EPA-600/4-78-014
February 1978
A PROLONGED, LARGE SCALE, OFF-SEASON
PHOTOCHEMICAL OXIDANT EPISODE
Gerard A. DeMarrais
Meteorology and Assessment Division
Environmental Sciences Research Laboratory
Research Triangle Park, N.C. 27711
ENVIRONMENTAL SCIENCES RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, N.C. 27711
-------
DISCLAIMER
This report has been reviewed by the Office of Research and Development,
U.S. Environmental Protection Agency, and approved for publication. Mention
of trade names or commercial products does not constitute endorsement or
recommendation for use.
Mr. DeMarrais is a meteorologist in the Meteorology and Assessment
Division, Environmental Sciences Research Laboratory, Environmental Research
Center, Research Triangle Park, N.C. 27711. He is on assignment from the
National Oceanic and Atmospheric Administration, U.S. Department of Commerce.
-------
ABSTRACT
o
Oxidant concentrations exceeding 160 yg/m were observed at many locations
in a 7-county area in southern California from February 25 to March 4,
1975. Because this was a violation of the air quality standard at a time
when relatively low concentrations were normally anticipated the meteorological
conditions associated with this large scale episode were evaluated. A more
complete understanding of the meteorology associated with the episode should
provide a better background for devising an abatement strategy. The episode
was associated with very slow air movement, slightly elevated temperatures,
abundant solar radiation, limited vertical mixing at the coast, and vertical
mixing varying from negligible at night to relatively deep in the daytime at
inland sites. The maximum temperatures were 3° to 6°C cooler than those
normally associated with high oxidant concentrations, but the solar radiation,
as deduced from sky cover and sunshine records, was about equivalent to that
at the end of the usual oxidant season. The differences in vertical mixing,
combined with the overall stagnation and weak sea breeze at the surface in the
afternoon, appeared to cause the oxidant concentrations to be higher inland.
111
-------
CONTENTS
Disclaimer ii
Abstract 111
Figures v1
Tables v11
1. Introduction 1
2. Conclusions 2
3. Background and Methods 3
Ozone and total oxldant monitoring stations and the data 3
Meteorology previously associated with high POX
concentration 3
Meteorological data 4
4. Results 6
POX concentrations 6
Surface weather observations 7
Daily weather maps 9
Special solar radiation data 9
Temporal and spatial variation of bases and tops of
inversions 10
5. Summary 12
References 14-16
-------
FIGURES
Number Page
1. POX monitoring stations 21
2. Maximum hourly POX concentrations (pphm), February 25, 1975. ... 22
3. Maximum hourly POX concentration (pphm), February 26, 1975 .... 23
4. Maximum hourly POX concentration (pphm), February 27, 1975 .... 24
5. Maximum hourly POX concentration (pphm), February 28, 1975 .... 25
6. Maximum hourly POX concentration (pphm), March 1, 1975 26
7. Maximum hourly POX concentration (pphm) March 2, 1975 27
8. Maximum hourly POX concentration (pphm) March 3, 1975 28
9. Maximum hourly POX concentration (pphm) March 4, 1975 29
10. Diurnal, clear sky values of k. The photodissociation rate constant
for N02 for Los Angeles (34.1°N, 118.3°W) 30
11. Variation of height and temperature (°C) of bases (0) and tops (a)
of inversions 31
vi
-------
TABLES
Number Page
1 Meteorology During Episode of February 25 to March 4, 1975. . . 17-19
2 Values of k for March 1 Divided by k for June 21 20
-------
SECTION 1
INTRODUCTION
The concentration of photochemical oxidant (POX) is considered a problem
when it exceeds the hourly National Ambient Air Quality Standard (NAAQS) of
3 1
160 yg/tn or 8 pphm . In California POX is measured as total oxidant* and ozone,
and the typical months of high POX concentrations are usually considered to be
1 A
May through October . The reasons suggested for the nonoccurrence of high
concentrations in the cool half of the year are that the temperatures are not
high enough and the solar radiation is insufficient for substantial oxidant
o
formation. However, a quarterly summary of the California Air Resources Board
shows that during the period of February 25 through March 4, 1975, a large
number of stations in 7 counties in southern California recorded concentrations
which violated the standard. Since a more complete knowledge of the meteorology
associated with these high concentrations could aid in the formation of an
improved abatement strategy, this investigation was undertaken to obtain that
knowledge. The meteorological conditions associated with the episode are
examined and summarized to suggest which phenomena appeared to contribute to
the high concentrations. The temperature and radiation observations of the
period are compared to those of the POX season. In addition, special con-
sideration is given to the temporal and spatial variation of the bases and tops
of inversions as shown by the vertical soundings made at Los Angeles Airport
and El Monte5.
*Specific spectroscopic measurements indicate ozone is the principal oxidant
in California air?.
1
-------
SECTION 2
CONCLUSIONS
On the basis of the analyses of the February 25 to March 4, 1975 southern
California data, the following conclusions are drawn:
1. This prolonged period of high POX concentrations occurred at a time
when high concentrations were not a normal occurrence.
2. The episode was associated with stagnation, slightly elevated tempera-
tures, abundant sunshine, limited vertical mixing at the coast, and
vertical mixing varying from negligible at night to relatively deep
in the daytime at inland sites.
3. The maximum temperatures were about 3° to 6°C cooler than those
normally assciated with high POX concentrations, but the radiation,
as deduced from the NOp photodissociation rate constant, k,, was
about equivalent to that at the end of the usual POX season (about
_3
11 hours duration and a maximum rate constant of 8 x 10 per
second).
4. The differences in vertical mixing combined with the overall stagna-
tion and weak sea breeze at the surface in the afternoon appeared
to cause the POX concentrations to be higher inland.
-------
SECTION 3
BACKGROUND AND METHODS
OZONE AND TOTAL OXIDANT MONITORING STATIONS AND THE DATA
The southern California area has a large network of ozone and total oxi-
dant monitoring stations. Although the total oxidant monitors react to
nitrogen dioxide and organic peroxides, ozone is the principal oxidant
o
in California air . All of the total oxidant monitors in southern California
are colorimetric instruments and are standardized against ozone. The ozone
concentrations are determined by instruments utilizing one of two physiochemical
processes: non-dispersive ultraviolet absorption or chemiluminescence. Both
2
types of instruments are calibrated using known constant ozone standards .
A special note is needed here because of a change in the recording of
POX values in California. There was a discrepancy in the POX values recorded
by the Los Angeles Air Pollution Control District and the other control
agencies. All POX data collected beginning June 1, 1975 are comparable and
to make all prior data comparable, the reported non-Los Angeles County data
are to be multiplied by 0.8 . Accordingly, all non-Los Angeles County data
in this report have been made comparable.
The locations of the ozone and total oxidant stations are shown in
Figure 1. Many stations record both ozone and total oxidant, and several
cities have more than one station. The interest in this study is the highest
concentration of POX for each day without regard to whether it was observed
as ozone or total oxidant. In the presentations that follow, only the highest
hourly concentration is shown, and ozone and oxidant are used interchangeably
with each other and with POX.
METEOROLOGY PREVIOUSLY ASSOCIATED WITH HIGH POX CONCENTRATION
The meteorological conditions associated with high POX concentrations
in southern California have been documented in many investigations . The
earliest study correlated high concentrations of POX with weak winds and
-------
8-11
stagnant air. Other early comprehensive investigations " related variations
in ozone concentrations to variations in the following: intensity and dura-
tion of solar radiation; surface temperature; the depth of the polluted layer
(the top coincided with the base of the subsidence inversion); and wind
speed and direction. In these early studies high concentrations were con-
12
sidered local, low-level problems. However, following the report that
winds aloft are important in transporting "second-hand" ozone to unsuspecting
downwind areas, investigators examined the three-dimensional picture and
I O 1C
long-range transport phenomena. Evidence ' confirms that high POX con-
centrations are frequently in the air aloft, even within the subsidence
inversion, and that the locations of these contaminated layers aloft are
determined by the winds aloft. Eventually, parts of the contaminated layers
17 18
are brought to the surface in daytime mixing. Other studies ' have shown
that the highest ozone concentrations occur with heat waves. Finally, although
19 20
some investigations ' have indicated that stratospheric ozone may contribute
to high surface ozone concentrations in other places, no similar finding has
been reported for southern California.
jMETEOROLOGICAL DATA
21 22
The surface weather observations ' in this report are from the follow-
ing stations: Burbank Airport, Los Angeles International Airport, Los Angeles
Civic Center, Ontario Airport, Riverside Airport, Norton Air Force Base (San
Bernardino), and San Diego International Airport. The meteorological parameters
summarized are: the daily maximum and minimum temperatures, the prevailing
wind direction and average speed for each quarter-day, the percent of possible
sunshine for each day, sky condition for each day and weather (obstructions to
visibility, precipitation) that occurred during the day.
Discussions of the synoptic conditions are based on the Daily Weather
?? 5
Map and the daily resumes of the National Weather Service Air Pollution
Forecaster in Los Angeles. The Daily Weather Map is used to locate high and
low pressure areas and fronts. The Daily Weather Map shows two maps for each
day based on 4 a.m. (all times are Pacific Standard) observations; one map is
TV the surface and the other for 500 millibars (mb) (about 5500 meters (m)
eoove the surface).
Special attention is given to solar radiation data with emphasis on the
4
-------
photodi^sociation rate constant, k,, for nitrogen dioxide, NCL. This con-
24
stant is explained in detail by Leighton . Ozone production in the presence
of ozone precursors is directly related to the value of k,.
A second phenomenon given special consideration is the time and spatial
variation of the bases and tops of inversions. Records from the National
Weather Service show that a variation does exist which may partially account
for higher concentrations in the eastern part of the Los Angeles basin.
-------
SECTION 4
RESULTS
POX CONCENTRATIONS
The highest hourly POX value for each day for each station is shown in
Figures 2 through 9.
On February 25 (Figure 2) there were violations of the standard (8 pphm)
in all 7 counties. Most coastal areas had concentrations at or just below
the standard, whereas at the inland locations concentrations generally were
higher than the standard by 25 to 75 percent.
On February 26 (Figure 3) the only coastal city with a violation was Chula
Vista in San Diego County and 4 inland citiesNewhall, Temple City, Upland,
and Fontana--had concentrations which were twice as high as the standard.
On February 27 (Figure 4) the coastal stations just below Los Angeles had
low concentrations whereas El Toro and the coastal stations in San Diego had
violations. Inland, 7 stations recorded concentrations twice the standard and
o
several exceeded 400 vig/m (20 pphm).
On February 28 (Figure 5) the only areas without violations were on the
immediate coast and areas within 16 km of the coast had readings ranging from
o
200 to 420 yg/m (10 to 21 pphm). Inland the average concentrations were
about twice the standard and a violation was noted at Victorville in the
desert to the north as well as at Palm Springs in the eastern desert.
On March 1 (Figure 6) violations occurred throughout the 7-county area
with the coast being relatively clean and inland areas badly contaminated.
On March 2 (Figure 7) violations were reported in only 4 counties, the
coast was relatively clean, and inland the concentrations were lower than
they were on March 1.
On March 3 (Figure 8) the concentration pattern was similar to that of
March 2, but fewer stations recorded violations, 20 versus 17.
6
-------
On March 4 (Figure 9) only 2 violations occurred in northwest Los Angeles
County and 1 occurred in eastern Orange County. Large parts of western San
Bernardino and Riverside counties had violations.
SURFACE WEATHER OBSERVATIONS
The maximum temperatures at the 7 stations (Table 1) reveal that the
period averaged slightly warmer than the long term average at the coast, while
inland it was 3° to 6°C warmer than average. However, these temperatures were
about 6° to 8°C colder than those of July. These maximum temperatures show the
normal condition of marked increase from the coast inland. Los Angeles Airport
had temperatures around 15°C while Ontario and San Bernardino had temperatures
in the range of 26° to 32°C (80's°F). These higher temperatures inland indicate
that such locations had vertical mixing to considerably greater heights than
the coastal locations.
The diurnal range of temperature (today's maximum minus tomorrow's mini-
mum) shows where radiation Inversions likely form at night; when the range
is 14°C or greater at a location in southern California there is a very high
25
probability that nocturnal surface-based inversions form . These maximum-
minimum temperature ranges in Table 1 indicate that inland locations must
have had nocturnal inversions almost every night while coastal areas did not
have these surface-based inversions. The Los Angeles and El Monte data,
which are limited to the workweek days and are presented in a following sec-
tion, showed that the coast generally did not have surface-based inversions
while El Monte did have them. The periods of warming and cooling, particularly
at inland locations, were neither associated with increases and decreases in
concentrations nor expansion and contraction of the affected areas.
The winds were generally light except during the third quarter of each
day. During this afternoon period, there was a sea breeze flow with a general
west-to-east movement, except at Burbank where a sea breeze comes out of the
south-southeast.
The two sunshine records reveal that the coastal area had two-thirds or
more of the possible sunshine on each of the first 7 days; on the eighth day
the sunshine was markedly less.
-------
The sky conditions (as well as the temperatures) at the inland stations
indicate that they had greater amounts of sunshine than the coastal sites.
Smoke and haze were consistently present after the first day. At the 4 suc-
cessive downwind stations, Burbank, Ontario, San Bernardino, and Riverside,
the smoke and haze were dense enough to partially obscure the sky; the visi-
bility generally was less than 5 km at these stations.
The overall indication was that the episode was not associated with
particularly high temperatures; there was slow moving air; the sunshine was
abundant; inland, there was limited nocturnal vertical mixing and relatively
deep daytime mixing; and obscuring phenomena tended to stay in the area.
The higher concentrations at inland than at coastal locations are assumed
to have been due, partially, to differences in vertical mixing. The typical
diurnal air movement shows ozone and its precursors being carried inland with
14
the sea breeze in the daytime while a weaker reverse flow exists at night.
The wind directions at Los Angeles, Ontario, and Burbank indicate that this
diurnal flow occurred during this period (Table 1). In the daytime, the more
polluted air (Figures 2-9) that was inland was dispersed by vertical mixing
through deeper layers than the polluted air in coastal areas. Then, at night,
there was a reverse flow and in the eastern areas radiation inversions formed
(Figure 11), cutting off mixing between the surface and layers aloft. Since
pc
the ground is a sink at which ozone is destroyed , a contrast was set up
between inland areas and the coast. Inland the ozone aloft remained intact,
except for scavenging by the NO present in that layer. At the coast, vertical
mixing continued through the night and the relatively shallow ozone reservoir
aloft was diluted by mixing with the surface air; part of the ozone was
destroyed at the surface so the concentrations aloft and at the surface de-
creased with time. The cleansing was augmented by having relatively clean
air advected in with the drainage winds from inland areas; these drainage
winds had little or no contact with the ozone aloft and the operations of
the sources of precursors (primarily autos) inland were greatly reduced. In
the following daylight periods during the first few hours, the emissions of
precursors increased tremendously throughout the Basin and the sea breeze winds
mo,^ the air eastward. The abundant sunlight (Table 1) reacted with the
precursors to produce ozone. The coastal areas had few upwind sources and
8
-------
they had relatively low concentrations while areas inland had high concen-
trations. As the day progressed both the coastal and inland areas had their
surface air mixed with the air aloft. The coastal areas had a relatively
small amount of ozone with which to mix while inland areas had a deep layer
with high concentrations of ozone. This gradient aloft, from inland to the
coast, although not documented on this occasion, has been documented on other
13
occasions when similar meteorological conditions prevailed . Thus the
inland areas had high concentrations due to the combined effects of advection
and the mixing downward of ozone from aloft. In periods of slow air movement,
this source of "second-hand" ozone, coming from aloft, adds to the ozone
problem associated with surface advection.
DAILY WEATHER MAPS
The 500-mb maps for February 25 through March 3 generally showed a weak,
flat ridge over or a little to the east of California. This condition ended
on March 4 when an upper level low with cool, moist air moved Into California.
The surface maps showed pressure gradients which allowed a very weak onshore
flow from February 25 to March 3. Weak cold fronts or troughs moved through
the area early on February 27 and March 2. On March 4 there was a moderate
onshore gradient; rain fell on some areas of southern California.
SPECIAL SOLAR RADIATION DATA
Since an episode developed during February 25 through March 4, it 1s
concluded that the solar radiation was sufficient for generation of signifi-
cant ozone concentrations. According to the weather observations, the indica-
tion is the radiation was intense for this time of year. No direct measure-
ments of solar radiation were made so an alternate method of evaluating the
radiational effects had to be employed. Because the N09 photodissociation rate
24
constant, k,, is a key factor in ozone generation , data on the temporal
27
variation of k, were sought. A new method for calculating the diurnal
variation cf k, for clear sky conditions (the prevailing situation) was used
for June 21 and December 21, the seasonal extremes, as well as for the midday
of the episode, March 1. The results are shown in Figure 10. The values of
k, on March 1 are considerably smaller than those of June 21, but markedly
greater than those of December 21. On June 21 photodissociation starts around
-------
5 a.m. and ends about 6:45 p.m. whereas on March 1 the starting time is about
6:45 p.m. and ending time 5:30 p.m.; the photodissociation occurs for 3
hours longer on June 21. Table 2 shows the ratio of the on-the hour values
of k.| for March 1 versus those for June 21. Only during the middle of the
day are the March 1 values 80 percent of those of June 21. The overall
indication is that the photodissociation can be considerably reduced from
the extreme value and duration, yet still be sufficient to generate high
ozone concentrations. In absolute values and durations, a maximum k, of
3 1
8 x 10 sec and a duration just short of 11 hours seems sufficient when
other conditions are right. Although the days in this episode are cold-
season days, the radiation results are not surprising. March 1 is comparable
to October 10 with regard to elevation angle of the sun and radiation, and
October 10 is considered to be near the end of the season with high ozone
2 3
concentrations ' . (Note: The maximum temperatures, when compared to October
10 averages, were about 6°C colder on the coast and 3°C colder inland.)
TEMPORAL AND SPATIAL VARIATION OF BASES AND TOPS OF INVERSIONS
The heights and temperatures of the bases and tops of inversions indi-
cate the potential for vertical mixing. When the bases are low and the
temperature differences between the bases and tops are large, there generally
is limited vertical mixing. When the bases are high or the temperature dif-
ferences are small (that is, the inversion is easily eliminated with additional
heating), vertical mixing can be extensive. In the Los Angeles area data on
the heights and temperatures of the bases and tops of inversions are provided
twice a day, 6 a.m. and noon, Monday through Friday, for 2 sites, Los Angeles
Airport (near Lennox) and El Monte (close to Temple City), by the National
23
Weather Service . A graphical presentation of these data for February 25
through March 4 is shown in Figure 11. The Los Angeles Airport, a coastal
location, usually observed inversions with elevated bases and temperature
differences exceeding 3.0°C (considered large and not easy to eliminate when
observed at noon ). The elevated bases were 460 m or lower most of the time
and the inversions remained intact and intense through the daytime; relatively
rapid vertical mixing occurred continually throughout the 24-hour day, but was
; united. At El Monte, an inland station, most of the 6 a.m. inversions were
surfaced-based, indicating that vertical mixing was very slow and limited at
10
-------
night. At noon over El Monte the Inversions were weak (averaging 1.0°C).and
probably eliminated in the afternoon; vertical mixing had no inversion lid.
Normally, this better daytime vertical mixing inland would mean greater dilution
by mixing with a larger volume of clean air aloft. However, the winds aloft up
to about 900 m from February 25 through March 3 were light and variable , indi-
11 12 13
eating very slow movement aloft. It is well-documented ' ' that ozone
buildup occurs during periods with sluggish air movement aloft and that the
layers aloft can be the source of "second-hand" ozone brought down to the surface
by vertical mixing. The "second-hand" ozone might have been a major contributing
factor to the extremely high concentrations observed at stations in the vicinity
of El Monte.
11
-------
SECTION 5
SUMMARY
1. During the cool part of the year when high POX concentrations do not nor-
mally occur, there was an 8-day period when a 7-county area in southern Cali-
fornia experienced a POX episode.
2. The episode was associated with stagnation; the winds at the surface and
aloft were light. At the surface, there was a very weak land breeze at night
and during the day an organized onshore flow.
3. The episode was associated with relatively warm temperatures and intense
radiation for the season, (as deduced from sky cover and sunshine records).
The maximum temperatures were considerably lower than those which occur during
the peak POX season and even 3° to 6°C lower than those which occur at the end
of the POX season in the fall. The radiation, as shown by the photodissocia-
tion rate, k,, for N02» was considerably less than that observed at the height
of the POX season, but similar to that at the end of the normal POX season.
4. There was a marked difference in the vertical mixing at the coast and
inland. Vertical mixing was continuous, but limited throughout the 24-hour
day at the coast, while inland there was negligible mixing at night and
relatively deep mixing in the daytime.
5. The differences in vertical mixing may have accounted, in part, for the
differences in the severity of the problem. The higher concentrations occurred
inland where vertical mixing during the daytime brought down oxidant from the
previous day that had been trapped aloft. Each day more POX was added near
the surface, and there was no clean air aloft with which to dilute the surface
concentrations. At the coast vertical mixing allowed for a relatively uniform
vertical distribution of POX, which enhanced destruction at night near the
surface. Additionally, the coastal area benefited from the organized afternoon
flu ~> at the surface that brought relatively clean air to the coast.
12
-------
Simultaneously, the inland areas were having high concentrations of ozone
advected in from the coast and brought down from aloft; the ozone problem
inland was compounded.
13
-------
REFERENCE
1. National Air Pollution Control Administration. Air Quality Criteria for
Photochemical Oxidants. AP-63, U.S. Department of Health Education, and
Welfare, Washington, D.C. 1975. 178 pp.
2. California Air Resources Board. California Air Quality Data, January,
February, March 1975. Technical Services Division, Sacramento, California,
1975. 75 pp.
3. Schuck, E.A., A.P. Altshuller, D.S. Barth, and G.B. Morgan. Relationships
of Hydrocarbons to Oxidants in Ambient Atmospheres. J. Air Poll. Control
Assoc., 20: 297-302 (1970).
4. Dimitriades, B. Photochemical Oxidants in the Ambient Air of the United
States. EPA-600/3-76-017, U.S. Environmental Protection Agency, Research
Triangle Park, North Carolina, 1976. 182 pp.
5. Lust, E. (Air Pollution Forecaster, National Weather Service, Los Angeles),
Daily worksheets for air pollution forecasts and radiosonde data for Los
Angeles and El Monte, February 24 through March 5, 1975.
6. California Air Resources Board. California Air Quality Data, July, August,
September 1975. Technical Service Division, Sacramento, California.
75 pp.
7. Middleton, J.T., J.B. Kendrick, and H.W. Schwalm. Injury to Herbaceous
Plants by Smog or Air Pollution. Plant Disease Reporter, 34(9): 245-252,
1950.
8. Neiburger, M. and J. Edinger. Meteorology of the Los Angeles Basin,
Report No. 1, Southern California Air Pollution Foundation, Los Angeles,
California, 1954. 97 pp.
9. Renzetti, N.A., Editor. An Aerometric Survey of the Los Angeles Basin
August-November 1954. Report No. 9, Air Pollution Foundation, Los Angeles,
California, 1955.
10. Hitchcock, L.B., W.L. Faith, M. Nieburger, N.A. Renzetti, and L.H. Rogers.
Air Pollution Situation in Los Angeles-An Aerometric Survey. In: Pro-
ceedings of the Third National Air Pollution Symposium, Pasadena, Cali-
fornia, 1955. pp. 12-23.
11. Rogers, L.H. Report on Photochemical Smog. J. of Chem. Education, 35(6):
310-313, 1958.
14
-------
12. Lea, D. A. Vertical Ozone Distribution in the Lower Troposphere Near an
Urban Pollution Complex. J. Appl. Meteorol., 7: 252-267, 1968.
i
13. Edinger, J.G. Vertical Distribution of Photochemical Smog in Los Angeles
Basin. Environ. Sci. Technol., 3: 247-252, 1973.
14. Gloria, H.R., G. Bradburn, R.F. Reinisch, J.N. Pitts, Jr., J.V. Behar,
and L. Zafonte. Airborne Survey of Major Air Basins in California.
J. Air Poll. Control Assoc., 24(7): 645-652, 1974.
15. Blumenthal, D.L., L.A. Farrow, and T.A. Weber. The Effects of Variations
in Bulk Meteorological Parameters on Ozone Concentrations. In Preprint
Volume: Symposium on Atmospheric Diffusion and Air Pollution, Amer.
Meteor. Soc., Santa Barbara, California, 1974. pp. 115-120.
16. Kauper, E.K. and B.L. Niemann. Los Angeles to Ventura Over Water Ozone
Transport Study. Report prepared for California Air Resources Board by
Metro Monitoring Services, Covina, California, 1975. 54 pp.
17. California Air Resources Board. California Air Quality Data, April, May,
June 1974. Technical Services Division, Sacramento, California, 1974.
83 pp.
18, Tiao, G.C., G.E.P. Box, and W.J. Hamming. Analysis of Los Angeles
Photochemical Smog Data: A Statistical Overview. J. Air Poll. Control
Assoc., 25(3): 260-268, 1975.
19. Danielson, E.F. and V.A. Mohnen. Ozone Measurements and Meteorological
Analyses of Tropopause Folding. Presented at the International Symposium
on Ozone, Dresden, German Democratic Republic, 1976. 36 pp.
20. Reiter, E.R. The Role of Stratospheric Import on Trosposp&eric Ozone
Concentrations. Presented at the International Symposium on Ozone,
Dresden, German Democratic Republic, 1976. 24 pp.
21. U.S. Department of Commerce, National Oceanic and Atmospheric Administra-
tion. Local Climatological Data. Published monthly for Los Angeles and
San Diego, 1975. 2 pp.
22. National Climatic Center, Surface Weather Observations, Burbank, Norton
AFB, Ontario, FAA Riverside, February 25-March 4, 1975. (Xerox copies of
original records).
23. U.S. Department of Commerce, National Oceanic and Atmospheric Administra-
tion. Daily Weather Maps. Published weekly 1975. 8 pp.
24. Leighton, P.A. Photochemistry of Air Pollution Academic Press, New York,
New York, 1961. 300 pp.
15
-------
25. DeMarrais, G.A., G.C. Holzworth, and C.R. Hosier. Meteorological Summaries
Pertinent to Atmospheric Transport and Dispersion Over Southern California.
Technical Paper. No. 54. U.S. Department of Commerce, Weather Bureau,
Washington, D.C., 1965. 86 pp.
26. Miller, A. and C.D. Ahrens. Ozone Within and Below the West Coast Tempera-
ture Inversion. Dept. of Meteorology Report No. 6, San Jose State College,
San Jose, California, 1969. 74 pp.
27. Schere, K.L. and K.L. Demerjian. Calculation of Selected Photolytic Rate
Constants Over a Diurnal Range-A Computer Alogorithm. EPA-600/4-77-015,
U.S. Environmental Protection Agency, Research Triangle Park, North
Carolina, 1977. 63 pp.
16
-------
i m
8?
1 f
1 o
cc
^c
0
1
CM
|
UJ
U.
o
LU
1
l+_
UJ
t i
1 a:
E
o
o
0
1 OC
0
UJ
1
LU
rJ
LU
_1
K-
s:
gco
t.
L
*'.
^
lUOO
U.CM
JO
cur-
U.JM
-Q
U- CM
.Q
QJ LO
licM
UJ
h-
o
LO CO
3
cn CM 3:
. r Z CO
""«. ""x. 3 ^D
^0 co in ^c
(jO UO UJ
Z >-
"co
3
CO CM
"- C^ 3
z^tr-a:
CM CO 3 CO -
10 *t U.
Z CM
CO 3
r- en
lO *» 3
Z CM
zn
z«n
»
cr> z r**
i- 00
*^*^-3 u> 3:
r- r-zwvo
V3f Z U.
Icn
z
zco
COO 3
5c3'3**S:ti
*O If) Z CM LL.
3
2S *
ICM
"~" °* ^ CO
co cn 3 10 *
t/> i
UJ
z: CM
ZCM
CO CM 3
^.^.3 CO
«* co _ coin
VO LT> 3 CO
Z CM
z: CM
3
r^ CTi ^
T-- Cft ^ r -t-
10 «a- J^-
o
t
o w
0. 0.
CO -r- Z? O" 2C -^
-l-> > . W +J
3-*
LO CM CO CO UI
r- r- 00 > -
m LO oo c*5 o u.
UJ
3Sr-
3CO
CO» 3 "* 31
r i Q *
in * z r cj *
LU CM _l ^£
in o
LU
3*^
3i CO
LO O
*~ r** 3 LO ^ 3C
*^»"-N. a *
CH O CO CM _l H
in in o
u
3 «» >-
a
<£O3in_ja:
i OZ r- >-
3 CM a.
3CO
to 3 m 3:
r-CO >-
~-\uj a v:
r- VO LO _1 -
LO ^ LU O U.
gCM
3 CO
m i a:
tn in o
z: co
3 CO
CM cn 3 in a:
CTt 00 LU CSJ UJ 5*:
UJ ^- O
^^^
o.
tj"G^3 O &
00 -r- VI Q
U-. U_ C 0) «- r C
0 0 -r- O) -O OJ (
a ^- -.^- a. c i- on.
t- -i- tO O Ol C
D i i -M -r
-xcotcn>,(o w>2
£ s s: Q.
"~eo o
S5*°
CM O>
!>>»*
i O
CMi
oor»
fx in
cn
er>
r**. cr> co
CM cr>
O co cn
^"^. .
1 0 0 X
: u. u-
J 0 0 CU
J h- h- -C
VI
* X C C
(O -r- 3
j s:s: to
17
-------
LO .
r^ i ;
= '
o
a:
z! '
Oj
LO
CM
OC I
g
CO ''
111 I
If
I_1_J
o
UJ
O i
o
in
a.
UJ
0
*^~
&. '
g
5
O!
i i
0 I
o
Ul
UJ
r- '
CQ
h
t-
^_
fQ CO
11
S-
n3 CM
s:
rO i
s:
J3
(U CO
U. CM
JQ
- -
-^ \ <; ro a ^
lO-
CO Kf
CO CM
D£
*X CO
"^ >_
LU CD
CM r-- UJ O "
cri LO a: >- -
r-^. *3" h-
ex
3J
^ CM
a:
» ^J- CO CM U.
CO
C£.
>>(t3 *-»
4_> t3n3-r-l_>_^(U C
CO CQEZS^CXtflCO^S. O
3:
ET co
CM CT> ^i£ LTl CO »
^^.^- CQ i^
en a> ex o -
^»
UJ ro
1^3- O «
CO <^ CO CO U_
UJ
Z CO
"Z.
UJ
zr co
CM \O 3 CO *
-^-^OO ^ CQ *£
^o CM 3 o «
z: CM
z: co
z: co
CO CO «* 1C
CM CM 3 CO -
"**^. "^«. CQ S£
«* ^O 3 CO O »
p^. co co u_
2r CM
"Z.
LU
2: co
CM C£
CM «5f IS U) >, (O S-
(T3 -r- 1- > ^
CM ^ ro nz
CM <,Q CO "
--- "*-^ L^. CQ ^i
i CO =£ i CD
0
o
co or:
CM CO 3: C-J e£ IL_
"^."^^ LU »
CM CO 0 _J ^,
CO CO O
L-Lj r
0
CD 31
CM CO 3 C*") CO -
CO CO 0 O
to co u_
o
co 3 «^- re
CM CO CO *
*d- CO O "
r*^ co LU u_
^*- f~~
UJ
UJ
CO i
CM \o co ni
^^^^.3 CO CQ *
O CM O ^
CO *T O
UJ r-
O
CM CO CO CO CO *
"-v-^ 3 CQ i^
«4J CO O *
r^. co o u_
0
CM 1C
CM CM 3 CO CO *
CM U3 0 O *
r-- co u_
0
o
CM * 3 CO
I h- fo o J^:
C > . 4_)
ra x c: QJ en >> to
LO (B -r- t. > Jy: QJ
2: 2: o_
-------
i-
o
>- 3:
}_i -
r- ^
O.
en
O
ai
NI
co :«£
o -
CO M
CMO
>, 10
a s-
3 3
O O
* (/)
O XI
o
* II
Q 00
_J 00
o o
tfl
o
O XI
o o
"O O
i. O> J- >>
3 -
OC K- _l
II II oo a.
ca ^
o
3 un
003;
uj ca >
z CM o :*:
a «
i c
s- o
0) t-
+J +J
s-
cr aj
in
O) XI
> o
ca ^
o -
o
u
o
ro
,
"i ^
5 §
1 E!
c s.
E
ro
in
o
a.
c: E c
ts
Q
1
C
o
u
ra
oo
3-- 0
CM cn « +->
ai
TD
(/I
s-
a>
>P_
DC:
C T3 -r-
* -I-"
fU rji >^ ro
s- > j^ aj
Q- <=C 00 3
-o
C
4-> 4-»
4->
l/)
C C
r- O
a
c
CO
X
ro
19
-------
TABLE 2. VALUES OF k FOR MARCH 1 DIVIDED BY k FOR JUNE 21
7 a.m.
8
9
10
11
Noon
0.17
0.49
0.70
0.79
0.83
0.85
1 p.m.
2
3
4
5
6
0.84
0.82
0.76
0.59
0.28
_
20
-------
/
/
Si
81
x_
0
^
tc
<
i
1
k
(A X
* \
« \
° =
ii
Ul
C9
ac
3
*
i
j
"';'.' f
', <
s '
i
411
8
O
tZ
i
O)
i j
21
-------
s! I /\
2lJ ^ -S
E^< i L
3r-=«L'°« y
' ^-^..r" .£ ">
22
-------
23
-------
o
5 :
tr '
r;
AIR
ir
z
4
.*,
!
S-r1
!2? ,»
iJ
"i -! «
1 § 2
2«
5«
/"
f
-s
"
<\
o1
*» "^
*cf
(O >
rf> '
£
«. "^s-
- x
/
I K °*
gzJ oc «
nig § SB
-' 8° |.
-i || tM n«
Si
in*
./
a»
7
I
lie
l:s
|)8
!
JL.
0>
u
§
X
O
a.
24
-------
£
-------
./
«irii
«-' /
o
CJ
z
1-
i
W
Ut
£t 1 "
. »z_l oc
nig
-' S°
_j
2
oc
<
2»
S«
"
r^
1
"
-=-N».
" V
*
"'A
"
ce«
zz
< D
oco
OO
7
"
/
01*
_r_.
CO
cu
i_
O)
26
-------
27
-------
o
z
0 >
,-3z
ri§
UJ 0
fO
!
^ *
il-
ir^l--
AIR S|
si
O 1
t»
O)
I I, I
" '«
£ i «°*
* r
9
o
r«.«
*
28
-------
£
o
z
Q
g£
FZ
1 OC
bU
1 03
Z
s
;
i
i
i
>
f-
z
D
o
fj
"
1
I
oa
<
z
o _
h- O
i ^
^«
J
i
^
£
=1 J |
8L§
-^-iv
ji
r*«
29
-------
^v»^ ~
^^^
1^^^^
^^x^
CO
o
C 3 ~,_ ~
*~ CO
(1)
-------
sj3jaui jo spaapunq 'IHDI3H
at & ro
0)
O
3
w_x
CD
O
1
(0
a)
09
tfl
U-l
O
o
o
0)
a)
M
a>
a
H
0)
.C
4-1
O
C
o
H
4J
rt
H
H
cd
0.
u
31
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1 REPORT NO.
EPA-600/4-78-014
2.
4 TITLE AND SUBTITLE
A PROLONGED, LARGE-SCALE, OFF-SEASON, PHOTOCHEMICAL
OXIDANT EPISODE
5. REPORT DATE
February 1978
6. PERFORMING ORGANIZATION CODE
3. RECIPIENT'S ACCESSION-NO.
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
Gerard A. DeMarrais*
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Environmental Sciences Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
10. PROGRAM ELEMENT NO.
1AA603 AD-07(FY-78)
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Sciences Research Laboratory - RTP, NC
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
FYPE OF REPORT AND P-ERIOQCOVERED
Inhouse War //-Dec 77
14. SPONSORING AGENCY CODE
EPA/600/09
15. SUPPLEMENTARY NOTES
*0'n assignment from the National Oceanic and Atmospheric Administration,
U.S. Department of Commerce.
16. ABSTRACT
Oxidant concentrations exceeding 160 yg/m were observed at many locations in a
seven-county area in southern California from February 25 to March 4, 1975. Because
this was a violation of the air quality standard at a time when relatively low con-
centrations were normally anticipated, the meteorological conditions associated with
this large scale episode were evaluated. A more complete understanding of the
meteorology associated with the episode should provide a better background for
devising an abatement strategy. The episode was associated with very slow atr move-
ment, slightly elevated temperatures, abundant solar radiation, limited vertical
mixing at the coast, and vertical mixing varying from negligible at night to
relatively deep in the daytime at inland sites. The maximum temperatures were
to 6°C cooler than those normally associated with high oxidant concentrations,
the solar radiation, as deduced from sky cover and sunshine records, was about
equivalent to that at the end of the usual oxidant season. The differences in
vertical mixing, combined with the overall stagnation and weak sea breeze at the
surface in the afternoon, appeared to cause the oxidant concentrations to be higher
inland.
3°
but
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
COSATl Field/Group
* Air pollution
* Ozone
* Meteorological
* Evaluation
Southern California
data
13B
07B
04B
13.
iSTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
41
20 SECURITY CLASS (This page)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
32
------- |