October 1982
METEOROLOGICAL FACTORS IN THE
FORMATION OF REGIONAL HAZE
ENVIRONMENTAL SCIENCES RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711
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METEOROLOGICAL FACTORS IN THE
FORMATION OF REGIONAL HAZE
by
James G. Edinger
and
Timothy F. Press
Atmospheric Sciences Department
University of California
Los Angeles, California 90024
EPA R806705010
Project Officer
George C. Holzworth
Environmental Sciences Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
ENVIRONMENTAL SCIENCES RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711
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DISCLAIMER
This report has been reviewed by the Environmental Sciences Research
Laboratory, U.S. Environmental Protection Agency, and approved for publica-
tion. Approval does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.
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ABSTRACT
The purpose of this research project was to determine the role of
meteorological factors in the formation of widespread areas of haze in the
eastern United States.
Three case studies were made: A summer haze episode, an off-season haze
episode and a non-haze episode.
Results showed that over the course of 2 or 3 days emissions from widely
separated sources such as St. Louis, Chicago, Cincinnati and Pittsburgh are
leafed together by vertical and horizontal shears and mixing by daytime con-
vection to form a dilution volume many hundreds to well over a thousand km in
extent and 2 or 3 km in depth. Almost all stations reporting haze during an
episode were confined to this dilution volume and most of these in that part
of the plume containing emissions that were 2 or 3 days old.
The dilution volume associated with the off-season episode was of about
the same magnitude as that of the summer case, but was shallower and horizon-
tally more extensive. Both of these 3-day haze volumes were much smaller than
the dilution volume associated with the non-haze case which blanketed almost
the entire eastern United States.
This report was submitted in fulfillment of Contract No. R806705010
Environmental Sciences Research Laboratory, Office of Research and Development
under the sponsorship of the U.S. Environmental Protection Agency. This
report covers a period from 8/1/79 to 12/31/81, and work was completed as of
12/31/81.
i i i
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CONTENTS
Abstract iii
Figures vi
Acknowledgment i*
1. Introduction 1
2. Conclusions 2
3. Method of Analysis 3
4. Case studies 8
Summer Haze 8
Off-Season Haze TO
Non-Haze Situation 12
5. Abbreviated techniques t 14
6. Haze-related Meteorological Quantities 16
References 5.8
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FIGURES
Number Page
1 Network of rawinsonde stations 18
2 Streamline maps, 00 GCT 25 February 1973, at 950 and 900 mb
levels 19
3 Streamline maps, 00 GCT 25 February 1973 at 850 and 800 mb
levels 20
4 Streamline map, 12 GCT 2 October 1974, 950 mb level 21
5 Streamline maps for 00 GCT and 12 GCT 3 October 1974, 950 mb
level 22
6 Streamline maps for 00 GCT and 12 GCT 4 October 1974, 950 mb
level 23
7 Technique for constructing the initial 24 hr dilution volume 24
8 Technique for constructing the subsequent 24 hr growth and
transport of already existing dilution volume. 24
9 Plume from St. Louis at 00 GCT 2 July 1973 resulting from 3
days of continuous emissions 25
10 Synoptic maps, 29 June 1973 26
11 Synoptic maps, 30 June 1973 27
12 Synoptic maps, 1 July 1973 28
13 Synoptic maps, 2 July 1973 29
14a Plume from Chicago at 00 GCT 2 July 1973 resulting from 3 days'
continuous emissions 30
14b Plume from Cincinnati at 00 GCT 2 July 1973 resulting from
3 days' continuous emissions 30
15a Plume from Pittsburgh at 00 GCT 2 July 1973 resulting from
3 days' continuous emissions 31
15b Consolidated plume containing 3 days' emissions from St. Louis,
Chicago, Cincinnati and Pittsburgh as seen at 00 GCT
2 July 1973 31
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Number Page
16a One-day-old emissions from St. Louis, Chicago,
Cincinnati and Pittsburgh, 00 GCT 2 July 1973. ' 32
16b Two-day-old emissions from St. Louis, Chicago,
Cincinnati and Pittsburgh, 00 GCT 2 July 1973 32
17a Three-day-old emissions from St. Louis, Chicago,
Cincinnati and Pittsburgh, 00 GCT 2 July 1973 33
17b Three-day consolidated plume from the four sources
and Birmingham's plume as seen at 00 GCT 2 July 1973 33
18 Consolidated3-day plume from St. Louis, Chicago,
. Cincinnati and Pittsburgh, 00 GCT 2 July 1973,
assuming mixing up to 700 mb level 34
19 Average horizontal area covered by the dilution volume
containing 24 hour of emissions as a function of
time since emissions began, 00 GCT 28 June 1973 to
12 Z GCT 1 July 1973 35
20 Position of cold front and distribution of haze,
00 GCT 3 July 1973 . 36
21 Synoptic maps, 26 February 1973 37
22 Synoptic maps, 27 February 1973 38
23 Synoptic maps, 28 February 1973 39
24 Synoptic maps, 1 March 1973 40
25a Plume from St. Louis at 00 GCT 1 March 1973 resulting
from 3 days' continuous emissions 41
25b Plume from Chicago at 00 GCT 1 March 1973 resulting
from 3 days' continuous emissions 41
26a Plume from Cincinnati at 00 GCT 1 March 1972 resulting
from 2 days' continuous emissions 42
26b Plume from Pittsburgh at 00 GCT 1 March 1973 resulting
from 3 days' continuous emissions 42
27a Consolidated plume containing 3 days' emissions from
St. Louis, Chicago and Pittsburgh and 2 days'
emissions from Cincinnati as seen at 00 GCT 1 March
1973 43
VII
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Number Page
27b One-day-old emissions from St. Louis, Chicago,
Cincinnati and Pittsburgh, 00 GCT 1 March 1973 43
28a Two-day-old emissions from St. Louis, Chicago,
Cincinnati and Pittsburgh, 00 GCT 1 March 1972 44
28b Three-day-old emissions from St. Louis, Chicago
and Pittsburgh, 00 GCT 1 March 1973 44
29 Synoptic maps, 2 October 1974 45
30 Synoptic maps, 3 October 1974 46
31 'Synoptic maps, 4 October 1974 47
32 Synoptic maps 5 October 1974 48
33a Plume from St. Louis at 00 GCT 5 October 1974
resulting from 3 days' continuous emissions 49
33b Plume from Chicago at 00 GCT 5 October 1974
resulting from 3 days' continuous emissions 49
34a Plume from Cincinnati at 00 GCT 5 October 1974
resulting from 3 days' continuous emissions 50
34b Plume from Pittsburgh at 00 GCT 5 October 1974
resulting from 3 days' continuous emissions 50
35a Consolidated plume containing 3 days' emissions
from St. Louis, Chicago, Cincinnati and
Pittsburgh as seen at 00 GCT 5 October 1974 51
35b One-day-old emissions from St. Louis, Chicago,
Cincinnati and Pittsburgh, 00 GCT 5 October 1974 51
36a Two-day-old emissions from St. Louis, Chicago,
Cincinnati and Pittsburgh, 00 GCT 5 October 1974 52
36b Three-day-old emissions from St. Louis, Chicago,
Cincinnati and Pittsburgh, 00 GCT 5 October 1974 52
37 Average 12 hour change in distance between pairs of
air parcels as a function of initial separation 53
38a Comparison of plumes constructed by the long and
short (approximate) methods, Pittsburgh, 00 GCT
1 March 1973 54
vm
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Number Page
38b Comparison of consolidated plumes constructed by
the long and short (approximate) methods, OQ GCT
1 March 1973 54
39 Comparison of plumes constructed by the long and
short (approximate) methods, Pittsburah, 00 GCT
5 October 1974 " 55
40 Time variation of: number of haze reports, H;
average 12 hour pair separation due to horizontal
shear, Al~^r > average 12 hour pair separations
due to _ vertical shear, AdTT ; average
wind speed, V; average rate of equivalent
potential temperature with height, dOe/JZ . 56
41 Map of area covered by statistical study. Lines
connecting rawinsonde stations identify the 66
station pairs. 57
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ACKNOWLEDGMENTS
We are indebted to Teddy Keller and Jeff Wright who carried out many of
the tedious and exacting calculations, constructions and map analyses in-
volved and to Joseph Spahr who skillfully managed the transformation of data
on magnetic tape to convenient computer print-out and graphic displays. And
special thanks go to our project officer, George C. Holzworth for his thought-
ful direction, assistance and encouragement.
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SECTION 1
INTRODUCTION
Extensive areas of hazy air covering major portions of the Eastern
United States have become a frequent summertime occurrence during the last
few decades. This regional haze, though well described by satellite observa-
tions and the conventional surface synoptic network, Lyons (1978), is not as
well understood as the smaller, meso-scale visibility blight associated with
plumes from individual point or area sources such as power plants and urban
complexes. A variety of models have been developed for these meso-scale
plumes. But, as is reported in a recent study by the National Academy of
Sciences, Middleton (1981), the modeling of regional haze is not nearly as
far advanced.
The present study is directed toward improving our understanding of the
meteorological mechanisms involved in the formation of such large volumes of
more or less uniformly polluted air. It is a diagnostic enterprise. Its pur-
pose is to provide information useful for constructing models of the regional
haze formation process.
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SECTION 2
CONCLUSIONS
Synoptic-scale motions revealed by rawinsondes and surface wind reports
combined with daytime vertical mixing motions up to the 800 or 700 mb levels
distribute emissions from widely separated continuous sources such as St. Louis,
Chicago, Cincinnati and Pittsburgh over a widespread area hundreds of miles
across and more than a thousand miles long in a period of 2 or 3 days.
The combined plumes (superposed dilution volumes) for these four cities,
constructed in accordance with the observed flow fields at the surface, 950 mb,
900 mb, 850 mb and 800 mb levels, coincide well with observed areas of wide-
spread haze.
When haze forms it tends to do so in emissions 2 or 3 days old and in mix-
tures of emissions from several locations.
Haze episodes appear to differ from non-haze situations in having smaller
dilution volumes, the result of smaller vertical and horizontal shears and
weaker winds.
The summertime haze episode examined occurred in the absence of persistent
(day and night) strong stable layers in the lower atmosphere. Strong low level
inversions were the rule at night, but during the day convection several kilo-
meters deep was typical with towering cumulus reported within the haze in a
number of locations.
Widespread haze areas occasionally develop in seasons other than summer
when there is considerably more stability in the lowest layer of the atmosphere.
Apparently in these cases mixing up to only about 1 or 2 kilometers is involved
as are somewhat stronger shears, resulting in shallower but horizontally more
extensive haze volumes.
Both vertical and horizontal shears significantly influence the horizontal
spreading of the dilution volumes with the vertical shear being the dominant
factor.
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SECTION 3
METHOD OF ANALYSIS
Air quality simulation models describing the long-range transport of air
pollution have been devised. Usually they are based on a requirement of mass
balance. The processes and mechanisms included are: emission, chemical trans-
formation, physical removal, turbulent diffusion and transport.
The air motions used in these models are observed atmospheric motions,
not air movement calculated from fundamental physical principles. Typically
they are the observed wind averaged over the depth of the polluted layer or
the wind observed at some standard level interior to the polluted layer, often
the 850 mb level, (Nordb et al., 1974; Eliassen et al., 1975; Pack et al.,
1978; Eliassen, 1980). A certain amount of observed detail in the wind field
is lost in the process of constructing vertically averaged wind fields or in
accepting the wind at any one level as being representative of the vertically
averaged flow. These neglected (dispersive^ motions are parameterized in the
models by eddy diffusion terms. Some air quality simulation models have taken
vertical wind shear within the polluted layer into account, notably Hidy et
al., (1978) and Veltishcheva (1979) for travel times out to 24 hours. In the
work reported here the winds at all levels within the polluted layer are used
to determine the long-range transport and dispersal of pollution out to 3
day's travel from the sources. It is done for a number of haze episodes
chosen from 30 years of record (1948-1978). The purpose is to discover the
meteorological mechanisms associated with the formation of these extensive
volumes of hazy air.
The analysis consists of constructing the previous 3-day history of the
hazy air. It is assumed that the responsible pollutants came from the major
air pollution sources in the eastern United States (large cities, power
plants, etc.). A 3-day dilution volume is constructed for each major source.
These individual dilution volumes overlap to form a conglomerate volume which
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contains all of the air which passed over the major sources. It may be
assumed that this large conglomerate volume would also contain air from any
other source, of whatever size, located in the area intermediate in location.
to the major sources.
The analysis makes use of the U.S. National Weather Services' surface
observational and rawinsonde network in the eastern United States (see Figure
1) to provide descriptions of the flow features involved in the transport and
dispersion of pollutant emissions. The streamline patterns shown in Figures
2 to 6 provide examples of the sort of mixing motions that can be resolved
using wind data from the synoptic observations network.
Figures 2 and 3 reveal the three-dimensional structure of several vor-
tices over the eastern United States, a definite continuity of pattern exist-
ing level to level from 950 to 900 to 850 to 800 mb. And Figures 4, 5, and
6 show the continuity in time over a three-day period of a large anticyclonic
vortex as it moves across the eastern United States. The range of eddy sizes
resolvable using the rawinsonde network is well illustrated by comparing the
small cyclonic vortex in southern Louisiana in Figure 3a with the large anti-
cyclone in Figure 5b which practically covers the entire eastern United States,
And a scan of the other streamline maps in these two map sets displays
eddies of many intermediate sizes within this range.
In reconstructing the extensive volume of hazy air the major sources of
emissions, i.e. the large urban centers, are taken as continuous point sources
Their nighttime emissions are treated as plumes moving with the surface winds
as reported on the 3-hourly surface synoptic maps. Their daytime emissions
are assumed to mix vertically by thermal convection through the lowest 2 or
3 km of the atmosphere and to move with the observed wind fields at each level
(50 mb intervals) within that layer. The shearing motions and translation
combined with the vertical mixing produce a dilution volume associated with
the particular source. The effects of horizontal motions on a scale smaller
than those described by the streamline analyses are neglected.
A number of techniques were tried before the method described below was
adopted as the one providing the best approximation of the volume of con-
taminated air produced by arrays of continuous point sources over periods of
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one, two and three days. The evolution moved from the approximate determina-
tions reported by Edinger (1980) to the more rigorous procedures represented
schematically in Figures 7 and 8.
Referring to Figure 7, at the initial instant, taken as 00 GCT, the
emissions of interest begin leaving the source. During the subsequent twelve
hours, nighttime, a plume is laid down at or near ground level. Its location
is determined by constructing a streak!ine from the three-hourly surface wind
maps. This streak!ine is constructed by connecting the 12 GCT end points of
the trajectories of the air parcels that passed over the source at times 00,
03, 06, 09 and 12 GCT. This plume is represented in Figure 7a. It is
assumed that vertical mixing motions are absent during this twelve hour in-
terval .
During the subsequent twelve hour, day-time interval, 12 to 00 GCT, mix-
ing motions distribute the emissions vertically through the layer from the
surface up to the 800 mb level. (The reasons for choosing 800 mb will be dis-
cussed later). It is assumed that at a time not far removed from 12 GCT the
surface plume develops vertically into a curtain which is subject to winds at
all levels up to 800 mb. Shears in the wind with height carry the emissions
at the various levels off in different directions. Figure 7b pictures the
streaklines extending from the source at five levels as seen at 00 GCT, 24
hours after emissions began. Figure 7c then describes the volume through
which the vertical mixing motions have distributed the first days emissions
by 00 GCT.
Figure 8 represents the further growth of this first day's 24 hour emis-
sions (dilution) volume during the next 24 hours due to shearing motions in
the vertical and another daytime period of vertical mixing. It also shows
the transport of this volume away from the source. In this case emissions
exist in diluted form at all levels up to 800 mb at the initial instant
(Figures 8a and 8c). At each level the perimeter of a polluted area (Figure
8b) is carried forward 24 hours by constructing trajectories originating at
significant points along each perimeter. The trajectories are not shown in
the sketch but the resulting transport and deformation of the perimeters are
indicated at each level ( Figure 8b). The dilution volume resulting from the
vertical mixing up and down of the pollution at these various levels is shown
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in Figure 8d.
To construct the dilution volume containing two days of continuous emis-
sions from the source one needs to construct the next day's 24 hour dilution
volume and add it to the volume shown in Figure 8d. These two 24. hour dilu-
tion volumes overlap and together constitute the two day polluted wake (48
hours dilution volume) of the continuous point source. In the case studies
to be discussed below these procedures were repeated for a third day's emis-
sions so that the dilution volume containing three day's emissions from a given
source were obtained. As an example refer to Figure 9. The shaded area re-
veals the horizontal extent of three day's continuous emissions from St.
Louis as seen at 00 GMT 2 July 1973.
The selection of the 800 mb level as the upper limit of the vertical
stirring and mixing followed unsuccessful efforts to define the top of the
mixing layer by inspecting the plotted radiosonde temperature and humidity
profiles at all stations in the eastern United States at both the 00 and 12
GCT times. Careful analysis of the profiles together with the associated
surface weather maps suggested that during typical summer haze episodes in
the eastern United States there is no extensive daytime stable layer in the
lowest few kilometers placing an upper limit on convective mixing. To the
contrary reports of towering cumulus frequently appear here and there within
the hazy volume suggesting that the mixing in some places reaches and exceeds
the 500 mb level. The upper limit to the vertical stirring and mixing is at
best ill-defined and irregular. In all of the case studies the top of the
stirred layer was assumed first to be at the 800 mb level. In one case, in
an attempt to improve the fit between the constructed haze volume and the
actual haze observations the level was raised to 700 mb with some improvement
of the fit with the observations. In the other case studies the fit with the
observed haze distribution was so good using an 800 mb level top to the mix-
ing that an adjustment in the level was considered unnecessary.
To select the major sources of emissions in the northeastern United
States the statistics appearing in EPA reports (1978) were used. In pre-
liminary case studies nine major urban industrial areas were chosen to .re-
present the sources of emissions. Each was treated as a point source.
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Several considerations resulted in the revision downward in the number of
these sources to just four: St. Louis, Chicago, Cincinnati and Pittsburgh.
They were: (1) Preliminary results suggested that it was emissions two or
three days old that were the major contributors to the haze and some of the
emissions from the cities along the Atlantic coast moved into the data void
over the ocean in less than three days preventing the completion of the
construction of their dilution volumes; (2) The two and three day dilution
volumes from individual point sources overlapped each other to such a large
extent that including sources more closely spaced than the four chosen would
have only a small effect on the size of their combined dilution volume; and
(3) A considerable saving in time and resources was realized by limiting the
number of sources to four.
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SECTION 4
CASE STUDIES
Summer Haze
This case study, 00 GCT 29 June 1973 to 00 GCT 2 July 1973, examines a
new relatively unpolluted air mass that has just invaded the source area from
the west following a cold front passage. (See Figures 10, 11, 12 and 13).
It terminates when the next front arrives from the west and begins to replace
the now hazy air mass over the northeastern United States. Presented here
is the dilution volume through which three days' emissions from St. Louis,
Chicago, Cincinnati and Pittsburgh are distributed as seen at 00 GCT 2 July
1973. This volume or plume is the consolidation of four, one from each of
the cities.
Figure 9 shows St. Louis' 3-day plume at 00 GCT 2 July 1973. It extends
all the way from the Mississippi River to the coast of New England and is
about 400 km wide. The undulating line within the plume is the streak!ine
for St. Louis at this time for the winds at the 850 mb level. It constitutes
the locus at 00 GCT 2 July 1973 of all air parcels that passed over St. Louis
at the 850 mb level during the three day period. The marks along the streak-
line indicate the locations of air parcels that passed over St. Louis at the
hours of 1200 and 0000 GCT. The streak!ine is included only to provide a
basis for comparing the plume as constructed here with model calculations in
which expanding puffs are arrayed along a streakline to form the plume. Such
a model plume compared with the plume in Figure 9 would in this instance
be displaced to the south and be narrow in the west and wide in the east, but
would, however, be of about the correct length.
Figure 14a shows the plume for Chicago at 00 GCT 2 July 1973. It
stretches out in a more northeasterly direction than St. Louis' and extends
beyond the edge of the map. It is somewhat narrower, averaging about 300
km in width. The 850 mb streakline again is indicated, its time marks
suggesting that most of the first day's emissions have passed the boundary of
the map. Apparently most of the Chicago dilution volume at this time is over
Canada.
Cincinnati's plume is shown in Figure 14b. Its orientation is even more
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northeasterly than Chicago's but because of Cincinnati's location to the
southeast of Chicago its plume exits the northern boundary of the map in
almost exactly the same place as Chicago's. The width is a bit more variable
than its predecessor's but averages about the same, somewhere between 300
and 400 km.
Pittsburgh's plume, Figure 15a, also exits the map near the northern
tip of Maine and falls completely within the Cincinnati plume. Apparently
about one half of Pittsburgh's emissions have moved beyond the map's bound-
aries at this time.
The superposition of these four plumes produces the dilution volume
shown in Figure 15b. It is a volume about 600 km wide extending from
Illinois 1500 km to the edge of the map in the vicinity of northern Maine
and for an undetermined distance beyond. This result suggests that synoptic
scale motions and diurnal vertical mixing up to the 800 mb level can distri-
bute the emissions from the four continuous point sources over a 1,000,000 ktrr
area in a period of three days. Black dots have been entered on the map to
designate stations reporting haze or smoke at this time so that comparisons
can be made between haze reports and plume location.
It is possible to indicate which part of this plume contains the one-
day old, two-day old and three-day old emissions. Figure 16a shows the part
of the plume containing material emitted during the last 24 hours, 1 July
1973. The plumes from the four sources have not yet merged. And very few
of the haze reports fall within these young (one-day-old) plumes. Figure 16b
indicates the location of the material emitted in the 24 hour interval, 30 .
June 1973, what was referred to above as two-day old emissions. This area
encompasses most of the stations reporting haze in the northeastern -United
States. It misses a few in New England. The dilution volume for the three-
day old emissions, those entering the atmosphere on 29 June 1973 from the
four sources, includes all the stations reporting haze in the northeastern
United States. (See Figure 17a). The results suggest that most of the haze
forms in air containing emissions which are two or three days old.
The consolidated plume described above does not explain the cluster of
haze reports in the vicinity of coastal Virginia and North Carolina. The
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technique used in constructing the plume was altered in two different ways in
an attempt to resolve this problem. First a search for an additional point
source was made using the emissions inventory in the EPA reports (1979). Un-
fortunately the contributions of such important sources as-Philadelphia, New
York and Boston could not be examined because of the lack of data'over the
adjacent ocean areas. Birmingham, Alabama seemed the most likely other candi-
date. So the dilution volume for this source was constructed. The results
are shown in Figure 17b. It failed. The three-day Birmingham plume does not
reach the coastal sections of North Carolina and Virginia. As a next try the
plume for the four sources was reconstructed allowing the mixing to extend to
the 700 mb level instead of just to the 800 mb level. The results are shown
in Figure 18. The additional spreading provided by flow patterns at these
higher levels extended the plume to the south and east to include the haze
reports in question.
The size of the area containing one day's emissions (sort of a 24 hour
urban puff) increased with time at all stations. Figure 19 shows a time
graph of the magnitude of these areas averaged over the four stations. The
areas are expressed in terms of equivalent radius, the radius of a circle
having the same area. The graph suggests that for the first 2^ days the peri-
meter of the dilution volume of one day's emissions from a single point
source moved radially out away from its centroid at something like 2 % ms" .
A new front moved into the midwest during 2 July 1973 and delivered a
new non-hazy air mass to Michigan, Indiana and Illinois. The old air mass
ahead of the front by 00 GCT 3 July 1973 had become even hazier. Figure 20
indicates the frontal position and the locations of the stations reporting
haze at 00 GCT 3 July 1973.
Off-Season Haze
This particular haze episode, 00 GCT 26 February 1973 to 00 GCT 1 March
1973, was chosen for study as an example of the off-season (not summer) occur-
rence. It begins 00 GCT 26 February 1973 with the arrival in the source area
of a fresh cold air mass. (See Figures 21,22,23 and 24). During the subse-
quent three day period ending at 00 GCT 1 March 1973 a ridge of high pressure
slowly moves across the eastern United States from west to east and by the
end of the third day an extensive area of haze has developed over the midwest
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that extends all the way from the Gulf of Mexico to the Great Lakes.
Figure 25a shows the plume from St. Louis at the end of the three day
period, 00 GCT 1 March 1973, resulting from continuous emissions from 00 GCT
26 February 1973 to 00 GCT 1 March 1973. The location of the one-two- and
three -day old emissions are indicated by the dashed, dotted and dot-dashed
curves within the plume. At this time the one- and two-day old emissions
are still in the vicinity of St. Louis but the three-day old emissions have
moved off to the south and have spread out horizontally to cover most of the
southeastern United States.
The three-day plume from Chicago is shown in Figure 255. It is roughly
the same size as St. Louis' plume but is displaced a little to the north and
west. However, most of the plume overlaps the St. Louis plume in such a way
that Illinois, Kentucky, Tennessee, Georgia, Alabama and Mississippi all are
exposed to a blend of both Chicago and St. Louis emissions at this time.
At the beginning of the three-day period, 00 GCT 26 February 1973, the
cold front had not yet passed Cincinnati. Consequently some of Cincinnati's
three-day old emissions were delivered to the pre-frontal air mass and some
to the new relatively unpolluted cold air mass behind the front. For this
reason only one- and two-day old emission volumes are seen in Figure 26a.
That portion of the emissions that entered the new air-mass on this, the
first day, has been neglected and the plume entered in the figure contains
only one- and two-day-old emissions.
The front had just passed Pittsburgh at 00 GCT 26 February 1973 so the
plume shown in Figure 26b contains a full three days' emissions from
Pittsburgh. It shows the same marked extension to the south due to the
rapid expansion of the three-day old emissions volume on its third day out.
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Figure 27a shows the consolidated plume resulting from the merger of
the four individual plumes. It covers a large area, most of the United
States east of the 95th meridian except the northeast states and southern
Florida. A few scattered haze reports exist west of the plume. Otherwise
all of the stations reporting haze fall within the constructed dilution volume.
Figure 27b shows the areas covered by one-day-old emissions. As in the
previous case study only a small fraction of the haze reports are found here,
9 of the 52 reports or 17%. The two-day-old emissions, as seen in Figure 28a,
encompasses 23 of 52 or 44% of the stations reporting haze. The remainder
of the haze reports are located predominantly in the gulf states, in that
part of the plume made up exclusively of three-day-old emissions, as seen in
Figure 28b. 44 of 52 haze reports or 87% fall within it.
The majority of the haze reports are at locations where a superposition
of emissions from different sources or different times occurs. In West
Virginia haze is reported where both two- and three-day-old emissions from
Pittsburgh appear together. In southwest Ohio both Cincinnati and Chicago
plumes are present at the haze reporting stations. The edges of the St.
Louis and Pittsburg plumes are close by. In the southern states there are
17 stations reporting haze within the overlapping Chicago and St. Louis plumes,
The six haze reporting stations in Illinois are in two- and three-day-old
emissions from Chicago and two-day-old emissions from St. Louis. It is
apparent that much of the haze forms in aged emissions from more than one
source and occurs sometimes at distances away from the sources that exceeds
TOGO km.
Non-Haze Situation
This is a study of a non-haze episode, 00 GCT 2 October 1974 to 00 GCT
5 October 1974. A synoptic situation was chosen that resembled as closely as
possible the typical haze episode but which, of course, generated no haze.
It is a post-cold frontal situation in which a large anticyclone covers the
entire eastern United States and over the course of three days, 2 October
1974 to 5 October 1974, gradually moves across the area to the east, as
shown in Figures 29, 30, 31 and 32.
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The plume generated for the emissions from St. Louis during these three
days is shown in Figure 33a. It is very extensive stretching all the way
from the Gulf of Mexico to southern Canada and from North Dakota to Pennsyl-
vania. Chicago's plume is about the same size, perhaps even more extensive
in the north-south direction and shifted a bit toward the east. See Figure
33b. Cincinnati's plume (Figure 34a) is a bit narrower but may be just as
large. Like the others it extends past the limit of the map over the Gulf
of Mexico. Figure 34b shows Pittsburgh's plume. It extends down the south-
east Atlantic coastline spreading both east and west at its southern extremity
to cover areas of unknown extent over the Gulf of Mexico and the Atlantic
Ocean.
The consolidated plume (Figure 35a) containing emissions from all four
sources covers most of the eastern United States extending from the 95th
meridian on the west to the 75th meridian on the east and including part of
southern Canada and an undetermined amount of the Gulf of Mexico and the
Atlantic Ocean. The dashed lines interior to the plume indicate the boundaries
of the St. Louis, Chicago, Cincinnati and Pittsburgh plumes.
Figures 35b, 36a and 36b show the area covered by the one-day-old, two-
day-old and three-day-old emissions respectively. The one-day-old plumes are
noticeably larger than those generated during the haze episodes discussed
above. And the two-day-old emissions cover an area so large that it compares
favorably with the largest of the three-day-old emissions volumes for the
haze episodes discussed earlier. The three-day-old emissions volume is ob-
viously much more extensive than its counterparts during the haze episodes.
How much larger is impossible to state since the plume extends beyond the map
border. No haze was reported at any time except at a station in southern
Canada at 12 GCT 4 October 1974. It is apparent that much larger dilution
volumes are generated in this no-haze case then in the haze cases.
13
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SECTION 5
ABBREVIATED TECHNIQUES
Constructing the plumes presented in each of the case studies involved
24 surface maps, 28 streamline maps and something like 1000 trajectories.
Before selecting such a difficult and elaborate technique a number of shorter
but more approximate methods had been attempted such as the one described by
Edinger (1980). And after the difficult long method had been applied to the
three case studies described above new attempts were made to abbreviate pro-
cedures without significantly degrading the results. Described now is an
abbreviated method that involves a great reduction in the number of traject-
ories required. Its results are compared with those of the long method.
In this method the first day's dilution volume was determined in exactly
the same way as it was in the long method. Then the centroid of this volume
(in the horizontal plane) was determined and entered at each level. 24-hour
trajectories, constructed at each level carried the centroids forward one
day. The perimeters of the volumes were reconstructed around the new posi-
tions. These new perimeters were the original ones expanded by amounts cor-
responding to the calculated average rate of separation of pairs of particles
as shown in Figure 37, where rates of separation are given as a function of
separation. In this case, separation is taken as the distance between sig-
nificant points on opposite sides of the perimeter. In all other respects the
long method was followed. The manner in which this rate of separation informa-
tion was determined will be described in the next section.
Figure 38a compares the 3-day plumes generated for Pittsburgh 00 GCT
1 March 1973 using the approximate and the rigorous method. The shaded
area designates the plume using the long procedure. The abbreviated method
produces a two-day dilution volume (dashed line labeled 2) that is perhaps
50% too large. On the other hand the three-day volume is more nearly the
right size, maybe 15% too big.
The combined plume from all four sources for 00 GCT 1 March 1973 as
determined using the abbreviated method is very nearly the same size as
that produced by the long method. Its location, shown by the dashed line in
Figure 38b, is pretty close although it is shifted toward the east and in
14
-------
doing so misses seven haze reporting stations in the west.
Pittsburgh's plume for the no-haze case is an example of a rather poor
fit between the results of the abbreviated and long methods. The comparison
is made on Figure 39. Both the two- and three-day old dilution volumes
differ markedly in shape. Obviously in this case the economy of tracking
only centroids comes at the expense of missing marked changes in the shape
and location of the dilution volumes.
The abbreviated method has not been adopted essentially because of its
insensitivity to shape and location changes in the dilution volumes. Its
determination of volume magnitude is pretty good and might be useful in appli-
cations where location is not as important as merely determining the dilution
potential of a given synoptic situation.
15
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SECTION 6
HAZE-RELATED METEOROLOGICAL QUANTITIES
The three synoptic situations involved in the case studies above provided
three quite different haze conditions. The first was a fairly typical summer
situation with the wide-spread haze area developing near the source areas and
then moving out to the northweast. The second was a winter episode of very
extensive haze that formed in the midwest. The last was an example of a large
cold autumn anticyclone moving across the eastern United States, wanning up as
it drifted southeastward in which no haze developed.
What meteorological quantities are associated with the occurrence and
non-occurrence of widespread areas of haze? In an attempt to answer this
question a number of quantities considered to affect dilution were computed
on a daily basis for six months running. The graph of these quantities ver-
sus time is shown in Figure 40.
As a measure of stability the vertical gradient between the 950 and 800
mb levels of the equivalent potential temperature was chosen.- The approximate
relationship 0 = 0 + 3.0 RH was used to compute the equivalent potential
temperature, where RH is the relative humidity expressed as a fraction. The
value plotted on the graph is the vertical gradient of the equivalent poten-
tial temperature, dG /dz, averaged over the 00 GCT and 12 GCT times and the
12 radiosonde stations indicated on Figure 41.
The following quantity was used to represent the effect of vertical shear
2 2 V2
Adi2 = [(u^t-Upt) + (v-|t-v2t) ] where subscripts 1 and 2 refer to dif-
ferent levels at the same station and u and v are wind speed components and t
is 12 hours. The plotted value is the average over the three 50 mb layers
from 950 to 800 mb averaged over all stations. It is a measure of the rela-
tive 12 hour horizontal displacement of a pair of air parcels originally se-
parated only in the vertical. A running 5 day mean was taken to smooth'the
trace.
16
-------
The effect of horizontal shear is given by the 12 hour change in hori-
zontal separation between horizontally separated pairs of air parcels as com-
puted using the following expression
o ? 1/2 9 9 1/2
A£12 = [(V-u^/ + (Vlt-v2t-£y/] - [£x(/ + £y/j
The subscripts refer to different stations and u, v and t are as defined
above. £ and £ are the horizontal components of the initial separation.
xo yo
Computations were made at each level individually and for each of the 66
pairs of rawinsonde stations represented by the lines between stations on
Figure 41. The value plotted is the average over all 66 pairs for the 800 mb
level. (The line of best fit for A£,2 plotted against the initial separation
produces the graph shown in Figure 37, that was used earlier in the approxi-
mate method of constructing perimeters.)
Translation, \T, was represented by the average resultant wind speed
averaged over all stations and all levels from 950 to 800 mb.
As a measure of the haziness of the day in question the number, H, of
surface weather stations reporting haze at 1800 GCT within the area circum-
scribed by the heavy line in Figure 41 was determined.
The results as shewn in Figure 40 reveal an obvious seasonal change in
the incidence of haze, a marked increase frcm winter to summer. Seasonal
trends in the meteorological variables are most pronounced in the stability
variable, the vertical gradient of the equivalent potential temperature. It
clearly shows a decrease in stability from winter to summer. This associates
summer, the hazy season, with the least stability, a result contrary to
common experience with meso-scale air pollution situations in which low level
stable layers are a requirement.
This poses a number of questions. Does low stability and the,associated
enhanced vertical mixing in some way contribute to the formation of summer
haze? Is a deep layer of mixing required to allow vertical shears to leaf
together emissions fron a number of large urban sources? Do emissions dis-
tributed through a layer of small stability 2 or 3 km deep have a longer re-
sidence time in the atmosphere than those trapped below a stable layer'based
at 1 or 2 km?
17
-------
The other meteorological variables are associated with the horizontal
spreading of emissions. Their seasonal changes are not so obvious but do
show some decrease in value from winter to summer. Generalizing, one might
conclude that winter dilution volumes are shallower but more expansive hori-
zontally than summer dilution volumes which are deeper but of smaller hori-
zontal extent. It is not clear which has the smaller volume and therefore
the highest average concentration of primary pollutants.
Husar (1979) has pointed out that in the last few decades summer, pre-
viously the time of best visibility, has become the season with the poorest
visibility. It is not likely that the meteorological patterns have changed
to that extent. Perhaps changes in the seasonal pattern of emissions has
tipped the scales, scales that are not too far from balance if the seasonal
change in dilution volumes is small.
The average values of the above meteorological variables were calculated
for the summer haze case study, 00 GCT 29 June 1973 to 00 GCT 2 July 1973.
They were averaged over all times, levels (up to 800 mb) and stations or
station pairs. The effect of hozirental shears expressed in terms of pair
a
-1
separation speed was about 1 1/2 ms . Vertical shears produced a 3 1/2 ms
pair separation speed. And the average translation speed as 5 ms
These results suggest that, in this case at least, vertical shears exert
a greater influence on the horizontal spreading of dilution volumes than do
horizontal shears. They also suggest that the expanding 24 hour dilution
volumes are advected away from their sources fast enough to separate from
them. That this is so can be seen in Figure 17a which shows the location of
the three-day-old 24 hour emissions volume separated from St. Louis and
Chicago for this case. That it need not always be so can be seen in Figure
25b for the other haze case study, where one-two- and three-day old dilution
volumes simultaneously cover the source, Chicago.
18
-------
(/I
c
o
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o
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"3
cr
S-
o
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cu
3
cn
18.5
-------
Figure 2b. Streamline map , 00 GCT 25 February 1973, at 9GO mb level
Figure 2a. Streamline map , 00 GCT 25 February 1973, at 950 mb level
19
-------
Figure 3b. Streamline map , 00 GCT 25 February 1973 at 800 mb level
Figure 3a. Streamline map , 00 GCT 25 February 1973 at 850 mb level
20
-------
21
-------
00 GOT 3 Oct 1974
a
Figure 5a. Streamline map for 00 GCT 3 October 1974, 950 mb level
12 GCT 3 Oct 1974
Figure 5b. Streamline map for 12 GCT 3 October 1974, 950 mb level
22
-------
00 GOT 4 Oct 1974
Figure 6a. Streamline map for 00 GCT 4 October 1974, 950 mb level
12 GCT 4 Oct 0974
Figure 6b. Streamline map for 12 GCT 4 October 1974, 950 mb level
23
-------
Figure 7. Technique for constructing the initial 24 hr dilution volume,
Figure 8. Technique for constructing the subsequent 24 hr growth and
transport of already existing dilution volume.
24
-------
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Figure 14a,
o
Plume from Chicago at 00 GCT 2 July 1973 resulting
from 3 days' continuous emissions.
Figure 14b.
Plume from Cincinnati at 00 GCT 2 July 1973 resulting
from 3 days' continuous emission.
30
-------
Figure 15a.
Plume from Pittsburgh at 00 GOT 2 July 1973 resulting
from 3 days' continuous emissions.
Figure 15b.
Consolidated plume containing 3 days' emissions from
St. Louis, Chicago, Cincinnati and Pittsburgh as seen
at 00 GCT 2 July 1973.
31
-------
Figure 16a. One-day-old emissions from St. Louis, Chicago,
Cincinnati and Pittsburgh, 00 GCT 2 July 1973.
Figure 16b. Two-day-old emissions from St. Louis, Chicago,
Cincinnati and Pittsburgh, 00 GCT 2 July 1973.
32
-------
Figure 17a. Three-day-old emissions from St. Louis, Chicago,
Cincinnati and Pittsburgh, 00 GCT 2 July 1973.
Figure 17b.
Three-day consolidated plume from the four sources
and Birmingham's plume as seen at 00 GCT 2 July 1973.
33
-------
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Figure 25a. Plume from St. Louis at 00 GCT 1 March 1973 resulting
from 3 days' continuous emissions.
Figure 25b. Plume from Chicago at 00 GCT 1 March 1973 resulting
from 3 days' continuous emissions.
41
-------
Figure 26a. Plume from Cincinnati at 00 GCT 1 March 1972
resulting from 2 days' continuous emissions.
Figure 26b. Plume from Pittsburgh at 00 GCT 1 March 1973
resulting from 3 days' continuous emissions.
42
-------
Figure 27a. Consolidated plume containing 3 days' emissions from
St. Louis, Chicago and Pittsburgh and 2 days' emissions
from Cincinnati as seen at 00 GCT 1 March 1973.
Figure 27b. One-day-old emissions from St. Louis, Chicago,
Cincinnati and Pittsburgh, 00 GCT 1 March 1973.
43
-------
Figure 28a. Two-day-old emissions from St. Louis, Chicago,
Cincinnati and Pittsburgh, 00 GCT 1 March 1972,
Figure 28b. Three-day-old emissions from St. Louis, Chicago and
Pittsburgh, 00 GCT 1 March 1973.
44
-------
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Figure 33a.
Plume from St. Louis at 00 GCT 5 October 1974
resulting from 3 days' continuous emissions.
Figure 33b. Plume from Chicago at 00 GCT 5 October 1974
resulting from 3 days' continuous emissions,
49
-------
Figure 34a. Plume from Cincinnnati at 00 GCT 5 October 1974
resulting from 3 days' continuous emissions.
Figure 34b. Plume from Pittsburgh at 00 GCT 5 October 1974
resulting from 3 days' continuous emissions.
50
-------
Figure 35a. Consolidated plume containing 3 days' emissions
from St. Louis, Chicago, Cincinnati and Pittsburgh
as seen at 00 GCT 5 October 1974
Figure 35b. One-day-old emissions from St. Louis, Chicago,
Cincinnati and Pittsburgh, 00 RCT 5 October"1974.
51
-------
,.»—•"* t
Figure 36a.
Two-day-old emissions from St. Louis, Chicago,
Cincinnati and Pittsburgh, 00 GCT 5 October 1974.
Figure 36b. Three-day-old emissions from St. Louis, Chicago,
Cincinnati and Pittsburgh, 00 GCT 5 October 1974,
52
-------
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i
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(& (T3
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•a: "3
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53
-------
Figure 38a. Comparison of plumes constructed by the long and
short (approximate) methods, Pittsburgh, 00 GCT
1 March 1973.
Comparison of consolidated plumes constructed by
the long and short (approximate) methods, 00 GCT
1 March 1973.
54
-------
55
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56
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57
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REFERENCES
Edinger, J. G., 1980: Analysis of Reduced-Visibility Episodes Over the
Eastern United States. Preprint Volume: Second Joint Conference on
Applications of Air Pollution Meteorology and Second Conference on
Industrial Meteorology. Published by American Meteorological Society.
Eliassen, A., 1980: A Review of Long-Range Transport Modeling. J. Appl.
Meteor., 19, 231-240.
Eliassen, A., and J. Saltbones, 1975: Decay and Transformation Rates for
SOp as Estimated from Emission Data, Trajectories and Measured Air
Concentrations. Atmos. Environ., 9, 425-429.
EPA (1979a) Protecting Visibility, An EPA Report to Congress EPA-450 5-79-
008, Office of Air Quality Planning and Standards, Research Triangel
Park, N.C.
EPA (1979b) Gridded Annual Air Pollutant Emissions East of the Rocky
Mountains, EPA-600/4-79-030, Environmental Sciences Research Laboratory,
Research Triangle Park, N.C.
Hidy, G. M., R. K. Mueller and E. Y. Tong, 1978: Spatial and Temporal
Distributions of Airborne Sulfate in Parts of the United States.
Atmos. Environ., 12, 735-752.
Husar, R. B., D. E. Patterson, J. M. Holloway, W. E. Wilson and T. G.
Ellestad, Trends of Eastern Haziness since 1948. Preprint Volume:
Fourth Symposium on Turbulence, Diffusion, and Air Pollution. Published
by American Meteorological Society.
Lyons, W. A., J. C. Dooley, K. T. Whitby, 1978: Satellite Detection of
Long-Range Pollution Transport and Sulfate Aerosol Hazes. Atmos-
pheric Environment 12: 621-631.
Middleton, J. T., 1981: On Prevention of Significant Deterioration of Air
Quality. Report by Committee to the Environmental Studies Board,
Commission on Natural Resources, National Research Council of National
Academy of Sciences.
Nordb, J., A. Eliassen, and J. Saltbones, 1974: Large-Scale Transport
of Air Pollutants. Advances in Geophysics, 18B, 137-150.
Pack, D. H., G. J. Ferber, J. L. Heffter, K. Telegadas, J. K. Angel!, '
W. H. Hoecker and L. Machta, 1978: Meteorology and Long-range Transport,
Atmos. Environ., 12, 425-444.
58
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Veltischeva, N. S., 1979: Paper presented at WMO Symposium on the Long-
Range Transport of Pollutants, Sofia, 1-5 October 1979, WMO Publ.
538 Ref. XI.3.
59
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1 REPORT NO.
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
METEOROLOGICAL FACTORS IN THE FORMATION
OF REGIONAL HAZE
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
James G. Edinger and Timothy F. Press
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Atmospheric Sciences Department
University of California
Los Angeles, CA 90024
10. PROGRAM ELEMENT NO.
CDTA1 0/Q3-1398 (FY-83)
17 CONTRACT,GRANT NO.
R806705
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Sciences Research Laboratory - RTF, NC
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final 8/1/79-12/31/81
14. SPONSORING AGENCY CODE
EPA/600/09
15. SUPPLEMENTARY NOTES
1,6. ABSTRACT
The purpose of this research project was to determine the role of meteorol-
ogical factors in the formation of widespread areas of haze in the eastern United
States. Three case studies were made: A summer haze episode, an off-season haze
episode and a non-haze episode.
Results showed that over the course of 2 or 3 days emissions from widely
separated sources such as St. Louis, Chicago, Cincinnati and Pittsburgh are leafed
together by vertical and horizontal shears and mixing by daytime convection to form
a dilution volume many hundreds to well over a thousand km in extent and 2 or 3 km
in depth. Almost all stations reporting haze during an episode were confined to
this dilution volume and most of these in that part of the plume containing emis-
sions that were 2 or 3 days olds.
The dilution volume associated with the off-season episode was of about the same
magnitude as that of the summer case, but was shallower and horizontally more
extensive. Both of these 3-day haze volumes were much smaller than the dilution
volume associated with the non-haze case which blanketed almost the entire eastern
United States.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b-IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
3. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report}
UNCLASSIFIED
21. NO. OF PAGES
70
20. SECURITY CLASS (This page)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
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