EPA-600/4-78-016
February 1978
THE 1974 OZONE EPISODE IN THE BALTIMORE-TO-RICHMOND CORRIDOR
by
Gerard A. DeMarrals
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
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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
11
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ABSTRACT
An ozone alert 1n July of 1974 1n the Washington, D. C., area is examined
in detail. Ozone data for 16 stations in the Baltfmore-to-Richmond corridor
are examined in conjunction with meteorological data for the alert period.
Emphases are given to trajectories of the air between the surface and 1000
meters and the mixing height and winds aloft data of the air pollution forecasts
of the National Weather Service. The investigation revealed: (1) the period
with high ozone concentrations was one when synoptic scale stagnation at the
surface and aloft prevailed most of the time together with high temperatures
and abundant solar radiation; (2) despite overall stagnation over a very large
region there were periods when 48-hour trajectories showed that ozone could
have been transported from potential source areas as far as 1000 kilometers
upwind; (3) that a) the Richmond-to-Balt1more corridor was at the southern
and eastern periphery of a large area in the industrial eastern United States
which had high ozone concentrations, and b) many of the distant potential
source areas implicated in the trajectory analyses observed high ozone concen-
tration; and (4) that any abatement strategy for this type of stagnation-ozone
alert will have to take into account both local and distant sources.
111
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CONTENTS
Abstract 111
Figures vl
Tables v1
1. Introduction 1
2. Conclusions 2
3. Background Information and Methods 3
Ozone stations, instruments, and records 3
Meteorology previously associated with high ozone
concentrations 4
The diurnal variation of ozone concentrations and the
associated meteorology 4
Meteorological inputs 5
4. Results 7
Ozone data 7
Observations at airports 7
Mixing height data 7
Synoptic weather situation 8
Trajectories of the surface-to-1000 meter layers 9
The temporal and spatial extent of the high ozone
concentrations 10
5. Summary 12
References. . . 13
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FIGURES
Number Page
1 Locations of ozone monitoring stations 17
2 Ozone concentrations at 16 stations, July 7-11, 1974 18-19
3a Surface weather map, 7:00 a.m., E.S.T., July 7, 1974 20
3b Surface weather map, 7:00 a.m., E.S.T., July 9, 1974 21
4 12 mps contour, 500 mb height, 7:00 a.m., July 7-11, 1974
(Weaker winds to south.) 22
5 Forty-eight-hour trajectories (12-hour increments) of layer
from surface to 1000 meters, July 7, 1974 23
6 Forty-eight-hour trajectories (12-hour increments) of layer
from surface to 1000 meters, July 8, 1974 24
7 Fcrty-eight-hour trajectories (12-hour increments) of layer
from surface to 1000 meters, July 9, 1974 25
8 Forty-eight-hour trajectories (12-hour increments) of layer
from surface to 1000 meters, July 10, 1974 26
9 Forty-eight-hour trajectories (12-hour increments) of layer 27
from surface to 1000 meters, July 11, 1974
TABLES
1 Ozone Stations and Locations 28
2 Atmospheric Conditions During Episode 29
3 Mixing Height Data, Washington Area, July 6-11, 1974 30
4 Maximum Ozone Concentrations (PPB) in Cities Surrounding the
Study Area 31-32
vi
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SECTION 1
INTRODUCTION
The Balt1more-to-Richmond corridor, which encompasses the nation's capital
and Includes a large population, 1s 250 kilometers (km) long. When the area
experiences an air pollution alert 1t 1s a source for real concern to many
people; causes of such an event should be determined so that similar episodes
can be anticipated and possible corrective action taken before the alert occurs,
1 2
Reports * from the Washington, D. C., area indicate that the District
experienced only one photochemical oxidant alert* 1n the summer of 1974.
Montgomery County, Maryland, records show that the alert occurred from July 8
2
through 11. The National Weather Service data disclose that A1r Stagnation
Advisories (warnings that pollution problems might develop during the day)
were issued for all 4 days. Since Advisories Imply potential hazards for a
large area, ozone data for all stations in the Richmond, Washington, and
Baltimore areas were obtained for study.
Preliminary examination of the data confirmed that the high concentrations
were widespread throughout the corridor and that the initial high concentra-
tions actually occurred on the 7th (Sunday). Concurrent meteorological data
were analyzed in detail to demonstrate the role of meteorology in the episode.
Emphases were given to the synoptic situations, to trajectories of the air
between the surface and 1000 meters (m), and to the seldom evaluated mixing
height and winds aloft data of the air pollution forecasts of the National
2
Weather Service . Finally, ozone data for stations in surrounding states were
examined to delineate the area affected by large scale stagnation and to show
the concentrations in areas upwind of the corridor cities, as implicated in
the trajectory analyses.
*An alert is called when adverse meteorological conditions are predicted and
photochemical oxidants exceed the 100 parts per billion (ppb) one-hour average
standard of Maryland'. This 1974 alert was based on ozone measurements.
1
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SECTION 2
CONCLUSIONS
On the basis of this study the following conclusions are drawn:
1. The meteorological conditions associated with the high concentrations
of ozone in the Baltimore-to-R1chmond corridor were those associated with
ozone episodes in other areas of the country: stagnation at the surface
and aloft; several days with relatively high temperatures; and intense
solar radiation.
2. Many of the high concentrations of ozone during this stagnation period
were associated with nearby (i.e., within several 10's of km of the
receptors) upwind sources; local emissions were a major factor in the
high concentrations much of the time.
3. The 48-hour trajectory analyses showed there were times during this
widespread stagnation when air from as far away as 1000 km was transported
to the Baltimore-to-Richmond corridor. The implications are that long
range transport occurred in spite of the stagnation and that it contributed
to the high concentrations observed on some days.
4. During this period the general area of high ozone concentrations,
which approximately coincided with the stagnation area, extended from
northern Tennessee and Virginia in the south, to Ohio in the northwest,
and Massachusetts in the northeast. The Balt1more-to-Richmond corridor
was on the southeastern edge of this region; many of the distant upwind
areas implicated as possible sources of ozone and its precursors did
experience high concentrations of ozone at the surface.
5. Inasmuch as long range transport readily occurred during this stagna-
tion-ozone episode, an effective abatement strategy for this type of alert
would require corrective action at distant as well as local sources.
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SECTION 3
BACKGROUND INFORMATION AND METHODS
OZONE STATIONS, INSTRUMENTS, AND RECORDS
Ozone monitoring stations are generally operated by State and local agen-
cies, with the State agency being responsible for providing the federal
government with a near-complete and accurate record. In the District of Colum-
bia, the Department of Environmental Services operates the instrumentation and
is responsible for the records. The main ozone data used in this report came
from 16 stations: the State of Virginia provided data for 2 stations in Rich-
mond and 6 in the suburbs of Washington, D. C.; the District agency provided
data for 1 station in the District; and the State of Maryland provided data for
4 stations in suburbs of Washington, 2 in Baltimore, and 1 in a Baltimore suburb.
The locations of the stations are shown in Figure 1 and are identified in
Table 1. About 10 separate agencies are responsible for operating these instru-
ments. One station in Richmond uses an ultraviolet Dasibi instrument and all
others use chemiluminescence instruments. Four Virginia stations record in
o
micrograms per cubic meter (yg/m ) and all others record in parts per million.
The National Ambient Air Quality Standard (NAAQS) not to be exceeded more than
once a year is 160 yg/m or 80 parts per billion (ppb); in this report, when
the NAAQS is violated, a concentration is called high. It should be noted
that most of these stations are close to heavy traffic, the source of most
local man-made ozone precursors . The literature indicates that peak ozone
concentrations are not at the precursor source, but are displaced a considerable
distance downwind. The ozone recorded at these stations is therefore reason-
ably attributed to upwind sources, both local (within several 10's of km of
receptors) and distant (further away than local sources). In order to show
the extent of the high ozone concentrations as well as the possibility for
long-distant transport, the ozone data from 10 surrounding states are examined.
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METEOROLOGY PREVIOUSLY ASSOCIATED WITH HIGH OZONE CONCENTRATIONS
Previous Investigations have shown that a number of meteorological
4-5 7-34
phenomena are associated with high ozone concentrations ' . The phenomena
mostly frequently associated with high concentrations are: low wind speeds or
stagnation conditions " low mixing heights (shallow surface-based layers
through which pollutants readily mix)8'10*14"17; intense solar radiation4'8'9'
11-14'18-20; high temperatures4'13'20'23; heat waves14'24'26; and advection
4-5 27-34
by surface winds and long-range transport winds aloft ' . It has been
suggested that only one alert occured in the Washington area in 1974 because
the area was more cloudy than usual during the months of June through Septem-
ber; in 1973, in the summer, cloudless skies and alerts were more frequent.
THE DIURNAL VARIATION OF OZONE CONCENTRATION AND THE ASSOCIATED METEOROLOGY
The typical diurnal variation of surface ozone concentrations, according
to findings for 4 areas in the United States and one in Canada14'22'35'36'23,
is as follows; low at night and in the early morning hours; increasing
rapidly starting 7 to 9 a.m. and peaking around 2 to 3 p.m.; and then declining
rapidly through the remainder of the afternoon until the low nighttime values
are first observed around 8 to 10 p.m.
7818
Early investigators ' ' described the high ozone concentrations as a
local photochemical phenomenon. Solar radiation reacting with the precursors
of ozone emitted by automobiles and industry brought about the high concentra-
37
tions. In 1961 it was reported that the photochemical production of ozone
exceeded ozone destruction (for example, by NO scavenging and surface uptake)
from 2 to 7 hours after the photochemical reactions were initiated by irradia-
tion. This timing readily accounted for the increases in concentrations
starting in the morning, peaking in the early afternoon and then declining.
After several hours of destruction exceeding production the low nighttime
concentrations are observed. The relatively high concentratons of the daytime
generally extended from a few km downwind from the sources to as many km as
the surface winds advected the polluted layers in the daytime period. These
relatively high daytime concentrations are thus local problems dependent on
nearby emissions and surface advection on the day of the occurrence of the
high concentration.
4
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27
Lea first reported that there could be a contribution from aloft to
high concentrations of ozone at the surface and that this contribution could
be associated with long-range transport. During the daytime, the upward
currents of vertical mixing carry ozone and ozone precursors aloft. At
night, when the vertical mixing is generally suppressed and restricted to a
shallow layer near the surface, the ozone aloft remains intact while that
at the surface is destroyed by reaction with fresh NO emissions and surface
/\
deposition. The diurnal variation of vertical mixing coupled with ozone aloft
produces, at the surface, a variation in ozone concentration similar to that
produced by photochemical reactions in the layers of air advected at the sur-
face; at night and during the early morning hours no ozone is brought to the
surface; as vertical mixing increases soon after sunrise there is a marked
increase in the ozone brought to the surface; when vertical mixing reaches
a maximum early in the afternoon ozone contained in the whole mixed layer is
subject to downward vertical mixing and concentrations at the surface approach
those in the layers aloft; after the maximum vertical mixing occurs the concen-
trations at the surface decrease as there is no fresh ozone from aloft being
brought into the mixing layer. Thus, it is very difficult to separate the ozone
concentrations associated with nearby (local) upwind emissions and those
associated with long-range transport coupled with vertical mixing because each
produces a similar pattern. A third, but rare, set of circumstances, complete
stagnation in the layer aloft, with high concentrations brought upward on one
day and downward the following day could also produce the same diurnal varia-
tion. However, there are relatively few conditions, under which there is no
wind movement in the mixing layer for periods as long as 24 hours (trajectories
to be presented later will show that layers of air are frequently moved several
hundred km in 24 hours during periods described as stagnant).
METEOROLOGICAL INPUTS
38
Daily weather data contained in the Local Climatological Data for
R. E. Byrd International Airport (Richmond), Washington National Airport,
and Friendship International Airport near Baltimore were used to determine
the following: the daily maximum and minimum temperatures, the prevailing
wind direction and average speed for each quarter-day, the percent of possible
5
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sunshine for each day, and the weather (cloud conditions, obstructions to
39
visibility, precipitation). Dally Weather Maps were also reviewed to
determine the air movement aloft, the locations of fronts, centers of high
and low pressure, and areas of precipitation and to relate the wind speeds
and directions to high ozone concentrations.
p
The National Weather Service records on mixing heights and average wind
speeds through these layers over the Washington area provide information on the
vertical mixing as well as horizontal movement of the layer of air over the
local area.
3
Trajectory analyses were used to supplement the mixing height data of
the local area by showing the likely paths of the layers of air prior to
arrival in the local areas. The trajectory analyses are based on the wind
data from the rawinscnde observations scheduled at 7 a..m. and 7 p.m. (all
times are Eastern Standard) and the winds aloft observations at 1 a.m. and
1 p.m. each day. In the basic calculation, a point along the trajectory is
determined every 3 hours and data within a radius of 300 nautical miles
(556 km) are evaluted. The model includes a distance weighting factor (the
closest observations receive the greatest weight), an alignment weighting
factor (observations upwind and downwind receive the greatest weight) and a
height weighting factor (the thicker the subpart of the trajectory layer which
the wind represents, the greater the weight). Trajectory segments are linked
together to produce a complete trajectory for a desired period of time.
Trajectories are usually started from a source or receptor 4 times daily,
1 and 7 a.m. and 1 and 7 p.m. In this report, the trajectories for each
receptor-city show the backward movements in 12-hour segments for ending
times of 7 a.m. and 1 p.m. Obviously, these trajectories are approximations;
they become progressively less reliable with each added segment. In this
report the trajectories are limited to 48 hours. A point on a trajectory
indicates the general area and not a specific location where the layer of air
was located at an earlier time.
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SECTION 4
RESULTS
OZONE DATA
The variations of the hourly ozone data for all 16 stations are shown
in Figure 2. Although some data are missing, it is obvious that every loca-
tion had high ozone concentrations on July 7 to 9. By July 10, there were
3
no violations of the 160 ug/m standard in the Baltimore area and concentra-
tions were decreasing in Washington and peaking in Richmond. By July 11,
only Richmond recorded violations of the standard.
OBSERVATIONS AT AIRPORTS
Pertinent weather observed at each airport is shown in Table 2. When
compared to the normals, the maximum and minimum temperatures Indicate
that the temperatures were high on the first 4 days at all 3 stations. A
heat wave prevailed during the 4-day period; the maxima averaged 3°C above
the expected averages (July maxima averaged 31°C at all 3 airports). The
wind directions varied locally and from airport to airport. On days of high
concentrations the wind speeds occasionally reached 8 mps, but commonly
were 4 mps or less. Overall, the winds were light and variable, indicating
local stagnation. The weather and percent of sunshine showed a consistent
pattern; the skies were predominantly clear and the amount of possible sun-
shine was relatively high. The main impedance to Incoming solar radiation
during the 5 days was haze.
MIXING HEIGHT DATA
2
Table 3 lists the mixing height data for each day; July 6 is included
because the low speed In the mixing layer may have contributed to the problem
on July 7 (that is, the winds would not have moved ozone aloft out of the
general area). The mixing heights of July 6 and 8 were relatively low and
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on tho other days near average (the 1971-1972 average mixing height for July
was 1760 m). The wind speeds appear to have been more significant than the
mixing heights for the first 4 days because they were considerably less than
the 5.4-mps average for July 1971-1972. The low speeds indicate that during
the episode pollutants aloft may have remained in high concentrations above
the three-city area.
SYNOPTIC WEATHER SITUATION
The Daily Weather Maps disclosed that most of Niemeyer's criteria
for forecasting synoptic scale high air pollution potential and the criteria
of Korshover for determining that large scale stagnation had occurred (a
post occurrence evaluation) were met. The primary criteria of the forecast
and evaluation schemes are that the winds at the surface and aloft up to
500 mbs (about 5500 meters above mean sea level) be relatively weak. Both
techniques included persistence criterion; the forecasts required conditions
to continue for at least 36 hours; the evaluations only counted episodes
that lasted at least 4 days. The minimum size area for a forecast was an
area equivalent to a longitude-latitude square of 4 degrees on a side. The
post analysis was based on longitude-latitude grid points at 2-degree intervals,
but focused on the pressure pattern around anticyclone centers. Both schemes
sought evidence of subsidence and an absence of precipitation and fronts.
The surface and 500-mb maps for July 7 to 11 showed that the winds were
relatively light as high pressure with weak pressure gradients was the domi-
nant synoptic feature over the eastern part of the nation. Two examples of
the surface maps are shown in Figure 3. On July 7, (Figure 3a), the first
day with the high ozone concentrations 1n the corridor, the isobaric pattern
was extremely weak over the eastern half of the country. A large fraction
of stations in the area bounded by Illino1s-Pennsylvania-Louis1ana-F1orida-
Illinois recorded calm conditions at 7 a.m.; very few reported speeds as
high as 3 mps. The stationary front just south of Pennsylvania was weak and
dissipating as the area of high pressure Immediately to its north amalgamated
with the high centered along the Carolina coast. By July 9, (Figure 3b), the
pressure distribution over the eastern states remained much like that on the
7th, except the gradient had increased slightly over the Great Lakes and had
8
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decreased over the southern Mississippi Valley. The front seen in southern
Canada on July 9, moved into southern parts of New England, New York and
Michigan on July 10 (position at 7 a.m.) and on July 11 pushed through the
corridor.
The 500-mb charts, 1n concert with the sea-level charts, showed high
heights (and pressure) and weak gradients over the eastern United States.
One of the criteria frequently employed in conjunction with other indicators
of stagnation is that the winds be less than 12 mps at the 500-mb level.
During this episode such speeds were exceeded only in the region north of our
area of interest. Figure 4 shows the northern boundary of the region where
the 500-mb winds were 12 mps or less, based on observations at 7 a.m. on each
day of the episode. Clearly, winds aloft conducive to stagnation covered the
eastern half of the nation except for the extreme northeast from July 7 to 10.
The rapid southwestward movement of the area of stronger winds on the llth
was associated with the termination of the episode as the front shown in
Figure 3b moved southward through the corridor.
TRAJECTORIES OF THE SURFACE-TO-1000 METER LAYERS
The mixing height data (Table 3) indicated that the afternoon well-mixed
layers ranged from 1160 to 1990 meters thick. In the case of the trajectories,
the conservative height of 1000 meters was employed; the bulk of the pollution
in the atmosphere would be contained in that depth. Two trajectories for each
day, for ending times of 7 a.m. and 1 p.m., and for Richmond, Washington and
Baltimore are shown.
On July 7, as seen in Figure 5, the recent 24-hour movement was very
slow (the recent 12-hour movement into each city averaged 1 mps) and the
48-hour movements covered 400 km or more (averaging about 2.3 mps or a little
more). As to potential upwind sources, the air reaching Baltimore had
passed over areas which were heavily populated and industrialized, while the
air reaching Washington and Richmond had passed over areas with few potential
sources.
On July 8, Figure 6, the 48-hour trajectories show the surface-to-1000
m layer moved with an average speed of 2 mps or less indicating stagnation
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was an important factor. Again, the air arriving 1n Richmond came from areas
with a few potential sources. In contrast, the air arriving in Baltimore and
Washington did come from potential source areas. Thus, stagnation both in
the local area and at distant locations was associated with high concentra-
tions in all 3 cities while long-range transport from potential source areas
probably contributed to the problem in Baltimore and Washington.
On July 9, Figure 7, most of the slow movement shown by the 48-hour trajec-
tories occurred with the July 7 and 8 winds; the most recent 12-hour flows
were rapid (these flows averaged 10 mps coming Into Baltimore and Washington
and 8 mps coming into Richmond). Again, the flows showed that the air over
Baltimore and Washington had prior movements over potential source areas
while the air came into Richmond from areas with few sources. Stagnation in
the local upwind areas appeared to be minor on this day, but stagnation at
distant locations on prior days and long-range transport were associated with
the high concentrations.
On July 10, Figure 8, most of the slow movement is traced back to the
July 8 winds and the air arriving over Baltimore and Washington show a history
of slow movement over the same distant areas; the most recent flows into all
3 cities averaged about 10 mps. Again, the Washington and Baltimore air had
passed over areas with large numbers of potential sources while the Richmond
air came from areas with few sources.
On July 11, Figure 9, there was rapid air movement into all 3 cities and
no evidence of stagnation during the prior 48 hours. Only Richmond had
violations of the ambient air standard and 1t was downwind of the Harrisburg-
Baltimore-Washington region as well as areas to the northwest. It appeared
that long-range transport rather than stagnation was associated with the high
concentrations in Richmond.
THE TEMPORAL AND SPATIAL EXTENT OF THE HIGH OZONE CONCENTRATIONS
The temporal extent of this pollution episode for the Richmond-to-
Baltimore corridor was July 7 to 11. In order to determine the spatial extent
of the episode and whether upwind areas had high concentrations which could
have contributed to high concentrations in the corridor, ozone data from
10
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the surrounding areas were sought. The data obtained were from more than 80
stations in 10 additional states extending from Tennessee and North Carolina
in the south to Ohio and Massachusetts in the north. No data were available
for West Virginia, and South Carolina. To conserve space, data for 42
representative stations were selected and are presented in Table 4. These
stations gave complete coverage to the limits of all available data; each
station which was omitted was very close to one which is listed and usually
had a concentration about the same as the nearby station.
In order to show the beginning of the episode in this enlarged area,
it was necessary to include data for July 6 (see Table 4); there were viola-
tions of the NAAQS at 17 of the 42 additional stations on July 6 (4 stations
had violations on July 5). Excluding those stations which had violations
on only one of the 6 days (July 6 to 11), it is concluded that the episode
did extend almost to the far borders of Ohio and Massachusetts in the north
and just into northern Tennessee and Virginia to the south.
The trajectories for Baltimore on July 7 and for Washington and Baltimore
from July 8 through 10 (see Figures 5 through 8), show that air arriving
in those cities came from areas which did have high ozone concentrations;
upwind areas may have contributed to the high concentrations that were
observed. The trajectories for Richmond for July 7 through 10 and those for
Washington on July 7, however, did not show major source areas in the upwind
direction.
11
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SECTION 5
SUMMARY
In the investigation of high ozone concentrations in the Baltimore-to-
Richmond corridor from July 7 to 11 , 1974, the following were determined:
1. There was large scale stagnation during the period, and it generally
extended west through north of the corridor. This stagnation was mani-
fest in the surface, 500-mb, and mixing layer winds, in the sea-level
pressure and 500-mb height patterns, and in the trajectory analyses.
2. The alert was associated with the meteorological phenomena typically
associated with high concentrations of ozone: low wind speeds; several
days with high temperatures and intense solar radiation. The mixing
heights were not, however, very low during the episode.
3. Trajectory analyses indicated that in spite of wide-spread synoptic
stagnation, some of the air arriving over Washington and Baltimore was
associated with air from distant areas with potential sources. Examina-
tion of the ozone data from the surrounding area for the same period
showed that high concentrations were a widespread phenomenon and that
many of the implicated, distant upwind areas with potential sources
actually observed high concentrations of ozone.
4. Any abatement strategy for this type of stagnation-ozone alert would
have to include a plan for minimizing that part of the high concentra-
tions resulting from long range transport and that part due to nearby
sources.
12
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United States. J. Air Poll. Control Assoc., 25(1): 19-24, 1975.
22. Oacobson, J.S. and G.D. Salottolo. Photochemical Oxidants in the
New York-New Jersey Metropolitan Area. Atmos. Environ., 9(3): 331-332,
1975.
23. Anlauf, K.G., M.A. Lusis, H.A. Wilbe, and R.D.S. Stevens. High Ozone
Concentrations Measured in the Vicinity of Toronto, Canada. Atmos.
Environ., 9(12): 1137-1139, 1975.
24. Niemeyer, L. E. , Summer Sun-Cincinnati Smog: A Recent Incident. J. Air
Poll. Control Assoc., 13(8): 381-387, 1963.
14
-------
25. Technical Services Division. Contaminant and Weather Summary, August
1970. Bay Area Air Pollution Control District, San Francisco, Cali-
fornia, 1970. 8pp.
:26. Air Resources Board. California Air Quality Data, April, May, June 1974.
Vol VI No. 2, Sacramento, California, 83 pp.
27. Lea, D.A. Vertical Ozone Distribution in the Lower Troposphere Near an
Urban Complex. J. Appl. Meteor., 7: 252-267, 1968.
28. Leone, I.A., E. Brennan, and R.H. Daines. The relationship of Wind
Parameters in Determining Oxidant Concentrations in Two New Jersey
Communities. Atmos. Environ., 2: 25-33, 1968.
29. Miller, A. and C.D. Ahrens. Ozone Within and Below the West Coast
Temperature Inversion. Dept. of Meteorology Report No. 6, San Jose
State College, San Jose, California, 1969. 74 pp.
30. Edinger, J.G. Vertical Distribution of Photochemical Smog in Los Angeles
Basin, Environ. Sci. Technol., 3: 247-252, 1973.
31. Gloria, H.R., G. Bradburn, R.F. Reinisch, J.N. Pitts, Jr., J.V. Behar,
and L. Zalfonte. Airborne Survey of Major Air Basins in California,
J. Air Poll. Control Assoc. 24(7): 645-652, 1974.
32. 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 Service, Covina, California, 1975. 54 pp.
33. Martinez, E.L. and E.L. Meyer, Jr., Urban-Nonurban Ozone Gradients and
Their Significance. Presented at the Air Pollution Control Association (
Specialty Conference on Ozone Oxidants Interactions with the Total
Environment, Dallas, Texas, March 10-12, 1976. 15 pp.
34. Lyons, W.A. and H.S. Cole. Photochemical Oxidant Transport: Mesoscale
Lake Breeze and Synoptic Scale Aspects. J. Appl. Meteor., 15(7):
733-743, 1976.
35. Pol gar, L.G. and R.J. Londergan. Ozone Formation and Transport. Pre-
sented at the 79th National Meeting of the American Institute of Chemical
Engineers, Houston, Texas, March 19, 1975. 17 pp.
36. Fowler, L.H., J.P. Gise, D.J. Johnson, R.G. Wallis. The Goober III
Study. Report of the Texas Air Control Board, Austin, Texas, 1975.
16 pp.
37. Middleton, J.T. and A.J. Haugen-Sm1t. The occurrence, Distribution and
Significance of Photochemical Air Pollution 1n the U.S., Canada and
Mexico. J. Air Poll. Control Asso., 11(3): 129-134, 1961.
15
-------
38. Environmental Data Service. Local Climatological Data. Monthly Sum-
maries for R.E. Byrd International Airport (Richmond), Washington
National Airport and Friendship International Airport (Baltimore),
National Oceanic and Atmospheric Administration, Ashevllle, North
Carolina, July 1973.
39. Environmental Data Service (NOAA). Daily Weather Maps (for selected
weeks). U.S. Government Printing Office, Washington, D.C., 1974.
40. Niemeyer, I.E. Forecasting Air Pollution Potential. Monthly Weather
Review 88(3): 88-96, 1960.
41. Korshover, J. Climatology of Stagnating Anticyclones East of the Rocky
Mountains, 1936-1970. National Oceanic and Atmospheric Administration
Technical Memorandum ERL ARL-34, Silver Spring, Maryland. 27 pp. 1971.
16
-------
Figure 1. Locations of ozone monitoring stations
17
-------
I I I I I I I
8 McLEAN
BALLS MILL RD.
I I I I I I
7 FALLS CHURCH
SEVEN CORNERS
200
150
100
50
^ J
1 i [ r
M
i i i r
5 ALEXANDRIA
ST. ASAPH ST.
I |
V
I I I I I
3 FAIRFAX, SOUTH
RICHMOND HWY.
I I I I T I I I
2 RICHMOND
FAIRGROUNDS
I I I I I
1 RICHMOND _
SPENCER RD.
Figure 2. Ozone concentrations at 16 stations, July 7-11, 1974.
18
-------
200
150
f 100
SO
0
200
150
o "I 100
< SO
3U
1 i i r
M
M
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16 ESSEX
(BALTIMORE)
15 BALTIMORE
(CALVERTST.)
1 1 I I
o
u
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200
150
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50
I I I I I I
14 BALTIMORE
(LOMBARD ST
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(1-495)
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12 BETHESOA
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(ROUTE 410)
o
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9 DISTRICT OF
COLUMBIA
g S 8 § |
M 00 95 CM S
§ :
CM I
T
9
JULY
1 i ° 1 I i
1*0
1*1
Figure 2 (Continued). Ozone concentrations at 16 stations,
July 7-11, 1974.
19
-------
Figure 3a. Surface Weather Map, 7:00 a.m., E.S.T., July 7, 1974.
-------
Figure 3b. Surface Weather Map, 7:00 a.m., E.S.T., July 9, 1974.
21
-------
Figure 4. 12 mps contour, 500 mb height, 7:00 a.m., July 7-11, 1974.
(Weaker winds to south.)
22
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TABLE 1. OZONE STATIONS AND LOCATIONS
Station
Location
1. Richmond
2. Richmond
3. Fairfax South
4. Fairfax
5. Alexandria
6. Arlington
7. Falls Church
8. McLean
9. Washington
10. Suitland
11. Hyattsville
12. Bethesda
13. Silver Spring
14. Baltimore
15. Baltimore
16. Essex
Spencer Road
State Fair Grounds
Richmond Highway
Page Avenue
St. Asaph Street
South Shirlington Street
Seven Corners
Balls Mill Road
New Jersey Avenue, NW
Suit!and Road
Route 410
National Institute of Health
1-495
Lombard Street
Calvert Street
Woodward Drive
28
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29
-------
TABLE 3. MIXING HEIGHT DATA, WASHINGTON AREA, JULY 6-11, 1974
^^\^ Data July July
Parameter ^~\^ 6 7
Afternoon mixing 1160 1830
height m
Average 200° 350°
direction
Average 2.3 2.6
speeda mps
July July July
8 9 10
1280 1690 1990
250° 300° 330°
2.8 4.2 5.7
July
11
1850
360o!
8.3
a
Directions and speeds are averages for mixing layer.
30
-------
TABLE 4. MAXIMUM OZONE CONCENTRATIONS
SURROUNDING THE STUDY
(PPB) IN CITIES
AREA .
^**v. Date
Station ^*«v<^
Connecticut
Greenwich
Groton
Hartford
New Haven
Stamford
Kentucky
McCarken County
(Paducah)
Massachusetts
Boston
Fall River
Fltchburg
Worchester
New Jersey
Ancora
Asbury
Bayonne
Trenton
New York
Babylon
Buffalo
New York
Niagara
Rochester
Syracuse
July
6
70
82
46
76
110
80
27
33
37
44
144
52
94
64
111
158
114
118
48
45
July
7
90
95
64
88
119
70
65
K
60
82
164
102
79
58
169
87
101
90
82
104
July
8
130
101
87
93
124
70
57
83
51
66
166
112
80
69
113
147
106
ISO
12S
110
July
9
130
114
98
130
133
70
87
118
94
100
184
89
100
93
127
138
116
140
103
98
July
10
90
53
72
74
83
70
40
65
41
M
138
67
84
59
104
77
99
100
30
34
July
11
40
38
27
19
46
40
22
36
32
32
52
51
40
21
43
38
49
> 55
26
32
(continued)
31
-------
TABLE 4. MAXIMUM OZONE CONCENTRATIONS (PPB) IN CITIES
SURROUNDING THE STUDY AREA
^V>1>v. Date
Station ^v^
North Carolina
Ashevllle
Charlotte
Ohio
Cleveland
Columbus
Dayton
Morgan County
Wilmington
Youngs town
Pennsylvania
All en town
DuBols
Harrlsburg
Johnstown
Philadelphia
Reading
Scranton
York
Tennessee
Kings port
Memphis
Morgan County
Sumner County
Virginia
Hampton
Norfol k
July
6
25
29
30
96
64
111
114
112
91
76
100
60
110
94
68
98
52
65
30
67
10
20
July
7
35
55
145
125
49
121
78
185
100
IS?
9?
125
IIS
121
69
9S
60
60
50
80
50
55
July
8
35
83
80
150
76
129
M
192
115
16!
122
203
110
126
87
no
67
55
70
160
130
ISO
July
9
45
52
75
96
54
99
IS!
140
180
156
128
152
165
201
116
144
65
40
50
85
60
M
July
10
45
76
60
90
57
81
122
112
125
115
118
122
115
135
75
110
75
60
50
108
55
80
July
11
45
63
M
80
44
60
82
68
65
71
49
50
M
43
50
48
65
75
70
.' 78
75
80
Notes: No data for West Virginia and South Carolina stations for these dates.
Italics show violations of Federal Standard.
M « Missing
32
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1 REPORT NO.
EPA-600/4-78-016
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
THE 1974 OZONE EPISODE IN THE BALTIMORE-TO-RICHMOND
CORRIDOR
5. REPORT DATE
Fqhruarv 1978
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Gerard A. DeMarrais*
8. PERFORMING ORGANIZATION REPORT NO.
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
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
13. TYPE OF REPORT AND PERIOD COVERED
Inhouse 8/76-8/77
14. SPONSORING AGENCY CODE
EPA/600/09
15. SUPPLEMENTARY NOTES
*0n assignment from the National Oceanic and Atmospheric Administration,
U.S. Department of Commerce.
16. ABSTRACT
An ozone alert in July of 1974 in the Washington, D. C.. area is examined
in detail. Ozone data for 16 stations in the Richmond-tp-Baltimore corridor are
examined in conjunction with meteorological data for the^alert period. Emphases
are given to trajectories of the air between the surface and 1000 meters and the
mixing height and winds aloft data of the air pollution forecasts of the National
Weather Service. The investigation revealed: (1) the period with high ozone concen**
trations was one when synoptic scale stagnation at the surface and aloft prevailed
most of the time together with high temperatures and abundant solar radiation;
(2) despite overall stagnation over a very large region there were periods when
48-hour trajectories showed that ozone could have been transported from potential
source areas as far as 1000 kilometers upwind; (3) that a) the Richmond-to-Balt1more
corridor was at the southern and eastern periphery of a large area in the industrial
eastern United States which had high ozone concentrations, and b) many of the distant
potential source areas implicated in the trajectory analyses observed high ozone
concentration; and (4) that any abatement strategy for this type of alert, even
though associated with stagnation, will have to take into account both local and
distant sources.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
* Air pollution
* Ozone
* Meteorological
Evaluation
data
Baltimore-to-Richmond
Area
13B
07B
04B
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
39
20. SECURITY CLASS (This
1ITY CLASS (TMspage)
UNCLASSIFIED
22. PRICE
EPA Forrrf 2220-1 (9-73)
33
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