73-Sit
EPA 901/9-76-007
Final Report
1977
OZONE IN THE NORTHEASTERN UNITED STATES
By: F. L. LUDWIG and E. SHELAR
Prepared for:
ENVIRONMENTAL PROTECTION AGENCY
REGION I, AIR BRANCH
ROOM 2113
J. F. KENNEDY FEDERAL BUILDING
BOSTON, MASSACHUSETTS 02203
Contract No. 68-02-2352
f / \ \ \ X
(SRI)
\ » i i j $ J
STANFORD RESEARCH INSTITUTE
Menlo Park, California 94025 • U.S.A.
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EPA 901/9-76-007
Final Report March 1977
OZONE IN THE NORTHEASTERN UNITED STATES
By: F. L. LUDWIG and E. SHELAR
Prepared for:
ENVIRONMENTAL PROTECTION AGENCY
REGION I, AIR BRANCH
ROOM 2113
J. F. KENNEDY FEDERAL BUILDING
BOSTON, MASSACHUSETTS 02203
EPA Project Officer: Donald C. White
Contract No. 68-02-2352
SRI Project 4967
Approved by:
R. T. H. COLLIS, Director
Atmospheric Sciences Laboratory
RAY L. LEADABRAND, Executive Director
Electronic and Radio Sciences Division
STANFORD RESEARCH INSTITUTE
Menlo Park, California 94025 • U.S.A.
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This air pollution report is issued by Region I, Environmental Protection
Agency, to assist state and local air pollution control agencies in carrying
out their program activities. Copies of this report may be obtained, for a
nominal cost, from the National Technical Information Service, 5285 Port Royal
Road, Springfield, Virginia 22151.
This report was furnished to the Environmental Protection Agency by
Stanford Research Institute, Menlo Park, California in fulfillment of EPA
Contract 68-02-2352. This report has been reviewed by Region I Air Branch,
EPA, and approved for publication. Approval does not signify that the
contents necessarily reflect the views and policies of the Environmental
Protection Agency, nor does mention of trade names or commercial products
constitute endorsement or recommendation for use.
Region I Publication No. EPA 901/9-76-005
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ABSTRACT
The data from the summer 1975 Northeast Oxidant Study have been
combined with routinely collected weather and pollutant data to demon-
strate that oxidant and its precursors are transported for distances
in excess of 100 km in the New York, New Jersey, and southern New England
region. Vertical cross sections of ozone concentration clearly show
urban ozone plumes. During a daytime passage of a weather front, strong
ozone gradients are observed between the warm polluted air ahead of the
front and the clearer, cooler air behind; at any fixed site, concentra-
tions drop rapidly as the front passes and clean air replaces polluted.
Nighttime frontal passages do not show the marked ozone gradients found
during a daytime frontal passage. High nighttime ozone concentrations
are associated with the simultaneous occurrence of unusual vertical mix-
ing and an ozone layer aloft. The ozone layer aloft appears to be the
remnant of daytime photochemical production in an urban plume.
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CONTENTS
ABSTRACT v
LIST OF ILLUSTRATIONS ix
LIST OF TABLES xv
ACKNOWLEDGMENTS xvii
SUMMARY AND CONCLUSIONS
I INTRODUCTION 1
II DATA 7
A. The Northeast Oxidant Study 7
1. General 7
2. Summary of Ground Station Data Obtained
by Participating Organizations 8
3. Summary of Flight Operations 9
B. SAROAD Data 15
C. U.S. Weather Service Analyses 15
III ANALYZING AND INTERPRETING THE DATA 19
A. Tracing the History of the Air 19
B. Graphical Data Displays 22
1. General 22
2. Isopleth Maps of Ozone Concentration 23
3. Weather Maps 23
4. Vertical Cross Sections 23
5. Time Sections 26
IV RESULTS 29
A. Photochemical Pollutant Transport in the
New England Area 29
1. Background 29
2. Statistical Evidence 31
3. Case Studies 35
a. Selection of Cases 35
b. Interpretations 38
vii
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B. Special Situations 56
1. Frontal Passages 56
a. General 56
b. Case Studies 57
c. Recapitulation 81
2. Occurrences of High Nighttime Ozone
Concentrations at Ground Level 81
a. Background 81
b. Case Studies 84
c. Further Discussion 95
3. Weekday and Weekend Ozone Concentrations 99
V LIMITATIONS TO THIS STUDY AND RECOMMENDATIONS FOR
FURTHER RESEARCH 101
REFERENCES 103
APPENDICES
A DAILY WEATHER MAPS A-l
B TRAJECTORIES OF AIR ARRIVING AT GROTON AND SIMSBURY B-l
C MAXIMUM-HOUR OZONE CONCENTRATIONS C-l
D VERTICAL OZONE CROSS SECTIONS D-l
Vlll
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ILLUSTRATIONS
1 Federal Air Quality Control Regions 2
2 Distribution of Maximum-Hour 0 Concentrations for the
Eastern United States for 22 May 1974 3
3 Counties with Average Annual NO Emissions Greater
— 2 — 1 x
than 75 t mi yr 5
4 Surface Wind Roses, July 6
5 Map of Study Area Showing Battelle, Washington State
University, and EPA Mobile Laboratory Locations 9
6 Example of Flight Track Data Provided by EPA/LV
(Flight No. 3 on 11 August 1975) 11
7 Example of Aircraft Data Gathered from EPA/LV (Flight
No. 2 on 22 August 1975) 14
8 Example of the Daily Weather Map Series 18
9 Schematic Diagram of Wind Averaging Scheme Used in
the Trajectory Calculation Model 20
10 Parameters Used by the Heffter and Taylor Trajectory
Calculation Model 21
11 Example of Ozone Isopleths and Isochrones 24
12 Example of an 0-j Vertical Cross Section Used in this
Study 25
13 Example of a Time Section 27
14 Emissions of Hydrocarbons (upper number) and Oxides
of Nitrogen (lower number) in Thousands of Tons
per Year 32
15 Observed Maximum Daily Ozone Concentrations at Seven
New England Sampling Sites 33
IX
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16 Observed Ozone Concentrations at Groton Versus the
Direction from Which the Air Came During the Preceding
6 Hours on Days Without Frontal Passages 36
17 Observed Ozone Concentrations at Simsbury Versus the
Direction from Which the Air Came During the Preceding
6 Hours on Days Without Frontal Passages 37
18 Weather Map, 10 August 1975, 0700 EST 39
19 Maximum Hour-Average Ozone Concentrations (ppb)
10 August 1975 40
20 Vertical Cross Section of Ozone Concentration Over
Western Connecticut and Long Island - 1110-1220 EST,
10 August 1975 42
21 Vertical Cross Sections Over Connecticut 1545-1715 EST,
10 August 1975 . 43
22 Weather Map, 11 August 1975, 0700 EST 45
23 Vertical Cross Sections of Ozone Concentrations Over
Eastern Connecticut and Eastern Massachusetts, 0855-
1230, 11 August 1975 46
24 Maximum Hour-Average Ozone Concentrations (ppb)
11 August 1975 48
25 Vertical Cross Section of Ozone Concentration (ppb)
Parallel to 850 mb Winds - 0930-1120, 11 August 1975 .... 49
26 Weather Map, 21 August 1975, 0700 EST 51
27 Vertical Cross Sections of Ozone Concentration (ppb)
0815-1055, 21 August 1975
28 Vertical Cross Section of Ozone Concentration (ppb)
1325-1550 EST, 21 August 1975 54
29 Example of High New England Ozone Concentrations
JO
Ahead of a Weather Front, 15 July 1974
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30 Example of High New England Ozone Concentrations Ahead of
a Weather Front, 14 August 1974 59
31 Example of High New England Ozone Concentrations Ahead of
a Weather Front, 30 August 1974 60
32 Example of High New England Ozone Concentrations Ahead of
a Weather Front, 18 September 1974 61
33 Ozone Concentrations (ppb) and Weather Maps for
25-26 July 1974 62
34 Air Trajectories Arriving in Northern Connecticut
24-26 July 1975 64
35 Ozone Concentrations (ppb) and Weather Maps for
28-29 July 1974 65
36 Location of Time Section Lines
66
37 Ozone Time Section Along Line from Bridgeport to
Amherst, 28 July 1975 .................... 67
38 Ozone Time Section Along Line from Greenwich to
Fairhaven, 28 July 1975 ................... 68
39 Ozone Concentrations (ppb) and Weather Maps for
5-6 August 1974 ....................... 70
40 Ozone Concentrations (ppb) and Weather Maps for
5-6 August 1974 ....................... 71
41 Ozone Time Section Along Line from Bridgeport to
Amherst, 5 August 1975 ................... 72
42 Ozone Time Section Along Line from Greenwich to 73
Fairhaven 5 August 1975 ...................
43 Ozone Concentrations (ppb) and Weather Maps for
14-15 August 1974 ...................... 74
xi
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44 Ozone Time Section Along Line from Bridgeport to
Amherst, 14 August 1975 76
45 Ozone Time Section Along Line from Greenwich to
Fairhaven, 14 August 1975 . 77
46 Cross Section of Ozone Concentration Based on Data
Collected Between 1035 and 1145 EST, 14 August 1975 .... 78
47 Cross Section of Ozone Concentration Based on Data
Collected Between 1354 and 1630 EST, 14 August 1975 .... 79
48 Ozone Concentrations (ppb) and Weather Maps for
18-19 August 1974 80
49 Ozone Time Section Along Line from Greenwich to
Fairhaven, 18 August 1975 82
50 Selected Pollutant and Meteorological Observations
at Groton Connecticut, During the Night of 13-14
August 1976 85
51 Later Positions of Air that Left New York at 1600 EST,
13 August 1975 87
52 Ozone concentrations at several Southern New England Sites
During the Night of 13-14 August 1975 88
53 Selected Meteorological and Pollutant Observations at
Groton and Simsbury During the Night of 21-22 August
1975 90
54 Later Positions of Air that Left New York at 1600 EST,
21 August 1975 91
55 Ozone Concentrations at Selected Stations During the
Night of 21-22 August 1975 92
56 Ozone Concentrations (ppb) on 18 July 1975 94
57 Later Positions of Air that Left New York at 1600 EST,
18 July 1975 95
xii
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58 Ozone Concentrations at Selected New England Sites During
the Night of 18-19 July 1975 96
59 Estimated Trough Positions 18 July 1975 97
60 Selected Meteorological and Pollutant Observations at
Groton and Simsbury During the Night of 18-19 July
1975 98
xiii
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TABLES
1 Summary of Data Obtained at Ground Stations ......... 10
2 Summary of Approximate Times (EDT) of Aircraft
Operations ......................... ^
3 List of Ozone Monitoring Stations .............. 16
xv
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ACKNOWLEGMENTS
The organizations responsible for all the data collection during
the original Northeast Oxidant Study all have been most cooperative.
These include the National Environmental Research Center in Las Vegas,
the Interstate Sanitation Commission (ISC), Washington State University
(WSU), Battelle Institute, and Research Triangle Institute. The data
collection programs of WSU, ISC and Battelle were sponsored by the
Environmental Science Research Laboratory (ESRL) of EPA. In addition,
the National Climatic Center and the Environmental Protection Agency (EPA)
offices in North Carolina and Boston have provided data and liaison help
without which this work could not have been completed. We especially
want to cite the assistance provided by the following EPA-Region I
personnel: Donna Morris, Susan Smith, Barbara Ikalainen, Thomas Devine,
Donald White, and Val Descamps.
Numerous people at Stanford Research Institute (SRI) assisted in
preparing the report, data gathering and analysis, and offering con-
structive comments. These include Warren Johnson, Hanwant Singh,
Ronald Ruff, Joyce Kealoha, Leonard Gasiorek, Robert Mancuso, Linda Jones,
Westina Ligon, Renee Troche, Albert Smith, and Russell Trudeau.
Very helpful comments and suggestions concerning this report were
received from George Wolff of the Interstate Sanitation Commission;
Karl Zeller of EPA - Las Vegas and Joseph Bufalini and William Lonneman
of ESRL.
xvii
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SUMMARY AND CONCLUSIONS
The premise that sources and effects always lie within the same air
quality control region does not seem to be valid when applied to the
ozone problem in much of the United States. The air pollutant emissions
from one region move freely to another. For some pollutants this is not
a severe problem, because normal atmospheric processes dilute the pre-
viously emitted materials. In the case of ozone, there are sometimes
countervailing processes in operation. These are the photochemical
reactions that produce oxidants, especially ozone, from the emissions
of the precursors, hydrocarbons and nitrogen oxides.
Considerable evidence exists that these reactions can, under favor-
able conditions, more than offset the atmospheric dilution for tens of
kilometers beyond a major emissions area, causing maximum oxidant con-
centrations to be found far from their precursor origins. Even after
the point where the rate of ozone production has fallen below the rates
at which it is being destroyed or diluted, urban plumes have been dis-
tinguished from the background air--at distances of hundreds of kilometers
on numerous occasions.
Many of the earlier observations of ozone plumes at long distances
downwind of their origins were made in the midwestern United States.
During the summer of 1975, an extensive program of field measurements
was conducted under EPA sponsorship by several organizations to accumulate
data so that a better understanding of the ozone problem in the north-
eastern United States could be obtained. At the same time, other investi-
gators were analyzing the existing, routinely collected data statistically
to explore the possibility that violations of the federal ozone standard
xix
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of 80 ppb in one part of the northeast were at least partly caused by
emissions in other parts of the region. This report describes new analy-
ses of the special data and the routinely collected data by methods that
are more those of the meteorologist than of the statistician. Reassur-
ingly, the conclusions reached by the meteorological and the statistical
approaches are essentially the same, i.e., there is often considerable
distance between emissions and effects in this part of the country.
Briefly, the objectives of the work reported here have been:
• To determine the importance of pollutant transport to the
oxidant problem in the northeastern United States.
• To determine how transport and ozone-formation processes
are affected by other factors, specifically
- The effects of weather fronts
- The importance of weekly emissions cycles
- The causes of high nighttime ozone readings.
As noted before, a considerable body of data was available for use in
the pursuit of the above objectives. In addition to the data that were
specially collected during the northeast oxidant study, hourly ozone
observations were also available from routinely operated sites through
the states of New Jersey, New York, Connecticut, Rhode Island, and
Massachusetts. Surface weather maps at 3-hour intervals and meteorologi-
cal data from higher altitudes at 6-hour and 12-hour intervals were used
in the analysis. The major problem was not scarcity of data during the
study period, 15 July to 31 August 1975, but developing the methods
required for the proper display and interpretation of that data.
Obviously, one of the most important factors bearing on the objec-
tives of this study is air history--where the air comes from and where
it goes. The wind observations were used to calculate air trajectories
for air arriving at two Connecticut sites, Groton and Simsbury. The
afternoon ozone data were then classified according to where the air had
xx
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come from. It was found that high ozone concentrations (above 80 ppb)
at Groton were associated with air arriving from both the New York and
the Hartford areas; at Simsbury, only air from the direction of New
York was associated with afternoon ozone observations above the federal
standard. Although not conclusive, the data suggested that the New York
emissions might be affecting ozone concentrations nearly 200 km downwind
and the Hartford emissions almost 100 km away.
Analysis of the data from the airborne operations showed the frequent
occurrence of regions of higher ozone concentrations, a few hundred meters
above ground level These observations are most easily explained as
"plumes" of ozone and ozone precursors trailing downwind from urban
areas. In a few cases, observations were also available upwind for the
same period as the downwind observations. These upwind cases showed
generally lower, much more uniform, distributions of ozone--a fact that
indicates that the higher downwind observations are the result of ozone
produced in elevated, urban pollutant plumes.
Other studies had shown that high ozone concentrations were most
apt to be found in conjunction with the northwestern parts of high-
pressure weather systems and in the warm air ahead of weather fronts.
The studies in New England showed similar relationships. The distribu-
tion of ozone concentrations during a daytime frontal passage are par-
ticularly striking. Typically, the winds are from the southwest preced-
ing the frontal passage, a condition that is conducive to the occurrence
of high ozone concentrations in southern Connecticut. As the weather
front moves through, the ozone-laden air is replaced by the cooler,
cleaner polar air behind the front. This causes rapid decreases in
ozone concentration and strong spatial gradients.
If the front passes through at night, then there is no photochemical
ozone production and fewer emissions in the air ahead of the front, so
that the strong gradients do not develop. This does not mean that
xxi
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nighttime ozone concentrations are never high. As noted before, the
ozone plumes from the cities are often present aloft. Generally, surface
cooling at night causes the atmosphere to be relatively stable, and mixing
in the vertical is suppressed. This leaves the ozone elevated and iso-
lated from the surface and the processes that would tend to destroy it.
Isolated from the surface, ozone can persist for long periods without
appreciable degradation. By virtue of being concentrated aloft, it will
generally remain undetected by surface-based instruments unless something
happens to transfer it to ground level.
Our studies of several cases of high nighttime ozone concentrations
at ground level in New England showed that there was evidence of atmospheric
instability in at least some of these cases. Such instability is quite
likely to be accompanied by vertical motions that could bring ozone aloft
down to ground level. In some cases, the areas of maximum ozone concen-
trations moved along the ground in a direction and at a speed consistent
with winds in the lower layers of the atmosphere. In these cases, de-
clining ozone concentrations at a series of sites marked the passage of
air that left the New York area during midafternoon. There was widespread
vertical motion, and the trailing edge of the high ozone area was moving
through it with the wind. In at least one case, the ozone was relatively
widespread, but the region of vertical motions was limited to the vicinity
of a low-pressure trough that moved at a speed greater than the wind.
It is apparent that the effects of long-range transport need not be con-
fined to the daylight hours.
The findings of this study--indicating that transport of ozone and
its precursors over distances of hundreds of kilometers in the north-
eastern United States plays a large part in determining the observed
concentration distribution in the region—will have important conse-
quences in the development of control strategies and policies. It is
obvious that there is no place in the entire region that has complete
xxii
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control over the air pollutants to which it will be exposed, and there is
no place that does not at times contribute to the problems of other
places within the region. For this reason, oxidant-control strategies
should encompass very large areas. Connecticut and Rhode Island will
require the cooperation of New York and New Jersey if they are to achieve
compliance with federal standards. Similarly, Massachusetts will require
cooperation from Connecticut and Rhode Island. This does not mean that
each place's problems always have their origins elsewhere. It does mean
that such is the case often enough that solutions must involve very
large-scale considerations that extend beyond the confines of the typical
Air Quality Control Region.
It may never be possible to fully quantify the impacts that one area
has on another. The non-linear chemical activity, the concurrent intro-
duction, transformation and removal of ozone and precursors, and the
transport and dilution are all so complicated that a simplistic identi-
fication of the source of any given amount of ozone at any particular
location just isn't possible. About the best that one can do is to say
that the pollutants came from a certain direction more often than from
somewhere else. For this reason cooperative emissions reductions efforts
will be much more effective than attempts to divide the problem into neat
little pieces to be assigned to their proper jurisdictions.
xxiii
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I INTRODUCTION
The motivation for the research described in this report has been
to answer some questions related to the development of oxidant-control
strategies in the northeast United States. Recent special observational
programs have provided more detailed data than have been available in the
past (Washington State University, 1976; Spicer, Joseph, and Ward, 1976;
Siple, Zeller, and Zeller, 1976; Wolff et al. , 1975). One of the reasons
why the special data collection programs were undertaken was because
other studies indicated that control strategies that focused on urban
areas alone might not be adequate for the achievement of federal oxidant
standards (e.g., EPA, 1975).
The underlying premise of the control strategies generally has been
that air quality problems and their causes are not widely separated
in space or time. It follows from this premise that air quality control
strategies can be applied within limited regions to control the problems
in those regions. Figure 1 shows the air quality control regions into
which the eastern United States has been divided. Their size is consistent
with the view of the problem that has been outlined above.
The discovery that violations of the federal oxidant standard were
frequent in rural areas raised questions concerning the validity of the
premise that effects of pollutant emissions were limited in spatial
extent. Martinez and Meyer (1976) have recently reviewed the accumulation
of evidence concerning longer-range transport of oxidants and oxidant-
producing primary pollutants. They concluded that an individual urban
area source can affect ozone concentrations as far as 300 km downwind.
This, of course, means that control strategies should have greater scope
than originally supposed.
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FIGURE 1. FEDERAL AIR QUALITY CONTROL REGIONS
Other evidence exists that also suggests that oxidant problems ex-
tend well beyond the confines of the typical air quality control region
(AQCR). Recently Ludwig et al. (1977) used SAROAD data (System for the
Automatic Retrieval 0_f Aerometric Data) to map the distribution of
maximum-hour ozone concentrations in the eastern United States for each
day during 1974. They found that the areas within which the Federal
ozone standard was violated often had dimensions of hundreds of kilometers.
Figure 2 shows one example of widespread high ozone concentrations in the
eastern United States; the high ozone areas tend to be considerably larger
than the typical AQCR of Figure 1.
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40
60 80
20
80 WQB060 40
FIGURE 2. DISTRIBUTION OF MAXIMUM-HOUR 03 CONCENTRATIONS FOR THE EASTERN
UNITED STATES FOR 22 MAY 1974
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The region of concern for this study has been New England. If pol-
lutant transport with its accompanying widespread violations of the
federal oxidant standard has been found to be important in other areas
of the United States, there is certainly no reason to expect it to be
unimportant to New England. The east coast of the United States has a
large number of major source areas. Figure 3 shows all the counties in
the eastern United States where average annual NO emissions exceed
-2 -1
75 tons mi yr . There are only 124 such counties in the entire United
States and Figure 3, based on data from the National Emissions Data
Service (NEDS), shows that a large number of them are along the northeast
coast. The importance of pollutant transport is compounded by the fact
that the winds often tend to parallel the coast during the summer months
when oxidant production is most pronounced. Figure 4 (United States
Department of Commerce, 1968) shows the frequency of different wind
directions at many United States cities. It is obvious from Figures 3
and 4 that the transport of pollutants into New England is likely to
be relatively frequent.
Others have studied ozone transport in the area (e.g., Cleveland
et al., 1975) and have concluded that it is an important factor in
determining the distribution of ozone in New England. It is our intent
to use the data from the special, summer 1975 monitoring programs cited
earlier to provide more detailed descriptions of the important features
of the New England ozone problem. In particular, we have been interested
in:
• The transport of ozone and precursors to and from
EPA Region I.
« The dimensions of pollutant plumes from urban areas.
• The effects of weather fronts on ozone distributions.
• The causes of high ozone concentrations at night in
New England.
• The differences between workday and nonworkday ozone
concentrations.
4
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Of course, we have not limited ourselves to the data collected during
special studies; we have also used conventional weather data, hourly
ozone data from the SAROAD system, and the findings of other investigations.
^'°?d--f-^'•-'' '"ff - '* \^'-' ^-\t^jf-'-• ^^-r
>i--'v; ^--^~~~\] /.- ' A ' '~ ?'..^ _,/'-A
FIGURE 3. COUNTIES WITH AVERAGE ANNUAL NOX EMISSIONS
GREATER THAN 75 t mi^yr1
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II DATA
A. The Northeast Oxidant Study
1. General
A comprehensive field measurement program was begun in the
New England area on 15 July 1975. The primary objectives of the pro-
gram were to monitor ozone, ozone precursors, and meteorological param-
eters throughout the New England and surrounding areas. The resulting
data were to be used to determine the origins of ozone levels in the
New England area.
The field study involved research teams from Battelle Columbus
Laboratories, Washington State University (WSU), the Interstate Sanita-
tion Commission (ISC), The Research Corporation of New England (TRC),
and EPA groups from Research Triangle Park (RTP), Las Vegas (LV), and
Region I. In addition, supporting data were made available from several
agencies. These data include:
• Air quality data from stations operated by agencies
reporting to the EPA SAROAD data base.
• Upper air wind measurements available through the
National Oceanic and Atmospheric Administration (NOAA)
for calculation of trajectories.
• Standard weather data as collected by the National
Weather Service (NWS); this is reported and stored at
the National Climatic Center (NCC) in Asheville,
North Carolina.
• Emission data collected by state and local agencies;
most of this is eventually reported to the EPA NEDS
data base.
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• Ozone soundings were taken at the Albany 'New York)
airport; some 6 valid soundings during the study period
were collected by NWS; Research Triangle Institute 'RTI)
is processing these data.
»» Aircraft data collected by RTI in late July as they
tracked a high-pressure system from the midwest to
the Atlantic.
Intensive field data acquisition operations span the period
from 15 July through 31 August, although all parties were not active the
entire period. Three groups (EPA, WSU, and Battelle) operated both air-
craft and ground stations. Locations of these ground stations and bases
of operations are illustrated in Figure 5. WSU was located on the southern
Connecticut coast near Groton; Battelle operated out of Simsbury, Con-
necticut (about 25 km northwest of Hartford). EPA had two groups operat-
ing out of the Boston area. The Environmental Monitoring and Support
Laboratory (Las Vegas) was responsible for aircraft operations; the
Environmental Sciences Research Laboratory operated the ground station.
Ozone, carbon monoxide, nitrogen dioxide, nitric oxide and meteorological
parameters were measured continuously at the ground station.
The Interstate Sanitation Commission (ISC) joined EPA, WSU,
and Battelle in the aircraft-monitoring program. Vertical and horizontal
profiles of ozone and temperature were the primary data gathered. Other
parameters measured by one or more aircraft included nitric oxide,
scattering coefficient, relative humidity (or dew point), and cloud-
condensation nuclei. In addition, WSU and TRC conducted pibal programs
from four locations, two each in Connecticut and Massachusetts.
2. Summary of Ground Station Data Obtained
by Participating Organizations
Three ground stations continuously recorded meteorological
parameters and pollutant levels for the duration of the field study.
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ALBANY e
NEW
YORK
^-Research Triangle Park
Las Vegas
CONNEC T/'cur\ !
Washington
State j
University J
FIGURE 5. MAP OF STUDY AREA SHOWING BATTELLE, WASHINGTON STATE
UNIVERSITY, AND EPA MOBILE LABORATORY LOCATIONS
Table 1 identifies the location of each of the special stations and the
data measurements made at each.
3. Summary of Flight Operations
Table 2 is an index of flight operations conducted during the
Northeast study. Figure 6 is an example of a flight pattern, and Fig-
ure 7 is the type of data gathered during the EPA flights. Other organ-
izations collected similar data.
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10
-------
C3>( SPIRAL* 3)
56
o
1 1 1
90
1 1 1
100
J
SCALE IN KM
FIGURE 6. EXAMPLE OF FLIGHT TRACK DATA PROVIDED BY EPA/LV
(Flight No. 3 on 11 August I975)
11
-------
Table 2 SUMMARY OF APPROXIMATE TIMES (EOT) OF
AIRCRAFT OPERATIONS
Date
July
15
18
18
18
19
19
20
20
20
21
21
22
22
23
23
24
24
26
26
27
27
28
28
29
29
30
31
August
2
2
3
5
5
EPA, Las Vegas WSU
Total Vertical Total
Flight Sounding Flight
16-17
13-14
16-17
10-13
16-19
15-17
19-20
11-14
16-18
8-9
13-16
8-12
15-17
9-12
14-17
10-13
15-18
9-12
15-18
10-12
14-17
9-12
15-18
21-23
12-15
21-23
10-13
13-15
ISC Battelle
Vertical
Sounding
16
14
16
10,12
17
15,16
20
12,13,14
16,17
8,9
14,15
9-10
16,17
10,12
15
10,11
16,17
10,11
15,17
11
15,17
10,11
15,16
22,23
13,14
21,22,23
11,12
13,14
Total Total
Flight* Flight
20-22
10-11
17-20
9-11
14-15
9-12
14-17
9-12
15-18
9-12
15-19
9-13
15-18
9-11
16-17
9-13
15-18
14-17
12-15
9-10
11-13
Vertical
Sounding
22
10
18
11
16
17
10,11
16,17
11,12
16,18
10,12
15,17
13
12
-------
Table 2 SUMMARY OF APPROXIMATE TIMES (EDT) OF
AIRCRAFT OPERATIONS (Con't)
EPA, Las Vegas
Total Vertical
Date Flight Sounding
August
5
6
6
9
9 14-15
10
10
10
10
11 12-14 12,13,14
12 10-11
12 13-16 14,15
13 10-13 11,12,13
13 15-17 15,16,17
14 12-13 12,13
14 15-18 15
15
15
15 15-18 16,17
17 10-12 10,11,12
18
18
18
19 10-12 10,11,12
19
19 15-17 15
19
20 9-12
20 14-16
20
21
21
21
WSU
Total
Flight
9-12
14-17
12-14
15-18
11-14
16-19
9-12
9-13
15-17
9-12
16-19
10-13
16-19
10-13
17-19
11-14
20-21
10-13
15-17
19-22
12-15
16-19
9-12
15-17
Vertical
Sounding
10,11,12
12,13
16,17
12,13,14
17,18
10,11,12
12
16
10,11
16,17,18
11,13
16,18
11,12,13
11,13
20
11,12
15,16
20,22
11
16,17
ISC
Total
Flight*
9-12
9-12
14-16
14-16
10-12
3-6
11-16
12-17
9-12
10-13
15-17
15-18
10-13
13-16
14-17
9-12
9-12
14-17
Battelle
Total Vertical
Flight Sounding
18-20 19-20
10-12
11-13 13
17-20 18
12-14 12,13
16-18 17-18
11-12
10-12 12 -
10-13 11,12,13
16-19 17-18
10-13 12,13
15-18 16,17
10-13 11,12
9-10
12-15 13,14
17-21 19
10-13
17-19 17,18
11-18 13,16,17,18
10-12 11
14-18
13
-------
Table 2 SUMMARY OF APPROXIMATE TIMES (EOT) OF
AIRCRAFT OPERATIONS (Con'd)
August
21
24
26
27
27
27
28
EPA, Las Vegas WSU ISC
Total Vertical Total Vertical Total
Flight Sounding Flight Sounding Flight*
14-17
10-12 10,11,12
17-18
10-12 11,12
14-16
16-17
11-12
Battelle
Total Vertical
Flight Sounding
Vertical soundings were taken approximately hourly during Interstate
Sanitary Commission Flights
300
. ZOO
o
z
CD
3
Si
150
100
50
0
14
UPPEB DOTS — TEMPfC.T.5), LOITER DOTS — QH°C«TJ).
SOLID — OjIPPBI. SHOUT DASH — BSCAT(50.lff"/m).
MED DASH — NOIPP6.5). LOW DASH — ALTtmXO.I)
14.2 14.4 14.6 14.6
EASTERN DAYLIGHT TIME — hours
15.0
FIGURE 7. EXAMPLE OF AIRCRAFT DATA GATHERED FROM EPA/LV
(Flight No. 2 on 22 August 1975)
-------
B. SAROAD Data
Hourly, ozone concentrations at the surface were obtained for many
stations in the northeast from the EPA SAROAD data base. Primarily,
monitoring stations from Connecticut, Massachusetts, Rhode Island, New
Jersey, and New York were included along with a few stations from New
Hampshire and Vermont. Table 3 lists the monitoring stations for which
hourly ozone concentrations were obtained. The table includes the SAROAD
station identification, the name, and the geographic location of each
monitoring site.
C. U.S. Weather Service Analyses
The primary Weather Service product used during this study was the
surface weather map. Figure 8 is an example of this type of map. The
map shown is from the "Daily Weather Map Series" published by NOAA.
The following description is quoted from that supplied by NOAA. "The
Surface Weather Map shows station data and the analysis for 7:00 a.m.,
EST. Tracks of well-defined low-pressure areas are indicated by chain
of arrows; locations of these centers at 6, 12, and 18 hours preceding
map time are indicated by small white crosses in black squares. Areas
of precipitation are indicated by shading."
In addition to the "Daily Weather Map" analyses that are reproduced
in Appendix A, we also had available to us surface weather maps for
3-hour intervals and upper-air maps for two times per day. These were
obtained on microfilm from the National Climatic Center.
15
-------
Table 3
LIST OF OZONE MONITORING STATIONS
• »***«**»*««*«•••* •••a oo«»* «•«•»« «»»««»«»•«»**««***•***••«»*»•««•«•*»*•»•••»•*•
EP* SAROAD OZONE AND OXIOANT DATA
15 JULY THROUGH 31 AUG 1975
NO.
1.
2.
3,
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
1*.
15.
16.
17.
18.
19.
20.
21.
22.
23.
2*.
25.
26.
27.
23.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
STATION JD
A070060123F01
A070175123F01
A07020POOiF03
A07025pl23FO]
A070330004F01
A07035P123F01
A07040P001F01
A076*26l23F01
A070478001F03
A07057n003F01
A07o70000«F01
A07108iil23F01
A07ll6lil23F01
Ap.7i52p,OOiF01
A220066001F01
A220240002F01
A22036P004F01
A2204000P4F01
A22FI48H002FOI
A220570001F01
A220580004F01
A220620003F01
A22o66ft002F01
A220780002F01
A22108P004F01
A221210001F01
A221220003F01
A221800004F01
A22188P002F01
A22l98rioOlF01
A22216«005F01
A22234nQ03F01
A222340004F01
A2226*0012F01
A300040007F01
A300420009F01
A300*3n005F01
A4103000HF01
A*lo33t>00?F03
A*70l«0003FQl
A33013000?F01
A33o2enon2F01
ST4TION LOCATION LON. LAT.
BRIDGEPORT CONN.
DAN3URYt CONN.
EASTFORO, CONN.
ENFIELO» CONN.
GREENWICH, CONN.
GROTON, CONN.
HARDEN, CONN,
HARTFORD, CONN.
LITCHFIELD CO, CONN.
MIDDLETOWN. CONN.
NEW HAVEN, CONN.
STAMFORD, CONN.
TOPPINGTON, CONN.
WINOSOR, CONN.
AMHtRSTt MASS.
BOSTON, MASS.
CAMBRIDGE, MASS.
CHICOPEE, MASS.
DANVERSt MASS.
FAIRHAyEN, MASS.
FALL RIVER, MASS.
FITCHBURG, MASS.
FRAMINQHAM, MASS.
GREENFIELD, MASS.
LOWELL, MASS.
MEDFIELD, MASS.
MEDFORD, MASS.
PITTSFlELD, MASS.
OUINCY, M«SS«
SALEM, MASS.
SPRINGFIELD, MASS.
WALTHAM, MASS.
W«LTHAM, MASS.
VOSCHEsTER, MASS.
BERLIN, N. H.
MANCHESTER, N. H.
NASHUA, N. H.
PROVIDENCE, R. I.
SCITUATE. R. I.
BUPLINGTON, VT.
AVHERST, N, Y.
BABYLON, N. Y.
WP731137
W0750000
W0720507
K0723420
W0734156
W0720137
W0725426
W0724001
W0730821
H0724428
H0725510
W0733215
W0730645
W0723947
W0723333
W0662100
W0710400
W0723718
W0705837
W0765428
W0710959
W0714702
WQ711039
W0733550
W0711904
W0712008
W0710653
W0731327
W0705833
W07Q5444
W072353S
W0711532
Wn7H«i6
H0744330
W07JH05
W0712734
W0712748
W0712452
»'07l34n9
W0733243
W0784556
W0750000
N4J1P51
N*12051
N415P26
K'4 15954
N410437
N4l?304
N4j?252
N4J461B
N414021
N3P5136
N411952
N410334
N414827
N4i5107
N423324
N7l6fOO
N422210
N42C9J4
N423531
N413B12
N414107
N423418
N421724
N423419
N423848
N421244
N422500
N42?753
N42i*52
N423P30
'1420512
N42P208
N42??42
N420f59
N44?754
N42592S
N424510
N414957
N414516
N442852
N42S928
N4Q4840
ZONE UTMX UTMY
18
18
18
16
18
18
18
16
' 18
18
16
IB
18
18
18
19
19
18
19
18
19
19
19
IB
19
19
19
18
19
19
18
19
19
18
19
19
19
19
19
18
17
18
651
500
742
701
609
748
674
693
654
696
674
622
656
693
700
595
329
696
337
341
319
271
320
697
309
307
326
646
336
342
699
313
315
522
326
299
?98
299
2R6
642
682
500
4560
4577
4635
4652
4547
45B5
4582
4626
4614
4303
4577
4546
4629
4635
4714
7890
4692
4669
4717
4610
4616
4716
4684
4715
4723
4675
4697
4702
4678
4707
4661
4692
4693
4666
4925
4762
4736
4633
4625
4926
4762
4517
16
-------
Table 3
LIST OF OZONE MONITORING STATIONS (Concluded)
43.
44.
45.
46.
47.
48.
49.
50.
51.
52.
53.
54.
55.
56.
57.
53.
59.
60.
61.
62.
63.
64.
65.
66.
67.
68.
69.
70.
71.
72.
73.
74.
75.
76.
77.
78.
79.
80.
81.
82.
83.
84.
85.
86.
87.
88.
89.
90.
91.
92.
93.
• •*»•<
A33048P007F01
A33066P005F01
A33066noC7F01
A33l88r>o03F01
A33?02POO?FC1
A33?480003F01
A3329000PSF01
A33350noP?F01
A334100002F01
A33466r>o03H01
A33468Q004H01
A334680005H01
A33468pOO<>Hai
A33468nOC7H01
A33468n01n"H01
A334680011H01
A33468P014H01
A33468001BH01
A33468P023H01
A334680034H01
A33468fl05oF01
A334686062H01
A33474000«.F01
A33568P001F01
A33576P004F01
A336020003F01
A33662C005F01
A33662POliF01
A33688000AF01
A310060001F01
A3l6lOOCP?F01
A3101BOOP3F01
A310640001F01
A3ln72P003'r01
A31072P004F01
A31074nOO]F01
A31130P003F01
A31J30POP4F01
A3116200PJF01
A3li62noOlFol
A31232POP2F01
A313300001F01
A313*8PC02F01
A3141400P3F01
A3141600C1F01
A31420POPJF01
A31422C003F01
A3I4H400P?F01
A31506P001~F01
A3l536o001r01
A3154000P2F01
»•••«••••»*•*•<
BU-'GHAwTON, -N. Y.
BUFFALO, N. Y.
BUFFALO, N. Y.
ELHIRA, N. Y.
ESSFX CO, N. Y.
GLENS FALLS, N. Y.
KE^'PSTFAO, N. Y.
KINGSTON, N. Y.
KAWARONECK, N. Y.
NEW YOSK CITY, H.
NEW YORK CITY, N.
.NEW YORK CITY, N.
NEW YORK CITY. N.
NEW YORK CITY, N.
NEW YORK CITY, N.
NEW YORK CITY, N.
NEW YORK CITY, N.
NEW YORK CITY, N.
NEW YORK CITY, N.
NEW YORK CITY, N.
NEW YORK CITY, N.
NEW YORK CITY, N.
NIAGARA FALLS, N.
RENSSELAEP, N. Y.
ROCHESTER, N. Y.
SCHENECTAOY, N. Y.
SYRACUSE, N. Y.
SYRACUSE, N. r.
UTICA, N. Y.
ASBURY PARK, N. J .
ATLANTIC CITY, N.
BAYONNE, N. J.
BURLINGTON, N, j.
CAMDEN, N. J.
CAMDEN. N. J.
CAMOEN CO, N. J.
ELIZABETH, N. J.
ELIZABETH, N. J.
FREEHOLD, N. J.
HACKENsACK. N, J.
JERSEY CITY. N. J.
MORR1STOWN, N. J.
NEWARK, KI. J.
PATERSON, N. J.
PAULSBORO. N. J.
PENNS GROVE, N. J,
PERTH AMBOY, N. j.
PHILLIPSBURG, N. J
SOMERVILLE, N. J.
TOUS RIVER, N. j.
TRENTON, N. J.
••••*»*••»••••»»•••
Y.
Y.
Y.
Y.
Y.
V.
Y.
Y.
Y.
Y.
Y.
Y.
Y.
Y.
J.
m
• ••
H0750000
HOB44836
W078S250
1(0764808
W0735429
*0733726
W0733513
W0735932
*0734S57
WQ735415
K0734909
W0735818
K0735330
K0735615
H0735910
W0735650
W0735620
W0735901
W07357S2
W0740757
W0735627
W0740011
K0785933
H0734504
W0770430
H0735619
W0761040
WQ760852
W0751148
W0740046
W0742622
W0740711
W0745129
¥0750550
W0750710
M0745145
W0741252
W0741228
W0741628
W0740228
W0740401
W0742904
W0741033
W0740920
W0751427
K0752613
W0741606
¥0751143
W0743649
W0741153
H0744554
••••••o»»»
N*?P?i6
N425237
N425309
N420634
N442154
N431900
N4Q4443
N421706
N4P555B
N404954
N404413
N404606
N405222
N403535
N404422
N404358
N404804
N404006
N404539
N403531
^404^01
N404315
N43Q509
N423739
N431000
N424755
N430341
N430243
N430559
N401258
N392127
N404052
N400440
N395523
N39565D
N394100
N403943
N403828
N40153B
N405256
N404352
N404745
N4J4411
N4Q5545
N394948
N394348
N403033
K'404113
N4Q3410
K395713
N461312
*••»••»*»*
IB
16
17
18
18
16
IB
18
18
18
18
18
18
18
18
18
18
18
18
18
18
IB
17
18
18
18
18
IB
IB
18
18
IB
18
18
18
16
18
18
18
18
IB
16
IB
18
18
18
18
18
16
18
18
•»•••«
500
678
673
350
587
611
619
5B3
603
592
599
586
593
589
585
588
589
585
587
573
589
584
663
602
331
586
404
406
483
584
548
574
512
491
489
511
566
566
561
580
578
543
569
571
479
459
561
483
532
568
519
• *»••
4653
4749
4750
4663
4912
4796
4511
4681
4531
4520
4510
4513
4525
4493
4510
4509
4517
4502
4512
4493
4513
4508
4772
4719
4781
4738
4768
4766
4771
4452
4356
4503
4436
4419
4421
4392
4501
4499
4456
4525
4509
4516
4509
4531
4408
4397
4484
4503
4490
4422
4451
•»»»••»
17
-------
WEDNESDAY, AUGUST 8», 1TO
^ «*< /£ ***&
te^% ' *& '-^
... 1 **; |tf iw ^ -.* " T52W
*^A«^**: C- ^P-
-,-tT-M
. -*
tS E X ^ ^*
» fl »*» oV
» 5 * * ** * **
' -i * -I •« »
*n ** ^%*
FIGURE 8. EXAMPLE OF THE DAILY WEATHER MAP SERIES
18
-------
Ill ANALYZING AND INTERPRETING THE DATA
<
A. Tracing the History of the Air
One method used to study the transport of pollutants into and
within a region is to trace the air movements, based on wind observations
in the area of interest. The history of air containing ozone or its pre-
cursors can be studied by calculating such trajectories. This enables
one to locate the various source areas over which the air passed before
arriving at a specific locale. For this study, the computer program
used to calculate trajectories is a version of Heffter and Taylor's
(1975) model that was provided to us by Mr. Dale Coventry of EPA,
Research Triangle Park, North Carolina.
For these applications, the model has used observed winds within
a "transport" layer to calculate the trajectories. Figure 9 illustrates
the observed winds above a point for a specific example; the general
form is:
— -»
v, AH-V
v = £_L_L
E AH
i
^ H.
where V is the vector average wind throughout the transport layer; V.
t~Vi
is the measured wind vector through the i layer; and H. is the depth
of that part of the i layer that lies within the transport layer.
The trajectory segments are calculated from the transport layer
winds according to the following formula:
..
1 L
19
-------
TOP OF TRANSPORT LAYER
AH.
AH;
AH,
BOTTOM OF TRANSPORT LAYER
SURFACE
— AH, V, + AH2 V2 + H3V3
AVERAGE WIND, V =
AH, + AH-;
Source: Heffter and Taylor, 1975
FIGURE 9. SCHEMATIC DIAGRAM OF WIND AVERAGING SCHEME USED IN THE
TRAJECTORY CALCULATION MODEL
20
-------
SEGMENT ORIGIN
MY;
Source: Heffter and Taj'lor, 1975
FIGURE 10. PARAMETERS USED BY THE HEFFTER AND TAYLOR TRAJECTORY
CALCULATION MODEL
where:
->
S =
D =
trajectory segment.
distance weighting factor
A. = alignment weighting factor
= 1-0.5 sin 9..
W. = 3-hour displacement for V..
r. = distance between W and wind observation point (see
Figure 10).
9. = angle between W^ and line connecting the trajectorv
segment origin and the wind observation point (see
Figure 10).
21
-------
R
£ indicates a summation over all observation points within
a distance, R, of the segment origin; following the example
of Heffter and Taylor, R was set equal to 300 nautical miles.
The lower bound of the transport layer has been taken to be 300 m.
The top of the transport layer was taken to be 1000 m, the average of
morning and afternoon mixing heights for this area, according to
Holzworth (1972). The measurements also showed this to be a typical
height to which ozone was mixed.
Application of the trajectory model along the east coast presents
some difficulties because of the lack of data over the Atlantic Ocean.
In such a situation, the winds that are interpolated for calculating
the trajectory will be based on observations to the west of the site.
Usually, this is not too serious, but when there are sharp gradients
in the wind field it can cause problems. In particular, when a weather
front approaches from the west, the trajectory calculation will begin
to reflect the shifted winds behind the front well before it arrives.
Appendix B shows the calculated trajectories of air arriving at Groton
and Simsbury, Connecticut, during the study period. Of course, the
reliability of these trajectories is increasingly suspect at the earlier
times. For the preceding 12 hours or so the trajectories probably "represent
air positions within a few tens of kilometers of the "true" path.
B. Graphical Data Displays
1. General
Several different kinds of graphical data display have been
used in the presentation of results in the following sections. We feel
that these displays aid the interpretation considerably, but they may
be somewhat unfamiliar to many readers. For this reason we have provided
the brief descriptions that follow.
22
-------
2. Isopleth Maps of Ozone Concentration
Two types of Isopleth maps were used to show the distribution
of ozone concentrations near ground level. Figure 11 illustrates the
first type. It shows isopleths of the maximum, hour-average ozone
concentration for the day and isochrones to indicate the time that
maximum concentration occurred. Isopleth maps similar to Figure 11
were also drawn to show the distribution of 0 concentration at a specific
hour. The isopleth maps help define pollutant patterns and make it
easier to see how these patterns relate to the meteorochemical processes
involved. In all the figures of this type, lines of constant ozone con-
centration are labeled in parts per billion (ppb). The isochrones indi-
cate the hour of maximum concentration in Eastern Standard Time (EST).
Appendix C presents the maximum-hour ozone maps for each day of the study
period.
3. Weather Maps
Time of frontal passage and prevailing meteorological condi-
tions were determined from surface weather maps from the U.S. Weather
Service. These maps have been described in Section II-C.
4. Vertical Cross Sections
Vertical cross sections showing the distribution of ozone in
a vertical plane were used to identify the effects associated with
weather fronts and their movement through an area and to show
graphically the urban plume structure. The presence of elevated 0 layers is
also seen easily in this kind of display. Figure 12 is an example of
a vertical 0 cross section showing the meanings of the symbols used.
Vertical cross sections are comparable to the ozone maps
discussed earlier except that the plane in which the concentrations are
23
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FIGURE 11. EXAMPLE OF OZONE ISOPLETHS AND ISOCHRONES
24
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NORWICH S.BOSTON AMESBURY
ALTITUDE PUTNAM BOXFORD -^_
(ft, MSL) 1605
8000
1650 1604
1640 1520-
60 0, CONTOURS IN ppb
• n »5
Location and
Time (EDT) of
profile
Location of
stable layer
(inversions
and isothermal
layers)
Extent of
vertical
profile
Location of cross section
850 mb wind direction
FIGURE 12. EXAMPLE OF AN 03 VERTICAL CROSS SECTION USED IN THIS STUDY
25
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measured is oriented perpendicular to the ground surface, as opposed to
being the ground surface itself. In the figures presented later in this
report, the line above which the cross section applies is shown on a
map of the region. The basic data were obtained from aircraft measure-
ments of ozone. The points at which the vertical ozone profiles were
measured are shown on the map, and the vertical extent of those measure-
ments is indicated by vertical lines on the cross section itself. The
presence of stable layers is indicated by stippled bars. Often the wind
directions at the 850 mb level (about 1500 m) are indicated by arrows--
streamlines--on the map. Times (EST) of the measurements are given
above the diagram. Those cross sections that were not used in the text
of this report are shown in Appendix D.
5. Time Sections
Time section analyses of ozone were carried out for two sets
of monitoring stations during periods of frontal passage. One series
of stations extended in a line from Greenwich, Connecticut, to Fairhaven,
Massachusetts. The other extended from Bridgeport, Connecticut, to
Amherst, Massachusetts. Figure 13 is an example of a horizontal time
section offset from its corresponding geographic position. The two
axes of the time section are time and distance (along the line of sta-
tions being used for the analysis). The isopleths in the analyses in
this report are ozone concentrations (ppb).
The components of the ozone gradient parallel to the time axis
represent the rate of change of concentration. The gradient in the
direction of the space axis is the rate of change with distance along
the measurement line. We have also plotted the passage of weather
fronts on these diagrams. The heavy line marking the front shows its
time of passage for each point along the line.
26
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o
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27
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IV RESULTS
A. Photochemical Pollutant Transport
in the New England Area
1. Background
In essence, the basic question to be answered by this study
concerns the distance that ozone precursors from some large source area
will travel before their contribution to ozone concentration falls to a
level where it cannot be distinguished from the contribution of other
sources. Recently, Martinez and Meyer (1976) reviewed data collected
around a number of U.S. cities. They found that the increase in ambient
ozone from individual urban areas could be detected nearly 300 km down-
wind, with maximum concentrations found anywhere from 8 km to 135 km
downwind.
Ludwig et al. (1977) examined the question from a different
viewpoint. They examined the trajectories followed by air arriving at
different rural locations and then examined the statistical relationships
among the emissions and meteorological conditions along the trajectory
and the ozone concentrations at its end point. They found significant
correlation between ()„ concentration and NO emissions as many as
3 x
36 hours earlier. Most of the variance in the ozone data could be ex-
plained in terms of air temperature and emissions during the last 12
hours of the trajectory. They found that when ozone concentrations
exceeded 80 ppb, the air movement was most often less than about 200 km
during the last 12 hours of the trajectory and less than about 500 km
during the last 36 hours. These studies suggest that the effects of
large area sources on ozone concentration can persist for at least
several hundred kilometers.
29
-------
The effects of the New York metropolitan area emissions on
surrounding areas have been studied by Cleveland et al. (1975a). They
compared maximum daily ozone concentrations measured during the summer
of 1974 at numerous New England monitoring sites with the wind directions
during the same day. Briefly, they showed that the highest ozone con-
centrations occurred with wind directions from New York at stations
throughout Massachusetts and Connecticut. Even Boston, nearly 300 km
from New York, showed the effect. They only considered days with well-
defined wind directions and temperatures above 70°F at Hartford.
The emissions of precursors clearly affect ozone concentra-
tions in downwind areas. The degree to which the effects are manifested
depends on the meteorological conditions. Several studies (e.g.,
Ludwig et al., 1977; Bruntz et al., 1974) have found that there are
certain meteorological conditions that are consistently associated with
high ozone concentrations. These are high temperatures, light winds,
and strong insolation. Ludwig et al. (1977) have also reported that
light, southerly through westerly winds are more often associated with
high ozone concentrations in the areas that they studied than are winds
from other directions.
The above discussion can serve to define the areas where we
might look for ozone-transport effects and the conditions under which
those effects are likely to be most pronounced. In general we should
expect to find the strongest evidence of ozone transport downwind of
the areas where hydrocarbon and oxides of nitrogen emissions are greatest.
The effects should increase with downwind distance for a few kilometers
or tens of kilometers and then decrease with distance beyond that. Past
studies also have shown that high daytime ozone concentrations are found
most often in anticyclones (high-pressure cells), especially in their
western parts. Another preferred location for high ozone concentration
is the warm air near a weather front.
30
-------
Following the clues provided by the above information we ex-
amined the spatial distribution of ozone concentrations to see what
evidence there might be of transport from the major emissions areas.
We studied in detail particular incidents where transport seemed
probable, emphasizing anticyclonic and prefrontal cases. We also
examined several nighttime incidents of relatively high ozone concentra-
tions to determine their causes.
2. Statistical Evidence
Figure 14 from Cleveland et al. (1975) shows the emissions of
ozone precursors in various parts of the region of interest. The figure
shows that the New York City-Northern New Jersey areas are far and away
the most important sources of the ozone-producing primary pollutants,
with the Boston and Hartford areas providing less important source
regions.
Figure 15 shows the observed maximum-hour ozone concentrations
at seven sites during the study period. The sites are arranged from
bottom to top in order of increasing distance from the New York City
area--ranging from Bridgeport at about 80 km to Boston at about 300 km.
Each asterisk represents one observation; if more than one observation
had approximately the same value,then the plotted numeral shows the
number of cases. The data have been divided into two categories, week-
days and weekends. For each location, the weekend values are plotted
just above the weekday values. This kind of plot makes the tendency
toward decreasing ozone concentrations with increasing distance from
New York quite apparent. The conclusion that can be drawn from a visual
examination of the figure can be verified statistically. The Spearman
rank correlation (Langley, 1970) between the upper decile ozone concen-
trations and the distance from New York shows that there is a negative
correlation that is significant at the 37= level. The upper decile values
31
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Source: Cleveland et al, 1975
FIGURE 14. EMISSIONS OF HYDROCARBONS (upper number) AND OXIDES OF
NITROGEN (lower number) IN THOUSANDS OF TONS PER YEAR
were chosen for the test because the effects should be greatest for the
high ozone cases, e.g., the top 10%.
As already mentioned, Cleveland et al. (1975) found that higher
ozone concentrations were most common at a wide variety of New England
locations when the observed wind directions indicated air motions from
New York. We have used the trajectories shown in Appendix B to examine
this same phenomenon for Groton, Connecticut. The trajectory calculations
32
-------
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should provide a better Indication of the air's past history than do low-
level wind measurements made at single locations in the area. We have
limited our investigation to those days when no weather fronts passed
through the area because the presence of fronts in the area reduces the
reliability of the trajectory calculations, as noted in Section III of
this report. The importance of weather fronts is treated in detail in a
following section of this report.
The work of Ludwig et al. (1977) has shown that weather condi-
tions are important determinants of ozone concentration apart from the
effects of emissions. We have tried to isolate the emissions effects
by selecting a data set of relatively uniform weather conditions and sub-
dividing it into two classes: those cases where the air has passed near
the New York-New Jersey area and those cases where it has not. Only
those days when the air came from directions between southeast and west
were used. By limiting ourselves to these wind directions, reasonably
similar meteorological conditions should have prevailed. When the air
had moved to Groton from a direction between southeast and southwest it
would not have been influenced by New York or other major emissions areas;
air arriving at Groton from directions between southwest and west would
have been influenced by New York emissions. The 1900 EST Groton ozone
concentrations were significantly greater when the air had come from the
New York area than for other directions of arrival. For the ten cases
influenced by New York, the average was 80 ppb and for the five non-New
York cases, 26 ppb. According to the Wilcoxon sum of ranks test
(Langley, 1970) there is less than a 17» chance that the two sets of
data could have been drawn from the same population.
For air arriving at Groton at the other hours for which the
trajectories were calculated (0100, 0700, 1300 EST), the differences
were not significant. This reflects the fact that the New York effects
will be most pronounced when the photochemical production of ozone can
34
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proceed to operate on early morning emissions through most of the day-
light hours.
If we use the data from both Groton and Simsbury, we can make
comparisons that illustrate the effects of both New York and Hartford.
Figure 16 shows ozone concentrations at Groton on the nonfrontal days
plotted against the direction from which the air has come during the
preceding 6 hours. Figure 16a shows ozone concentrations observed at
1300 EST and 16b those measured at 1900 EST. The directions to New York
and Hartford are marked in the figure. It should be noted that in each
case most of the ozone concentrations above 80 ppb occurred in air
that had passed over either New York or Hartford. If it were possible
to remove the emissions from one or the other of these cities, we could
get some idea of how much effect they have on ozone in surrounding areas.
Obviously it isn't possible to actually remove the cities, but
if we look at conditions just upwind of one of them, it should provide
much the same information. Figure 17 is the same as Figure 16 except
the data are from Simsbury, located northwest of Hartford. Figure 17
shows that the only high concentrations that were observed at Simsbury
were found in air that had come from New York. Even though the frequency
of trajectories from directions between 288° and 325° is about the same
at Simsbury as at Groton, there was but one instance when the concentration
exceeded 80 ppb in air arriving from those directions. The major reason
for this lack of high concentrations at Simsbury is the fact that the
Hartford area emissions that are present in the Groton air are not in the
Simsbury air from those directions.
3. Case Studies
a. Selection of Cases
In most of the discussions in this report, we deal with
data selected from the entire period when special studies were under way
35
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DIRECTION DIRECTION
TO NEW YORK TO HARTFORD
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FIGURE 16. OBSERVED OZONE CONCENTRATIONS AT GROTON VERSUS THE
DIRECTION FROM WHICH THE AIR CAME DURING THE PRECEDING
6 HOURS ON DAYS WITHOUT FRONTAL PASSAGES
36
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DIRECTION
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FIGURE 17. OBSERVED OZONE CONCENTRATIONS AT SIMSBURY VERSUS THE
DIRECTION FROM WHICH THE AIR CAME DURING THE PRECEDING
6 HOURS ON DAYS WITHOUT FRONTAL PASSAGES
37
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in the Northeast during 1975, that is from mid-July until the end of
August. The following case studies have all been taken from that limited
period when the airborne activities of the four participating groups were
most intensive, from about 10 August to 21 August, because this is the
only period for which the vertical cross sections could be constructed.
The vertical cross section has proved to be a most useful tool for
showing the anatomy of the urban plume. This method of analysis provides
several quite interesting examples of ozone downwind of the major urban
centers. Because the highest concentrations are often aloft, the vertical
cross sections tend to provide a better picture than the more conventional
surface analyses, such as were used by Rubino, Bruckman, and Magyar (1975)
to show transport from New York to Connecticut.
b. Interpretations
10 August 1975 was a day of weak pressure gradients and
light winds in the southern New England area as can be seen from the
weather map shown in Figure 18. The pressure gradient should cause the
general surface air flow to be from the west or west-southwest. The
winds at 850 mb, approximately 1500 m altitude, shifted during the day
from west-northwest to west-southwest. We can expect the pollutants
from the urban areas to travel generally toward the east or east
northeast through the day. Using this as a guide, we know about where
to look for the urban plumes.
Figure 19 shows the distribution of the maximum observed
values of hour-average ozone concentration on this day. The figure shows
that concentrations exceeded 150 ppb along the south coast of Connecticut.
Although the lack of data from eastern Long Island prevents confirmation,
it appears that the highest concentration probably occurred over Long
Island or Long Island Sound. The hours at which the highest values were
observed along the Connecticut coast were in the early afternoon, around
1300 or 1400 EST.
38
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50
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150 175 200 MILLS
25 0 25 50 75 100 125 150 175 200 KILOMETERS
FIGURE 19. MAXIMUM HOUR-AVERAGE OZONE CONCENTRATIONS (ppb) 10 AUGUST 1975
40
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Several of the organizations participating in the northeast
northeast oxidant study conducted coordinated aircraft observations
on this day, allowing use of vertical cross sections to analyze the data.
Figure 20 shows the ozone distribution in a vertical plane, along a line
that is nearly north-south. The analysis shows that the highest concen-
trations are at an altitude of about 300 m above Bridgeport. There are
probably two mechanisms contributing to this elevated plume. First is
the buoyancy that may come from the heat that is usually associated with
pollution-generating processes. The second is the difference in the
chemical reactions between ground level and the more elevated layers.
At ground level the ozone-producing reactions are to some extent being
offset by competing ozone-destroying reactions. In particular, NO re-
leased near ground level will quickly combine with the ozone. Eventually
the NO produced by this reaction may result in increased ozone, but on
the shorter term the net result is a reduction in ozone concentrations
near ground level.
Figure 21 shows two cross sections based on data collected
later in the day. In this figure we have also drawn the streamlines for
the 850 mb winds that were observed at 1900 EST. The cross sections are
based on data collected between 1545 and 1715 EST. These two analyses
show the presence of elevated ozone layers. Concentrations over
Bridgeport, Connecticut, exceed 180 ppb and over western Long Island
Sound they exceed 140 ppb. If the 850 mb streamlines shown in the figure
represent the air motions affecting the ozone transport around this time,
then the air that passed over Bridgeport also will have passed over Groton.
If so, the two cross sections show a decline in the ozone concentrations
from values above 180 ppb to about 125 ppb.
At the south end of the cross section over Groton in
Figure 21 there are very high concentrations aloft, in excess of 230 ppb.
The air reaching this area had passed over the Newark-Jersey City region
41
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\k
LONG *" -v-^—-• ^ GREAT
ISLAND BRIDGEPORT WARREN HARRINGTON
1200
1220
!D
6000
5000
4000
3000
2000
1000
0
03 CONTOURS IN ppb
140
160
FIGURE 20. VERTICAL CROSS SECTION OF OZONE CONCENTRATION OVER
WESTERN CONNECTICUT AND LONG ISLAND, 1110-1220 EST,
10 AUGUST 1975
42
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43
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of New Jersey, then over the south tip of Manhattan and the Queens-Brooklyn
areas. The high ozone concentrations aloft seem very likely to have had
their genesis in emissions from those upstream regions.
There even seems to be a region of lower concentrations
separating the high concentrations in the air that passed over the New
York-Newark complex from those associated with the air that traveled
along the populated Connecticut coast. Although no vertical profile is
available to fully substantiate the lower concentrations in the air that
traveled the length of Long Island Sound, a horizontal flight at 1000 feet
shows that concentrations reached a minimum over the Sound and hence the
analysis shown in the figure can be justified.
Even outside the plumes, the ozone concentrations exceed
80 ppb. This suggests that rather high concentrations of ozone may
already be present in the air before it reaches these urban areas. This
was confirmed by the ISC observations (Wolff et al, 1975) on this day.
Concentrations as great as 160 ppb were observed in vertical profiles
above upwind areas over New Brunswick and Trenton, N.J.
11 August 1976 is an instructive example because it illus-
trates some important meteorological effects when taken in conjunction
with the preceding case. Figure 22 is the morning weather map for this
day. In many respects it is similar to the preceding day, but there is
a low-pressure trough in the New England area. The 3-hour weather maps
shows that this trough moved slowly from west to east during the day.
It was accompanied by generally unstable air; convective clouds gave
evidence of mixing taking place through relatively deep layers.
Figure 23 shows two cross sections for the morning of this
day. The effects of the emissions from the New York area can be seen in
the lower levels of the western cross section. The plume of high concentra-
tions in this case is much nearer the surface than the day before. This
44
-------
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45
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ALTITUDE
(ft, MSL)
ALTITUDE pTVMnilTH ATLANTIC
(ft MSL) FALMOUTH PLYMOUTH___^ ,
ATLANTIC LONG IS. GROTON PUTNAM ' 112° 1145 115812201230 EST
0855 0930 1000 1040 EST 700°
FIGURE 23. VERTICAL CROSS SECTIONS OF OZONE CONCENTRATIONS OVER EASTERN
CONNECTICUT AND EASTERN MASSACHUSSETS, 0855-1230, 11 AUGUST 1975
probably is a reflection of two effects. 'First, the greater vertical
mixing on this day has probably brought material to the surface from aloft
and caused somewhat more uniform vertical profiles. Secondly, the air
intersecting the cross section has had a recent passage over Long Island
Sound where there were no NO emissions to lower the ozone concentrations
at the surface.
46
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The cross section off the east coast of Massachusetts
gives slight evidence of a plume, perhaps from the Providence area.
The northern end of this cross section does not show much evidence of
transport from the Boston area. This may be because of a Seabreeze that
developed during the day. Figure 24 shows the maximum-hour ozone con-
centrations in the New England area on 11 August 1975. There are areas
where concentrations during the day exceeded 125 ppb on either side of
Boston, both to the northwest and to the southeast. The minimum concen-
trations over Boston, between the two higher areas, are probably the
result of NO scavenging of ozone in the city. The 3-hour weather maps
show that the surface wind at Boston switched from light WNW to a light
wind from the SE between 0700 EST and 1000 EST. It may be that the
pollutants were first carried to the east, and then returned westward
with the onset of the Seabreeze. The Seabreeze had begun before the
time of the cross section shown in Figure 23 so the fact that an
identifiable plume from Boston is not found is not too surprising.
Figure 25 shows a cross section parallel to the morning
850 mb wind direction. The vertical profiles and surface measurements
used to prepare this figure show the plume to be elevated over the
urbanized area. The relatively high concentrations aloft drop below
80 ppb over the eastern parts of Long Island. This cross section
provides evidence that the plume becomes diffuse rather quickly when
there is good mixing, at least during the morning hours. Zeller et al
(1976) have analyzed data for this day and they were able to identify
an 0 plume 50-km downwind of the Boston area in the early afternoon.
47
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FIGURE 24. MAXIMUM HOUR AVERAGE OZONE CONCENTRATIONS (ppb) 11 AUGUST 1975
48
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NEW
ALTITUDE BRUNSWICK GLENCOVE
(ft, MSL) 1035 0945
8000
LONG IS. GROTON
0930 1000
R.I.SOUND
1120 EST
FIGURE 25. VERTICAL CROSS SECTION OF OZONE CONCENTRATION (ppb)
PARALLEL TO 850 mb WINDS, 0930-1120, 11 AUGUST 1975
49
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21 August 1975 provides an example of the behavior of
urban plumes when the area is under the influence of a large anticyclone
(high-pressure cell) to the east. According to EPA (1975) and Ludwig
et al. (1977) this is one of the favored meteorological situations for
ozone formation. Figure 26 is the morning weather map for this day,
showing the high-pressure area centered just off the coast.
Vertical cross sections based on data collected during
the morning of this day show high ozone concentrations aloft that are
almost certainly the result of urban emissions. Although the two cross
sections in Figure 27 are reasonably close together, the line that is
more to the northwest is based on data collected upwind of, or above,
the major urban centers. Ozone concentrations over Trenton and New
Brunswick exceed 80 ppb, but no values as great as 100 ppb were found.
In general,concentrations are quite uniform with height, but tend to
decrease toward the northeast at all altitudes. This uniformity with
height is indicative of a well mixed body of air that can be considered
to represent "background conditions."
The other cross section has a very different appearance.
Ozone concentrations as great as 140 ppb are observed in a layer between
1500 and 2000 feet, even though the measurements were made in mid-morning,
well before the time when one would expect maximum photochemical production
of ozone. On the basis of the 850 mb morning wind patterns shown in the
figure, it appears that the high concentrations observed aloft over the
Atlantic ESE of Sandy Hook could be explained by emissions in the Newark-
New York area. The vertically uniform low concentrations at the north-
east end of this line, where it is very close to the other line, show
much the same "background" conditions seen in the other cross section.
50
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The high values above Bivalve (Point C in the figure),
in Southern New Jersey are more difficult to explain. The only metro-
politan area lying to the WNW, the direction from which the 850 mb winds
were blowing, is Wilmington, Delaware. Another possibility is that
these concentrations are the northern edge of a plume from Baltimore.
This would require that the air motions had a component from the south.
The surface weather maps show light winds from the south-southeast, so
it is possible that the net transport at 2000 feet has the necessary
direction to bring pollutants from Baltimore over Bivalve.
One final comment is in order concerning these cross
sections. It is quite reasonable to ask why there is no evidence of a
plume of high ozone concentration downwind of Philadelphia. The lack
of such evidence is because no vertical profiles of concentration were
made between Bivalve and the location ESE of Sandy Hook. It seems
quite likely that such measurements, had they been made, would have
revealed evidence of Philadelphia's effects.
Figure 28, based on data collected during the early and
mid-afternoon hours displays a very complex pattern of ozone aloft that
is quite difficult to interpret. Concentrations at 4000 feet above
Bridgeport, Connecticut, were nearly 200 ppb. Concentrations of ozone
in excess of 140 ppb are found over New Jersey and over Martha's Vine-
yard. Some of the difficulty that arises in the interpretation of
these patterns probably comes from the rather large time span covered
by the data, from 1325 to 1550 EST. Presumably, the patterns would have
been somewhat more organized had the measurements been made at more
nearly the same time. However, the observed complexity is more likely
the result of the very light winds that prevailed in the area. The
pressure gradients at the surface and 850 mb were very weak, a condition
that is usually accompanied by light, variable winds. According to
Wolff et al. (1975), the early morning winds were light and from the
53
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north to northeast, but shifted to southwest in the afternoon.
Wolff et al (1976) have analyzed the events of this day
extensively. They have concluded that ozone and precursor emissions from
urban areas, such as Philadelphia, Baltimore and Washington, had accumulated
during a period of light winds that lasted from late evening on 20 August
until the early morning hours of the following day. These accumulated
pollutants were calculated to have moved to the northeast during the
afternoon of 21 August. By late evening the movement was quite rapid.
The extended period of pollutant accumulation during the period of light
and variable winds, followed by the long travel distances, could easily
account for the complicated distribution of ozone seen in the cross-
sections of Figure 28. It may be, as Wolff et al (1976) have suggested,
that the ozone observed later this day had come from as far away as
Washington, B.C. Zeller (1976) believes that the plumes seen in Figure 28
may have come from Philadelphia, New York and Hartford, having traveled
to the southwest in the morning and then returned toward the north later
in the day.
No attempt has been made to discuss all the available
cross sections. Others are presented in Appendix D. The reader will
see in many of them the same kinds of patterns discussed above, but there
are also other examples that are rather plain and "uninteresting." Of
course, the upwind cross section shown for the morning of 21 August 1975
would also have been rather uninteresting had it not been for the avail-
ability of a downwind cross section with which it could be contrasted to
show the presence of the urban plumes.
The three days that were discussed here illustrate several
of the more important factors influencing ozone concentrations. The
55
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effects of urban emissions, of transport by moderate and by weak winds,
the effects of vertical mixing, and of scavenging by NO are all illustrated.
Most important is the fact that the urban plume is clearly discernible
in many of the cross sections at considerable distances downwind of the
source. Also quite important is the fact that the center of the urban plume
is often well above the surface. This separation from the surface may have
important consequences under some special nighttime conditions where
mixing downward from aloft could lead to increased concentrations of
ozone at the surface.
B. Special Situations
1. Frontal Passages
a. General
In the preceding sections, it has been shown that ozone
concentrations in southern New England can be affected significantly by
precursors emitted elsewhere. Winds that are aligned with the generally
southwest-northeast orientation of the source areas can collect large
amounts of precursors and transport them into New England. If the other
conditions are right, considerable ozone can form during the journey.
Reviewing, the conditions that are favorable to the transport of precursor
emissions to New England from the New York-New Jersey areas and to the
formation of ozone along the way include:
* winds from the southwest or west during the
daylight hours
• Warm, sunny conditions.
The typical weather front passing through the area will produce the condi-
tions listed above, provided that its time of passage through New England
is in the afternoon or early evening.
56
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Ludwig et al. (1977) have analyzed the distribution of
maximum daily ozone concentrations for every day of 1974. Among those
analyses are numerous examples showing the formation of high ozone
concentrations over New England in the warm air ahead of an approaching
weather front. Four examples are shown in Figures 29 through 32. In
each case the morning weather map (0700 EST or 1200 GMT) shows a frontal
system approaching New England with high ozone concentrations preceding
it.
Behind the front, there is a relatively fresh mass of
polar air. This air has usually traveled from the northwest over areas
that have few major emissions, so the cold-air side of the front should
be relatively clean. Figures 29 through 32 show this effect. An observer
at a fixed location would see ozone concentrations rise as the front ap-
proached and then fall rapidly as it passed.
In the following sections, five case studies are presented
to illustrate the effects associated with frontal passages through the
area of interest. The SAROAD data for Connecticut, Rhode Island, and
Massachusetts have been used to provide detailed distributions of ozone
at 3-hour intervals. The analyses of Figures 29 to 32 show only maximum-
hour concentrations and not how the concentrations change with the frontal
passage. Also Ludwig et al. (1977) used more smoothing in the preparation
of their analyses than is done in the more detailed case studies that
follow. The frontal positions were determined directly from the 3-hour
weather analyses of the U.S. Weather Service.
b. Case Studies
25 July 1975 was a day that illustrates the importance of
the direction of the air movement ahead of the front and of time when the
front passes through the area. Figure 33 shows the weather maps for the
eastern United States for 0700 EST on 25 July and 26 July. The ozone
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FIGURE 33. OZONE CONCENTRATIONS (ppb) AND
WEATHER MAPS FOR 25-26 JULY 1974
62
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concentrations and frontal positions are shown at 3-hour intervals from
1600 EST on 25 July to 0100 EST on 26 July. As the front approaches the
area at 1600 EST, the ozone concentrations are not very high, generally
less than 60 ppb. Three factors contributed to the relatively low con-
centrations :
(1) The area had been overcast for most of the day,
suppressing photochemical 0 production.
(2) The air arriving in the region had passed north
of the major emissions areas (see Figure 34).
(3) The time was past the period of peak photochemi-
cal activity.
With the already low concentrations, it is not surprising that the
frontal passage does not produce any pronounced effects. About the
only evidence of the type of frontal passage described earlier, with high
ozone concentrations in the warm air ahead of it, is the line of 0-^ con-
centrations above 50 ppb that lies just ahead of the front at 1900 EST.
28 July 1976 was a day when ozone patterns behaved much
closer to the idealized situation described earlier. Figure 35 shows
the ozone patterns from 1300 to 2200 EST and the 0700 EST weather maps
for 28 and 29 July 1976. Skies were clearer on this day than in the
first case and the front arrives just past midday at a time when the
photochemical activity should still be quite high. Although the air
ahead of the front has come from the west and passed north of the area
of maximum emissions, the wind speeds were lower, allowing more time to
accumulate the emissions. Furthermore, during the morning rush hour the
air ahead of the front had been over the Hudson River Valley. Although
not ideal, the conditions ahead of the front in this case were more con-
ducive to ozone production than they were in the preceding case.
As the front moves through the area, the highest concentra-
tions stay just ahead of it until about 1900 EST when the front appears
63
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1300 EST oo
ace 26 JULY—"°0
ccccc /
/ CC -•' D
0700 EST C"Ccc,.2C
26 JULY cc/P o
FIGURE 34. AIR TRAJECTORIES ARRIVING IN NORTHERN CONNECTICUT,
24-26 JULY 1975
-------
28 JULY, 1300 EST
1600 EST
1900 EST
2200 EST
28'JULY_1974, 0700 EST
/ - '•§. S-
29 JULY 1974, 0700 EST
FIGURE 35. OZONE CONCENTRATIONS (ppb) AND
WEATHER MAPS FOR 28-29 JULY 1974
65
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to have overrun them. The frontal position shown in Figure 35 was taken
directly from the Weather Service analyses. It appears from the 0
concentration that the actual frontal position at the time may have
been about 30 km northwest of the analyzed position.
Time section analyses of the passage of this front through
the area are shown in Figures 37 and 38. The map in Figure 36 shows the
location of the stations used for these analyses. The approximate time
that the front passed each location along the time section lines is
shown in the figures along with the time-space ozone distributions.
The buildup of ozone before the front arrives is evident in the figures,
as is the rapid replacement of the ozone-laden air ahead of the front
with the cleaner, polar air behind it.
•4-
FIGURE 36. LOCATION OF TIME SECTION LINES
66
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5 and 6 August 1975 were rather complex meteorologically
in the New England area. Figure 39 shows the ozone concentrations from
0700 through 1600 EST on 5 August. As shown on the maps, an occluded
frontal system passed through the area during the morning. Contrary to
the discussion to this point, the maps show a buildup of ozone after this
front rather than before it arrived. This was a rather weak front with
little precipitation associated with it. The Weather Service analyses
showed it to be followed by a stronger system. There was some fog behind
the first front, but it had generally cleared by 1000 EST. Because the
first front arrived in the area during the early morning, it is not
surprising that it was not preceded by high 0 concentrations.
Figure 40 shows the ozone patterns from 5 August at 1900
EST to 0400 EST of the next day. The arrival of the second front during
the late afternoon allowed the ozone concentrations to build up during
the daylight hours as can be seen in the figure. The trajectory analyses
show this to be a somewhat anomolous case in that the air motions leading
to the high concentrations are generally from the north-northwest, which
may explain why the centers of highest midafternoon 0 concentrations are
located approximately downwind of Boston and Hartford.
As the second front moved through the area, the 0 con-
centrations fell rapidly. This is probably the result of two processes,
the general decline in 0 at night when the photochemical processes are
no longer active and the flushing of the area by the newly arrived polar
air behind the front. Figures 41 and 42 are time sections that show more
clearly that much of the decline in ozone concentration had already taken
place before the second front arrived.
14 August 1975 is a day when a slow-moving cold front passed
through the area during the daylight hours. Figure 43 shows that the front
was well into the area by 1000 EST, but moved very little during the next
3 hours. By 1600 EST, the front was nearly to the Connecticut-Rhode Island
69
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1000 EST
1300 EST
1600 EST
5 AUGUST 1974, 0700 EST 10"
- 6 AUGUST 1974, 0700
FIGURE 39. OZONE CONCENTRATIONS (ppbl AND
WEATHER MAPS FOR 5-6 AUGUST 1974
70
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5 AUGUST, 1900 EST
2200 EST
0400 EST
5 AUGUST 1974, 0700 EST
1&£*A\1 -
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6 AUGUST 1974, 0700 EST
FIGURE 40. OZONE CONCENTRATIONS (ppb) AND
WEATHER MAPS FOR 5-6 AUGUST 1974
71
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1600 EST
1900 EST
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FIGURE 43. OZONE CONCENTRATIONS (ppb) AND
WEATHER MAPS FOR 14-15 AUGUST 1974
74
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coast, and the ozone-heavy air that had been there earlier was replaced
with the cleaner, polar air behind the front. In this case the decrease
in ozone as the front passes is clearly caused by the incoming clean air,
because midafternoon is an unlikely time for the decrease to have been
caused by declining photochemical activity.
Figures 44 and 45 are time sections showing the frontal
passage through the area. The time section in Figure 44, along the line
oriented nearly north and south (Figure 36) gives only slight evidence
of the front, because the cleaner air replaces the polluted air before
the ozone concentrations have had much chance to build up. The time
section in Figure 45, along the coast line (Figure 36), shows the frontal
passage quite clearly.
As shown in Table 2 (Section II), EPA Las Vegas, Washing-
ton State University, and Battelle all operated aircraft and measured
vertical ozone profiles on this day, so it was possible to construct
vertical cross sections. This is one of the few instances when aircraft
data were collected during a frontal passage. Figures 46 and 47 show
the cross sections and the approximate location of the front during the
time when the data were collected. In both cases the front intersected
the line of the cross section and the higher ozone concentrations ahead
of it are apparent. The later cross section (Figure 47) shows quite
clearly the sharp gradient in concentration that is associated with the
front. It also shows that the high concentrations extend upward to about
2000 feet. Some of the gradient probably is caused by the difference in
the time that the two easternmost soundings were taken, but frontal effects
were almost certainly responsible for much of it.
18 August 1976 was quite similar to the case just dis-
cussed except that the front moved through the area somewhat more rapidly.
As shown in Figure 48, the front had entered the region of interest by
1000 EST. It was cloudy, but not overcast in the warm air ahead of the
75
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POUGHKEEPSIE HARTFORD
ALTITUDE BATTLEBORO LOWELL ROCKLAND
(ft, MSL)
1035
1120 1145
1130
1100 EST
03 CONTOURS IN ppb
FIGURE 46. CROSS SECTION OF OZONE CONCENTRATION BASED ON DATA
COLLECTED BETWEEN 1035 AND 1145 EST, 14 AUGUST 1975
78
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-f
(ft, MSL)
9000
8000 -
ABINGTON CHAPPAQUIDDICK IS,
NORWICH NAVSHON IS.
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03 CONTOURS IN ppb
FIGURE 47. CROSS SECTION OF OZONE CONCENTRATION BASED ON DATA
COLLECTED BETWEEN 1354 AND 1630 EST, 14 AUGUST 1975
79
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18 AUGUST, 1000 EST
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1600 EST
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FIGURE 48. OZONE CONCENTRATIONS (ppb) AND
WEATHER MAPS FOR 18-19 AUGUST 1974
80
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front so the 0 concentrations ahead of the front rose with the photo-
chemical activity during the morning and early afternoon. Concentra-
tions in excess of 150 ppb were reached along the Connecticut coast ahead
of the front. These dropped to about 50 ppb with the passage of the front
between 1600 and 1900 EST. The time section shown in Figure 49 for the
line along the Connecticut coast clearly shows the rapid decrease in ozone
concentrations as the front moves through.
c. Recapitulation
The preceding case studies illustrate the conditions under
which high ozone concentrations are likely to be found ahead of weather
fronts in southern New England. Briefly these conditions are:
• The weather front must pass through the area
during the daytime so that photochemical activity
can take place in the air ahead of the front.
• It must not be too cloudy in the warm air so that there
is sufficient sunlight for ozone production.
• The front must be oriented more-or-less southwest
to northeast so that the low-level winds ahead
of the front will carry precursors from the high-
emissions areas into southern New England.
Obviously there will be exceptions to the above "rules,"
such as occurred in the case of 5 and 6 August with its complex pair of
fronts. Nevertheless, frontal passages during the summer that meet the
above criteria are quite likely to be preceded by high ozone concentra-
tion in Connecticut and Rhode Island.
2. Occurrences of High Nighttime Ozone
Concentrations at Ground Level
a. Background
Before discussing the reasons for high concentrations of
ozone near ground level at night, the more common case--low nighttime
81
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concentrations--should be discussed. By sundown, of course, the photo-
chemical production of ozone has ceased, but the destruction processes
will continue. The most effective destruction processes occur at the
ground where the surface provides sites for ozone destruction and where
most emissions of nitric oxide are found. When the sun is low, or has
set, the surface cools and a surface-based inversion forms so that verti-
cal mixing is inhibited. The ozone is quickly destroyed in the lowest
layers and whatever ozone may still exist at higher layers is effectively
isolated.
During the daytime there is continual formation of ozone
throughout the mixed layer, and the destruction processes near the surface
are offset by formation and by mixing downward of ozone from aloft. Even
though the ozone formed during the daytime may persist aloft at night,
usually it will not be mixed downward to be measured at the surface.
However, if for one reason or another, there should be vertical mixing
at night then we might expect that any ozone plumes that were aloft would
be brought to ground level where they could be observed. The above dis-
cussion indicates there are two conditions that must be met if high
nighttime ozone concentrations are to be found at ground level. These
are:
(1) There must be a reservoir of ozone aloft.
(2) There must be sufficient vertical mixing
to bring ozone from that reservoir to ground
level.
The first condition usually will be met if conditions
during the preceding day were conducive to ozone formation and if the
winds have been such as to transport ozone and its precursors from source
areas to the observing site. The second condition requires either that
the atmospheric dynamics be favorable to vertical motions, as they often
are near low-pressure troughs, or that the cooling of the air in the
83
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lowest layers be inhibited. Low-level cooling is subdued during overcast
sky conditions, or when the air passes from a cooler to a warmer surface.
As we have seen in earlier sections of this report, urban
ozone plumes aloft are not uncommon in the summer. There are meteorolo-
gical "symptoms" that identify cases of nighttime mixing in the vertical.
These symptoms are strong winds and warm temperatures at ground level.
The surface acts as a sink for heat at night. It is also a sink for
momentum through friction losses. If there is good mixing, momentum and
heat will be transferred to the ground from aloft, and temperatures and
wind speeds at the surface will remain relatively high. Hence, warm
temperatures and strong winds are symptomatic of vertical mixing.
Following the example of preceding sections of this report,
case studies will be used to illustrate how the factors outlined above
can be used to explain at least some of the occurrences of high nighttime
ozone concentrations at ground level.
b. Case Studies
13-14 August 1975 provides one of the most clear-cut
examples of the processes operating to produce high ozone concentrations
at night. Figure 50 shows average hourly values of ozone, Freon-11, wind
speed, and temperature measured by Washington State University (1976)
at their Groton, Connecticut, site. The figure shows an abrupt rise in
ozone concentrations beginning around 1800 to 1900 EST, a time of day
when photochemical processes have largely ceased and there is normally
a decrease in ozone concentrations. The anthropogenic origins of this
ozone are confirmed by the concurrent rise in Freon-11 concentrations.
The importance of downward mixing iri this case is shown
by the increase in wind speed at the onset of the higher pollutant con-
centrations. The increase in temperature somewhat later, and at the
time of normal temperature decrease, also indicates vertical mixing.
84
-------
.d
o.
E
30
Q
W
a 20
5 10
»
r. 0
UH
L 85
i 80
i
£ 75
S
B
70
400
P.
O.
300
O
H
OS
O
o.
a
O
o
o
H
2;
H
O
Z;
O
(J
200
100
50
I I I
16 18 20 22 24
TIME (EST)
02
04
FIGURE 50. SELECTED POLLUTANT AND METEOROLOGICAL OBSERVATIONS AT
GROTON, CONNECTICUT, DURING THE NIGHT OF 13-14 AUGUST 1975
85
-------
The Weather Service surface weather map for 1900 EST shows a trough along
the western borders of Connecticut and Massachusetts; the trough is ac-
companied by overcast skies and signs of convection such as recent showers
and cumulus clouds. The weather map supports the other evidence of verti-
cal mixing; we can feel confident that the sudden increase in ozone
around sunset was caused by an onset of vertical mixing.
Between 2300 and 0100 there is a sharp drop in ozone con-
centration. This cannot be explained by a cessation of mixing because
Freon-11 concentrations and wind speeds actually increase during the
same period and temperature remains relatively constant. All this points
to continued mixing, as do the Weather Service analyses showing the trough
passing over Groton during the same period. If our list of requirements
for high nighttime ozone at ground level is complete, then we must assume
that the supply of ozone aloft has disappeared, although other anthropo-
genic pollutants—as represented by Freon-ll--continue to affect the
Groton site.
Suppose we hypothesize the following:
(1) The New York-Newark area is a major source of
the pollutants reaching Groton.
(2) Pollutants emitted from that area after about
1600 EST will not undergo sufficient photochemi-
cal activity to produce large amounts of ozone.
The first point of the hypothesis can be tested by constructing air
trajectories from New York. Figure 51 shows an approximation of a swath
of pollutants that left the New York area about 1600 EST. The approximate
positions of the pollutants at subsequent hours is also shown. It can be
seen that the 1600 EST New York pollutants passed Groton at just about
the same time that the ozone-concentration decline began.
The hypothesis can be further tested by looking at the
hourly ozone concentrations at other locations. Figure 52 shows the time
86
-------
FIGURE 51. LATER POSITIONS OF AIR THAT LEFT NEW YORK AT
1600 EST, 13 AUGUST 1975
histories of ozone concentration at several other monitoring stations.
The hatched bars in the figure mark the time at which the pollutants that
left New York between 1400 and 1600 EST should have passed each of the
sites. It is apparent that these sites did not show the sharp drop found
at Groton when the 1600 EST New York air passed by. They did show marked
decreases in concentrations beginning two to three hours before, correspond-
ing to the passage of air that left the New York area earlier in the after-
noon. The second part of our hypothesis should be revised to indicate
that pollutants emitted later than about 1400 EST do not undergo suf-
ficient photochemical activity to achieve the oxidant concentrations that
are produced from precursor emissions earlier in the day. The measure-
ments at Groton, upon reexamination, show a leveling off of ozone concen-
tration when the air that had left New York at 1300 to 1400 EST passed
the site. The measurements at Hartford, being generally outside the
plume, show no pronounced indications of its passage.
87
-------
150
.a
a
P.
W
O
CJ
I I I I I I I I I I I I
Time of passage of air
that left New York
between 1400-1600EST
BRIDGEPORT
100 r
75
50
- PROVIDENCE
125
100
75
50
25
150
125
100
75
50
J 25
100
75
50
25
P.
O.
Ft
O
I
O
o
I
J I
16 18 20 22 24 02 04
TIME (EST)
FIGURE 52. OZONE CONCENTRATIONS AT SEVERAL SOUTHERN NEW ENGLAND
SITES DURING THE NIGHT OF 13-14 AUGUST 1975
-------
21 August 1975 was another occasion with nighttime ozone
concentrations in excess of the federal standard, but the causes are not
quite so clear as in the preceding case. Vertical mixing appears to have
been present, at least to some degree. Figure 53 shows the wind speed,
temperature, and freon and ozone concentrations during the evening of
this day and the following morning at Groton and through late evening
at Simsbury. (The Simsbury records end at the time shown in the figure.)
Judging by the wind records, the onset of vertical mixing was around
1800 EST. Some shower activity began in the area between 1900 EST and
2200 EST, providing further evidence of vertical mixing after this time.
However, the Groton records show that ozone concentrations began to
decline by 1900 EST and the Simsbury values increased, but did not
reach very high levels. This suggests that there may not be a very
strong reservoir of ozone aloft at these two sites.
Air movement in the area indicates that Groton and Sims-
bury were at opposite edges of the swath of air that passed over the
New York area during the afternoon. Figure 54 shows the movement of the
air that left the New York area at about 1600 EST. The Groton and Sims-
bury records can be used to establish the presence of vertical mixing in
the area; records from other locations have to be used to determine
whether the same kinds of things happen to ozone concentrations on this
day as were found in the preceding case study.
Figure 55 shows the ozone concentrations at four locations
along the path of the air from New York. Again, the shaded bars show when
air passed that had been over New York between 1400 EST and 1600 EST.
Qualitatively, the behavior is similar to the preceding case, but the
declines are less abrupt and they begin later relative to the passage
of air that left New York during the latter part of the afternoon.
89
-------
,
Q.
B
Groton
w
I
o
80
70
65
400
o.
a
300
O
w
£
o,
a
200
fn
O
W
O
8
100
50
Simsbury
Groton
OZONE
i
j i
16 18 20 22 24 02 04
TIME (EST)
FIGURE 53. SELECTED METEOROLOGICAL AND POLLUTANT OBSERVATIONS AT GROTON
AND SIMSBURY DURING THE NIGHT OF 21-22 AUGUST 1975
90
-------
FIGURE 54. LATER POSITIONS OF AIR THAT LEFT NEW YORK AT
1600 EST, 21 AUGUST 1975
This day is probably more typical, because there should
not be an abrupt change from air that was subjected to photochemical pro-
cesses and air that was not; the decline should be more gradual through
the afternoon. Superimposed on this gradual change in photochemical
activity are changes in emissions rates and the effects of turbulent diffu-
sion, both of which further blur the end of the ozone for the day. The
data do fit the general hypothesis presented earlier to explain observed
nighttime ground-level ozone concentrations.
18 July 1975 illustrates how meteorological factors can
cause misinterpretation of observed ground-level ozone concentrations.
91
-------
Time of passage of air that left
New York between 1400-1600 EST
100
ft
ft
o
o
o
I—f
EH
o
o
100 _
_ 100
- 75
-150
•a
100 r-
75
50
I I i I I
16 18 20 22 24 02
TIME (EST)
04
FIGURE 55. OZONE CONCENTRATIONS AT SELECTED STATIONS
DURING THE NIGHT OF 21-22 AUGUST 1975
92
-------
Figure 56 shows the observed ground-level ozone concentrations at three
different times during the late afternoon and night of 18 July 1975.
The apparent motion of the center of high ozone concentration is from
southwest to northeast at about 35 km hr during the 6-hour time span
covered in the figure. Air trajectory calculations in the area and during
the same general time period indicate a somewhat slower 25 to 30 km hr
in about the same direction, as shown in Figure 57. Figure 58 shows the
ozone histories at several stations generally along the direction of air
movement. The peak concentration at Middletown, Connecticut, is sepa-
rated from the peak at Salem, Massachusetts, by about 4 hours and 190 km.
If we assumed that the onset of declining ozone concentrations at night
always corresponded with the arrival of midafternoon emissions from the
major upwind source area, then we would estimate a speed of motion of
nearly 50 km hr
In the two case studies discussed in the preceding sections,
vertical mixing was quite widespread and the onset of the nighttime decline
in ozone concentration did correspond to the passage of the last photo-
chemically affected air from New York. In this case it appears that the
opposite situation prevailed--an area of vertical mixing moved rapidly
through the area while high ozone concentrations aloft were still quite
widespread. The National Weather Service weather map for 1600 EST shows
a trough in the surface pressure field. Subsequent maps have dropped
this feature from the analysis, probably because the sparsity of weather
observations off the east coast makes its detection difficult, if not
impossible.
If we assume that the trough persisted for at least a
few more hours and moved eastward at a reasonable rate, then it might
have moved more-or-less as shown in Figure 59. Low-pressure troughs are
often accompanied by instability and enhanced vertical mixing. A trough
moving as shown in Figure 59 would easily explain the ozone traces shown
in Figure 58.
93
-------
1600 EST
1900 EST I
40
4.
80
2200 EST
FIGURE 56. OZONE CONCENTRATIONS (ppb) ON 18 JULY 1975
94
-------
_u
FIGURE 57. LATER POSITIONS OF AIR THAT LEFT NEW YORK AT
1600 EST, 18 JULY 1975
The above explanation is further supported by the more
detailed observations at Groton and Simsbury, shown in Figure 60. If
correct, the trough should have passed Simsbury at around 1800 EST to
1900 EST and we might expect to see just the kind of behavior that is
seen in the ozone concentration. Unexplainably, the wind speed and
temperature histories are not much like what would be expected. At
Groton, there are slight indications of a trough passage in all traces
at about the right time, circa 2200 EST.
c. Further Discussion
The three cases of high nighttime ozone concentrations
at ground level have illustrated the importance of the simultaneous
95
-------
125
I i I
1 1 1 I i
1 l 1 I
.Q
P.
p.
Eq
o
o
l-H
H
2;
O
O
Time of passage of air
that left New York
between 1400-1600 EST
I I I I I I I I I I I I
125
100
75
50
25
0
150
125
100
75
50
25
•a
p.
En
O
O
f-H
H
O
o
-> 0
150
125
100
75
50
25
16 18 20 22 24 02 04 06
TIME (EST)
FIGURE 58. OZONE CONCENTRATIONS AT SELECTED NEW ENGLAND SITES DURING
THE NIGHT OF 18-19 JULY 1975
96
-------
FIGURE 59. ESTIMATED TROUGH POSITIONS, 18 JULY 1975
occurrence of two factors--vertical mixing and a reservoir of the pol-
lutant aloft. In two cases, declining ozone concentrations at a series
of stations marked the passage of the trailing edge of the ozone
reservoir aloft.
97
-------
A
O.
s
20 -
10 -
0
85
80
75
70
400
300
2;
O
Q
JD
D.
Q.
O
O
O
H
w
O
2;
O
O
200
100
50
Groton
/ > Simsbury
OZONE
i i i i
16
18
20 22 24
TIME (EST)
02 04
FIGURE 60. SELECTED METEOROLOGICAL AND POLLUTANT OBSERVATIONS AT
GROTON AND SIMSBURY DURING THE NIGHT OF 18-19 JULY 1975
98
-------
In the third case, it appears that a line of atmospheric
instability—with its associated vertical mixing—passed through the
area. It caused a rise and fall of ground-level ozone concentration as
ozone was transferred to the surface from the layer aloft. Of course
the passage of the trough through the area would have gone unreflected
in the ozone observations had it happened later at night, after the
ozone aloft had been advected beyond the region.
If high nighttime ozone concentrations are a product of
vertical mixing and ozone aloft, then it would be worth speculating
where these conditions might be found in combination. The cases pre-
sented show their joint occurrence downwind of a major source area
during periods of atmospheric instability. Certain geographic features
can also produce the necessary transfer of ozone aloft to ground level.
One obvious example would be on a mountain where the ground surface is
at the level of the ozone layer. In their discussion of transport and
mixing, Coffey and Stasiuk (1975) present data from Whiteface Mountain
in New York state that seem to illustrate this effect.
Although no examples are available to illustrate the point,
it seems quite possible that any place where the surface tends to be
warmer then its surroundings at night might cause enhanced vertical mix-
ing that could bring ozone down to ground level. Large urban "heat
islands" and bodies of water are two possible examples. Under some
circumstances it seems possible that the warmer city surfaces and the
increased mechanical mixing over the urban area might lead to higher
nighttime ozone readings than in the surrounding countryside, provided
that there is a layer of ozone aloft to be mixed groundward.
3. Weekday and Weekend Ozone Concentrations
Cleveland et al. (1975b) have found that the average ozone
concentration between 0500 EST and 1300 EST is significantly higher on
99
-------
Sundays than on workdays. However, they also found very little difference
between the two types of day when maximum hour-average ozone values were
compared. Figure 15 summarizes the data that we have examined on this
project in an attempt to differentiate between weekday and weekend ozone
values. A casual examination of this figure indicates little systematic
difference between the weekend maximum daily ozone readings (the upper
line of points for each location) and the weekday values (the lower line
of points). The data sets for each of the locations were tested for sig-
nificant differences. Although the mean values of weekday maximum ozone
concentration exceeded those for the weekend at five of the seven sites,
no site showed a difference that was significant at the 57o level. Wil-
coxon's sum of ranks test (Langley, 1970) was used. It is a nonparametric
test that should be quite suitable for data such as these that do not
have a normal frequency distribution.
Cleveland et al. (1975b) have explained the tendency toward
higher Sunday average ozone concentrations as a reflection of reduced
scavenging by NO. Scavenging is reduced because there are fewer emissions
of NO during Sundays, at least in urban areas. In rural areas, where the
differences in NO emissions between weekdays and weekends might be expected
to be smaller, the differences in scavenging should also be smaller. If
the ozone in these same rural areas is the product of emissions transported
from cities, then higher weekday concentrations might be expected, a
result that is at least hinted at by the data from five of the seven
stations analyzed, the exceptions were Providence and Quincy. This is
a hypothesis that might be tested with a larger data sample.
100
-------
V LIMITATIONS TO THIS STUDY
AND RECOMMENDATIONS FOR FURTHER RESEARCH
At the same time that the analyses described here were being con-
ducted, another project was archiving the data from the Northeast Oxidant
Study in a computer-compatible form. This second study was not completed
in time for automated data processing techniques to be applied to these
initial studies. As a result, we feel that we have not been able to
use the rich body of data provided by the Northeast Oxidant Study as
fully as possible.
Another limitation to this work is the geographical area studied.
It has been limited to the southern New England states, plus New York
and New Jersey. The original concept of the project recognized the
importance of northern New England, but time, data, and funds have not
been sufficient to treat this area adequately. The studies that have
been completed indicate that the states of Maine, New Hampshire, and
Vermont may often be "the end of the line," at least within the United
States, for the pollutant-transport processes along the northern part
of the east coast, and hence they have an importance that has not been
fully reflected in this report.
Our examination of weekday versus weekend ozone concentrations was
based on a data sample that was too small to provide conclusive results.
Cleveland et al. (1975b) have pointed out that the differences in
emissions between Sundays and workdays constitute an experiment of sorts
to demonstrate the effects of changes in emissions and emissions schedules.
This experiment represents too valuable a source of information to neglect-
particularly because the preliminary, inconclusive results given here
101
-------
suggest that control strategies may be more effective well downwind of
the locale in which they are enacted than they are within the controlled
area itself.
Although further research in this area is clearly desirable, field
studies are not warranted at this time. In some instances, the analysis
of larger collections of routinely archived data—from 1974 and 1976, as
well af from 1975, or from a more extensive geographical area—should
be sufficient. In other instances, more efficient reexamination of the
data already analyzed will provide valuable new information. Four tasks
are strongly recommended to take full advantage of the existing data
base:
• Develop and use automated data analysis techniques to
provide better descriptions and better understanding of
the elevated urban ozone plumes.
• Extend the geographical area of the study to include
northern New England so that we will know the extent to
which it is influenced by emissions from elsewhere and
also to provide information on the behavior of ozone
plumes in areas with relatively few anthropogenic emissions.
• Examination of more instances when ground-level ozone con-
centrations were high at night so that we can study trans-
port and surface destruction of ozone under conditions
when there is no photochemical production to obscure the
transport and removal processes.
• Use a larger data base to study the "weekend effect" to be
able to relate changes in emissions to the resulting changes
in the distribution of ozone concentration, a relationship
that has obvious strategic implications.
102
-------
REFERENCES
Bruntz, S. M. , W. S. Cleveland, B. Kleiner, and J. L. Warner, 1974:
The Dependence of Ambient Ozone on Solar Radiation, Wind, Tempera-
ture, and Mixing Height, Proc. Symp. Atmos. Diff. and Air Poll.,
Santa Barbara, California. Am. Met. Soc., Boston, Massachusetts,
pp. 125-128.
Cleveland, W. S., B. Kleiner, J. E. McRae, and J. L. Warner, 1975a:
The Analysis of Ground-Level Ozone Data from New Jersey, New York,
Connecticut, and Massachusetts; Transport from the New York City
Metropolitan Area, Mimeo Report, Bell Laboratories, Murray Hill,
New Jersey, 65 pp.
Cleveland, W. S., T. E. Graedel, B. Kleiner, and J. L. Warner, 1975b:
Sunday and Workday Behavior of Photochemical Air Pollutants in
New Jersey and New York. Mimeo Report, Bell Laboratories, Murray
Hill, New Jersey, 12 pp.
Coffey, P. E., and W. N. Stasiuk, 1975: Evidence of Atmospheric Trans-
port of Ozone into Urban Areas, Environmental Science and Technology,
9., pp. 59-62.
Environmental Monitoring and Support Laboratory, 1975: Meteorological
Data for the Northeast Oxidant Transport Study. EPA, Las Vegas,
Nevada, 89114. Xerox Draft.
Environmental Protection Agency, 1975: Control of Photochemical Oxidants-'
Technical Basis and Implications of Recent Findings, EPA Report
No. 45012-75-005. 37 pp.
Heffter, J. L. and A. D. Taylor, 1975: A Regional-Continental Scale
Transport, Diffusion and Deposition Model, Part I: Trajectory
Model. NOAA Tech. Memo ERL ARL-50. pp. 1-16.
Langley, R., 1970: Practical Statistics Simply Explained. Dover Pub.
Inc., New York, 399 pp.
103
-------
Ludwig, F. L., E. Reiter, E. Shelar, and W. B. Johnson, 1977: The
Relation of Oxidant Levels to Precursor Emissions and Meteorological
Features, Part 1: Analysis and Findings, Final Report EPA Contract
68-02-2084, Stanford Research Institute, Menlo Park, California.
Martinez, E. L., and E. L. Meyer, Jr., 1976: Urban-Nonurban Ozone
Gradients and Their Significance. Paper presented at Air Poll.
Cont. Assoc. Tech. Specialty Conf. on Ozone/Oxidants: Interaction
with the Total Environment, Dallas, Texas, 12 Mar 1976, 15 pp.
Rubino, R. A., L. Bruckman, and J. Magyar, 1975: Ozone Transport.
Paper No. 75-7.1, presented at 68th Meeting Air Poll. Cont. Assoc.,
Boston, Massachusetts, June 15-20.
Siple, G. W., K. F. Zellcr, and T. M. Zeller, 1976: Air Quality Data
for the Northeast Oxidant Transport Study, EPA Office of Res. and
Devel., Environ. Monitoring and Support Lab., Las Vegas, Nevada.
Spicer, C. W., D. W. Joseph, and G. F. Ward, 1976: Final Data Report
on the Transport of Oxidant Beyond Urban Areas, Final Report EPA
Contract 68-02-2441, 388 pp.
U.S. Department of Commerce, 1968: Climatic Atlas of the United States,
80 pp.
Washington State University, 1976: Measurement of Light Hydrocarbons
and Studies of Oxidant Transport Beyond Urban Areas. Final Report
EPA Contract 68-02-2339, 317 pp.
Wolff, G. T., P. J. Lioy, G. D. Wight, and R. E. Pasceri, 1975: An
Aerial Investigation of Photochemical Oxidants over New Jersey,
Southeastern New York and Long Island, Western Connecticut, Northern
Delaware, Southeastern Pennsylvania and Northeastern Maryland.
Interstate Sanitation Commission, New York, 118 pp.
Wolff, G. T., P. J. Lioy, R. E. Meyers, R. T. Cedarwall, G. D. Wight,
R. E. Pasceri and R. S. Taylor, 1976: Anatomy of Two Ozone Transport
Episodes in the Washington, D.C. to Boston, Massachusetts, Corridor.
Paper presented at the 10th Annual Mid. Atlantic States Section of
the Amer. Chem. Soc. Philadelphia, PA, 23-26 February 1976.
Zeller, K. F., 1976: Personal Communication.
104
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Zeller, K. F., R. B. Evans, C. K. Fitzsimmons and G. W. Siple, 1976:
Mesoscale Analysis of Ozone Measurements in the Boston Environs.
Pres. at Symp. on Non-Urban Tropospheric Compos., Hollywood, FLA,
10-12 November 1976.
105
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Appendix A
DAILY WEATHER MAPS
A-l
-------
The daily weather maps given in this appendix have been copied
from the National Oceanic and Atmospheric Administration's "Daily
Weather Map" series. One map is presented for each day during the period
15 July to 31 August 1975. They represent conditions prevailing at
1200 GMT, or 0700 EST.
A-2
-------
TUESDAY, JULY 15, i»76
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1 AT 7 00 A M £ > T
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MONDAY, AUGUST 18, 1975
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m mJ& k -wf^'-* "Ff & •
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-------
TUESDAY, AUGUST 19,1975
vm\ v "i' "x^jy« ^. ^-~_
^> v&3^
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ss» f- i1: B3 ^ ^
-------
WEDNESDAY, AUGUST 20,1975
-------
THURSDAY, AUGUST 21,1976
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as:
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t3 "^ S1 T
5 a
-------
SATURDAY. AUGUST 23, 1975
tv.V** **><»'*, *?&
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-------
SUNDAY, AUGUST 24,1976
•rr£**si—'T&yt&F es^WV **%*!!•*
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s*"^ i£^^*=v* .:£ >.
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f \ I'*-. / ^, !*_"»>? . -«
-------
MONDAY, AUGUST 25, 1975
&r ^
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/ ' f% W - - ., ^" ) v-
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' v.«ri«t .j. -^ . _ A 5j^
-------
TUESDAY, AUGUST 26, mi,
*•
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%^tyc*
^-> ^S^li^^-Jf,
-------
WEDNESDAY, AUGUST 27, 1975
3£iL S-fift \ %" • f,|»;" -* S,f"^;-*> ^
^ UM £|?w, ^^V1^^^4'^
r \ ^_!C6.^B' « . J--W.7-* , *'» -W>1
*'?'.- -
-------
THURSDAY, AUGUST % 1975
T «><• '
"/ s-^*:* i
-------
FBI0AY, AUGUST 29, 1975
$f " J*£W| £\ '*
*>7" *^SS\^"V3
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•2,1^^^*
-------
SATURDAY, AUGUST 30, 1975
%
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AT 7 00 A M E S T
, * •* " » s fi » i. " s- 'n « a-S « ***
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C f' /- * - 4 «, « * * » *«^
*-'*., :; " x .' . * * *
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-------
SUNDAY, AUGUST M, 19T5
..../•:.«»";• V "«
>-\ 's.*^>'-w>-*4£K- T-la
V /^ J^"«:*_.^ ,4' v\
-------
Appendix B
TRAJECTORIES OF AIR ARRIVING
AT GROTON AND SIMSBURY
B-l
-------
This appendix shows the calculated trajectories of air arriving
at 6-hour intervals at Groton, and Simsbury, Connecticut, during the
period from 16 July to 31 August 1975. The methods and data used to
calculate these trajectories are described in the text of this report.
Anyone who uses these trajectories should consult that discussion in
the report so that they would be aware of the assumptions involved
and of some of the shortcomings of the results.
Trajectories shown on the following pages were plotted on
computer line printer so that the north-south and east-west axes are
of different scales. This is the reason for the distortions in the
maps. Trajectories arriving at the end point at 0000 GMT (1000 EST
of the preceding day) are marked by the symbol "A". Those arriving
at 0600 GMT (0100 EST) are marked by "B", those arriving at 1200 GMT
(0700 EST) by "C" and trajectories arriving at 1800 GMT (1300 EST)
are shown by the symbol "D". When two or more trajectories passed
through the same point, an "X" is shown. The positions of the air
at 6-hour intervals are marked by numerals. This position 6 hours
prior to arrival at the end point is shown by a "1", 12 hours prior
to arrival is indicated by a "2", and so forth.
B-2
-------
16 JULY 1975
B-3
-------
17 JULY 1975
B-4
-------
18 JULY 1975
B-5
-------
19 JULY 1975
B-6
-------
20 JULY 1975
CC
ICC ^
CC
CC
CC
CC DDOOODOAX
CC DODD x.i
CC^DO Aixf
CCOD AXB '
CCDO AAB
?QD AABB
CCO AAAHR
CCOO AAA 8
CCCOO AAA B
IC3C
ccc .,
CCC I X>X
<• CCC
/ CCC AA4X - UBS
f}t CCCC 3AOO BBB
; xCC AADD 638
ADO PBB
B-7
-------
21 JULY 1975
\>
) ^J
B-8
-------
22 JULY 1975
ccc
•>CC i. ,
cccc on /
6 CCCCC P /
BH CC3CCCCCCCCCCCCCSCCCCCCCCCCCOCIJ „
1C j
A3« —
' ^ ! - i\
! t)x A
bL-aS-rtat^r.E- ;
Hf^SP^biiripfl,
AAAS^oU^ S /
:cc3cc o
ccccccccccczcecccccccccon :
ccxci I, A ,:
ODC ;
ICC /
B-9
-------
23 JULY 1975
I
,J
-1
CC 3B
CtC 8d
DO CC ae
5 C3C Bfl
03 i-CCCCC -
'
A /_
i~o'orooo7^7"^"""l-cxxx0 ' J
DDDiJO j CCXXHlXl
000 x ClfCAXK
r>?mj ; ccxxxx
/"xno^/^e-
—.-
U-.A ^-J
CCCCCC3CC CCC2X3CCCCCCCC A
CCCCCC BB CCX1C /
OOOODDO BPBPBBBblBXlXCC /
LOOOJHO _DOP3£DD dOOZM BXXXXX^LC.
QODOO i XXXX-
\ OD10 | 00
j DC/D ! 00
>X (
li
B-10
-------
24 JULY 1975
j ! 80 CC 3
I i tt£ 5i££»CiCC
B-ll
-------
25 JULY 1975
B-12
-------
26 JULY 1975
B-13
-------
27 JULY 1975
B-14
-------
28 JULY 1975
1 J',x,J V. ! \
KXXX
OD2D
OOnDDD DODO Afa
DODO&Q ODDD A 8
CD1X Ad
CC XXlQi B
c
CC sxxxx
B-15
-------
29 JULY 1975
CC2CCCCCCCCCCCCCC1 I I
B-16
-------
30 JULY 1975
rfi
\
B-17
-------
31 JULY 1975
B-18
-------
1 AUGUST 1975
CCC DO
C»C k
CC 00
es4i> ccc o
BPBBAAAAXXXA3A CC
BBB5XA4AA BBttAAA
A BBBXAA
6 5 B3XA
B A BXA
7X6A &X2A OC CH
Xx BBXA /_>c ?
u_7» -x s? *-«~^—<•-
* 8HAH
BBXXA CC 03
B3XAA 3 HO I ^
B8X?A C rB '.
BPAA CC l£E..A_
BAAA CC?C ;2
28 AA Ot 0
AA / CCO
1 / 1
X
B-19
-------
2 AUGUST 1975
B-20
-------
3 AUGUST 1975
5CCCCCCCC / C I
000 C ' '
CnoOODl) ;
AA4A 4 DOOfiO
XA3AAAAAiAOD30
C
BBB8BBBB4BHBRX8BB
C B IA / 00
C B JA 1 02
C B I A ) U
C B I 1 { 0 s
3C 3 U.-i n ^1
CXCCC2A T
B/ CX 0
ACC 0
A CC 0
A Cl
-^-^-.
060
ODD DOrjD
D7D 0?
CO 8AAAA 00
80 A C.TO/<
B6B4 CC
BB58 ba CCCC
i6BHB P CCCC3CCCCC
"T
.00 \
DODDDO l-
\ DDOOO j /
4AAA)tAAAAA3AAAAAAAADDC3DO/
t CnODOD /
0!>2
o
A | ,jb
A I ll
A CCtC~"o
A / CC1
I - - n
di^B A / X
63BBB A/ X
.^- BBBBB&B!i< i...
/
'l
1
A J
\
B-21
-------
4 AUGUST 1975
6AAAAAAAAWA7AAAAAA* 66S3b«8PK
s
* "\ B fc
A ! B 1C
A | b|c
A i Bi'c
X10U2 A B
DPA 4 5 PD
CC XLP B C 6
XXCX DSC 0
XXXCDO B C 0
1 2 1)03 C 0
BHC 3R *
BXC X C b
bCXDOC D
RHXCDX 0
2 C30DO D
B-22
-------
5 AUGUST 1975
B-23
-------
6 AUGUST 1975
B X06
BODODOO c D
DD70PD3 » 0
8000DDDOUO B ,---6-B-
u .-^ I" «
rF
-/ !
X/ CO
A c n
/ x c o
' X C 1
B-24
-------
7 AUGUST 1975
CC B
I > X7CCCCCC6C
• / B
I 1 « V 3
B-25
-------
8 AUGUST 1975
00 CC
! 0 / CC BB
1(0 JtCC BB
0\C
i i no c
) 0 1C I BB
t ', DD C -^1 B8
B-26
-------
9 AUGUST 1975
B-27
-------
10 AUGUST 1975
ccc
A4AAXXX
CC A3AAAAAAAAAA
!ccc
* cccT
3cs
CGC'CCC ] R B8BBBaP8ft3RB0BSB83B
I 4
B-28
-------
11 AUGUST 1975
cxx
50000 OOOUDODD3DO CXB
OOOBt'On«D 0000 XX /
DO XX
JO 1 /
020 XX| I" 1
DO Ix i
DO I XXX I \
00| CXX
X. on xx
DPDODO CC XX
030DnO DDOZD CC X /
nr,or. UK cic x /
coo ODD ccc yx
oo ccc-t"
B-29
-------
12 AUGUST 1975
B-30
-------
13 AUGUST 1975
B-31
-------
14 AUGUST 1975
0000 DO
onoo 0?
00 00
ay oo
0000 f 00
AA7 DO
OOD0300 A>»A AA 000
CCCCCCCCC4CCC ! CCCCC
cc ccccccdccccscccccccccc
cicoin /
.^CC CCCODO (
fcc\ cc 00 r
A CC < CCCIJPO i ,
AA CCC 1 «rCDDO I \
»5A CCC V ! CCCt-0
CCCXAA
CC?C AA
R
sBorj
VH6B ^V 6B5iaBdBB8e64R
)i B™*8
or
ODD
C1XD
CCC CX1D
CC CXDO
ccc ccxn /
cccc c»»t> /
cccc cxxn /
; -1 ,/cccccr—-«
:cc»cccc
-------
15 AUGUST 1975
cc p
» no
a cc oo
c oon
sa cc onooo
d CC 00*0000
88 CCC
B CCCC / 00
B CC3CC // 00
AA39 ^yt DD j
AAAA AJ f* X
—"V •fw' "-x—t—,
\ I AX l : 'i
i I ~~ - i i
B-33
-------
16 AUGUST 1975
« AXG
CC AXBR
C AAX6RB
CC AAAXbfiRB
CC AA5-XRBRhd
CCC BOXAAAAX
rccc
CC7CC ., ,
c DOAxn
CCC HDA5
CC
CC 07XB
CC OXX8
(. OXXP
cc oxxps
AA BBRRBB
J5AA RBR
AAAAAA Btl
B-34
-------
17 AUGUST 1975
B-35
-------
18 AUGUST 1975
030 0
onon 0
ODDO 00
CCCCCCC2CC DO /
D0 3CCC CCCCCDO /
06 ccc cci /
0000000*5^ C7CC CCCCC4CC x/
C C5CC
B-36
-------
19 AUGUST 1975
cccc n I )
CCCC D ; '• f
cccc r, ^_..i
cxc-
[KCCC
*"""x>, "„ Cc ! \
1 Fxxxxo c •
X \ ^^
5-37
-------
20 AUGUST 1975
AAA
AAAA
bSB CCCCCCCC3CCCC A3
CCCCCCCC A 0
BBBB CCCZXCC 0
A CCCCC
BUR A CCCC
—-x -. ; -i—T-
\ « »
* CCCC 0
C?CCC 0 S
CCCCC D I !
CCCC 0 I
CC1 I '
! I .-•
B-38
-------
21 AUGUST 1975
D1XX /
X»«
luuix „
! "*• TV
B-39
-------
22 AUGUST 1975
AAAA DO
AAAA on
AAA7 XIX
A CC XXX
ACCC XXX
ex xxx
CC A XXX
CCC A XXXX /
CC A XXX;
„«< ^ !-—-—-T--
B-40
-------
23 AUGUST 1975
B-41
-------
24 AUGUST 1975
B-42
-------
25 AUGUST 1975
(.000
00
DO ;tc*.\.^ •> j
ODD CCCX A I
0000 CCC \ A I
i 00004D CCCC /N A
DDD[iDOOOOOODDOOD
-------
26 AUGUST 1975
AA
AAA
AA BtB
AA B8 Pfli
AAA RB
AAA EC bB
AA CC BXCCC
AA CC BB CCCC
AA CCCBSB CCC 3
DOS | XtfOOOOOUOAA CC Bfl C»
AAAf AAAAAXXAfciiAAAAAAAAAAASOXX BH n
AftaAA DO / ! 6C BXOO I
"Sr-j u[> i I cc BB D5° D
0 / ' _C
PDOI
•C_B on
\ bB ., ., TlfS 'I
^BB
6BPRHXO
oRBB 00
BCXXCCCCCCCCiCCCCCCCCCT
j " ccjbB",. ",^ mfs MJT-I
iBB7>BBRbBRXXBB86 / \ J \ OUor ,1 ]
/ c i /•' i yLi
-A
*&
^
AAA D
AAAA D
AAA BtBR 0
I CSCCCC AA BB9B BRXBB
I CC AXCCCCCCXBB D BRBB
I CC AA BP CCCC 0
<£
-------
27 AUGUST 1975
S D3on\i
-Sji \JOODOOD
VI
-------
28 AUGUST 1975
X I
B-46
-------
29 AUGUST 1975
B-47
-------
30 AUGUST 1975
B-48
-------
31 AUGUST 1975
B-49
-------
Appendix C
MAXIMUM-HOUR OZONE
CONCENTRATIONS
C-l
-------
Maps of the maximum-hour ozone concentrations (ppb) in the study
are shown on the following pages for the period from 15 July to 31 August
1975. Isochrones, showing the hour (EST) at which the maximum occurred
are also plotted (as dashed lines) on the maps. The interpretation of
these maps is discussed in more detail in the body of this report.
C-2
-------
15 JULY 1975
50
+
72f
C-3
-------
16 JULY 1975
50
12-"
50^
72('
70°
C-4
-------
17 JULY 1975
18
70°
C-5
-------
18 JULY 1975
100
72"
C-6
-------
19 JULY 1975
70'
C-7
-------
20 JULY 1975
50
-h
70°
C-8
-------
21 JULY 1975
70
C-9
-------
22 JULY 1975
<
(
*\
1
1
1
f
;
f
/
»
t
/
1
i
i
|
V
f
^
4-
72r
C-10
-------
23 JULY 1975
70U
C-ll
-------
24 JULY 1975
12
'"S
C-12
-------
25 JULY 1975
70°
C-13
-------
26 JULY 1975
25
70°
C-14
-------
27 JULY 1975
{
-t-
70°
C-15
-------
28 JULY 1975
\
50
06-
12- -
C-16
-------
29 JULY 1975
-t-
C-17
-------
30 JULY 1975
C-18
-------
31 JULY 1975
100
70
C-19
-------
1 AUGUST 1975
100
C-20
-------
2 AUGUST 1975
75
- - 12
70"
C-21
-------
3 AUGUST 1975
+
T2r
100
C-22
-------
4 AUGUST 1975
70°
C-23
-------
5 AUGUST 1975
50
C-24
-------
6 AUGUST 1975
72f:
-t-
70C
C-25
-------
7 AUGUST 1975
25
12
(
n
I
i
06
I 06 12
^-^-.S, 25->fl8
> ^ ri~C\ i
C-26
-------
8 AUGUST 1975
C-27
-------
9 AUGUST 1975
C-28
-------
10 AUGUST 1975
50
C-29
-------
11 AUGUST 1975
50
'"S
70°
C-30
-------
12 AUGUST 1975
'"S
70'
C-31
-------
13 AUGUST 1975
70
C-32
-------
14 AUGUST 1975
06
70"
C-33
-------
15 AUGUST 1975
C-34
-------
16 AUGUST 1975
v^
72°
C-35
-------
17 AUGUST 1975
50
C-36
-------
18 AUGUST 1975
25
-t-
70C
C-37
-------
19 AUGUST 1975
\
JV/~*\*\
^T// 100 74°
-h
7(!v
C-38
-------
20 AUGUST 1975
-h
70°
C-39
-------
21 AUGUST 1975
50
-h
70°
C-40
-------
22 AUGUST 1975
25
<
(
25 \
/ 1
' 1
I
1
50
i
J
(
/
/
i
1
(
\
I
1
\
(
\
\
50
-------
23 AUGUST 1975
70°
C-42
-------
24 AUGUST 1975
25
C-43
-------
25 AUGUST 1975
70°
C-44
-------
26 AUGUST 1975
50
C-45
-------
27 AUGUST 1975
70°
C-46
-------
28 AUGUST 1975
25
<
/
"\
25 '
i
I
1
1
j
50,
f
J
(
/
1 i
I i
1
I 1
1 (
r*
( 50
1
1
1
\
(
\.
V
I
y
"* J
j"*4
75
x -~-u — -
7(r
C-47
-------
29 AUGUST 1975
50
C-48
-------
30 AUGUST 1975
70°
C-49
-------
31 AUGUST 1975
12
C-50
-------
Appendix D
VERTICAL OZONE CROSS SECTIONS
D-l
-------
During the course of this investigation, numerous vertical cross
sections of ozone concentration were prepared. Not all of these analyses
were used in the discussions presented in the text of this report. This
appendix reproduces those analyses not presented elsewhere. The symbols
used are discussed in the text.
D-2
-------
^
D-3
-------
i —
en
CNl
D-4
-------
D-5
-------
CD
O
33
80
eo
.3
W
M " O O
H 4-J O O
t-] 4-| O O
D-6
-------
D-7
-------
Q
8
PS
w
>
O
Q 03
H **
O
O
O
D-8
-------
D-9
-------
D-10
-------
f s
D-ll
-------
D-12
-------
D-13
-------
un
4- ,c
D-14
-------
D-15
-------
LO
r-~
en
CO
D-16
-------
D-17
-------
D-18
-------
LT>
r--
cn
CD
o o o o o o o
o o o o o o
o o o o o o
D-19
-------
LO
D-20
-------
D-21
-------
D-22
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing}
1. REPORT NO.
EPA 901/9-76-005
3. RECIPIENT'S ACCESSION-NO.
4 TITLE AND SUBTITLE
Ozone in the Northeastern United States
5. REPORT DATE
October 1976
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
F.L. Ludwig and E. Shelar
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Stanford Research Institute
333 Ravenswood Avenue
Menlo Park, California 94025
1O. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-02-2352
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Protection Agency
Region 1, Air Branch
Room 2113, J.F. Kennedy Federal Building
Boston, Massachusetts 02203
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The data from the summer 1975 Northeast Oxidant Study have been combined with
routinely collected weather and pollutant data to demonstrate that oxidant and its
precursors are transported for distances in excess of 100 km in the New York,
New Jersey, and southern New England region. Vertical cross sections of ozone con-
centration clearly show urban ozone plumes. During a daytime passage of a weather
front, strong ozone gradients are observed between the warm polluted air ahead of
the front and the clearer, cooler air behind; at any fixed site, concentrations
drop rapidly as the front passes and clean air replaces polluted. Nighttime frontal
passages do not show the marked ozone gradients found during a daytime frontal
passage. High nighttime ozone concentrations are associated with the simultaneous
occurrence of unusual vertical mixing and an ozone layer aloft. The ozone layer
aloft appears to be the remnant of daytime photochemical production in an urban plume.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Ozone
Atmospheric Transport
Photochemistry
Air Quality
New England
13. DISTRIBUTION STATEMENT
Release unlimited
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
276
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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