.174 ppm predicted for EKMA-derived NM0C con-
trols under the most extreme conditions.
Future scenario results from the two less reactive groups appear to indi-
cate that in those cases where nearly the full oxidant-formation potential
was realized and controlled by the EKMA-derived NM0C controls, only small
or no increases in the hourly maximum ozone concentration might be expec-
ted for even the more extreme future conditions. On the other hand, it
must be kept in mind that the time required to achieve these daily maximum
concentrations is shortened by the additional energy input. This, in
turn, could result in extra cumulative human exposure even though the
maximum concentration changes little.
Finally, for the the Group 4 data, we obtained simulation results that,
if verified by future measurements and modeling studies, would provide a
different set of conditions, also very sensitive to future changes in
temperature and ozone column density. The EKMA calculations for these
data sets required little NM0C control because high N0X conditions were
combined with the lower light intensity of northern locations and unique
mixing depth conditions. However, when the light intensity was increased
to account for less stratospheric ozone absorption, these same conditions
led to a highly reactive, poorly diluted, precursor-rich air parcel that
8 7 1 2 36
146
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was capable of producing high levels of ozone and oxidized products (see
Table 4-4). Although these data and simulations need to be verified, it
is interesting to note that the ozone traces from the base-case simula-
tions were similar to the Group 1 results, in which concentrations were
still increasing at the end of the EKMA calculation (1800 hours). How-
ever, unlike the Group 1 simulations, where the system's oxidant-forming
potential might have been nearly reached in one or two more hours of
simulation, it is unlikely that this would have occurred before sunset
in the Group 4 data sets. Therefore, in these situations, there does not
even appear to be a simple method of estimating (or justifying) the amount
of additional NMOC reduction that would be needed to curtail such
unanticipated formation of ozone.
The city-specific simulation results for H2O2 production are somewhat more
reassuring. These simulations indicate that in all cases studied, H2O2
production is far more sensitive to varied NMOC and ultraviolet radiation
conditions than is ozone predictions. That is to say, reduction of ^2
to concentrations far below the original values was effectively performed
through reduction of NMOC emissions as prescribed to achieve the NAAQS for
ozone. On the other hand, the loss of this benefit was rapid with
decreasing overhead ozone column. The most sensitive test cases were the
most reactive Group 1 sets that required the highest NMOC controls. How-
ever, in almost all cities, a 16.7 percent decrease in ozone column
density still resulted in the production of less H2O2 than in the original
base-case simulation. At smaller ozone columns, more rapid increases were
predicted, depending on the overall reactivity of the specific test group
(see Table 4-3), to concentrations greater than the original H2O2 concen-
trations.
DISCUSSION OF MULTI-DAY RESULTS
The chemical processes that occur for the multi-day simulations do not
differ greatly from those of the single-day simulations, though one may
have a different perspective when viewing a multi-day event. The results
of the Phoenix simulations are shown in Figure 4-9. Whereas earlier plots
showed the four extreme scenarios of temperature and overhead ozone column
density, these plots and the following set of Los Angeles plots show the
base-case, moderate, and extreme combinations of test conditions. A com-
parison of these figures shows that enough (N0X) emissions occur later in
the day to continue ozone production throughout the afternoon, yielding
the maximum hourly concentration at 1900 hours in all cases. The poten-
tial global climate changes represented by the future scenarios conditions
increased the maximum predicted ozone concentration of 0.100 ppm (base
case) to 0.123 ppm for the most extreme future conditions (+5 K/0.200 cm-
atm). This is an interesting consequence of the Phoenix data set used, in
87123y 6
147
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Table 4-4. Group Averaged Ozone Responses to Moderate (+2 Kelvin/0.25 cm-
atm) and Extreme (+5 Kelvin/0.20 cm-atm) Changes to Future Scenario
Conditions.
Percent Ozone Increase Calculated Ozone (ppm)
Scenario:
Moderate
Extreme
Base
Moderate
Extreme
Test Group
1
23.3
45.1
0.120
0.148
0.174
2
5.4
9.0
0.120
0.126
0.131
3
0.4
0.4
0.120
0.120
0.120
(4)
(24.9)
(72.1)
0.120
0.150
0.207
Total (1,2,3)
10.8
20.2
0.120
0.133
0.144
Total (all)
(12.6)
(27.1)
0.120
0.135
0.153
87123 W
148
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Phoenix, AZ — Compliance Day
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FIGURE 4-9. Ozone, N02» H2O2. and PAN plots for extreme scenarios inthe future sensitvity tests--
multi-day simulationof an ozone NAAQS attainment scenario for Phoenix, Arizona.
a 71 ? 1
-------
that afternoon N0X and VOC emissions provide a higher oxidant-forming
potential because they occur during a key ozone-forming period. Not all
data for the Group 2 and 3 city-specific scenarios had such emissions data
available for that time of day. This lack of emissions data could arti-
ficially reduce the calculated oxidant forming potential for those test
cases.
Other predicted impacts of the potential future scenarios are as might be
expected from the single-day discussion. The maximum hydrogen peroxide
concentrations increased by nearly a factor of 10 between base case and
extreme conditions. This is as expected since the increased radiant
energy prolongs the afternoon period when H2O2 production is viable. PAN
concentrations also decrease with increasing temperatures; this was seen
in the single-day results and is explained by the extreme temperature-
dependency of the PAN decomposition reaction. In all scenarios, the
hourly emissions profile can be detected in the NO2 plot, though the ozone
"left over" after the first and second days of simulation tends to reduce
NO2 levels during the second and third nights, and increase the NO2 levels
on the second and third mornings by converting emitted NO to NO2. Other
than these commonly seen, second-day effects, little difference is appar-
ent from day to day for any of the future condition test sets. However,
this is not the case for the Los Angeles simulations.
The results of the multi-day Los Angeles simulations are shown in Figure
4-10. These days follow trends similar to those just described, but we
also see the effect of the unique characteristics of the Los Angeles
Basin. Two very different sets of parameters for the Los Angeles and
Phoenix multi-day simulations are the mixing height and emission pro-
files. Whereas the Los Angeles data set provides very high emissions into
a relatively poorly diluted air parcel, the Phoenix attainment simulation
has rather low emissions with a large increase in mixing height throughout
the day. Of course, these multi-day profiles assume that the air parcels
have not been transported outside the urban area, and therefore are impac-
ted by similar emissions and mixing depths on each day. For the Los
Angeles simulations, these conditions result in increasing ozone and oxi-
dized product yields for each successive day.
Unlike the Phoenix attainment simulations, future Los Angeles scenarios
show interesting and different multi-day effects for the proposed global
conditions. In the single-day Los Angeles simulations, ^2 concentra-
tions were predicted to be so low for the future base case simulation that
percent increases could not be calculated. This is again true for the
first day of the multi-day future tests (since it is the same simulation
for that period), but interesting differences begin to develop as the
8 7 1 2 3)- 6
150
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Los Angeles, CA —
26-27 June 1974
0.M
0.24 -
1«00 WDO 400 1000 1000 MOO 400 1000 1«0 MOO 400 1000 im
Simulation Tfm« (WT)
0.16
0.00 t " ' " f » » " » | ' * " I 1 » « ' ' « I I I I I I I I I
100 TX>0 400 1000 1«K> MOO 400 1000 1«00 1200 400 1000 1000
simulation Thn« (WT)
FIGURE 4-10. Ozone, NOo, HgOo, and PAN
multi-day simulationof 26-27 June 1974,
plots for extreme scenarios in the future sensitivity tests--
Los Angeles, California.
-------
second- and third-day concentrations begin to vary between scenarios. The
reason ^2 concentrations are low in the late afternoon is that N0X emis-
sions and concentrations are large enough to hold hydroperoxy radical
concentrations to low values. As conditions change and ozone concentra-
tions build significantly, N0X is titrated by the ozone and the hydro-
peroxy radical (and its combination product hydrogen peroxide) increases
in concentration rapidly. These trends are apparent in both the ozone and
NO2 traces for the second and third nights. For the most extreme future
conditions, the model predicts ozone concentrations nearly at the standard
prior to sunrise of the third day. The corresponding high nighttime val-
ues resulted in very low NO2 concentrations and NO levels approaching
zero. The model predicts that these conditions allow HO2 radicals to be
produced, even at night, to concentrations that allow H2O2 buildup. The
primary source appears to be the reaction of ozone with available VOC,
which also produces peroxyacetyl radicals, the source of increasing PAN.
Extreme condtions also yield ozone concentrations of about 0.25 ppm by the
third day (as opposed to about 0.11 ppm for the base case). This amplifi-
cation of photochemical oxidant formation appears to be due to the ability
of the higher radiant and thermal energy conditions in the extreme future
scenario case to more efficiently convert the ample Los Angeles precursors
to oxidized products. Of course, this effect is maximized by our assump-
tion that the air parcel remain in the Los Angeles Basin for three days.
DISCUSSION OF ALTERNATE MECHANISM SIMULATIONS
The alternate (CALL) mechanism was used in this study only to verify that
simulation results were not due completely to mechanism singularities. We
selected two different test cases with which to perform this test. The
CALL mechanism results are provided for nine future scenarios for the test
days of 5 July 1984 in Phoenix and 13 July 1979 in Philadelphia (Tables
3-23 and 3-24). These results can be compared with the CBM-X results
already provided in Tables 3-14 and 3-8, respectively. We note that the
maximum hourly ozone predicted for the Phoenix day was little affected by
the future changes in either mechanism, and that ^2 and PAN concentra-
tions tracked well between mechanisms in both magnitude and percent
change.
The Philadelphia test was a Group 1 day and, therefore, more sensitive to
the proposed future global changes. The comparison of the results of the
mechanisms for this test points out some differences. In a very cursory
fashon, we note some of these differences in the PAN and radical-radical
chemical reactions. We see, for instance, that the CALL mechanism gener-
ates more PAN and less H2O2 than the CBM-X. On the other hand, the base-
case and moderate ozone predictions are almost identical, with CBM-X pre-
dicting slightly less that CALL for extreme conditions. Since these mech-
anisms are primarily evaluated for ozone prediction capabilities, it is
8 7 1 2 3r 6
152
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not suprising that those predictions are closer than the ^2 and PAN con-
centrations. In addition, though this is only one test of the more reac-
tive systems, we perceive it as some evidence that (1) the project results
are not mechanism artifacts, and (2) the CBM-X mechanism could prove to be
slightly conservative in its predictions compared to the newer CALL and
CBM-IV mechanisms.
87 1 2 3r 6
153
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SECTION 5
CONCLUSIONS AND RECOMMENDATIONS
This report describes the investigation of two specific, but related,
topics. The goal of this work was to evaluate the potential impacts of
future (1) decreases in stratospheric ozone concentrations and (2)
increases in surface temperature on urban photochemical systems. Although
most photochemical kinetics models allow direct input of temperature
values, it is necessary to convert the projected values for overhead ozone
column density into parametric representations such as photolysis rates.
Therefore, the first task was to assess the data and methodologies cur-
rently available for calculating the photolysis rates used in air quality
simulation models. From this assessment, we determined the appropriate
data and numerical algorithms to describe these relationships. Following
these determinations, we began the second task, which was to calculate the
variation (with ozone column density) in photolysis rates, and, in combin-
ation with assumed temperature variations, to use these values to deter-
mine the sensitivity of urban atmospheres to global changes in these para-
meters. This sensitivity evaluation consisted of analyzing the impact
that these increases in thermal and radiant energy input might have on the
chemistry of future urban air parcels. In the following subsection we
summarize separately the conclusions of these two tasks, followed by
recommendations derived from these conclusions.
ASSESSMENT OF PHOTOLYTIC RATE CALCULATIONS
In this phase of the work, we focused on the ultraviolet photolysis of
ozone [to O^D) ] and formaldehyde since these are the most significant,
radical-generating photolysis reactions in the troposphere; thus, their
associated uncertainty translates almost directly into uncertainty con-
cerning the radical production rate of polluted air masses. We also
identified data and algorithms we felt to be potentially useful in the
development of a new generation of ultraviolet actinix flux calculation
schemes for current and developing models. Our predictions were then com-
pared with actual measurements and the uncertainty associated with each
step of the process was examined. Because the calculation of atmospheric
8 7 1 2 37
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photolysis rates is the product of actinic flux and specific molecular
properties integrated over wavelength, we addressed three separate
areas: (1) the methods and data needed to calculate actinic flux, (2)
uncertainties in experimentally derived values for molecular properties,
and (3), the integration approach and related uncertainties.
The first of these three areas was the most difficult to assess because
the calculation of actinic flux for differing conditions and locations
requires consideration of a wide range of complex atmospheric inter-
actions. The most rigorous attempt at this complex description is the
work of Braslau and Dave (1973a and b). Demerjian and coworkers (1980)
later used a somewhat simplified version of this model to generate a
number of actinic flux data sets for various conditions. These data sets
have been used extensively over the last decade in almost all photochemi-
cal modeling studies of tropospheric air masses. We believe that an up-
date of this work in now in order, 1f for no other reason than to include
more recent extraterrestrial flux data in these calculations, and to pro-
vide actinic flux results for conditions not addressed in the original
work (e.g., variable ozone column densities), but which are now becoming
more important. These new calculations must also be carried out at smal-
ler integration intervals to provide flux data resolved to a magnitude
comparable with that of molecular data, so that mathematical averaging
errors in the photolysis rate calculations can be limited. This new data
would also be very useful in improving the mathematical formulations that
are used to estimate actinic fluxes for conditions not directly included
in the data (e.g., those of Schippnick and Green, 1982).
Our analysis of molecular data focused on the short wavelength photolysis
reactions of ozone and formaldehyde. The greatest individual area of
uncertainty in those reactions is found in the absorption cross-section
formaldehyde data Two studies in this area (Bass, 1980; Moortgat, 1979)
obtained results that differed by about 30 percent. Since formaldehyde is
a very important photolytic species in the troposphere, these numbers
translate into a large uncertainty in the radical production capacity of
organic oxidation products. We believe that this discrepancy should be
alleviated, either through reevaluaton of existing data sets or through
additional experimental work to develop more data. Absorption cross-sec-
tion and quantum yield data for ozone are less uncertain, primarily
because they have been the objects of experimental investigation for a
longer period of time. A somewhat larger associated error developes for
ozone photolysis to form O^D), however, because this process occurs at
the surface ultraviolet cutoff, where actinic flux calculations are less
certain. An experimental program designed to measure surface flux distri-
butions in the middle ultraviolet range (particularly in the region near
the solar cutoff) would provide information with which the error of jgip
87123f 7
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calculations might be diminished, and could also yield important data for
evaluating and improving actinic flux calculation schemes.
We also investigated the methodology involved in calculating photolysis
rates. In cases where two or more of the product terms (actinic flux,
quantum yield, and absorption cross section) were highly wavelength-
resolved, errors resulted if the wavelength intervals used in numerical
integration were much larger than the significant resolved features in the
individual functions. This averaging error was only on the order of ten
percent, but could be easily eliminated if calculations were performed at
1 or 2 nm intervals. Again, this finding points to the need for a new set
of more highly resolved actinic flux calculations, performed in the manner
of Demerjian and coworkers (1980).
We believe that the current actinic flux, absorption cross section, and
quantum yield data sets result in calculations of ozone [to form 0(*D)]
and formaldehyde photolysis rates within an uncertainty of about 50 per-
cent. These are the most important photolysis rates in the modeling of
tropospheric photochemistry, and more confidence in model results would be
gained if this uncertainty could be limited.
EVALUATION OF THE IMPACTS OF GLOBAL CHANGES
ON TROPOSPHERIC PHOTOCHEMISTRY
This phase of the report focused on simulating the photochemistry of urban
air parcels and evaluating the effects of potential future changes in
ozone column density and surface temperature. Because these changes are
expected to occur in the future (within a few decades), when many cities
would ideally have attained compliance with the ozone NAAQS through reduc-
tion of NMOC emissions, we utilized existing information from 1982 and
1987 State Implementation Plans to formulate future scenarios of ozone
NAAQS attainment. These scenarios were based on the ideal performance of
the EKMA calculations, providing future inputs that resulted in the pro-
duction of ozone at or below the standard for base-case conditions. The
future data sets were carefully developed and screened for errors and to
represent as many different cities and general types of original non-
attainment situations as possible.
Fifteen future test cases were obtained. For discussion purposes, these
were grouped into four general categories based on original ozone produc-
tion: (1) high non-attainment days with ozone concentrations greater than
0.17 ppm, (2) moderate non-attainment days with original ozone levels
8 7 1 2 37
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between 0.14 and 0.17 ppm, (3) near-attainment days with ozone concentra-
tions below 0.14 ppm, and (4), a special set of data with unique condi-
tions based on a somewhat uncertain data set from a 1981 Seattle measure-
ment program. The first group was a collection of high ozone production
days from Northeast Corridor cities and Los Angeles. Test cases of the
second group were from a number of differing cities, thought to have fewer
emissions and more beneficial meteorological scenarios than the first
group; the third group had even more beneficial conditions.
The changes in photochemical dynamic processes that could be caused by
potential global changes in stratospheric ozone and surface temperature
have been explained earlier. However, some general concepts and the
specific numerical results that evolve from these processes are summarized
here. Of primary importance to the impact that future temperaure
increases or ozone column decreases might have on an urban system is the
method by which the additional energy associated with those changes is
input into that system. Increased surface ultraviolet irradiation caused
by a diminished ozone absorption capacity in the stratosphere follows a
diurnal curve dependent on the elevation of the sun. On the other hand,
energy input to the earth's surface through Greenhouse warming takes a
less direct route.
Regarding impacts on ozone concentrations and other oxidized species, two
distinct types of effects can be seen in the future scenarios; these
effects can be linked to the differences in energy input dynamics.
Because global surface temperature increases were simulated by the addi-
tion of 2 and 5 K to the original, city-specific temperature profiles
evenly across the day, the impacts resulting from temperature increases
resulted in slight increases in reaction rates, and somewhat greater
formation of ozone and oxidized products across the entire simulation
period. This is to be expected since most temperature-dependent reaction
rates increase with increasing temperature. The second type of impact,
resulting from the enhanced (due to depleted stratospheric ozone) ultra-
violet irradiation function, was an increase in the rate of photochemical
reactivity centered around midday.
In all test cases studied, an increase in photolysis rates due to
decreased stratospheric ozone caused a more rapid formation rate for ozone
and other oxidized products. Because most additional energy input was
concentrated in an already photochemically reactive period of the day,
the impact was often more dramatic than that of the temperature change.
Levels of ozone at or near the NAAQS (0.12 ppm) were achieved much
earlier, sometimes hours earlier, at the time when an air parcel might be
over more populated areas earlier in the trajectory. This would occur
because the midday enhancement of photolysis rates provides a greater
radical production rate and radical concentrations, thereby increasing
8 7 1 2 3y 7
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short-term reactivity so that these photochemical systems can convert pre-
cursors to oxidant more efficiently. However, this enhanced reactivity
may not not always result in greater maximum ozone concentrations because
that measure of oxidant-forming potential is also a function of available
precursors and meteorological conditions. Hence, while increased ultra-
violet irradiance from depleted stratospheric ozone is predicted to
increase short-term reactivity in a urban air parcel, these conditions
will not always result in greater maximum concentrations because such
long-term measures are more a function of the specific system. Air par-
cels with low precursor emissions and beneficial meteorological conditions
may actually produce lower maximum concentrations of oxidized products
because the enhanced reactivity may consume a large fraction of the pre-
cursor species under conditions earlier in the day that are less favorable
for oxidant formation.
For the general groups of scenarios just described, our simulations pre-
dict increases in maximum hourly ozone (over the 0.12 ppm of the future
base-case scanarios) at about 1.4 + 0.5 percent per degree Kelvin increase
(2.5 + 0.9 percent per degree Fahrenheit) for the first three groups, with
the Group 1 cities at the more reactive extreme. With respect to changes
in ozone column density, we predicted a 1.1 percent increase in maximum
hourly ozone concentration for each percent decrease in ozone column for
the Group 1 cities, while the rates of increase for the Groups 2 and 3
cities were very near zero. Some of this variability was seen as an arti-
fact of the EKMA calculation procedure (as applied in various SIPs and in
our future scenario determinations). That is, since the EKMA procedure
terminates its calculations at 1800 hours, additional oxidant-forming
potential, which is only realized after 1800 hours, cannot be accounted
for. For the Group 1 EKMA attainment and future base-case simulations,
0.12 ppm of ozone was formed at 1800 hours, but there was an increasing
slope at that time, indicating additional oxidant-forming potential.
Future conditions of enhanced ultraviolet irradiance utilized this poten-
tial more efficiently to produce higher levels of ozone prior to 1800
hours. Therefore, those test cases (Group 1) showed more extreme sensi-
tivity to future changes in stratospheric ozone column densities. Such a
trend also occurred for the Group 4 days, though for a somewhat different
reason. In those tests, a unique set of emission and meteorological vari-
ables combined to create a base-case simulation with an apparently large
ozone-forming potential, but with fairly low energy input, leading to very
little calculated NM0C control to achieve the NAAQS. As the additional
energy for the future scenarios was added, however, this system became
very reactive and achieved much higher levels of ozone than the base-case
simulations. Again, the EKMA procedure, as presently applied, could not
be used to account for the overall oxidant-forming potential of this sys-
tem.
8 7 1 2 3f 7
158
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We recognize that simulations in which some of the rates in the chemical
mechanism vary between present and future scenarios was never an intended
application of the EKMA. On the other hand, when it is possible to
account for a large fraction of the oxidant-forming potential, such as in
the base-case simulations for Groups 2 and 3 where the ozone maximum con-
centration occurred prior to 1800 hours, very little additional ozone
formation was predicted with changes in future parameters because a large
fraction of the oxidant-forming potential was already accounted for.
Using our estimates of moderate (+2 K and -16.67 percent ozone column
density) and extreme (+5 K and -33.3 percent ozone column density) condi-
tions, we predicted group-average ozone concentrations of 0.132 and 0.120
ppm for Groups 2 and 3 at the extreme conditions. Hence, though ozone
forms more rapidly in these future scenarios, the concentrations do not
accumulate to much over the NAAQS for even the most extreme conditions
tested. Conversely, the Groups 1 and 4 average concentration results were
0.148 and 0.150 ppm for moderate conditions and 0.174 and 0.207 ppm for
extreme tests. Because of the rather significant changes predicted for
the Group 1 and 4 test cases, we also analyzed the data for an indication
of whether synergistic interaction between the two perturbations was pre-
dicted to occur. We found that, for the cases available, the combined
effects of coincident increases in both parameters were sometimes addi-
tive, but not synergistic. Such a finding is consistent with our descrip-
tion of the urban photochemical processes, assuming that there is a limit
to the oxidant-forming potential of an air mass.
The formation of other oxidized products such as nitric acid and hydrogen
peroxide was found to be specifically dependent on the types of processes
by which they form in an urban atmosphere. For instance, the formation
rate and eventual yield of nitric acid is related to the hydroxyl radical
concentration and the amount of N0X available. These two parameters are
closely linked to ozone concentration, since N0X is an ozone precursor and
ozone photolysis is the key source of hydroxyl radicals in these sys-
tems. Hence, the impacts of potential global changes on nitric acid
formation parallel those of ozone and are limited by available N0X. On
the other hand, hydrogen peroxide is formed by the combination of hydro-
peroxy radicals, which only accumulate after N0X is depleted. An increase
in photochemical reactivity will deplete N0X faster and allow hydroperoxy
radical (and therefore, hydrogen peroxide) to form for longer periods and
at higher concentrations. In this study, the predicted future increases
in photochemical reactivity stem mainly from projected future decreases in
ozone column density; thus, hydrogen peroxide was found to be very sensi-
tive to this parameter.
We have also found that NM0C emission control designed to attain the NAAQS
for ozone appears to be a very effective hydrogen peroxide control since
one net effect of NM0C control is to reduce the reactivity of a system,
8 7 1 2 3 y 7
159
-------
thus, to reduce the consumption rate of N0X. Since hydroperoxy radical
concentrations are highly sensitive to N0X concentration, the additional
remaining N0X holds down the hydrogen peroxide formation rate. Con-
versely, as projected conditions of future global change were implemented
in our test cases, N0X was again depleted more rapidly and hydrogen pero-
xide concentrations began to increase significantly. For our moderate
test conditions, control of NMOC to attain the ozone NAAQS was predicted
to also limit hydrogen peroxide to about 70 to 80 percent of its original
base-case concentration. However, as ozone column conditions were changed
to the extreme case, more hydrogen peroxide was formed than in the origi-
nal base case, even with the added NMOC control.
RECOMMENDATIONS
Our experience in both the photolysis rate sensitivity study and the urban
photochemical kinetics investigation yields certain recommendations for
future study. We have pointed out that the calculation of photolysis
rates for ozone [to 0(^D) ] and formaldehyde are very critical to atmo-
spheric simulation modeling, and yet are uncertain to unacceptable
limits. We feel future efforts to limit this uncertainty would provide
additional confidence in all air quality simulation modeling. These
efforts should follow two paths: (1) The use of currently existing
information to develop improved actinic flux data sets and computer formu-
lations, and (2) additional experimental measurements, particularly of
formaldehyde absorption cross sections, short wavelength actinic flux dis-
tributions, and actinometrically determined j-values, to provide critical
information in the most uncertain areas.
We have established some limits to the extremes of change that could occur
in urban scenarios, and suggest that continuation of such an effort should
focus on four aspects: (1) Use of the newest and more extensive 1987 SIP
data along with the recently developed Carbon-Bond Mechanism-IV/OZIPM-4
model to obtain more specific information related to the extent of the
impacts found in this study, (2) use of such models and data to study
parameters not varied in this study, but now predicted by GCMs to be vari-
able (including water vapor, mixing height and cloud cover), (3) utiliza-
tion of regional models such as the ROM or RTM-III, to analyze linked,
multiple, urban trajectories in a unified regional domain, and (4), use
of a more complex gridded urban model, such as the Urban Airshed Model, in
conjunction with demographic data to evaluate the exposure-related impacts
of reactivity changes predicted to occur with smaller ozone column densi-
ties.
a 712 3f 7
160
-------
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Testing of the CBM-IV for Urban and Regional Modeling." U.S.
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CBM-X or Optional Mechanisms. Volume 1. Description of the Ozone
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Jeffries, H. E. 1986. Personal communication.
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Trace gas trends and their potential role in climate change.
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87123 9
164
-------
Appendix A
INPUT DATA USED FOR THE OZIPM/EKMA SIMULATIONS
The values in this appendix were used as input for the OZIPM/EKMA simula-
tions described in the text. As noted in the text, the temperature values
shown were used in the base case simulations. These values were incre-
mented by 2 K and 5 K for the future sensitivity simulations.
87 123 5
165
-------
BOSTON
Elevation = 5 m
Regional Albedo =0,14
Hours from Start
DATE
0
1
2
053078
293.1
294.2
295.1
072178
298.4
299.4
300.1
08137B
292.5
293.3
294.0
081578
295.0
295.6
296.1
081678
297.1
297.6
298.0
062979
291.4
293.0
294.4
071079
294.0
294.1
294.1
Hours from
Start
DATE
0
1
2
053078
250.0
305.7
359. S
072178
25Q.0
568.2
874.2
081378
250.0
293.6
335.0
081578
250.0
331.4
408.8
0B167B
250.0
485.3
704.5
062979
449.0
532.1
612.0
071079
360.0
692.0
1007.4
5712= S
Longitude = 71.1 W
Latitude = 42.3 N
Temperature (K) Profiles:
3
4
5
6
7
8
9
10
295.8
296.3
296.6
296.6
296.3
295.8
295.1
294.1
300.6
300.7
300.6
300.1
299.4
298.4
297.2
295.9
294.6
295.0
295.3
295.3
295,2
294.9
294.4
293.7
296.4
295.7
296.8
296.3
296.6
296.3
295.9
295.5
298.2
298.4
298.5
298.5
298.5
298.4
296.2
298.0
295.5
296.3
296.7
296.7
296.4
295.7
294.7
293.3
294.0
293.8
293.5
293.2
292.8
292.4
292.0
291.6
Mix-lnq Heiqht (m)
Profiles:
3
4
5
6
7
8
9
10
410.5
456.3
495.9
528.0
551.6
566.1
571.0
566.1
1156.1
1403.3
1606.1
1756.8
1849.7
1381.0
1849.7
1756.8
372.2
403.2
426.6
441.1
446.0
441.1
426.6
403.2
478.2
536.2
579.8
606.8
616.0
606.8
579.8
536.2
892.8
1037.2
1128.0
1159.0
1128.0
1037.2
892.8
704.5
685.7
750.2
803.2
842.6
866.8
875.0
866.3
842.6
1290.2
1526.5
1704.2
1814.6
1852.0
1814.6
1704.2
1526.5
-------
CHICAGO
Elevation = 185 m Longitude = 87.7 W
Regional Albedo = 0.14 Latitude = 41.8 N
Temperature (K) Profiles:
Hours from Start
DATE
0
1
2
3
4
5
6
7
8
9
10
071079
294.9
295.2
295.2
295.1
294.8
294.3
293.7
293.0
292.2
291.3
290.4
071179
296.3
297.2
297.9
298.5
298.8
298.9
298.8
298.4
297.8
297.1
296.2
082680
297.6
298.3
298.9
299.2
299.3
299.1
298.7
298.0
297.2
296.2
295.1
Mixing Height (m)
Proflles
^ •
Hours from
Start
DATE
0
1
2
3
4
5
6
7
8
9
10
071079
250.0
606.4
949.2
1265.0
1541.9
1769.1
1937.9
2041.9
2077.0
2041.9
1937.9
071179
250.0
383.1
511.0
628.9
732.2
817.1
880.1
918.9
932.0
918.9
880.1
082680
250.0
533.9
806.8
1058.4
1278.8
1459.8
1594.2
1677.0
1705.0
1677.0
1594.2
8 7 12 3 5
-------
LOS ANGELES
Elevation
= 0 m
Longitude =118
.33 W
Regional
Albedo =
0.14
Latitude =34.1
N
Temperature (K)
Profiles:
Hours from Start
Temperature
(K)
DATE
0
1
2
3 4
5 6
7
8
9
10
062674
307.8
307.3
304.7
303.8 300.5
303.3 300.3
298.3
296.9
296.5
296.1
11
12
13
14 15
16 17
18
19
20
21
295.7
295.3
294.9
296.4 298.8
301.9 304.8
307.9
310.1
311.7
314.0
22
23
24
315.5
316.6
314.6
Hours from Start
Temperture (K)
Mixing Height (m) Profiles:
DATE
062674
10
335.8
314.2
267.7
212.3
176.6
137.2
137.9
107.8
103.0
94.8
90.2
11
12
13
14
15
16
17
18
19
20
21
85.4
80.0
73.9
72.2
79.3
70.1
116.2
156.3
300.7
356.9
447.5
22
23
24
528.4
539.1
523.9
87123 5
-------
NASHVILLE
Elevation = 180 m Longitude = 86.8 W
Regional Albedo = 0.14 Latitude = 36.2 N
Temperature (K) Profiles:
Hours from Start
DATE
0
1
2
3
4
5
6
7
8
9
10
070280
298.3
300.1
301.7
303.0
304.0
304.5
304.7
304.5
303.9
302.9
301.5
072580*
298.3
300.2
301.9
303.3
304.3
304.9
305.1
304.9
304.3
303.3
301.9
080180*
299.6
301.2
302.5
303.6
304.5
305.0
305.1
305.0
304.5
303.6
302.5
081080*
299.8
301.8
303.6
305.1
306.1
306.7
306.8
306.4
305.6
304.4
302.8
091181
291.0
293.8
296.3
298.3
299.8
300.8
301.1
300.8
299.8
298.3
296.2
091281
293.1
295.7
298.0
299.8
301.2
302.1
302.4
302.1
301.2
299.8
298.0
Mixing Height (m)
Proflles
: (DILU
option used)
Hours from
Start
DATE
0
1
2
3
4
5
6
7
8
9
10
070280
250.0
530.5
881.9
1209.7
1451.4
1622.0
1747.3
1845.0
1845.0
1845.0
1845.0
072580*
250.0
546.6
908.6
1233.5
1466.6
1629.8
1750.3
1845.0
1845.0
1845.0
1845.0
080180*
250.0
542.0
904.9
1232.7
1467.1
1630.4
1750.7
1845.0
1845.0
1845.0
1845.0
081080*
250.0
527.5
889.2
1224.0
1463.8
1629.6
1750.5
1845.0
1845.0
1845.0
1845.0
091181
250.0
516.9
892.4
1238.3
1477.0
1637.3
1753.3
1845.0
1845.0
1845.0
1845.0
091281
250.0
503.1
874.5
1226.0
1470.9
1634.8
1752.5
1845.0
1845.0
1845.0
1845.0
* Multiple trajectories for this date had identical profiles
87123 5
-------
NEW YORK
Elevation = 2 m
Regional Albedo = 0.14
Longitude = 73.9 W
Latitude = 40.8 N
Hours from Start
Temperature (K) Profiles:
DATE
10
062480*
296.9
297.3 297.6
297.7
297.7
297.5 297.2
296.8
296.4 295.9
295.3
Hours from Start
Mixing Height (m) Profiles:
O
DATE
10
062480*
300.0
611.5 907.4
1172.9 1394.6 1561.4 1664.9 1700.0 1664.9 1561.4 1394.6
* Multiple trajectories for this date had identical profiles
87123 5
-------
PHILADELPHIA
Elevation = 2 m Longitude = 75.2 W
Regional Albedo = 0.14 Latitude = 40.0 N
Temperature (K) Profiles:
Hours from Start
DATE
0
1
2
3
4
5
6
7
8
9
10
071379
298.7
299.8
300.6
301.2
301.6
301.8
301.6
301.3
300.7
299.9
299.0
071979
295.8
296.2
296.5
296.8
296.9
297.0
297.0
297.0
296.9
296.8
296.5
062480
298.7
299.8
300.6
301.2
301.6
301.8
301.6
301.3
300.7
299.9
299.0
061581
292.9
293.9
294.6
295.0
295.2
295.0
294.5
293.7
292.6
291.3
289.8
061681
297.9
298.8
299.5
300.0
300.2
300.3
300.1
299.8
299.3
298.6
297.7
081982
293.9
294.5
294.8
295.0
295.0
294.8
294.5
294.0
293.5
292.9
292.2
062783*
296.1
297.1
297.9
298.6
299.0
299.1
299.0
298.7
298.2
297.5
296.5
Mixing Height (m)
Profiles:
Hours from Start
DATE
0
1
2
3
4
5
6
7
8
9
10
071379
250.0
468.5
676.1
862.3
1017.8
1134.8
1207.4
1232.0
1207.4
1134.8
1017.8
071979
250.0
478.3
691.0
873.7
1013.8
1101.9
1132.0
1101.9
1013.8
873.7
691.0
062480
250.0
413.6
619.2
811.8
954.3
1055.0
1129.0
1186.0
1235.0
1235.0
1235.0
061581
250.0
476.8
698.1
908.3
1102.3
1275.3
1423.1
1542.0
1629.0
1682.1
1700.0
061681
250.0
487.4
713.0
915.3
1084.2
1211.3
1290.2
1317.0
1290.2
1211.3
1084.2
081982
250.0
598.0
928.6
1225.1
1472.8
1659.1
1774.8
1814.0
1774.8
1659.1
1472.8
062783*
250.0
434.2
609.3
766.2
897.4
966.0
1057.2
1078.0
1057.2
996.0
897.4
* Multi
pie trajectories
for this
date had
identical
profiles
87123 5
-------
PHOENIX
Elevation = 340 m
Regional Albedo = 0.28
Longitude = 112.0 W
Latitude = 33.4 N
Temperature (K) Profiles:
Hours from Start
DATE
070584
082984
083184
091484*
Mixing Height (m) Profiles:
0
1
2
3
4
5
6
7
8
9
10
306.5
307.1
307.5
307.7
307.6
307.2
306.6
305.7
304.5
303.2
301.8
307.2
306.9
306.4
305.7
304.8
303.7
302.5
301.1
299.7
298.3
297.0
307.8
306.7
305.5
304.2
302.9
301.5
300.2
299.0
297.9
296.9
296.1
305.2
305.7
306.0
306.1
305.8
305.3
304.5
303.5
302.3
300.9
299.4
Hours from Start
DATE
070584
082984
083184
091484*
530.0
250.0
250.0
250.0
1
730.0
300.0
300.0
300.0
1000.0
600.0
350.0
350.0
1200.0
944.0
600.0
850.0
1400.0
1488.0
1050.0
1350.0
1600.0
2032.0
1650.0
1850.0
1800.0
2576.0
2250.0
2000.0
2000.0
2938.0
2750.0
2150.0
8
2200.0
3119.0
3050.0
2300.0
2400.0
3300.0
3300.0
2400.0
10
2400.0
3300.0
3300.0
2400.0
* Multiple trajectories for this date had identical profiles
87123 5
-------
SEATTLE
Elevation = 122 m Longitude = 122.3 W
Regional Albedo = 0.14 Latitude = 47.6 N
Temperature (K) Profiles:
Hours from Start
DATE
0
1
2
3
4
5
6
7
8
9
10
080781*
296.7
298.4
300.0
301.2
302.0
302.5
302.6
302.3
301.6
300.6
299.3
081081*
297.8
300.3
302.4
304.1
305.3
306.1
306.2
305.8
304.9
303.5
301.6
081181*
297.8
300.1
302.0
303.6
304.7
305.3
305.4
304.9
304.0
302.7
300.9
Mixing Height (m)
Prof1les:
Hours from
Start
DATE
0
1
2
3
4
5
6
7
8
9
10
080781*
250.0
343.7
432.7
512.5
579.2
629.3
660.4
671.0
660.4
629.3
579.2
081081*
250.0
357.3
459.1
550.5
626.8
684.3
719.9
732.0
719.9
684.3
626.8
081181*
250.0
397.8
538.1
664.0
769.1
848.2
897.4
914.0
897.4
848.2
769.1
* Multiple trajectories for this date had Identical profiles
87123 5
-------
TULSA
Elevation = 198 m
Regional Albedo = 0.18
Longitude = 96.0 W
Latitude = 36.2 N
^¦4
-P»
Temperature (K)
Profiles
•
•
Hours from
Start
DATE
0
1
2
3
4
5
6
7
8
9
10
070181
298.4
298.9
299.3
299.4
299.4
299.1
298.6
297.9
297.0
296.0
294.8
071681*
300.8
301.5
301.9
302.1
302.0
301.6
301.0
300.0
298.8
297.5
296.0
080681
302.0
302.3
302.5
302.5
302.3
301.9
301.3
300.5
299.5
298.4
297.2
062982
296.9
297.8
298.5
298.9
299.0
298.8
298.2
297.4
296.3
294.9
293.4
080682
301.2
301.5
301.6
301.5
301.3
300.8
300.2
299.4
298.4
297.4
296.2
082382
299.3
299.7
299.9
299.7
299.2
298.5
297.4
296.0
294.4
292.7
290.8
072683
301.4
302.3
302.8
303.1
303.0
302.6
301.9
300.9
299.6
298.0
296.3
082783
299.9
299.5
299.0
298.3
297.4
296.4
295.3
294.1
292.8
291.6
290.4
082883
299.1
298.5
297.9
297.1
296.2
295.2
294.2
293.1
292.1
291.1
290.1
Mixing Height (m)
Profiles:
Hours from
Start
DATE
0
1
2
3
4
5
6
7
8
9
10
070181
250.0
500.6
743.5
971.5
1177.5
1355.4
1499.7
1606.0
1671.1
1693.0
1671.
071681*
250.0
586.7
913.2
1219.5
1496.4
1735.4
1929.2
2072.1
2159.5
2189.0
2159.!
080681
250.0
550.4
841.7
1115.0
1362.0
1575.3
1748.2
1875.7
1953.7
1980.0
1953.;
062982
250.0
538.8
818.8
1081.5
1319.0
1523.9
1690.2
1812.7
1887.7
1913.0
1887.
080682
250.0
550.4
841.7
1115.0
1362.0
1575.3
1748.2
1875.7
1953.7
1980.0
1953.:
082382
250.0
760.0
1254.5
1718.5
2137.9
2499.9
2793.5
3009.9
3142.4
3187.0
3142..
072683
250.0
616.2
971.3
1304.5
1605.6
1865.6
2076.4
2231.8
2327.0
2359.0
2327.1
082783
250.0
732.0
1199.4
1638.0
2034.4
2376.5
2654.1
2858.6
2983.8
3026.0
2983.1
082883
250.0
684.5
1105.7
1501.0
1858.3
2166.6
2416.8
2601.1
2714.0
2752.0
2714.1
* Multiple trajectories for this date had identical profiles
87123 5
-------
WASHINGTON
Elevation = 4 m
Regional Albedo = 0.14
Hours from Start
DATE
0
1
071680
300.9
301.5
071780
300.9
301.5
072180
300.9
301.5
080780
299.5
300.5
062980
301.0
301.5
Hours from
Start
DATE
0
1
071680
160.0
438.0
071780
160.0
438.0
072180 160.0 438.0
080780 420.0 594.9
082980 150.0 443.7
Longitude = 77.1 W
Latitude = 38.9 N
Temperature (K) Profiles:
Mixing Height Profiles:
10
301.9
302.0
301.8
301.4
300.6
299.5
298.1
296.5
294.7
301.9
302.0
301.8
301.4
300.6
299.5
298.1
296.5
294.7
301.9
302.0
301.8
301.4
300.5
299.5
298.1
296.5
294.7
301.2
301.7
302.0
301.9
301.4
300 .7
299.6
298.3
296.7
301.8
301.G
301.6
301.0
300.2
299.1
297.6
296.0
2 94.1
10
711.3
975.1
1225.0
1456.7
1666.1
L849.8
2004.6
2127.9
2217.4
711.3
975.1
1225.0
1456.7
1666.1
1849.8
2004.6
2127.9
2217.4
711.3
975.1
1225.0
1456.7
1666.1
1849.8
2004.6
2127.9
2217.4
766.8
932.8
1090.0
1235.7
1367.5
1483.1
1580.5
1658.0
1714.3
732.3
1011.0
1275.0
1519.7
1741.0
1935.0
2098.6
2228.7
2323.3
87123 5
-------
Appendix B
PHOTOLYSIS RATE RATIOS AS A FUNCTION OF
ZENITH ANGLE FOR A NUMBER OF TEST CITIES
This appendix contains pliatsly&is rate ratios (to as a function of
zenith angle for a number of test cities. These values differ for each
city only in regard to regional albedo and elevation- Because elevation
and albedo are very similar for our set of test cities, only minor varia-
tions are evident- The values were compiled using the formulation of
Schippnick and Green (1982) and the extraterrestrial flux data of WRC
(Iqbal, 1988} for three different ozone column densities. The rate ratios
for 0.300 cm-atm (300 Dobson Units} were used in the base-case simula-
tions^ 0.250 and 0.200 cm-atm values were employed in future scenario
simulations.
07123 5
176
-------
Table B-l
. Photolysis Rate Ratios to k
Hjq (x 1000) for Boston,
Zenith
3-values (ttiin x 1000)
Angle
(deq.)
03=>0(iD)
HCH0=>rads
HCH0=>stab
ALD2
0.300 cm-
atm:
0
4.084
3.428
4.234
0.746
10
3.976
3.399
4.218
0.735
20
3.658
3.312
4.170
0.702
30
3.154
3.161
4.085
0.646
40
2.505
2.941
3.954
0.569
50
1.774
2.642
3.763
0.471
60
1.056
2.250
3,486
0.357
70
0.482
1.756
3.081
0.234
78
0.215
1.302
2.638
0.145
86
0.094
0.802
2.039
0.074
0.250 cm-
atm:
0
5.415
3.706
4.344
0.869
10
5.279
3.676
4.329
0.856
20
4.879
3.585
4.281
0.819
30
4.243
3.429
4.195
0.757
40
3.417
3.200
4.065
0.670
50
2.476
2.887
3.875
0.560
60
1.529
2.474
3.598
0.430
70
0.739
1.951
3.191
0.288
78
0.343
1.462
2.741
0.182
86
0.147
0.904
2.121
0.093
0.200 cm-
¦atm:
0
7.483
4.050
4.472
1.036
10
7.305
4.019
4.457
1.021
20
6.784
3.924
4.409
0.979
30
5.951
3.761
4.324
0.909
40
4.862
3.522
4.194
0.810
50
3.606
3.193
4.004
0.683
60
2.317
2.757
3.727
0.532
70
1.192
2.197
3.318
0.365
78
0.582
1.666
2.861
0.236
86
0.245
1.034
2.215
0.121
H,0
2-2-
1.151
1.143
1.120
1.081
1.024
0.946
0.842
0.708
0.580
0.427
1.220
1.213
1.188
1.147
1.087
1.005
0.896
0.754
0.617
0.452
1.309
1.301
1.275
1.231
1.167
1.080
0.964
0.812
0.665
0.484
87123 5
177
-------
Table B-2. Photolysis Rate Ratios to kNQo (x 1000) for Chicago, IL
Zenith
Angle
(deflO
j-values (mirT^, x 1000)
03=>0(^D) HCH0=>rads HCH0=>stab
ALD2
HgOg
)0 cm-atm:
0
4.131
3.459
4.266
0.753
1.160
10
4.021
3.430
4.250
0.742
1.153
20
3.702
3.342
4.202
0.709
1.130
30
3.194
3.192
4.118
0.653
1.091
40
2.540
2.973
3.988
0.576
1.034
50
1.803
2.674
3.799
0.478
0.956
60
1.077
2.281
3.523
0.362
0.852
70
0.494
1.783
3.116
0.239
0.717
78
0.222
1.323
2.664
0.149
0.586
86
0.099
0.826
2.073
0.077
0.435
50 cm-atm:
0
5.482
3.741
4.378
0.878
1.231
10
5.345
3.711
4.363
0.866
1.223
20
4.943
3.621
4.315
0.828
1.199
30
4.301
3.465
4.231
0.766
1.158
40
3.469
3.236
4.102
0.679
1.098
50
2.518
2.923
3.913
0.569
1.016
60
1.561
2.510
3.637
0.437
0.907
70
0.759
1.982
3.228
0.294
0.764
78
0.356
1.486
2.769
0.187
0.625
86
0.156
0.931
2.156
0.097
0.461
0.200 cm-atm:
0
10
20
30
40
50
60
70
78
86
7.586
7.406
6.881
6.041
4.942
3.673
2.367
1.225
0.603
0.259
4.091
4.061
3.966
3.804
3.565
3.236
2.799
2.234
1.694
1.065
4.509
4.494
4.447
4.363
4.234
4.046
3.769
3.357
2.891
2.252
1.048
1.034
0.991
0.920
0.821
0.694
0.542
0.373
0.242
0.126
1.322
1.313
1.288
1.244
1.180
1.092
0.976
0.824
0.674
0.494
07 1 2 3 5
178
-------
Table B-3
. Photolysis Rate Ratios to k
(x 1000) for Los Angeles
, CA.
Zenith
j-values
(min-1, x 1000)
Angle
1
(deq.)
03=>0(1D)
HCH0=>rads
HCH0=>stab
ALD2
HoOo
0.300 cm-
atm:
c—c—
0
4.105
3.442
4.248
0.749
1.155
10
3.996
3.413
4.233
0.738
1.147
20
3.677
3.325
4.184
0.705
1.125
30
3.171
3.175
4.099
0.649
1.086
40
2.520
2.955
3.969
0.572
1.028
50
1.787
2.656
3.779
0.474
0.950
60
1.065
2.264
3.502
0.359
0.847
70
0.487
1.768
3.097
0.236
0.712
78
0.218
1.311
2.649
0.147
0.583
86
0.096
0.813
2.055
0.076
0.431
0.250 cm-
atm:
0
5.444
3.721
4.359
0.873
1.225
10
5.308
3.691
4.344
0.860
1.217
20
4.907
3.601
4.296
0.823
1.193
30
4.268
3.445
4.211
0.761
1.152
40
3.440
3.216
4.082
0.674
1.092
50
2.495
2.903
3.892
0.564
1.010
60
1.544
2.490
3.615
0.433
0.901
70
0.748
1.965
3.208
0.291
0.759
78
0.349
1.473
2.754
0.184
0.621
86
0.151
0.917
2.137
0.095
0.456
0.200 cm-
atm:
0
7.528
4.068
4.489
1.041
1.315
10
7.350
4.037
4.473
1.027
1.306
20
6.826
3.943
4.426
0.984
1.281
30
5.991
3.780
4.341
0.914
1.237
40
4.898
3.541
4.212
0.815
1.173
50
3.636
3.212
4.022
0.688
1.085
60
2.339
2.775
3.746
0.536
0.969
70
1.207
2.213
3.336
0.369
0.817
78
0.591
1.679
2.874
0.239
0.669
86
0.251
1.048
2.232
0.123
0.488
87123 5
179
-------
nu2
— * * "»
Zenith
j-values
x 1000)
Angle
1
(deq.)
03=>0(1D)
HCH0=>rads
HCH0=>stab
ALD2
H?0o
u—C —
300 cm-atm:
0
4.130
3.458
4.265
0.753
1.160
10
4.020
3.429
4.249
0.742
1.152
20
3.701
3.342
4.201
0.709
1.130
30
3.193
3.192
4.117
0.653
1.091
40
2.539
2.972
3.987
0.575
1.034
50
1.802
2.673
3.798
0.477
0.956
60
1.076
2.280
3.522
0.362
0.852
70
0.494
1.783
3.115
0.239
0.717
78
0.222
1.322
2.663
0.149
0.586
86
0.099
0.826
2.072
0.077
0.435
250 cm-atm:
0
5.480
3.740
4.377
0.878
1.231
10
5.343
3.710
4.362
0.865
1.223
20
4.941
3.620
4.314
0.828
1.199
30
4.300
3.464
4.230
0.766
1.158
40
3.467
3.235
4.101
0.679
1.098
50
2.517
2.922
3.912
5.683
1.016
60
1.560
2.509
3.636
0.437
0.906
70
0.759
1.981
3.227
0.294
0.764
78
3.552
1.486
2.768
0.187
0.625
86
0.155
0.931
2.155
0.097
0.461
200 cm-atm:
0
7.583
4.090
4.508
1.047
1.321
10
7.404
4.060
4.493
1.033
1.313
20
6.879
3.965
4.446
0.991
1.287
30
6.038
3.803
4.362
0.920
1.244
40
4.940
3.564
4.233
0.821
1.180
50
3.672
3.235
4.044
0.694
1.092
60
2.366
2.798
3.768
0.542
0.976
70
1.225
2.233
3.356
0.373
0.823
78
0.602
1.694
2.890
0.242
0.673
86
0.259
1.064
2.251
0.126
0.493
87 123 5
180
-------
Table B-5. Photolysis Rate Ratios to k^ (x 1000) for New York, NY,
Zenith
j-values (min~^t x 1000)
Angle
1
(deq.) 0
3=>0(1D>
HCH0=>rads
HCH0=>stab
ALD2
H2O2
0.300 cm-atm:
0
4.084
3.428
4.234
0.746
1.151
10
3.975
3.399
4.218
0.735
1.143
20
3.658
3.312
4.170
0.702
1.120
30
3.153
3.161
4.084
0.646
1.081
40
2.504
2.941
3.954
0.569
1.024
50
1.774
2.642
3.762
0.471
0.946
60
1.056
2.250
3.486
0.356
0.842
70
0.482
1.756
3.081
0.234
0.708
78
0.215
1-301
2.637
0.145
0.580
86
0.094
0.802
2.039
0.074
0.427
0-250 cm-atm:
0
5.415
3.705
4.344
0.869
1.220
10
5.278
3-676
4.328
0.856
1.212
20
4.878
3.585
4.280
0.819
1.188
30
4.242
3.429
4.195
0.757
1.147
40
3.417
3.199
4.065
0.670
1.087
50
2.475
2.886
3.874
0.560
1.005
60
1.529
2.474
3.597
0.430
0.896
70
0.739
1.950
3.191
0.288
0.754
78
0.343
1.462
2.741
0.182
0.617
86
0.147
0.904
2.120
0.093
0.452
0.200 cm-atm:
0
7.482
4.049
4.472
1.035
1.309
10
7.305
4.018
4.457
1.021
1.301
20
6.783
3.923
4.408
0.979
1.275
30
5.949
3.761
4.324
0.908
1.231
40
4.861
3.522
4.194
0.810
1.167
50
3.606
3.192
4.004
0.683
1.079
60
2.316
2.756
3.726
0.532
0.963
70
1.192
2.196
3.318
0.365
0.812
78
0.681
1.665
2.861
0.236
0.665
86
0.245
1.034
2.214
0.121
0.484
87123 5
181
-------
Table B-6. Photolysis Rate Ratios to kNQo (x 1000) for Philadelphia, PA.
Zenith
Angle
(deg.) 03=>0(1D)
0.300 cm-atm:
j-values (min~l, x 1000)
HCH0=>rads
HCH0=>stab
ALD2
HgOg
0
4.083
3.428
4.234
0.746
1.151
10
3.975
3.399
4.218
0.735
1.143
20
3.657
3.311
4.169
0.701
1.120
30
3.153
3.161
4.084
0.646
1.081
40
2.504
2.941
3.953
0.569
1.024
50
1.773
2.641
3.762
0.471
0.946
60
1.056
2.250
3.486
0.356
0.842
70
0.481
1.755
3.081
0.234
0.708
78
0.215
1.301
2.637
0.145
0.579
86
0.094
0.802
2.039
0.074
0.427
>0 cm-atm:
0
5.414
3.705
4.344
0.869
1.220
10
5.278
3.676
4.328
0.856
1.212
20
4.878
3.584
4.280
0.819
1.188
30
4.242
3.428
4.195
0.757
1.147
40
3.416
3.199
4.065
0.670
1.087
50
2.475
2.886
3.874
0.560
1.005
60
1.529
2.474
3.597
0.430
0.896
70
0.739
1.950
3.191
0.288
0.754
78
0.343
1.461
2.741
0.182
0.617
86
0.147
0.904
2.120
0.093
0.452
)0 cm-atm:
0
7.481
4.049
4.472
1.035
1.309
10
7.304
4.018
4.456
1.021
1.301
20
6.783
3.923
4.408
0.979
1.275
30
5.949
3.760
4.323
0.908
1.231
40
4.860
3.521
4.194
0.809
1.167
50
3.605
3.192
4.003
0.683
1.079
60
2.316
2.756
3.726
0.532
0.963
70
1.192
2.196
3.317
0.365
0.812
78
0.581
1.665
2.860
0.236
0.665
86
0.244
1.034
2.214
0.121
0.484
87 123 5
182
-------
Table B-7. Photolysis Rate Ratios to kNQ (x 1000) for Phoenix, AZ.
Zenith
Angle
(deg») o^of1^
0.300 cm-atm:
j-values (min"*, x 1000)
HCH0=>rads
HCH0=>stab
ALD2
_h2o2.
0 4.150
10 4.041
20 3.720
30 3.211
40 2.554
50 1.812
60 1.082
70 0.497
73 D.225
86 0.103
0.250 cm-atm:
0 5.511
10 5.374
20 4.969
30 4.325
40 3.488
50 2.532
60 1.569
70 0.764
73 0.360
86 0.161
0.200 cm-atm:
0 7.630
10 7.450
20 6.922
30 6.075
40 4.969
50 3.692
60 2.378
70 1.232
78 0.610
86 0.268
3.450
3.421
3.333
3.183
2.963
2.664
2.273
1.780
1.326
0.842
3.732
3.702
3.611
3.455
3.225
2.912
2.501
1.979
1.490
0.949
4.082
4.050
3.955
3.793
3.553
3.224
2.789
2.230
1.699
1.086
4.254
4.238
4.190
4.106
3.975
3.786
3.512
3.110
2.665
2.096
4.366
4.351
4.303
4.219
4.089
3.900
3.625
3.222
2.771
2.180
4.497
4.481
4.433
4.349
4.220
4.032
3.757
3.351
2.893
2.277
0.753
0.742
0.708
0.652
0.575
0.477
0.362
0.239
0.150
0.079
0.878
0.865
0.828
0.765
0.67B
0.568
0.436
0.294
0.188
Q.010
1.048
1.034
0.991
0.920
0.820
0.693
0.541
0.373
0.243
0.129
1.158
1.150
1.127
1.088
1.031
0.953
0.850
0.716
0.587
0.441
1.228
1.220
1.196
1.155
1.095
1.013
0.904
0.763
0.626
0.467
1.319
1.310
1.285
1.241
1.176
1.089
0.973
0.822
0.675
0.500
87123 5
1B3
-------
j-values (min x 1000)
Table B-8. Photolysis Rate Ratios to kN0^ (x 1000) for Seattle, WA.
Zenith
Angle
(deg.) 03=>0(10)
0.300 cm-atm:
HCH0=>rads
HCH0=>stab
ALD2
_h2o2_
0
4.115
3.448
4.255
0.751
1.157
10
4.006
3.420
4.240
0.740
1.150
20
3.687
3.332
4.191
0.706
1.127
30
3.180
3.182
4.107
0.651
1.088
40
2.528
2.963
3.977
0.573
1.031
50
1.793
2.663
3.787
0.475
0.952
60
1.070
2.271
3.511
0.360
0.849
70
0.490
1.774
3.104
0.237
0.714
78
0.220
1.316
2.655
0.148
0.584
86
0.098
0.818
2.062
0.076
0.432
50 cm-atm:
0
5.459
3.729
4.367
0.875
1.227
10
5.322
3.699
4.351
0.862
1.220
20
4.921
3.609
4.304
0.825
1.196
30
4.282
3.453
4.219
0.763
1.154
40
3.451
3.224
4.090
0.676
1.094
50
2.504
2.911
3.900
0.566
1.012
60
1.550
2.498
3.624
0.435
0.903
70
0.752
1.972
3.216
0.292
0.761
78
0.352
1.478
2.760
0.185
0.622
86
0.153
0.922
2.145
0.096
0.458
)0 cm-atm:
0
7.551
4.077
4.497
1.044
1.318
10
7.372
4.046
4.814
1.029
1.309
20
6.848
3.952
4.434
0.987
1.283
30
6.010
3.790
4.350
0.916
1.240
40
4.915
3.551
4.221
0.817
1.176
50
3.651
3.222
4.032
0.690
1.088
60
2.350
2.785
3.755
0.539
0.972
70
1.214
2.221
3.344
0.370
0.820
78
0.596
1.685
2.881
0.240
0.671
86
0.254
1.055
2.240
0.124
0.490
87123 5
184
-------
Table B-9. Photolysis Rate Ratios to (x 1000) for Tulsa, OK.
Zenith
it n — 1
Angle
1
(deq.) 0
^O^D)
HCH0=>rads
HCH0=>stab
ALD2
HoOo
—t-t-
0.300 cm-atm:
0
4.130
3.450
4.256
0.752
1.158
10
4.021
3.422
4.241
0.741
1.150
20
3.701
3.334
4.192
0.707
1.127
30
3.193
3.184
4.108
0.652
1.088
40
2.539
2.964
3.978
0.574
1.031
50
1.801
2.665
3.789
0.476
0.953
60
1.075
2.273
3.513
0.361
0.850
70
0.493
1.778
3.109
0.238
0.715
78
0.222
1.321
2.660
0.149
0.585
86
0.010
0.827
2.075
0.077
0.435
0.250 cm-atm:
0
5.485
3.733
4.370
0.877
1.229
10
5.347
3.703
4.354
0.864
1.221
20
4.945
3.613
4.307
0.827
1.197
30
4.303
3.457
4.222
0.765
1.156
40
3.469
3.228
4.093
0.678
1.096
50
2.518
2.916
3.904
0.567
1.013
60
1.560
2.504
3.629
0.436
0.905
70
0.758
1.978
3.222
0.294
0.763
78
0.356
1.485
2.767
0.187
0.624
86
0.156
0.934
2.160
0.098
0.462
0.200 cm-atm:
0
7.589
4.083
4.500
1.046
1.319
10
7.410
4.052
4.485
1.032
1.311
20
6.884
3.958
4.438
0.990
1.285
30
6.042
3.795
4.354
0.919
1.241
40
4.942
3.556
4.225
0.820
1.177
50
3.672
3.227
4.036
0.693
1.090
60
2.365
2.791
3.761
0.540
0.974
70
1.224
2.229
3.351
0.372
0.822
78
0.603
1.693
2.888
0.242
0.673
86
0.260
1.068
2.256
0.127
0.495
87 123 5
185
-------
Table B-10. Photolysis Rate Ratios to kNQ^ (x 1000) for Washington, DC.
Zenith
Angle
j-values (min-1. x 1000)
(deg.) 03=>0(1D) HCH0=>rads
0.300 cm-atm:
HCH0=>stab
ALD2
_h2o2_
0
4.084
3.428
4.234
0.746
1.151
10
3.976
3.399
4.218
0.735
1.143
20
3.657
3.312
4.170
0.701
1.120
30
3.154
3.161
4.084
0.646
1.081
40
2.504
2.941
3.954
0.569
1.024
50
1.774
2.642
3.763
0.471
0.946
60
1.056
2.250
3.486
0.357
0.842
70
0.482
1.756
3.081
0.234
0.708
78
0.215
1.301
2.637
0.145
0.580
86
0.094
0.802
2.039
0.074
0.427
50 cm-atm:
0
5.414
3.705
4.344
0.869
1.220
10
5.278
3.675
4.328
0.856
1.212
20
4.879
3.585
4.280
0.819
1.188
30
4.242
3.429
4.195
0.757
1.147
40
3.417
3.200
4.065
0.670
1.087
50
2.476
2.886
3.874
0.560
1.005
60
1.529
2.474
3.598
0.430
0.896
70
0.739
1.950
3.191
0.288
0.754
78
0.343
1.462
2.741
0.182
0.617
86
0.147
0.904
2.120
0.093
0.452
)0 cm-atm:
0
7.482
4.049
4.472
1.036
1.309
10
7.305
4.019
4.457
1.021
1.301
20
6.783
3.924
4.409
0.979
1.275
30
5.950
3.761
4.324
0.909
1.231
40
4.862
3.522
4.194
0.810
1.167
50
3.606
3.193
4.004
0.683
1.079
60
2.316
2.756
3.727
0.532
0.963
70
1.192
2.196
3.318
0.365
0.812
78
0.582
1.666
2.861
0.236
0.665
86
0.245
1.034
2.214
0.121
0.484
87 123 5
186
------- |