CONCEPUTAL DESIGN FOR A GULF COAST OXIDANT TRANSPORT
AND TRANSFORMATION EXPERIMENT
Workshop Proceedings and Recommendations
by
Walter F. Dabberdt William Viezee Hanwant B. Singh
Atmospheric Science Center
SRI International
333 Ravenswood Avenue
Menlo Park, California 94025
CONTRACT NO. 68-02-3752
Project Officer
Jason K. S. Ching
Meteorology and Assessment Division
Atmospheric Sciences Research Laboratory
Research Triangle Park, North Carolina 27711
ATMOSPHERIC SCIENCES RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711
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NOTICE
The information in this document has been funded by the United
States Environmental Protection Agency under Contract No. 68-02-3752 to
SRI International. It has been subject to the Agency's peer and admin-
istrative review, and it has been approved for publication as an EPA
document. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
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ABSTRACT
Thirty atmospheric scientists from government, industry, academia,
and the private research sector participated in a workshop held during
November 15-17, 1983, in Durham, North Carolina, to develop a conceptual
design for a study of ozone transport and transformation in the western
Gulf Coast area. The purpose of the study would be to better understand
the unique meteorology and chemistry of the region, and to effectively
adapt the EPA Regional Oxidant Model to that geographic area. Two
working groups focused on the problems of meteorology and atmospheric
chemistry, and- measurement needs and methods. A conceptual design was
developed for a five-year program that would include preparatory
studies, the 3-month primary experimental program, and data analysis.
The preparatory studies would consist of the collection and analysis of
all existing data, simulation modeling, smog chamber studies, instrument
development, and preliminary, limited field measurements. The primary
experiment would consist of an enhanced routine monitoring network
operated continuously, and frequent, intensive short-term experiments;
the geographical domain of the study would be about 300 km east-west and
800 km north-south. The routine monitoring would include boundary-layer
profiles (to 3000 m) of aerometric parameters by light aircraft, and
enhanced radiosonde coverage. The intensive studies would rely heavily
on sophisticated aircraft platforms such as doppler radar, UV and IR
lidar, backscatter lidar, and in-situ gas concentration and flux
measurements; gaseous and fluorescent particulate tracers would also be
used. The cost of the total program was estimated at 9.5 to 12.4
million dollars.
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CONTENTS
Abstract Ill
Illustrations. vi
Tables vii
Acknowledgements . ..... viil
1. Executive Summary . ....... 1
Introduction .......... 1
Working Group Considerations ... 2
Recommendations for a Conceptual Program Design ..... 10
2. Introduction 17
Objectives 17
Background 18
3. Working Group Considerations 53
Chemistry 53
Chemicals of Interest 53
Emissions Data. 56
Recommendations ...57
Meteorology 58
General 58
Identification of Relevant Phenomena. ........ 59
Design of Mesoscale Sea-Breeze Experiment . 62
Design of Medium Range Transport Experiment 64
Enhanced Surace and Upper Air Monitoring Network. . . 66
Long-Range Transport Experiment ...........67
4. Recommendations For A Conceptual Program Design. 69
5. Conclusions and Recommendations. . ........ 77
References .80
List of Participants 83
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ILLUSTRATIONS
Number Page
1 Projected area for intermediate transport experiment
(dotted lines) showing location of vertical planes
or "curtains" for horizontal flux measurements
(dash-dot lines) . 9
2 Conceptual program design and approximate costs 13
3 Workshop agenda 20
4 Example of typical synoptic-scale weather conditions
along the U.S. Gulf Coast during summer 24
5 Mean number of thunderstorms--annual 25
6 Three-dimensional air-parcel trajectories near the
surface and near 5000 ft predicted by LFM-II
for the 24-hour period of 19 July, 18:00 CST to
20 July, 18:00 CST 27
7 Three-dimensional air-parcel trajectories near the
surface and near 5000 ft predicted by LFM-II for
the 24-hour period of 22 August, 18:00 CST to
23 August, 18:00 CST 29
8 Gridded annual emissions (10 ton y~*); values
less than 40,000 ton y"1 not shown 30
9 Ozone trends in Houston 32
10 Backward boundary-layer trajectories 35
11 Ozone concentrations (pg ra~3), air trajectories
and sea level pressure distribution
for October 20, 1975 flight 36
12 Air parcel trajectories during July 14-20, 1977,
and ozone concentrations patterns ............ 38
13 Schematic illustration of the "dynamic" layer
structure of the regional scale model and the
phenomena each layer is designed to treat ... 46
14 Schematic view of sea-breeze regime
characteristic of Gulf Coast 60
15 Projected area for intermediate transport experiment
(dotted lines) showing location vertical
planes or "curtains" for horizontal flux measurements
(dash-dot lines) 65
16 Conceptual program design and approximate costs 75
vi
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TABLES
Number
1 Trace chemicals in air
2 Trace chemicals in liquid water and
particulate matter .. ......... 4
3 Inert tracers of interest 4
4 Preparatory studies 11
5 Ozone (ppb) trends in Louisiana 33
6 NMHC/NOX ratio for ambient air 41
7 03/PAN Ratios in Los Angeles, Hoboken,
St. Louis, and Houston 42
8 Important trace chemicals to be measured 43
9 Platforms data centers operated
during PEPE/NEROS 49
10 Air quality and meteorological parameters
available for each platform ........ . 50
11 Schedule of missions flown 51
12 Trace chemicals in air ............. 54
13 Trace chemicals in liquid water 55
14 Particulate matter . 55
15 Inert tracers of interest 56
16 Preparatory studies 69
vii
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ACKNOWLEDGMENTS
Dr. Jason Ching of the Meteorology and Assessment Division (MAD), U.S.
Environmental Protection Agency contributed substantially through his
enthusiastic encouragement and technical expertise. Dr. John Clarke
and Dr. Fran Pooler , also of MAD, contributed significantly in the
technical planning and execution of the workshop. Special thanks to Dr.
William Pennell, Battelle-Pacific Northwest Laboratories, and Mr. Gary
Tannahill, Exxon Company, U.S.A., who chaired the meteorology and
chemistry working groups, respectively. Also, special thanks to Ms.
Dorothy Sevela for helping with pre-conference arrangements and typing
the report manuscript.
On assignment from National Oceanic and Atmospheric Administration
(NOAA).
viii
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SECTION 1
EXECUTIVE SUMMARY
INTRODUCTION
Regional-scale episodes of photochemical smog have been documented
in the Northeast and Midwest United States. The transport of ozone and
oxidant-precursor emissions from the industrial areas of the Gulf Coast
to other areas of the United States, particularly the Northeast and
Midwest, may exacerbate the smog problems in those areas. The extent of
this transport is unknown.
This document presents the output of a workshop held in Durham, NC,
November 1982, on a conceptual design for a Gulf Coast transport and
transformation experiment. It outlines a field study designed to
quantify the amounts of material injected into the large-scale flow and
the amount remaining in the Gulf Coast area. Results of the field study
will help to describe such transport, and aid in the application of the
Regional Oxidant Model (ROM) to the Gulf Coast area to perform
sensitivity studies on the regional transport of ozone and precursors.
The basic objective of such a Gulf Coast oxidant study would be to
"investigate the unique meteorological and chemical processes in the
Gulf Coast region that must be understood to effectively adapt the EPA
Regional Oxidant Model to that geographic area." Some of the more
important and relevant processes to be studied include:
• Three-dimensional transport by land- and sea-breeze circulations
• Transport and diffusion under near-stagnation conditions
• Ozone (and precursor) venting or mixing by precipitating and
non-precipitating cumulus clouds
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• Washout of nitrogeneous and oxygenated species and the Impact on
oxidant production
• Parameterization of the over-water atmospheric surface layer
• Large-scale inflow and outflow to/from the region
• Investigation of anomalously low values of the ratios of
NMHC/NOX and PAN/03 and the concentration of PAN
• Nocturnal NOX removal and transformation mechanisms.
Thirty atmospheric scientists from government, industry, academla,
and the private research sector participated in a three-day workshop to
develop a conceptual design for the field study. Two working groups
were formed, focusing on problems of meteorology and atmospheric
chemistry, and measurement needs and methods. The conceptual design
consisted of an interrelated series of studies that would have a high
probability of: (1) determining which processes are most important in
controlling regional oxidant concentrations, and (2) providing data to
quantify the transport and transformation mechanisms involved, so that
(3) a data base would be available for diagnostic evaluation of ROM,
with subsequent improvements made to the model.
WORKING GROUP CONSIDERATIONS
The atmospheric chemistry working group addressed and prioritized
the trace chemicals that must be measured during any planned Gulf Coast
oxidant study. The exact platforms to be employed, frequency of
measurements, and spatial density of monitoring stations were issues
which could not be considered by the working group since a detailed
design of the Gulf Coast study did not exist. The group, therefore,
focused on broader considerations dealing with trace chemical
measurements and emissions data requirements.
Trace chemical measurements (both gas and liquid phases) were
identified and ranked according to the importance and feasibility of the
measurements. Tables 1-3 provide a listing of the species of interest
and rank these by the above criteria. Among the nonchemical parameters,
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TABLE 1. TRACE CHEMICALS IN AIR
*
Chemicals
03
NO
N00
2
PAN
HN03
CH4
CO
THC
HC.
i
RCH=0
H202
HN02
N2°5
HO
H02
R02
N03
NH3
so2
Rankf
A
A
A
A
A
A
A
A
A
A
A
B
B
B
B
B
B
C
C
1
1
1
2
3
1
2
2
2
3
3
3
3
3
3
3
3
2
1
t
Measurement of Liquid water
content and UV radiation
(300-500 nm) were ranked as
A2 and Al respectively.
Key:
A = important measurement
B = desirable measurement
C = optional measurement
1 = measurement technique
is state-of-the-art
2 = measurement methods not
yet fully developed or
only applied with difficulty
3 = measurement methods
currently unacceptable
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TABLE 2. TRACE CHEMICALS IN LIQUID WATER AND PARTICIPATE MATTER
Chemicals
N03
ROH
RCH=0
HC..^ (vac)
°3
H2°2
Rank
Cloud^
Water
B
C
A
C
C
A
Rain ^
Water
B
C
C
C
C
B
Aerosols
B
C
A
C
C
B
Particulate
Matter
Elements
S04
N03
NH,
Rank
C 1
C 2
B 2
C 2
Measurements are at levels of difficulty of 2-3.
TABLE 3. INERT TRACERS OF INTEREST
Tracer Type
Tracers of opportunity
Injected tracers
Species
7Be
33P
Fluorocarbons
Elements
Methane-21
Perfluorocarbons
SF6
Rank
C 2
C 2
A 1
C 1
A 2
A 2
A 1
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liquid water content and ultraviolet radiation measurements were highly
emphasized. It was generally believed that gas-phase processes provide
the dominant source for ozone formation and hence constitute the most
important measurements. The role of aldehydes and I^C^ in liquid phases
is not well understood but may be potentially important (Table 2).
Nitrate measurements in the aqueous phase (Table 2) were ranked high
because of the sink potential of the aqueous phase for NC^ and HNO-j.
Despite the recognized importance of gas-phase chemistry, the working
group felt that liquid-phase processes may play a more important role in
the wet and humid environment of the Gulf Coast as compared to
relatively dry regions.
Tracers of opportunity were suggested, but only chlorofluorocarbons
were considered high priority. Be or ^P stratospheric tracers were
ranked low due, in part, to the complexity of data interpretation.
Injected speciality tracers are unique tools to study long range
transport, but are to be measured only when a planned tracer experiment
is underway.
Recommendations and guidelines were developed for the emissions data
required for input to ROM or other photochemical models; these
included:
(1) A 2-km x 2-km gridded inventory of emissions
(2) Hourly temporal resolution, i.e., diurnal and seasonal
emission patterns
(3) Vertical resolution of emission sources
(4) Source types (stationary, mobile, area, point, natural, etc.)
(5) Natural VOCs on land
(6) Gulf Coast water emissions.
It was felt that some sensitivity studies should be performed with
existing models to get an idea of the importance of source emissions,
particularly natural VOCs of land or water origin. One of the most
pernicious problems is the very nature of the emissions inventory. In
principle, emissions data (temporally and spatially resolved) should be
available for individual species. This is not possible in practice.
Current models can use groups of chemicals (alkanes, alkenes, and
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aromatics) and this is a desirable speciation of emission data. It was
felt, however, that carbon bond mechanisms may be employed in a future
version of ROM. It does not appear feasible that emissions information
can be obtained in a format directly applicable to the carbon bond
model. It is assumed that some algorithms must be devised to solve this
problem.
The meteorology working group discussed a wide range of atmospheric
circulations and phenomena which were judged to be potentially important
in determining oxidant concentrations in the Gulf Coast and interior
regions downwind; these features included
• Land and sea-breeze circulations
• Convective cumulus cloud venting
• Synoptic-scale transport and disturbances
• Surface deposition and destruction
• Synoptic-scale subsidence
• Low-level jet
• Characteristics of planetary boundary layer over the Gulf
of Mexico.
On the basis of these discussions, the working group made
recommendations and developed conceptual designs for a mesoscale
sea-breeze experiment, a medium-range transport study, and an enhanced
routine monitoring network. However, a long-range transport (-1000 km)
component was not recommended. Within the budgetary guidelines
presented by EPA, it was concluded that the resources could more
effectively be used to undertake the other components, and that
long-range experiments would best be undertaken as an adjunct to or in
conjunction with separate studies conducted by other agencies.
The working group considered two possible experimental designs for a
mesoscale sea-breeze experiment, finally integrating the two into a
single study; the two designs are as follows:
(1) A spatially fixed (Eulerian) box-budget study to quantify the
net transport into or out of the sea breeze/emission area
(2) A tracer (Lagrangian) experiment to study the role of the sea
breeze in recirculating pollution.
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The Eulerian box-budget experiment would be carried out in a
rectangular area, 300 km north-to-south, and 200 to about 400 km
east-to-west. This area would include the sea-breeze circulation and
coastal emission sources. The Houston-Galveston-Lake Charles area was
considered most suitable for this program. The box would be 3 km deep
(the average depth of the sea-breeze).
A wide variety of in situ and remote measurement systems were
considered necessary for successful completion of the study; these
included airborne backscatter and differential-absorption laser radar
(lidar) systems, airborne doppler radar and ground-based doppler sodar,
in situ aeroraetric sampling aircraft, and meteorological profiling
systems. Even with these systems, it was concluded that a budget study
of the box cannot be readily done by closing the box with observations.
It was, therefore, recommended that available observations be used in
conjunction with a modeling approach to estimate pollutant fluxes within
and through the box.
The release of multiple tracers for a sea-breeze experiment was also
considered. Tracers should be released near ground-level on the coastal
side of the convergence zone and inside the convergence zone. Injection
of tracers in cumulus clouds should be carried out to study
recirculation of pollutants by the sea-breeze, and cloud venting in the
sea-breeze front.
The sea breeze program should also include studies of venting by
cumulonimbus and cumulus congestus clouds that form in the afternoon
inland along the sea breeze convergence zone. Because of the lengthy
extent of the zone roughly parallel to the coastline and its high
frequency, it may be an effective mechanism for transport of ozone
precursors out of the Gulf Coast emissions source region, thereby
possibly minimizing local ozone formation and impacting regions further
downwind. It was recommended that inert gas tracers would provide a
useful method for quantifying the effects of cumulus-cloud venting. One
or more tracers released at or near the surface in the convergence zone
would be measured aloft by aircraft, both in the boundary layer and at
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the level of outflow near the cloud tops. For practical reasons,
cumulus congestus or small cumulonimbus clouds would be preferable as
£heir tops are within the capabilities of available research aircraft.
An intermediate-range oxidant transport experiment would involve a
total time of 30-48 hours for atmospheric measurements, and would cover
a horizontal distance of 400-500 km from the Gulf Coast emissions
source. This distance would take the experiment from the
Houston-Galveston area northward into Oklahoma and Arkansas, and would
focus on ozone and its precursors, and on released tracers. The
intermediate transport experiment would take place under conditions of
synoptic-scale southerly flow, preferably during the occurrence of a
nocturnal low-level jet.
During daytime and possibly during nighttime, convective cumulus
clouds can be expected to develop in the southerly flow of warm, moist
(mT) air. Thus, cumulus convective transport will be part of the
experiment. Figure 1 shows the projected area (stippled boundaries) for
an intermediate range (high-level and low-level) transport experiment.
Measurements are recommended across three vertical planes or "curtains"
(dash-dot lines in Figure 1). Tracers and tetroons should be released
at a low level (e.g., 1500 m in the mixed layer under the clouds), and
at a high level (e.g., at the level of the cumulus clouds). Measurements
would be made for the purposes of
• Computing fluxes out of the mixed layer and out of the cloud
layer
• Validating parametric schemes for cumulus convection transport
in ROM.
Tracer releases in the low-level jet were also recommended in order
to define the transport characteristics of this phenomenon. It was
agreed, however, that more knowledge and information on the occurrence,
location, and spatial extent of the low-level jet is needed before a
detailed plan can be designed.
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100° W
30° N
• '^
A__iiizzi£ 7 —\"
• wi^~% • • * • • * * * ** * I • * i * * *
"s^—< ' »
. FT WORTH »%
k^ SHREVEPORT/ JACKSON
% " ' _K
\
®'
SAN ANTONIO _ HOUSTON •
is-
NEW ORLEANS
^
I
MOBILE
• . • I • «
Figure 1. Projected area for intermediate transport experiment (dotted lines) showing location of
vertical planes or "curtains" for horizontal flux measurements (dash-dot lines).
The work group recommended that an enhanced network of surface and
upper-air observations be operated throughout the time period that the
mesoscale sea-breeze and intermediate transport programs are conducted.
The network area was outlined as extending from Fort Worth, Texas,
eastward to the Alabama border (about 300 km), and then 600 km southward
to a point approximately 200 km offshore. The existing National Weather
Service (NWS) radiosonde stations within the network area (about 6)
would be enhanced by 5-6 additional stations, including two stations
offshore to double the spatial resolution of the NWS network. Vertical
profiles of ozone would be obtained to 700 mb (10,000 ft msl) by
single-engine aircraft at each of 12 available radiosonde locations.
The network would be operated for a 3-month period.
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The benefits of the enhanced observational network would be:
• Provision of offshore data
• 6-hour resolution on radiosonde ascents
• Vertical profiles of air quality obtained three to four times
per day.
An important element of the routine monitoring network should be
the acquisition of satellite, radar, and lightning data from existing
systems for the purposes of enhancing the definition of mesoscale
circulations and convective phenomena. Although these systems (for the
most part) are in place and operating, special attention should be
devoted to the archiving of these data (not routinely done). Satellite
data should include visible and infrared observations from both
geostationary and polar-orbiting satellites. High-resolution,
false-color radar displays are available from several commercial sources
using data from National Weather Service radars.
Operational lightning detection networks (e.g., the lightning
position and tracking system available from Atlantic Scientific Corp.,
Melbourne, FL) already cover most of the Gulf Coast area and should
blanket the study region on the time frame of the Gulf Coast oxidant
program.
RECOMMENDATIONS FOR A CONCEPTUAL PROGRAM DESIGN
The two working groups recommended that some preparatory research
and development efforts should be undertaken in addition to the
principal components of the major study itself. As summarized in Table
4, the preparatory efforts comprise both modeling and data analysis
studies, and experimental studies or hardware development. In some
cases, these efforts are not unique to the Gulf Coast oxidant study or
are already being actively pursued, and these efforts are not included
in the conceptual experimental design presented later. In many cases
the study would be seriously affected in the event the efforts are
either unsuccessful or not completed in time. The working groups
provided subjective cost estimates which should be considered indicative
of the order of magnitude of each effort. Each preparatory study is
10
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TABLE 4. PREPARATORY STUDIES
Description
Estimate of
Cost ($000)t
Priority
Modeling and Data Analysis:
- collection, analysis and interpretation of
existing air quality and meteorological data
- application of Urban Airshed Model to Houston
- evaluation of Regional Oxidant Modelf (being
done by USEPA for northeastern states)
- ROM sensitivity study to evaluate impact of
natural hydrocarbon emissions*
• Experimental Studies and Hardware Development:
- develop gaseous aldehyde measurement
techniques (surface and airborne)^
- hydrogen peroxide instrument developmentf
(work ongoing elsewhere)
- smog chamber studies of Gulf Coast
atmospheres
- in-cloud chemistry studies (coordinate with
on-going studies)f
- continued development/improvement of airborne
wind-finding doppler radar (work on-going
elsewhere)t
- improvements in tracer technology, e.g.
fluorescent dye, perfluorocarbons, tetroons,
reactive tracers (work on-going elsewhere)
- improvements in remote measurement of ozone,
profiles by UV and IR DIAL (ongoing elsewhere)f
- exploratory, limited-duration mobile (air-
borne) aerometric measurement program and
data analysis (limited)
- enhanced routine monitoring network for ozone,
hydrocarbons, and PEL structure
200-300 (p)
50-100 (g)
nc
nc
100-200 (p)
50 (p)
300 (p)
<500 (p)
nc
nc
nc
500-1000
1250-1500
M
H
H
M
M
M
M-H
M-H
H
H
•t
L-H
f
H = high; M = medium, L = low priority
p = contract research; g = USEPA study
Study is not unique to Gulf Coast
Priority is constrained by availability of funds.
11
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also given a subjective priority ranking. In general, the high-priority
efforts are essential for a high-quality Gulf Coast oxidant study, while
the moderate-priority efforts are highly desirable. A low priority
indicates that the results would be very useful, but not essential.
The overall conceptual program design (Figure 2) is divided into
four elements:
(1) Preparatory analyses
(2) Preparatory measurement studies
(3) Gulf Coast regional oxidant transport study
(4) Reporting.
In the preparatory-analysis phase, currently available air quality
and meteorological data from the study region would be compiled to
create a comprehensive data base. The data would be analyzed to provide
a better understanding of temporal and spatial variations of oxidant
throughout the region, and to develop an improved understanding of the
importance of (for example) moisture, synoptic-scale wind flow, long
range transport, land-sea breeze circulation, and low-level jet in the
formation of high oxidant concentrations. Additionally, a photochemical
simulation model would be applied to the Houston metropolitan area as a
test of the hypothesis that oxidant concentrations are anomalous or that
the combination of relatively high HC-to-NOx ratio, high ambient
humidity, and intense sunlight result in chemical conditions that are
different from other regions.
As part of the preparatory measurement/study phase, an enhanced
routine monitoring network would be established and operated for three
months to provide a comprehensive Eulerian aeroraetric data base. The
purpose would be to gain an improved understanding of oxidant formation
and transport, and to develop a detailed'research plan for the primary
experimental program. The ERN* would include aerometric soundings by
light aircraft at each of 12 radiosonde locations. An exploratory
mobile sampling and data analysis task is also recommended to refine and
coordinate mobile sampling methods and to provide a limited data base
ERN - Jjnhanced Routine Monitoring Network,
12
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o
u
x
2
Q.
Q.
re
T3
to
I
i
o
re
u
o
O
fN
2
§>
13
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for the purpose of optimizing the use of the various aircraft in the
primary study. This limited sampling program would focus on developing
sampling strategies, and on obtaining limited data for the mesoscale
land/sea breeze, cloud venting, and medium-range transport experiments
that are anticipated to be conducted later during the primary field
study. Lastly, smog chamber studies would be conducted to simulate
photochemical oxidant production unique to the precursor mixture of the
Gulf Coast, and to explore the possible effects of high relative
humidity.
A preliminary, detailed research plan and study design would be
developed for the experimental and analysis phases of the principal Gulf
Coast oxidant transport and transformation study. The plan would
specify numbers and types of airborne platforms, instrumentation
specifications, and sampling strategies and protocols. Also specified
would be comprehensive specifications for the surface aerometric
network, including parameters for measurement, analytical methods, site
locations, sampling frequency, data processing and so forth. All
aspects of tracer applications in the mesoscale and medium-range
transport studies would also be delineated, such as tracer-types, and
release, sampling and analysis methods. Scheduling of the intermediate
range transport case-studies would also be addressed, including
definition of criteria for determining when or where experiments are to
be conducted, and for contingency plans in the event meteorological
conditions are not optimum for the fulfillment of the primary study
objectives.
The three-month primary field study of oxidant transport and
transformation would have two major aspects: (1) operation of the
enhanced routine monitoring network, and (2) short-term case studies of
mesoscale and medium—range transport and transformation. The short—term
case studies would consist of (1) mesoscale studies of pollutant
transport and oxidant production within the domain of the land/sea
breeze circulation and (2) medium-range (ca 400-500 km) studies of
oxidant transport out of the Gulf emissions source region. Cloud
venting studies would be an integral component of the mesoscale
14
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experiments. The raesoscale studies would constitute the majority of the
10 case studies recommended, and would rely heavily on a full complement
of airborne platforms in addition to the use of gas tracers with
airborne and surface in situ sampling. Each study would cover a 30-hr
period. On the order of three medium-range transport experiments are
contemplated. Analysis of the processed data would address several
basic issues: (1) relation of ozone formation to the precursor mix of
the region, (2) impact of high humidity, (3) role and significance of
cumulus clouds in venting ozone or precursors out of the boundary layer,
(4) nature and significance of medium-range oxidant and precursor
transport into and out of the region, (5) role of land/sea breeze
circulation in production of locally high ozone concentrations, and (6)
three-dimensional spatial distribution of ozone on episodic days.
The overall program could be accomplished in about five years at an
estimated cost that ranges between 9.5 and 12.4 million dollars. In the
event that the preparatory field studies (i.e., ERN and exploratory
mobile sampling) are deleted from the program, the estimated cost range
would decrease to about 7.75 to 9.9 million dollars; the schedule might
be compressed by approximately six months. The working groups did not,
however, recommend the deletion of the preparatory field studies. On
the contrary, they were highly recommended as necessary to the ultimate
success of the program.
Finally, the Gulf Coast oxidant study should seek to integrate and
coordinate its activities with those of other major atmospheric studies
planned for the same time frame and geographic domain. The multi-agency
national STORM program (STormscale Operational and Research Meteorology)
appears to be one such potentially viable raesoscale study. STORM has
been proposed by a steering committee composed of 13 representatives of
member institutions of the University Corporation for Atmospheric
Research (UCAR), and would be supported at an annual cost of 60 to 120
million dollars per year for 10 years, (UCAR, 1983). A second candidate
program is a projected 100 million dollar acid precipitation study
(MATEX) of long-range atmospheric transport and transformation being
considered by the Electric Power Research Institute. A MATEX design and
15
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feasibility study is currently underway, and should be completed later
this year. Preliminary indications are that it could overlap the
geographical domain and schedule of the Gulf Coast oxidant study.
Integration of the Gulf Coast oxidant study with programs like STORM and
MATEX should be pursued because of the benefits of technical synergism
and cost savings that would result.
16
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SECTION 2
INTRODUCTION
OBJECTIVES
As stated by the U.S. Environmental Protection Agency (EPA), the
basic objective of a Gulf Coast oxidant transport and transformation
experiment would be "to investigate the unique meteorological and
chemical processes present in the Gulf Coast region that must be
understood to effectively adapt the EPA Regional Oxidant Model (ROM) to
that geographic area." Examples of the more important, relevant
processes that require study include the following:
• Three-dimensional transport by land- and sea-breeze circulations
• Transport and diffusion under near-stagnation conditions
• Ozone (and precursor) venting or mixing by precipitating
and non-precipitating cumulus clouds
• Washout of nitrogeneous and oxygenated species and its
impact on oxidant production
• Parameterization of the over-water atmospheric surface layer
• Large-scale inflow and outflow to/from the region
• Investigation of anomalously low values of the ratios of NOX/NMHC
and PAN/03 and the concentration of PAN
• Nocturnal NOX removal and transformation mechanisms.
17
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BACKGROUND
General
The western portion of the U.S. Gulf Coast has several unique
meteorological and (air pollutant) emissions characteristics that must
be better understood in order to project or control atmospheric
concentrations of ozone. The high concentration of refining and
petrochemical industries along the Louisiana and northeastern Texas
coasts results in a higher-than-normal ratio of atmospheric
concentration of hydrocarbons to oxides of nitrogen; at the same time,
PAN (peroxyacetylnitrate) concentrations are significantly less than
those found in other source regions around the country. High ozone
concentrations are infrequent in Houston and Baton Rouge and, when
present, do not persist for extended periods as is common elsewhere
(e.g., Los Angeles; northeast corridor, Washington-New York). There are
conflicting views as to whether the western Gulf Coast is a significant
regional exporter of ozone or precursors, or whether it is itself
adversely impacted by the advection of pollutants into the region.
Perhaps the most unique aerometric feature of the region is not any
one of the meteorological or chemical (emissions) characteristics, but
rather the fact that many occur simultaneously in combination. Emission
densities are greatest near the coastline, and (except for Dallas)
decrease markedly inland. The diurnal land-sea breeze regime
encompasses most of the significant source regions. In addition to the
diurnal reversal of wind flows, convergence along the sea breeze front
induces afternoon and evening cumulonimbus development. This in turn,
can cut off photochemical ozone production in the boundary layer while
transporting ozone and precursors out of the boundary layer into the
free troposphere. A further complication occurs at night when a
low-level nocturnal jet is frequently formed between the top of the
surface-based nocturnal radiation inversion and the bottom of the
subtropical high-pressure subsidence inversion. On the larger scale,
the location of the source region at the northerly edge of the
subtropical easterly waves makes regional-scale advection poorly defined
18
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and difficult to simulate in numerical models. The lack of upper-air
meteorological data in the western Gulf is an added complication. On
the regional scale, the role of the nocturnal midwestern low-level jet
(created by the slope of the Great Plains) is largely unknown insofar as
its effectiveness and importance in transporting coastal emissions to
the upper Mississippi Valley.
In developing a conceptual design for a Gulf Coast oxidant transport
and transformation experiment, the working groups considered the
potential significance of these aerometric characteristics or processes,
and developed an outline for an interrelated series of studies that
would have a high probability of: (1) determining which processes are
most important in controlling regional oxidant concentrations, and (2)
providing data to quantify the transport and transformation mechanisms
involved, so that (3) a data base would be available for diagnostic
evaluation of ROM with subsequent improvements made to the model.
The approach to the development of a conceptual design at the
workshop involved a sequence of introductory, informal lectures followed
by a series of meetings of small working groups. The workshop agenda is
given as Figure 3. The lecture topics included: background profiles of
regional meteorology, chemistry and emissions; overview of ROM; and
summaries of relevant previous and future experimental studies. Two
working groups were established: Group A was chaired by Mr. Gary
Tannahill of Exxon Company, U.S.A., with Dr. Hanwant B. Singh, SRI
International, and Dr. Fran Pooler , USEPA, serving as vice-chairmen.
Group A focused on atmospheric chemistry measurement needs and
resources. Group B was chaired by Dr. William Pennell of the
Battelle-Pacific Northwest Laboratories, with vice-chairmen Dr. John
Clarke*, USEPA, and Mr. William Viezee, SRI International. Group B
directed its efforts toward the identification and prioritization
(relative) of atmospheric processes and development of a framework for
the design of a series of experiments.
On assignment from the National Oceanic and Atmospheric Administration
(NOAA).
19
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TUESDAY, 15 NOVEMBER 1983
08:00 - 09:00 a.m. Registration
09:00 - 09:15 Welcome, K. Demerjian, Director, Meteorology and
Assessment Division, Environmental Sciences
Research Laboratory, Office of Research and
Development, U.S. Environmental Protection
Agency
09:15 - 09:30 EPA Goals and Objectives, J. Ching, MAD, ESRL, U.S.
Environmental Protection Agency
09:30 - 10:15 Summary of Synoptic Meteorological Features and
Transport Characteristics of the Region, W. Viezee,
SRI International
10:15 - 10:35 BREAK
10:35 - 11:15 Summary of Emissions and Ambient Ozone Features of
the Region, W. Dabberdt, SRI International
11:15 - 12:00 p.m. Overview of Photochemical Features and Processes,
H. Singh, SRI International
12:00 - 1:30 LUNCH
1:30 - 2:00 Overview of the EPA Regional Oxidant Model, K. Shere,
MAD, ESRL, U.S. Environmental Protection Agency
2:00 - 2:30 Review of the PEPE/NEROS Experimental Program.
J. Clarke, MAD, ESRL, U.S. Environmental Protection
Agency
2:30 - 3:00 Preview of Other Prospective Atmospheric Studies in
the Region, F. Pooler, MAD, ESRL, U.S. Environmental
Protection Agency
3:00 - 3:20 BREAK
3:20 - 4:00 Conceptual Framework for a Gulf Coast Regional
Oxidant Transport and Transformation Study,
W. Dabberdt, SRI International
4:00 - 4:30 Group Discussion of the Proposed Conceptual
Framework
Figure 3. Workshop agenda.
20
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4:30 - 4:45 p.m. Charge to the Working Groups
4:45 - 5:15 Initial Working-Group Meetings:
Group A — G. Tannahill, Chairman
F. Pooler, Vice Chairman
H. Singh, Vice Chairman
Group B — W. Fennel1, Chairman
J. Clarke, Vice Chairman
W. Viezee, Vice Chairman
WEDNESDAY, 16 NOVEMBER 1983
08:00 - 09:00 a.m. Plenary Session
09:00 - 10:00 Working Group Sessions
10:00 - 10:20 BREAK
10:20 - 10:00 Working Group Sessions
12:00 - 1:15 p.m. LUNCH
1:15 - 2:00 Plenary Session
2:00 - 3:00 Working Group Sessions
3:00 - 3:20 BREAK
3:20 - 5:00 Working Group Sessions
6:00 - 8:00 DINNER
8:00 - 9:30 Working Group Sessions
Figure 3. (continued)
21
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THURSDAY, 17 NOVEMBER 1983
08:00 - 09:00 a.m. Plenary Session
09:00 - 10:00 Working Group Sessions
10:00 - 10:20 BREAK
10:20 - 12:00 p.m. Working Group Sessions
12:00 - 1:15 LUNCH
1:15 - 2:15 Final Working Group Sessions
2:15 - 3:15 Final Plenary Session
3:15 ADJOURNMENT
Figure 3. (concluded)
The following subsection summarizes the lectures, while
Chapter II of this report summarizes the discussions of the two working
groups. Chapter III contains recommendations for a conceptual program
design, while Chapter IV summarizes the workshop and its
recommendations. The Appendix provides names and addresses of the
workshop participants, and identifies the working group in which each
participated.
Summary of Presentations
The following discussions are summaries of five technical
»
presentations given at the beginning of the workshop. They represent
three limited summaries of background conditions in the region as well
as the scope of several local significant experimental studies; also
included are overviews of (1) EPA's Regional Oxidant Model, which may be
applied to the Gulf Coast region, and (2) an earlier, major
aerometric-oxidant study conducted in the northeast, which in some
respects might be similar to various aspects of a Gulf Coast oxidant
22
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study. The five presentations were originally given to familiarize the
workshop attendees with the region and its characteristics and problems;
the summaries are given here with a similar purpose—to orient the
reader. It should, however, be reemphasized that these discussions do
not necessarily constitute any of the recommendations of the working
groups; they are simply an assemblage of background information
presented by the organizers of the workshop.
Synoptic Meteorological Features and Transport Characteristics
of the Gulf Coast Region (W. Viezee, SRI International)—
The meteorological conditions that prevail along the Gulf Coast
during the summer months of June, July, August, and September were
reviewed. Summertime weather conditions are unique with respect to
those in other regions of the United States for the following reasons:
• The Gulf Coast is under the influence of a maritime-tropical
(mT) air mass of large vertical extent. This air mass is
associated with a westward extension of the quasi-stationary
subtropical high pressure system centered at 30°N latitude over
the Atlantic Ocean (also called "high of the Azores" or "Bermuda
high"). Horizontal pressure gradients are weak, and winds are
light and variable from ground level to 500 mb (18,000 ft MSL)
and above. No persistent "steering" currents exist. Figure 4
shows an example of some operational weather maps (surface
weather map and 500-millibar height-contour chart) that
illustrate the typical pressure distribution found in the Gulf
Coast area during summer.
• Over the Gulf of Mexico, the average sea surface temperature
(83°F) is higher than the average air temperature, which
accounts for large values of relative humidity in the air mass.
The average air temperature inland over the coastal plain is
higher than that over the water from June to August. This
land/water air-temperature difference is most evident along the
Gulf Coast of northeast Texas and Louisiana. Significant
sea-breeze circulations are observed in these areas.
• Along the Texas and Louisiana coasts, the daily maximum
temperature can reach and exceed 100°F. The 24-hour values of
relative humidity rarely fall below 60 percent.
23
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f /* ^$^^^Sr^^^ ^'\^^
* d^f% V^ro: #as?^%-
J?V> -I ^/f^¥ -f" ^^ -%- ^*
^ ^ ^/J^'L/'- ^"^^-rV1^/
^. / m°H^'-x^-!t -I/ "rf' '" rV^££ \\. /
n &
?f*I
SOURCE: Dept. of Commerce, NOAA, 1983
Figure 4. Example of typical synoptic-scale weather conditions along the U.S. Gulf Coast
during summer (18 July 1983, 07:00 EST).
24
-------
• In the warm, moist, and uniform air mass with light and variable
wind flow, local and regional weather conditions are frequently
controlled by diurnal radiative heating and cooling. Convective
showers and thunderstorms during the day, fog, and low-level
stratus clouds at night, and local land- and seabreeze
circulations are very much evident. High speed winds near the
top of the boundary layer (low-level jet), and the persistent
occurrence of the sea-breeze front or convergence zone can be
considered as unique features of the Gulf Coast meteorology.
Figure 5 shows the annual mean number of thunderstorm days for
the United States. The maximum occurrence along the flat Gulf
Coast area, which coincides with the mean position of the
sea-breeze front, exemplifies a unique meteorological feature.
Figure 5. Mean number of thunderstorms — annual.
25
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Synoptic-scale, three-dimensional air parcel trajectories near the
surface and 5000 ft (1500 m) were presented for the periods 19-21 June
and 22-24 August 1983, when high ozone concentrations were observed in
the Houston, Texas area. These data were presented for the purpose of
identifying typical summertime air transport characteristics.
During the afternoon of 20 July, 1-hour average 0- concentrations in
the Houston area ranged from 140 to 210 ppb. No elevated readings were
recorded near Baton Rouge and New Orleans, Louisiana. Figure 6 shows
the three-dimensional air parcel trajectories near the surface and 5000
ft (1500 m) generated by the Limited Area Fine-Mesh (LFM-II) numerical
prediction model of NOAA* for the 24-hour period of 18:00 GST, 19 July
to 18:00 GST, 20 July. Thus, the trajectories are the predicted paths
of air parcels that terminate at the indicated locations during the late
afternoon of 20 July near the times of elevated 0, readings at Houston.
The mean 24-hour vertical motion of the air parcels, expressed in units
of cm per second, is printed at the trajectory end-points; mean
descending motions are negative, ascending motions are positive. [The
LFM-trajectories, however, are subject to considerable uncertainty,
particularly in the Gulf Coast region and within the planetary boundary
layer. Much of this uncertainty derives from the weak pressure
gradients at these low latitudes and the effects of secondary
circulations and migratory easterly waves. As a consequence, these
trajectories should be viewed as only a general indication of multi-day
atmospheric transport.] The trajectories are typical of those found
during the summer. The air parcels move anti-cyclonically around the
prevailing high-pressure system with a general downward (subsiding)
motion. On the west side of the high-pressure system, air parcels are
transported by southerly winds from locations over the Gulf of Mexico,
across the Texas coast, and toward Oklahoma, Arkansas, and northern
Louisiana. Depending on the position of the prevailing high pressure
system and the strength of the horizontal pressure-gradient field, this
general area can be one of northward transport of Gulf Coast emissions.
Trajectory data were supplied by Ronald M. Reap, Techniques Development
Lab. (TDL)/NOAA, Silver Spring, Maryland.
26
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-•= I—-
*•• I »• • • * 1 * * * *
. .100°W ..... nog . 90°.,.
§$L« . \. . A. .
-0.09 -U-0.09 I* '
ll* ' ' I ' '
LFM -II
24-HOUR SURFACE TRAJECTORIES
7/20/OOZ - 7/21/OOZ
1983
VERTICAL MOTION IN cm/sec
.90°
"]~r\ A
•i •*• V • -v •
LFM- II
24-HOUR 5000-FT TRAJECTORIES
7/20/OOZ-7/21/OOZ
1983
VERTICAL MOTION IN cm/sac
Figure 6. Three-dimensional air-parcel trajectories near the surface and near
5000 ft predicted by LFM-II for the 24-hour period of 19 July,
18:00 CST to 20 July, 18:00 CST.
Air parcel positions are indicated at 6-hour time intervals (squares).
24-hour mean vertical motion is printed at end of trajectory with
downward motion shown as negative.
27
-------
In southern Louisiana and Mississippi, air parcels move from the coastal
area southward over the Gulf of Mexico. Figure 6 strongly suggests that
air parcels recirculate from land to water and back to land.
During the period 22-24 August, hourly 0^ concentrations as high as
130 to 210 ppb were recorded in the Houston area during daytime. Near
Baton Rouge, Louisiana, occasional readings of 107 and 112 ppb occurred,
while in New Orleans the highest concentration for the month was only 85
ppb on 23 August. Figure 7 shows the LFM-II air parcel trajectories
predicted for the 24-hour period of 18:00 CST, 22 August, to 18:00 GST,
23 August. The general anticyclonic flow of the air parcels associated
with the high pressure system is evident. The speed of the air parcels
both near the surface and near 5000 ft, however, is much less than on 20
July (Figure 6). In fact, the flow field near the 5000-ft level is
close to stagnation. Southerly transport of air is seen along the Texas
coast. Southern Louisiana and Mississippi show little air movement.
Except perhaps for the Texas area, no defined large-scale transport out
of the Gulf Coast region is evident.
A look at other days throughout the summer of 1983 showed
characteristics of air-parcel transport quite similar to those of
Figures 6 and 7. Under such conditions of low wind speed (i.e., small
pressure gradients), the presence or absence of high-oxidant events may
be controlled primarily by local circulations associated with: the sea
breeze and the sea-breeze convergence zone; daytime convective clouds
(e.g., fair weather cumulus, towering cumulus, and thunderstorms); and
the nighttime land breeze and/or low-level jet.
Summary of Emissions and Ambient Ozone Features of the Region
(W. Dabberdt, SRI International)—
The major source areas for hydrocarbon and nitrogen oxides emissions
along the western Gulf Coast are the Houston-Galveston-Port Arthur and
Baton Rouge-New Orleans corridors; secondary source areas are Lake
Charles (LA), Dallas, Fort Worth, Corpus Christi, San Antonio, and
Oklahoma City—see Figure 8, adapted from Clark (1980). Point-source
hydrocarbon emissions in the Port Arthur (250,000 tons y ) and Houston
28
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_. _
• • e • • • » ^w^ •
w ". . . i. +0.08-go0--? I--^-T—• •*%
• ® / 7 \ \7
*^c^J- j*' ( ' ™* V • -V •
. +0.13 « •
+0.02 " ~\ -0.02 '
• • « • I
LFM -
* 24-HOUR SURFACE TRAJECTORIES
8/23/OOZ - 8/24/OOZ
1983
VERTICAL MOTION IN cm/sec
I • .100°W . . . i. ^°3 • 90°--r-—\-"^-T^"**
I . . px^^.^l.^f®. / . / +006\. . \. .
LFM-
24-HOUR 5000-FT TRAJECTORIES
8/23/OOZ - 8/24/OOZ
1983
VERTICAL MOTION IN cm/sec
Figure 7. Three-dimensional air-parcel trajectories near the surface and near
5000 ft predicted by LFM-II for the 24-hour period of 22 August,
18:00 CST to 23 August, 18:00 CST.
Air parcel positions are indicated at 6-hour time intervals (squares).
24-hour mean vertical motion is printed at end of trajectory with
downward motion shown as negative.
29
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68 10 12 14 16 18
2 4
20 22
(a) HYDROCARBONS
2 4
20 22
(b) OXIDES OF NITROGEN
Figure 8. Gridded annual emissions (10 ton y ); values less than
40,000 ton y not shown.
30
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(190,000 tons y~*) grid squares (approximately 125 km on a side) are
greater than those of any similar grid in the eastern two-thirds of the
United States, while Baton Rouge, Galveston and New Orleans (about
140,000 tons y ) are comparable to the emissions in New Jersey and
Delaware (130,000 tons y ). Area-source hydrocarbon emission densities
in New Orleans and Houston are comparable to those of St. Louis, but are
a factor of four less than New York and Chicago. Together, area- and
point-source emission densities in the New Orleans-Baton Rouge and
Houston-Port Arthur-Galveston areas are nearly comparable to the major
source regions of the upper midwest and northeast. Emission densities
of nitrogen oxides are generally less than those in the major midwestern
and northeastern source regions. As seen in Figure 8, NOX emissions are
fairly uniform all along the coast from Bay City, TX (southwest of
Galveston) to New Orleans. A significant feature of both hydrocarbon
and nitrogen oxides emissions along the Gulf Coast is the high
concentration in two major source regions and the very low concentration
in most of the surrounding areas. This contrast is highlighted in
Figure 8 by the omission of emission-values that are less than 40,000
tons y •
Ozone concentrations at ground level in Houston and southern
Louisiana are infrequently high and spatially variable. Trijonis (1979)
summarized ozone levels during the period 1974-78 at two locations in
Houston; three indicators were used, as shown in Figure 9: (1) average
daily peak-hour concentration during the smog season; (2)
95th-percentile ,of daily peak-hour concentrations during smog season;
and (3) second-highest hourly concentration for the year. The Mae Drive
location (Figure 9a) shows little interannual variation of the
smog-season average concentration (Item 3 above) of about 70 ppb, while
the 95th-percentile value varies from 140 to 175 ppb and the
second-maximum values vary from 200 to 265ppb, with the peak
second-maximum value recorded in 1976. Ozone concentrations at Aldine
(Figure 9b) are generally similar, except that the second-maximum peak
of 300 ppb occurred in 1975. Ozone trends in southern Louisiana are
tabulated in Table 5 for the period 1976-81 from data compiled by the
31
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£
o>
(O
r*
en
in
i—
o>
UI
z
8 8 8 S S S S
6 6 d d 6 6 d
ujdd — NOU.VH1N30NOO 3NOZO
o
tt
o
S
S
o
o-
3
- o
s s
D w
Ix
-------
Louisiana Department of Natural Resources. Mean annual concentrations
are lowest at New Orleans and highest at Baton Rouge. New Orleans had
only four days (in six years) with hourly concentrations in excess of
the 120-ppb ambient air quality standard; Lake Charles averaged about
five days per year, and Baton Rouge averaged 13 days. While annual
maximum hourly concentrations averaged 190 ppb in Baton Rouge, they were
only 152 ppb in Lake Charles and 121 ppb in New Orleans.
TABLE 5. OZONE (ppb) TRENDS IN LOUISIANA
Baton Rouge
Maximum
Mean
Days >120
Lake Charles
Maximum
Mean
Days >120
New Orleans
Maximum
Mean
Days >120
'76
201
28
16
144
25
14
118
16
0
'77
188
25
11
145
16
1
120
14
0
'78
214
24
28
167
17
5
137
16
2
'79
140
19
2
117
17
0
122
15
1
'80
218
21
13
187
22
4
126
14
1
'81
179
22
10
_
_
-
104
14
0
Of the many specialized aerometric studies conducted over the past
10 years in the region, two relevant experimental studies of regional
oxidant distribution in Louisiana and eastern Texas were reviewed: the
1975 Gulf Coast oxidant study conducted by Research Triangle Institute,
RTI (Decker et al., 1976) and the 1976 southern Louisiana oxidant study
by Radian Corporation (Lambeth, 1978). The RTI study provides: (1)
48-hr backward trajectory-estimates from Houston, DeRidder and Nederland
33
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for the upper- and lower-decile days of the 1975 ozone "season"—July-
October 1975; and (2) ozone concentrations along extended aircraft
flight tracks (usually a rectangular pattern), together with backward
•
air trajectories for selected points on the track (e.g., corners).
There is no unambiguous distinction between the trajectories associated
with the upper-decile ozone cases and those of the lower-decile cases.
In general, however, the high days have more of an eastward component to
them and are somewhat shorter (i.e., lower wind speed). Figure 10
illustrates: (a) high-ozone days at Houston, and (b) low-ozone days at
DeRidder, LA. Figure 11 is typical of the "high-ozone" aircraft tracks
from the RTI study: background concentrations for this low-level flight
(225 m) appear to be in the 60-80 ppb (120-160 g m~3) range with peak
values of 125 and 143 ppb at different locations. Along the Louisiana
coast, morning (triangles) and evening (squares) trajectories diverge
little, while there is significant divergence in the northern part of
the state. However, quantitative analysis of the aircraft data is
limited by sampling difficulties associated with the use of a single
aircraft in the large area of the sampling domain.
In the Radian study, continuous surface measurements of ozone were
made from July 17 through October 17, 1976, at nine sites in southern
Louisiana—an area about 500 km (E-W) by 200 km (N-S). Lambeth (1978)
concludes that the data indicate that dense precursor emissions from the
Baton Rouge area result in high ozone levels downwind; the effect was
most prominent 15-25 km downwind, although "still quite noticeable"
50—80 km downwind. Similar results were observed downwind of New
Orleans. Comparison of ventilation conditions during each of several
multi-day case studies generally indicated that widespread high ozone in
southern Louisiana is associated with poor ventilation, and low ozone
with good ventilation. There is also evidence to imply that ozone is
depleted" less rapidly over the Gulf of Mexico and unpopulated coastal
areas compared to the normal decline in ozone after sunset in inland
areas of southern Louisiana." Also, increased cloud cover and improved
dispersion near "large rain areas" may explain the low ozone levels
observed in areas of extensive shower activity.
34
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SOURCE Decker «t •! . 1978
(•I UPPER DECILE OZONE MAXIMA 10, • 271 14 m-3| FOR HOUSTON
SOURCE OKfcvr *t •! 1976
Ib) LOWER DECILE OZONE MAXIMA <03 < 75 in m-3| FOR DlRIDDER
Figure 10. Backward boundary-layer trajectories.
35
-------
o
TS
0>
0)
^
a
aj
8
13
a
(A
9>
O
25;
s "
§8"
§ s
N O
o o
36
-------
On a larger spatial scale, Wolff and Lioy (1980) and Wolf et al.
(1977) examined the possibility of regional-scale ozone transport from
the western Gulf Coast to the northeast corridor. Their analyses are
primarily qualitative and involve the interpretation of daily synoptic
maps of peak-hour ozone distribution and corresponding multi-day,
boundary-layer air trajectories; an example is given as Figure 12. The
conclusion is made that "under certain meteorological conditions, high
ozone concentrations were transported from the western Gulf Coast area
to the Midwest and the Northeast... The circulation around the
high-pressure systems which caused these episodes traveled northward
from the Texas-Louisiana Gulf Coast to the Midwest and then eastward to
the Northeast and the Middle Atlantic Coast. Ozone concentrations
within this river averaged -120-130 ppb and were as high as 328 ppb in
Connecticut... The ozone produced is undoubtedly supplemented by
emissions into the ozone river en route through the Mississippi and Ohio
Valleys to the Northeast."
The concept of a cross-country "ozone river," however, is open to
substantial question as to whether it indeed reflects the long-range
transport of ozone, or is the result of a continuum of source regions
and associated downwind areas where ozone production and destruction
occur on the mesoscale. This countercontention has been suggested by
Niemeyer (1977) who states that "an alternative analysis would show that
in regions of limited dispersion (associated with the weak gradient
region of the high pressure cell) conditions are optimum for the limited
dilution of ozone precursors and that the elevated ozone levels observed
are due to precursors emitted not too far distant from the point of
measurement."
The obvious conclusion would appear to be that the potential
significance of an actual "ozone river", which transports ozone in high
concentrations for thousands of kilometers, is sufficiently great to
warrant further study to document the extent and magnitude of ozone
transport away (or toward) the high emission areas of the Gulf Coast.
37
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TRAJECTORIES
A. 8 Day Forward
from Hotwton
8.6 Day ft
C. 6 O«v
tram O. C.
Ozone on 7/14/77
Hf 80-99 ppb
H| 100-149 ppb
[~| 150-199 ppb
• > 200 ppb
Ozone on 7/16/77
|H 80-99 ppb
H100-149 ppb
Ql50-199ppb
• > 200 p
Ozone on 7/19/77
|H 80-99 ppb
H| 100-149 ppb
[""] 150-199
• > 200 ppb.
SOURCE: Wolf and Lioy, 1980.
Figure 12. Air parcel trajectories during July 14-20, 1977, and ozone concentrations patterns.
Atmospheric Oxidant Chemistry: Features and Measurement
Technologies (H. Singh, SRI International)—
The existing literature was reviewed with two objectives in raind:
• What are the typical or atypical features of the Gulf Coast area
as far as oxidant formation is concerned?
• What new measurement technologies are likely to be available
to the planned Gulf Coast oxidant study?
One of the key features of the Gulf Coast region is its somewhat
unique meteorology. Typical weather conditions are characterized by hot
temperatures (daily maximum temperatures of 80-110°F for the year) and
intense morning sunshine followed by afternoon thundershowers. While
high temperatures and intense sunlight are likely to accelerate
38
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Oo-forming processes, frequent showers most likely decelerate them.
Direct knowledge of the effect of thundershowers on a pre-existing
photochemical mix is limited, but it can be speculated that such
processes would remove free radicals, aldehydes, NO acids, and
possibly, some nonmethane hydrocarbons.
The key photochemical processes that result in ozone formation were
reviewed briefly. In addition, the principle processes that oxidize and
ultimately remove nitrogen oxides from the atmosphere were also
reviewed. It was pointed out that while nighttime and daytime removal
of NOX proceeds via substantially different processes, in both cases
heterogeneous processes play an important role. This feature of NOV
X
removal is likely to be more important in the Gulf Coast region compared
to other, drier regions. Indeed, the direct wet deposition rate of NC>2
can be as high as 25 percent of the nitrate aerosol rate (5 x 10 ~^s~*).
Review of precursor data from Houston indicated the following
generalizations:
• Typical average nonmethane hydrocarbon concentrations
are of the range 0.8 to 1.2 ppmC in the morning hours
(6-9 AM) and about 40 percent lower in the afternoon.
• The NMHC mix is typically composed of 60-70 percent parafin,
10-20 percent olefin, and 15 to 25 percent aromatics.
• Mean hourly concentrations of nitrogen oxides (NO ) are 10
to 50 ppb with maximum (1-h) concentrations of 80 to 200 ppb.
• Average NMHC/NOx ratio (ppmC/ppm) is 10 to 20, but a
range of 5-50 can be encountered.
The above precursor levels were compared with limited data from other
cities to point out that ambient precursor concentrations in Houston
were fairly typical of those encountered in other United States cities.
Compared to data from other regions (Table 6), the HC/NO ratio is
X.
slightly on the high side, and may reflect somewhat more rapid removal
of NOX by wet processes in Houston or excess hydrocarbon sources from
the nearby ship channel.
The behavior of secondary pollutants (ozone and PAN) was also
examined. The highest average 03 levels are encountered during the
summer (April-September). A limited analysis of 0-j data from 4 stations
39
-------
in Houston during July-September 1983, was used to make the following
two observations:
• Although hourly 03 levels as high as 200-300 ppb are
encountered in Houston, the frequency of such exceedences
is very low.
• High 0^ levels (>120 ppb) rarely occur on consecutive
days or on days immediately following extensive shower activity.
There was no evidence that air from the Gulf contained high Og or
precursor concentrations. The Beasley Oo monitoring station (outside
Houston) has collected data for a number of years. When days with winds
from Houston are excluded, 0^ levels (corrected) were typically in the
60 to 100 ppb range for 1977-1979. NMHC levels in the vicinity of this
station with Gulf winds were 10 to 20 ppb.
Data from a number of stations from southern Louisiana also showed
relatively low 0-j levels. When the Louisiana data are corrected for
calibration errors (by -18 percent), the 0^ exceedences (>120 ppb)
during August and October 1976, are virtually nonexistent. In addition,
available PAN data from Houston show extremely low concentrations with
80 to 100 percent of data falling in the 0-2 ppb range. As Table 7
shows, not only are PAN levels low, but 0^ to PAN ratios are exceedingly
high. The precise reasons for this low PAN abundance have not been
explored.
Available technology for measurement of trace chemicals from ground
and airborne platforms was also reviewed. It was suggested that
significant improvements in technology have occurred which could enhance
the success of a Gulf Coast oxidant study. Table 8 summarizes the key
species that must be measured and the status of technology that is
likely to become available by 1985. It was also suggested that research
efforts on some of these technologies could be accelerated to bring them
on line by 1985.
In addition, the following observations were made:
• There is a significant body of existing data from the Gulf
Coast that must be thoroughly analyzed.
• The precursor concentrations in Gulf Coast cities are not
atypical of other urban centers.
40
-------
TABLE 6. NMHC/NOX RATIO FOR AMBIENT AIR (Source: Cantrell, et al., 1982)
Location
Chicago, IL
Washington, D.C.
New York City, NY
Camden, NJ
Los Angeles, CA
Denver, CO
Baltimore, MD
Houston, TX
Austin, TX
Tulsa, OK
Philadelphia, PA
Huber Heights/
New Carlisle, OH
Phoenix, AR
Phoenix, AR
Jetmore, KA
Liberty Mounds, OK
Wynona , OK
General Rural Area
Beverly, MA
Site
Type
Urban
Urban
Urban
Urban
Urban
Urban
Urban
Urban
Urban
Suburban/
Impact ion/
Rural
Suburban/
Impaction/
Rural
Suburban/
Impaction/
Rural
Suburban/
Impaction
Rural
Rural
Rural
Rural
Rural
Rural
NMHC/NOX*
ppmc/ppmv
4.4
6.4
7.9
7.5
10.0
14.3
18.4
21.4
33.1
10.9
10-20
27
10
-15
10
45
170
<30:1
13
Comments
year long average
year long average
year long average
year long average
year long average
year long average
year long average
High NMHC emissions
Ground Station
Urban Plume —
Aircraft Measurement
Reference
Horie et al. (1979)
Horie et al. (1979)
Horie et al. (1979)
Horie et al. (1979)
Horie et al. (1979)
Horie et al. (1979)
Horie et al. (1979)
Horie et al. (1979)
Horie et al. (1979)
Eaton et al. (1979)
Chan et al. (1979)
Spicer et al. (1976a)
Spicer et al. (1978)
Spicer et al. (1978)
Martinez and
Singh (1977)
Eaton et al. (1979)
Eaton et al. (1979)
U.S. EPA (1977)
Spicer et al. (1981)
Average value for 6 a.m. to 9 a.m. period.
41
-------
TABLE 7. O3/PAN RATIOS IN LOS ANGELES, HOBOKEN, ST. LOUIS,
AND HOUSTON
Location
Los Angeles, California i"
Hoboken, New Jersey
St. Louis, Missouri"*"
Houston, Texas
Aldine Site
Crawford Site
Fuqua Site
Range of
PAN Levels
(ppb)
0-10
10-20
20-30
30-40
40-50
50
0-2
2-4
4-6-
6-8
8-10
0-2
2-4
4-6
6-8
8-10
10-12
>12
0-2
2-4
4-6
0-2
2-4
0-2
03/PAN
Ratio*
9. it
7.6
6.0
5.2
4.5
4.9
28.0
25.3
24.0
22.8
25.1
16.3
16.2
10.0
7.4
5.4
5.0
3.2
96.4
31.9
20.2
76.3
32.8
237.3
Number
of
Samples
19
59
27
6
5
2
14
15
4
8
2
3
31
60
31
14
5
10
78
10
3
60
7
20
Ratio is for (average 03)/(average PAN), the averages
corresponding to the specified PAN range.
Adapted from Lonneman et al., (1976)
TFor Los Angeles, the ratio is for (average total
oxidants)/(average PAN).
42
-------
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• Based on a cursory analysis of data, it appears that Gulf
Coast air is typically characterized by low ozone and PAN
levels with interspersed high-ozone events.
• The high frequency of thundershowers (one every 2 or 3 days)
is a feature that is unique to frhe Gulf Coast and impacts
photochemical processes in a way that cannot be defined
clearly at present.
• Significant new technologies involving remote sensing and
optical techniques can be brought to bear on the
successful conduct of a Gulf Coast oxidant study.
Overview of the EPA Regional Oxidant Model (K. Schere, U.S. EPA)—
A theoretical framework for a multi-day 1000-km scale simulation
model of photochemical oxidant has been developed. It is structured in
a highly modular form so that eventually the model can be applied
through straightforward modifications to simulations of particulates,
visibility and acid rain. The regional oxidant model (ROM) is currently
being completed for application to the upper midwest and northeast
section of the United States.
The model structure is based on phenoraenological concepts and
consists of three and one-half layers. The interface surfaces
separating the layers are functions of both space and time that respond
to variations in the meteorological phenomena that each layer is
intended to treat. Among the physical and chemical processes affecting
passage and distribution of photochemical concentrations that the model
is designed to handle are: horizontal transport; photochemistry;
nighttime wind shear and the nocturnal jet; cumulus cloud effects;
mesoscale vertical motion; mesoscale eddy effects; terrain effects;
subgrid-scale chemistry processes; natural sources of hydrocarbons,
NOX, and stratospheric ozone; and wet and dry removal processes, e.g.,
washout and deposition.
Lamb (1982) also has considered the predictibility of pollutant
concentrations at long range, along with such related problems as the
parameterization of "mesoscale" diffusion and the design of model
"validation" experiments. A basis is established for estimating
quantitatively the levels of uncertainty associated with dispersion
model predictions.
44
-------
Figure 13 is a schematic illustration of the layered structure of
the ROM, and describes the function of each layer; Part (a) considers
daytime phenomena and Part (b) , nighttime phenomena.
Review of the PEPE/NEROSJJ Experimental Program
J. Clarke, U.S.
Together, the PEPE and NEROS* studies included three or four
(depending how they are tallied) separate and coordinated programs. The
first NEROS study (e.g., see Ruff, Gasiorek, and Shigeishi, 1979) was
designed to provide a semi-quantitative understanding of the nature and
extent of ozone in the northeast. A regional air mass characterization
study was conducted in the summer of 1979; the objective was to provide
data to substantiate or refine assumptions or parameterizations of the
ROM. A regional-scale urban plume study and regional oxidant studies
were conducted in summer 1980. Urban plume studies were conducted out
of Baltimore, while regional and urban plume studies were conducted out
of Columbus, Ohio. The following discussion describes the scope of the
latter effort and is extracted from a summary article by Vaughan, Chan,
Cantrell and Pooler (1982).
The Regional Field Studies Office (RFSO) of the United States
Environmental Protection Agency (EPA) sponsored a field study in
July-August 1980, to examine the transport and chemical transformation
of polluted air masses extending over hundreds of kilometers. EPA's
Meteorology Division was a cosponsor of the field study. It desired to
examine the dynamics of oxidant formation, transport, and removal in
developing a data base for the regional" oxidant model. Its focus was on
regional characterizations as well as detailed understanding of urban
plume dynamics for providing various parameters to the model. The
Meteorology Division's activities were organized as the Northeast
Regional Oxidant Study (NEROS).
PEPE - Persistent Elevated Pollution Episodes
NEROS - Northeast Regional Oxidant Study
45
-------
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Air quality and meteorological measurements were carried out from
surface platforms (fixed, mobile, and moving) and airborne platforms;
Table 9 provides a summary of the measurement platforms and data
centers. Within the collection of measurements from PEPE/NEROS is
information on gaseous pollutants (particularly SC>2, NO, NOX, 0^, and
hydrocarbons); aerosol indicators (bgcat» SO^, Aitken nuclei count,
aerosol filters, chemical analyses, and particle size distribution); and
meteorological parameters, multiple tetroon trajectories, temperature,
wind speed, dew point, and mixing height (from various lidar
measurements)]. Vertical profiles of these parameters exist from spiral
flights and ramping flights, while horizontal gradients are available on
a large scale for regional missions and on an intermediate scale for
urban plume missions. A total of 353 flight hours were logged by the
CHEM-1, CHEM-2, SCOUT, and CHOPPER aircraft in 100 missions. Table 10
indicates which air quality and meteorological parameters were recorded
by each platform.
The NEROS missions for urban and regional studies involved release
of small tetroon clusters at various altitudes and a large tetroon
(tracked by FAA radars). Once the transport field was marked with
tetroons, the aircraft and mobile platforms were deployed to document
the air quality and mixing conditions in the air mass. CHOPPER and
NOAA-Turbulence were fairly heavily dedicated to urban plume surveys.
EPA Lidar carried out mostly plume-oriented studies, but occasionally
conducted regional studies outside Ohio. Moving Lab conducted frequent
ground-level surveys near Columbus, but also was deployed to West
Virginia and Kentucky for PEPE-oriented regional surveys. NEROS
regional measurements were carried out to characterize the northeastern
grid used in the regional oxidant model between the 70°W and 85°W
longitude, and 38°N and 45°N latitude. SCOUT, CHEM-1, and CHEM-2
It should be noted that EPA, through the Office of Air Quality Planning
and Standards, operated the Northeast Corridor Regional Monitoring
Program (NECRMP) during the summer of 1980 from Baltimore to Boston.
The program involved augmented air quality and meteorological
measurements. These data are valuable in characterizing the eastern
edge of the study grid.
48
-------
TABLE 9. PLATFORMS AND DATA CENTERS
OPERATED DURING PEPE/NEROS
Airborne Laboratories
CHEM-1 (Chemistry aircraft)
CHEM-2 (Chemistry aircraft)
SCOUT (Chemistry aircraft)
ELECTRA (Lidar system)
CHEM-3 (Chemistry aircraft)
LAS* Queenair
EPA-Lidar
Turbulence aircraft
Cloud chemistry aircraft
CHOPPER
Surface-based laboratories
Moving laboratory
Doppler Sodar 1 and 2
Aerosol laboratory
Lidar van
Small tetroon tracking
Large tetroon tracking
GC laboratory
Special photochemistry
precursors
Tethered balloon
NOX, Ozone network
Bertin sodar
Dry deposition experiment
MARS*
Sunphotometry
Data center
Weather center
source: Vaughan et al., 1982.
*
UV-DIAL = Ultraviolet-Differential
Adsorption Lidar.
HSRL = High Spectral Resolution
Lidar.
LAS = Laser Adsorption Spectrometer,
MARS = Microwave Atmospheric
Remote Sensor.
49
-------
TABLE 10. AIR QUALITY AND METEOROLOGICAL PARAMETERS AVAILABLE
FOR EACH PLATFORM (Source: Vaughan, et al., 1982)
Airborne
CHEM-I1
CHEM-2
Scout
Elect ra
CHEM-3
LAS
Turbulence
Chopper
EPA Lidar
Surfacr-baitd
Moving lab
Sodarl
Sod*r2
Aerosol lab1
Lidar van
Special
Photochemical
Tethered balloon
Network
Benin sodar
Dry dtp.
MARS
fr
*y $• ff
2-8 X X
12 X X
0.4 X
1-60
10
10-30
if // ///A/ //
X X X X X X
X X X X X X X
X X X X X X
PRO-
HTD X X
XX XXX
X X
PRO- *
X XX
PRO PRO PRO
PRO PRO PRO
X X
PRO"
X X
PRO PRO PRO PRO
X
PRO PRO
PRO PRO X X
PRO PRO
X - Point measurement available.
PRO - Profile showing variations with altitude.
HTD - Heated nephetometer.
SO, - Continuous readings from a modified Meloy 285
INT - Integrated burden (for SO, these measurements were from correlation spectrometers)
a - Aerosol size distribution measurements were conducted as well.
b - Hydrocarbon cannuters were analysed in EPA's GC Laboratory in Columbus, Ohio.
c - Filters were collected with a 3.S iun cut point and analysed for SOI and NO;
d - Seven second readings reported as 15 mm averages.
e - The lidar signal is not a true profile of the parameter "DM," but is related to it, since tt records the backscalter of light
from layers of atmospheric aerosol It gives a good indication of mixing depth.
provided frequent In situ surveys across various parts of this NEROS
box. They were usually vectored back to the location of the large EPA
tetroon, in order to follow the aging of the air mass in the vicinity of
this specific marker. Moist air masses moving in from the west and
southwest, and Canadian polar air masses were characterized by these
flights. ELECTRA was deployed for its regional surveys out of Wallops
Island, VA., in support of NEROS and PEPE regional objectives. CHEM-3
provided correlative in situ measurements at selected locations below
50
-------
ELECTRA's flight path (as it had done earlier in the program for
LAS-Queen Air flights).
PEPE regional surveys were less restricted, and involved flights
into stagnant air masses (two to five days old) or into moving air
masses that experienced regional visibility degradation, as reported by
FAA and NWS wire services and by satellite imagery. These regional
surveys extended into New York and New England during the first week in
August 1980, following development of large-scale haziness in the area.
In the middle of the second week in August, several flights into
Tennessee, Alabama, and Arkansas were carried out to characterize a
maritime tropical air mass associated with an extension of the Bermuda
high that had stagnated over Georgia and Tennessee for four days.
Measurements also were made as this aged air mass swept out to the
Atlantic. On two occasions. 25 July and 11 August, tetroons were placed
in or near power plant plumes, and flights were made to characterize the
mixing of these plumes into the general air mass. A summary of the
types of missions flown during the study period is shown in Table 11.
TABLE 11. SCHEDULE OF MISSIONS FLOWN (Source: Vaughan, et al.. 1982)
Urban Plume
Limited
Full scale
Regional
PEPE
NEROS
July
20 23 24 25 26 29 30 31
XX X
X XX
p
p p
August
1 2 4 5 6 7 8 9 10 11 12 13 15
XX XXXX XX
B X X (X)
X XXXXXPP
XX X
51
-------
It is obvious that with the resources available to the project, only
limited urban plume flights could be carried out while regional surveys
were in progress.
52
-------
SECTION 3
WORKING GROUP CONSIDERATIONS
CHEMISTRY
The working group addressed and prioritized trace chemicals that
must be measured during any planned Gulf Coast oxidant study. The exact
platforms to be employed, frequency of measurements, and spatial density
of monitoring stations were issues which could not be considered by the
working group since a detailed design of the Gulf Coast study did not
exist. The group, therefore, focused on broader considerations dealing
with trace chemical measurements and emissions data requirements. The
working group strongly felt that a number of mini-studies should be
completed and their results employed to design a major Gulf Coast study.
The following sections briefly describe the working group
recommendations.
Chemicals of Interest
Trace chemical measurements (in gas and liquid phases) were
identified and ranked according to their importance and feasibility of
the measurements. These rankings were as follows:
Importance of Measurement: Status of Measurement;
A. Important 1. Methods well defined and
applied with ease
B. Desirable 2. Methods not fully developed
and applied with difficulty
C. Optional 3. Methods unacceptable
Tables 12-15 provide a listing of the species of interest and rank
these by the above criteria. Among the nonchemical parameters, liquid
53
-------
TABLE 12. TRACE CHEMICALS IN AIR
*
Chemicals
°3
NO
N02
PAN
HN03
CH4
CO
THC
HC.
RCH=0
H2°2
HN02
N2°5
HO
H02
R02
N03
NH3
SO 2
Rankf
A
A
A
A
A
A
A
A
A
A
A
B
B
B
B
B
B
C
C
1
1
1
2
3
1
2
2
2
3
3
3
3
3
3
3
3
2
1
Measurement of liquid water
content and UV radiation
(300-500 nm) were ranked as
A2 and Al respectively.
Key:
A =
B =
C =
1 =
2 =
3 =
important measurement
desirable measurement
optional measurement
measurement technique
is state-of-the-art
measurement methods not
yet fully developed or
only applied with difficulty
measurement methods
currently unacceptable
54
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TABLE 13. TRACE CHEMICALS IN LIQUID WATER
Chemicals
NO
ROH
RCH=0
HC..^ (vac)
°3
H2°2
Rank*
Cloud
Water
B
C
A
C
C
A
Rain
Water
B
C
C
C
C
B
Aerosols
B
C
A
C
C
B
Measurements are at levels of
difficulty of 2-3.
TABLE 14. PARTICULATE MATTER
Type
Elements
so4
N03
NH,
Rank
C
C
B
C
1
2
2
2
55
-------
TABLE 15. INERT TRACERS OF INTEREST
Tracer Type
Tracers of opportunity
Injected tracers
Species
7Be
33P
Fluorocarbons
Elements
Methane-2 1
Perf luorocarbons
SF6
Rank
C 2
C 2
A 1
C 1
A 2
A 2
A 1
water content and ultraviolet radiation measurements were highly
emphasized. It was generally felt that gas-phase processes provide the
dominant source term for ozone formation and hence constitute the most
important measurements. The role of aldehydes and I^Oo in liquid phases
are not well understood but may be potentially important (Table 13).
Nitrate measurements in the aqueous phase (Table 13 and 14) were ranked
high because of the sink potential of the aqueous phase for N02, HN03,
and nitrate aerosols. Despite the recognized importance of gas-phase
chemistry, the working group felt that liquid-phase processes may play a
more important role in the wet and humid environment of the Gulf Coast
compared to relatively dry regions.
Tracers of opportunity were suggested, but only chlorofluorocarbons
were considered high priority. 7 Be or 33P stratospheric tracers were
ranked low in part due to the complexity of data interpretation.
Injected speciality tracers are unique tools to study long range
transport, but are to be measured only when a planned tracer experiment
is underway.
Emissions Data
It is anticipated that ROM or other models would be employed in the
Gulf Coast region. The working group provided guidance on what is
56
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highly desirable and what must be obtained at a minimum. The following
general guidelines were suggested:
(1) A 2-km x 2-km gridded inventory of emissions.
(2) Hourly temporal resolution, i.e., diurnal and seasonal
emission patterns
(3) Vertical resolution of emission sources
(4) Source types (stationary, mobile, area, point, natural, etc.)
(5) Natural VOCs on land
(6) Gulf Coast water emissions.
It was felt that some sensitivity studies should be performed with
existing models to get an idea of the importance of source emissions,
particularly natural VOCs of land or water origin. One of the most
pernicious problems is the very nature of the emissions inventory. In
principle, emissions data (temporally and spatially resolved) should be
available for individual species. This is not possible in practice.
Current models can use groups of chemicals (alkanes, alkenes, arid
aroraatics) and this is a desirable speciation of emission data. It was
felt, however, that carbon bond mechanisms may be employed in a future
version of ROM. It does not appear feasible that emissions information
can be obtained in a format directly applicable to the carbon bond
model. It is assumed that some algorithms must be devised to solve this
problem.
Recommendations
For all surface and aircraft sampling, all chemicals ranked "A" must
be measured. Those ranked "B" should be attempted when possible. Prior
to the Gulf Coast study a number of mini-studies are recommended. These
would provide many of the answers that are needed to better design the
Gulf Coast oxidant studies. The following mini-studies were
recommended:
(1) Analyze all existing air quality and meteorological data to
critically examine the oxidant problems in the Gulf Coast
and the relationship of ozone concentrations to meteorological
and emissions conditions.
57
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(2) Fully analyze Che data from the NEROS experiment to focus
on the strengths and weaknesses of the ROM model as applied
to the Northeast. Also, a sensitivity analysis of emission
sources to better gauge the role of natural VOCs and the effect
of the inherent uncertainties in the emissions data base needs
to be undertaken.
(3) Efforts should be initiated now to ensure a reliable field
measurement capability by 1985, particularly for
aldehydes and l^C^.
(4) Employ an existing airshed model in the Houston area to see
if Houston ozone levels are less than those predicted
by existing knowledge.
(5) Conduct smog chamber/fog chamber irradiation studies to
simulate the Gulf Coast air precursor mixtures.
(6) Because of the humid and cloudy environment of the Gulf Coast,
a better knowledge of in-cloud processes—especially as a sink
mechanism—is desirable.
Item Nos. 1 to 3 were rated as necessary. Other suggestions were
considered highly desirable but contingent on resource availability.
The working group felt that suggestions 2-6 can be implemented with a
budget of 0.7 to 1.3 million dollars. It was assumed that
recommendation No. 1 would be performed by EPA at no cost to this
proposed study.
METEOROLOGY
General
After background material had been presented, and after some
preliminary discussion by the workshop attendees on the objectives and
rationale for a Gulf Coast Oxidant Transport and Transformation
Experiment, the Chairman of Work Group B, William Pennell, presented the
following meteorological topics for discussion by the group:
• Land and sea breeze circulations
• Convective cumulus cloud venting
• Synoptic-scale transport and disturbances
• Surface deposition and destruction
58
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• Synoptic-scale subsidence
• Low-level .-jet
• Characteristics of planetary boundary layer over the
Gulf of Mexico.
The above meteorological features were judged to possibly play
important roles in determining events of high and low oxidant
concentration along the Gulf Coast area of the United States.
Walter Lyons then presented the major weather categories relevant to
the Gulf Coast area for consideration by the work group members
throughout the discussions:
• Tropical disturbances (easterly waves, tropical depressions,
tropical storms, and hurricanes)
• Frontal disturbances (infrequent and weak during summer,
but strong and followed by cold northerly winds during winter)
• Strong onshore flow of southerly and southeasterly winds
• Sea breeze regime without showers or thunderstorms ("dry"
sea breeze) or accompanied by rainshowers or thunderstorms
along the on-land convergence zone under conditions of weak
synoptic-scale wind flow (weak horizontal pressure gradients).
Identification of Relevant Phenomena
Mesoscale and regional scale atmospheric transport are determined by
three-dimensional circulations that vary in scale from local or micro to
intermediate or meso, and synoptic. Included are mesoscale convective
systems and land/sea breeze circulations as well as the low-level
coastal jet and the mid-continental nocturnal jet. Not only can these
circulations significantly impact mesoscale advection, but convective
phenomena may be important for their role in the two—way exchange of
polluted boundary-layer air and clean mid-to-upper tropospheric air (and
possibly stratospheric air). Accordingly, the Gulf Coast oxidant
transport and transformation study must seek to measure and analyze
three-dimensional, unsteady transport phenomena.
Shih-Ang Hsu characterized the land- and sea-breeze regime as it has
been studied on the upper Texas Gulf Coast. Under conditions of weak
59
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"Bermuda High" southerly (onshore) flow of about 5-10 knots (2.5 - 5
m/s), a fully developed sea breeze extends from about 30 miles (50 km)
offshore to 30-40 miles (50-65 km) inland between noon and 6 p.m. The
dimensions are 60-70 miles (100 km) in the horizontal (perpendicular to
the coast) with half over land and half over the Gulf, and 3 km in the
vertical. The mean wind speed for the sea breeze is about 6 m/s (12
knots). Figure 14(a) shows a schematic sea-breeze circulation in the
vertical plane perpendicular to the coast line. The convergence zone is
3 KM
RECIRCULATED AIR
CONVERGENCE
ZONE
COASTLINE
-30-40 Ml -
• 30 Ml •
-100 KM-
(•) FULLY DEVELOPED SEA-BREEZE CIRCULATION (NOON TO 6 PM)
SUBSIDENCE INVERSION
LOW-LEVEL JET
COLD DOME
(b> LOW-LEVEL JET ASSOCIAtED WITH SEA BREEZE (9 PM TO 3 AM)
Figure 14. Schematic view of sea-breeze regime characteristic of Gulf Coast.
60
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located 30-40 miles (50-65 km) inland. It has front-like characteris-
tics and is often identified by a distinct line of cumuliform clouds.
Near the time of maximum surface temperature in the afternoon, convect-
ive showers and thunderstorms can develop.
On the basis of his experience with the Lake Michigan sea-breeze,
Walter Lyons noted that the convergence zone can be like a chimney 1-2
km wide with updrafts of over 1 m/s. When the sea breeze overlies an
area of pollutant emmissions (such as can be the case in the Houston,
Galveston, Lake Charles and New Orleans regions) it can recirculate
pollutants from land to water and back to land. At the same time, the
convergence zone and cumulus clouds can vent pollutants upward to higher
levels, and thunderstorm downdrafts along the sea-breeze front can
transport clean air from high levels in the troposphere to the ground.
Under such conditions, a "pollution front" can develop between
recirculated old polluted air and clean downdraft air as indicated in
Figure 14(a) by the heavy dashes. The persistence of this front may
provide a prevalent and important mechanism for transport of anthropo-
genic pollutants to the free troposphere, thereby constituting a pseudo
emissions line source of sufficient vertical and horizontal extent to be
a potentially important contributor to global tropospheric air quality.
Shih-Ang Hsu pointed out that a shallow cold-air dome (100-200 m in
depth) frequently develops over land near 9 p.m. when radiational
cooling of the land surface begins. When this process intensifies, a
low-level jet-type windflow is observed above the cold dome over land
from about 9 p.m. to 3 a.m. the next morning, as illustrated in Figure
14(b). Around 6 a.m., the windflow reverses to a land breeze. Offshore
heavy cumulus clouds and light rainshowers produced by the land breeze
convergence over the water can then be observed.
The potential role of the land- and sea-breeze circulation in the
local and regional transport and redistribution of pollutants in the
Gulf Coast area was recognized by all working group members. It was
agreed, however, by the workshop at large that the existing data base of
meteorological and air quality observations (e.g. , HAOS aircraft and
ground data) should be examined and analyzed to provide better evidence
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that a raesoscale experiment involving the sea-breeze front, and
nighttime low-level jet winds have pollution implications that are
related to high and low ozone events .
Intermediate transport out to a distance of about 400 km, and
long-range transport out to 1000 km were also identified as
meteorological phenomena relevant to a summertime Gulf Coast oxidant
study. The area where transport of pollutants from Gulf Coast emission
sources may be important lies on the west side of the subtropical
"Bermuda High" (see Section 2B, Figures 6 and 7). It includes Texas and
Louisiana, under conditions of relatively large horizontal pressure
gradient and southerly winds. When southerly winds extend over the
western Great Plains, as is the case when the western end of the
"Bermuda High" covers the Mississippi Valley, a low-level jet can
develop between midnight and sunrise at about 1500-2500 ft (500-800 m)
above ground level; wind speeds of 25-30 knots (12-15 m/s) are common.
Some work group members suggested that emissions from the
Texas-Louisiana coastal region can be transported northward into
Missouri and even Minnesota by such southerly wind flow.
No measurements currently exist that conclusively demonstrate
long-range ozone transport events out of the Gulf Coast region. It was
agreed that an intermediate and, possibly a long-range transport
experiment, should be considered in the Gulf Coast oxidant experiment
design study.
Design of Mesoscale Sea-Breeze Experiment
After having identified the sea breeze as a significant
meteorological phenomenon, the work group proceeded to discuss a
possible mesoscale experiment design. Two experiments were considered:
For example, some workshop members expressed the opinion that easterly
and northeasterly windflow along the Gulf Coast is more important to
high ozone in Houston than the sea breeze. This wind flow regime is
frequent during spring and fall on the southside of a continental polar
high-pressure system.
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• A spatially fixed (Eulerian) box-budget study to quantify the
net transport into or out of the sea breeze/emission area
• A tracer (Lagrangian) experiment to study the role of the sea
breeze in recirculating pollution.
The Eulerian box-budget experiment would be carried out in a
rectangular area, 300 km north-to-south and 200 to about 400 km
east-to-west. This area would include the sea-breeze circulation and
coastal emission sources. The Houston—Galveston—Lake Charles area was
considered most suitable for this program. The box would be 3 km deep
(the average depth of the sea-breeze).
After lengthy discussion of the measurement systems and platforms,
and their use and deployment, it was concluded that a budget study of
the box cannot be readily done by closing the box with observations. It
was, therefore, recommended that available observations be used in
conjunction with a modeling approach to estimate pollutant fluxes within
and through the box.
The release of multiple tracers for a sea-breeze experiment was also
considered. Tracers should be released near ground-level on the coastal
side of the convergence zone and inside the convergence zone. Injection
of tracers in cumulus clouds should be considered also. Ground-based
and airborne tracer sampling should be carried out to study
recirculation of pollutants by the sea-breeze and cloud venting in the
sea-breeze front.
The sea breeze program should also include studies of venting by
cumulonimbus and cumulus congestus clouds that form in the afternoon
inland along the sea breeze convergence zone. Because of the lengthy
extent of the zone roughly parallel to the coastline and its high
frequency (see Figure 5), it may be an effective mechanism for transport
of ozone precursors out of the Gulf Coast emissions source region,
thereby possibly minimizing local ozone formation and impacting regions
further downwind. It was recommended that inert gas tracers would
provide a useful method for quantifying the effects of cumulus-cloud
venting. One or more tracers released at or near the surface in the
convergence zone would be measured aloft by aircraft, both in the
63
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boundary layer and at the level of outflow near the cloud tops. For
practical reasons, cumulus congestus or small cumulonimbus clouds would
be preferable, as their tops are within the capabilities of available
research aircraft.
The work group recommended that a mesoscale sea breeze program
include on the order of 10 intensive studies carried out over a time
period of 10-12 weeks (3 months).
The following systems were considered necessary for the experiment:
• Aircraft with backscatter lidar for vertical profiling of
ambient particle and injected fluorescent particle-tracer
(Uthe, 1983; Ching et al., 1984)
• Aircraft with UV and IR DIAL (lidar) systems for vertical ozone
profiles
• Airborne capability for remote wind sensing, i.e., airborne
doppler radar (Hildebrand, 1983)
• Chemical aircraft with in-situ instrument measurement capability
• Scout aircraft for initial observations and atmospheric profiling
• Routine (ground-based) monitoring systems, such as the following:
- Doppler sodar (5-6 units)
- Doppler radar (1-2 units)
- T,p-sondes (5-6 units)
- Towers of opportunity
- Portable Automated Mesonet (PAM) systems (30-40 units)
- Rawinsondes (3 units)
Design of Medium Range Transport Experiment
An intermediate-range oxidant transport experiment would involve a
total time of 30-48 hours for atmospheric measurements, and would cover
a horizontal distance of 400-500 km from the Gulf Coast emissions
source. This distance would take the experiment from the
Houston-Galveston area northward into Oklahoma and Arkansas and would
focus on ozone and its precursors, and on released tracers. The
intermediate transport experiment would take place under conditions of
synoptic-scale southerly flow, preferably during the occurrence of a
nocturnal low-level jet.
64
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During daytime and possibly during nighttime, convective cumulus
clouds can be expected to develop in the southerly flow of warm, moist
(mT) air. Thus, cumulus convective transport will be part of the
experiment. Figure 15 shows the projected area (stippled boundaries)
for an intermediate range (high-level and low-level) transport
experiment. Measurements are recommended across three vertical planes
or "curtains" (dash-dot lines in Figure 15). Tracers and tetroons
should be released at a low level (e.g., 1500 m in the mixed layer under
the clouds) and at a high level (e.g., at the level of the cumulus
clouds). Measurements would be made for the purposes of:
100° W
90°
30° N
/ • /
\ ' * ' 1 * LITTLE ROCK /T /""?"" \ "" "~~T
_>: ". t_JlL. / \ S
• —^~% . • • « • • . » ' I • • 1* ••
'^^--^ ! ' »
. FT WORTH •
| BIRMINGHAM
» ® X I «l .
"V SHREVEPORT/ JACKSON
SAN ANTONIO _ HOUSTON
Figure 15. Projected area for intermediate transport experiment (dotted lines) showing location of
vertical planes or "curtains" for horizontal flux measurements (dash-dot lines).
65
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• Computing fluxes out of the mixed layer and out of the
cloud layer
• Validating parametric schemes for cumulus convection transport
in ROM.
Tracer releases in the low-level jet were also recommended in order
to define the transport characteristics of this phenomenon. It was
agreed, however, that more knowledge and information on the occurrence,
location, and spatial extent of the low-level jet is needed before a
detailed plan can be designed.
Enhanced Surface and Upper-Air Monitoring Network
The work group recommended that an enhanced network of surface and
upper-air observations be operated throughout the time period that the
mesoscale sea-breeze and intermediate transport programs are conducted.
The network area was outlined as extending from Fort Worth, Texas,
eastward to the Alabama border (about 300 km), and then 600 km southward
to a point approximately 200 km offshore. The existing National Weather
Service (NWS) radiosonde stations within the network area (about 6)
would be enhanced by 5-6 additional stations, including two stations
offshore to double the spatial resolution of the NWS network. Vertical
profiles of ozone would be obtained to 700 mb (10,000 ft msl) by
single-engine aircraft at each of 12 available radiosonde locations.
The network would be operated for a 3-month period.
The benefits of the enhanced observational network would be:
• Provision of offshore data
• 6-hour resolution on radiosonde ascents
• Vertical profiles of air quality obtained three-four times
per day.
An important element of the routine monitoring network should be the
acquisition of satellite, radar, and lightning data from existing
systems for the purposes of enhancing the definition of mesoscale
circulations and convective phenomena. Although these systems (for the
most part) are in place and operating, special attention should be
devoted to the archiving of these data (not routinely done). Satellite
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data should include visible and infrared observations from both
geostationary and polar-orbiting satellites. High-resolution,
false-color radar displays are available from several commercial sources
using data from National Weather Service radars. Operational lightning
detection networks (e.g. the lightning position and tracking system
available from Atlantic Scientific Corp., Melbourne, FL) already cover
most of the Gulf Coast area and should blanket the study region on the
time frame of the Gulf Coast oxidant program.
Some work group members raised the question whether or not the
enhanced routine monitoring network should be operated during an entire
summer prior to the mesoscale and intermediate transport experiments.
This could provide the 3-month data base needed to better understand the
impact of local and regional wind flow on high and low oxidant events (a
better understanding from an analysis of already existing data was
recommended by the workshop at large). Study of this special data base
would also help design a more effective (non-redundant) mesoscale
experiment.
The question of effects from stratospheric ozone was brought up
also. Since the mesoscale sea-breeze experiment and the medium-range
transport experiment are planned during the summer, upper tropospheric
low-pressure troughs with stratospheric ozone intrusions are not
expected to directly affect the Gulf Coast area. It was decided,
however, that background ozone measurements should be made in the middle
and upper troposphere to assess a possible stratospheric ozone
influence. These measurements can be part of the enhanced routine
monitoring network.
Long-Range Transport Experiment
The working group recommended that a long-range transport (-1000 km)
experiment not be conducted. Within the budgetary guidelines presented
by EPA, it was felt that the resources would more effectively be used to
conduct comprehensive mesoscale and intermediate-range studies.
Long-range experiments would best be undertaken as an adjunct to or in
67
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conjunction with separate programs such as long range acidic deposition,
transport and transformation studies conducted as joint multi-agency or
multi-organizational programs.
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SECTION 4
RECOMMENDATIONS FOR A CONCEPTUAL PROGRAM DESIGN
In their deliberations, the two working groups recommended that
research and development efforts should be undertaken preparatory to the
principal components of the major Gulf Coast oxidant study. As
summarized in Table 16, the preparatory efforts comprise both modeling
and data analysis studies, and experimental studies and hardware
development. In some cases, these efforts are not unique to the Gulf
Coast oxidant study or are already being actively pursued; these efforts
are not included in the conceptual experimental design presented later,
although in many cases the study would be seriously affected in the
event they are either unsuccessful or not completed in time. The
working groups provided subjective cost estimates which should be
considered indicative of the order of magnitude of each effort. Each
preparatory study is also given a subjective priority ranking. In
general, the high-priority efforts are essential for a high-quality Gulf
Coast oxidant study, while the moderate-priority efforts are highly
desirable. A low priority indicates that the results would be very
useful, but not essential. In one case, the priority would appear to be
ambiguous: a preparatory effort involving the operation of the enhanced
routine monitoring network (for a three-to-four-month period) one or two
years before the primary study, is prioritized both low and high. In
principle, the working groups suggested that operation of the network
and analysis of the data would be extremely desirable, provided it did
not jeopardize the overall study by excessively stretching the timetable
or expanding the costs beyond those likely to be available. In essence,
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TABLE 16. PREPARATORY STUDIES
Description
Estimate of
Cost ($000)f
Priority
Modeling and Data Analysis;
- collection, analysis and interpretation of
existing air quality and meteorological data
- application of Urban Airshed Model to Houston
- evaluation of Regional Oxidant Modelf (being
done by USEPA for northeastern states)
- ROM sensitivity study to evaluate impact of
natural hydrocarbon emissions?
• Experimental Studies and Hardware Development;
- develop gaseous aldehyde measurement
techniques (surface and airborne)T
- hydrogen peroxide instrument development*
(work ongoing elsewhere)
- smog chamber studies of Gulf Coast
atmospheres
- in-cloud chemistry studies (coordinate with
on-going studies) f
- continued development/improvement of airborne
wind-finding doppler radar (work on-going
elsewhere)f
- improvements in tracer technology, e.g.
fluorescent dye, perfluorocarbons, tetroons,
reactive tracers (work on-going elsewhere)
- improvements in remote measurement of ozone,
profiles by UV and IR DIAL (ongoing elsewhere):
- exploratory, limited-duration mobile (air-
borne) aerometric measurement program and
data analysis (limited)
- enhanced routine monitoring network for ozone,
hydrocarbons, and PEL structure
200-300 (p)
50-100 (g)
nc
nc
100-200 (p)
50 (p)
300 (p)
<500 (p)
nc
nc
nc
500-1000
1250-1500
H
M
H
H
M
M
M
M-H
M-H
H
H
L-H
**
**
H = high; M = medium, L = low priority
p = contract research; g = USEPA study
Study is not unique to Gulf Coast
-------
the decision to retain or delete the preparatory ERN* is a pragmatic one
that must be addressed by the Agency. The conceptual experimental
design that is presented below has retained the preparatory ERN.
The overall conceptual program design is summarized in Figure 16,
which includes a description of the major tasks as well as the
scheduling and estimated cost. The program is divided into four
elements:
(1) Preparatory analyses
(2) Preparatory measurement studies
(3) Gulf Coast regional oxidant transport study
*
(4) Reporting
In the following, a brief description is given of each task:
Tasks 1.1-1.2: All of the available and relevant air quality and
meteorological data from the study region would be
compiled to create a comprehensive data base. Both
routine long-term monitoring programs and short-term
case studies would be used. The data would be analyzed
to provide a better understanding of temporal and
spatial variations of oxidant throughout the region, and
to develop an improved understanding of the importance
of (for example) moisture, synoptic-scale wind flow,
long range transport, land-sea breeze circulation, and
low-level jet in the formation of high oxidant
concentrations.
Task 1.3: The SAI Urban Airshed photochemical simulation model,
or another suitable model, would be applied to the
Houston metropolitan area as a test of the hypothesis
that oxidant concentrations are anomalous; or that the
combination of relatively high HC-to-NO ratio, high
ambient humidity, and intense sunlight results in
chemical conditions that are different from other
regions.
Task 2.1: The enhanced routine monitoring network would be
established and operated for three months
(July-September). It would provide a comprehensive
ERN - Enhanced Routine Monitoring Network.
Systems Applications, Inc., San Rafael, California.
71
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Eulerian aerometric data base for the purpose of gaining
an improved understanding of oxidant formation and
transport, and of developing a detailed research plan
for the primary experimental program. The ERN would
include six-hourly light-aircraft soundings of
temperature, humidity, aerosol backscatter, and ozone at
each of 12 radiosonde locations; radiosondes would also
be released at six-hourly intervals. A two-part
analysis phase is suggested so that extended analyses
might be conducted where indicated by the results of a
basic analysis; e.g., in the event significant mesoscale
ozone transport or production is observed.
Task 2.2: An exploratory mobile sampling and data analysis task is
recommended to refine and coordinate mobile sampling
methods, and to provide a limited data base for the
purpose of optimizing the use of the various aircraft in
the primary study. The aircraft would include the
following sensors or sampling technologies:
wind-finding doppler radar, in situ ozone concentration
and flux, remote ozone profiling by UV or IR DIAL
(lidar), in situ gas tracer sampling and remote sensing
of injected fluorescent particle tracers by backscatter
lidar. This limited sampling program would focys on
developing sampling strategies and obtaining limited
data for the raesoscale land/sea breeze, cloud venting,
and medium-range transport experiments that are
anticipated to be conducted later during the primary
field study.
Task 2.3: Smog chamber studies would be conducted to simulate
photochemical oxidant production unique to the precursor
mixture of the Gulf Coast, and to explore the possible
effects of high relative humidity.
Task 3.1: A preliminary, detailed research plan and study design
would be developed for the experimental and analysis
phases of the Gulf Coast oxidant transport and
transformation study. This preliminary plan would be
based on the analysis of the historical aerometric data
base (Task 1.2) and the preliminary analysis of the
preparatory ERN effort (Task 2.1); preliminary
qualitative inputs from the exploratory mobile sampling
program (Task 2.2) would also be considered. The plan
would specify numbers and types of airborne platforms,
instrumentation specifications, and sampling strategies
and protocols. Also specified would be comprehensive
specifications for the surface aerometric network,
including parameters for measurement, analytical
methods, site locations, sampling frequency, data
processing and so forth. All aspects of tracer
applications in the mesoscale and medium-range transport
73
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Task 3.2:
Task 3.3;
Task 3.4:
Task 3.5:
studies would also be delineated, such as tracer-types,
and release, sampling and analysis methods. Scheduling
of the intermediate range transport case-studies would
also be addressed, including definition of criteria for
determining when or where experiments are to be
conducted, and contingency plans in the event
meteorological conditions are not optimum for the
fulfillment of the primary study objectives.
The preliminary research plan and study design would be
refined and finalized based on the results of the
analysis of the exploratory mobile sampling data (Task
2.2), and other available inputs.
Conduct the three-month primary field study of oxidant
transport and transformation. The study would have two
major aspects: (1) operation of an enhanced routine
monitoring network, and (2) short-term case studies of
mesoscale and medium-range transport and transformation.
The ERN operation is described in Task 2.1. The
short-term case studies would consist of (1) mesoscale
studies of pollutant transport and oxidant production
within the domain of the land/sea breeze circulation,
and (2) medium-range (ca 400-500 km) studies of oxidant
transport out of the Gulf emissions source region.
Cloud venting studies would be an integral component of
the mesoscale experiments. The mesoscale studies would
constitute the majority of the 10 case studies
recommended, and would rely heavily on a full complement
of airborne platforms in addition to the use of gas
tracers with airborne and surface in situ sampling.
Each study would cover a 30-hr period. A minimum sample
requirement would be three medium-range transport
experiments. The number of sampling platforms would be
reduced, and would consist primarily of two or three
remote ozone-profiling aircraft, and two or three in
situ ozone and gas tracer sampling aircraft. Multiple
gas tracers would be used to document effects of
altitude and release time-period on ozone transport;
variation of the ratio of tracer release rates of
multiple tracers with altitude or time would constitute
a unique identification of the time of release, and
would provide information on transport time and
longitudinal diffusion.
The data collected during the primary study (Task 3.3)
would be reduced and processed under this task.
Analysis of the processed data would occur under this
task, and would address several basic issues: (1)
relation of ozone formation to the precursor mix of the
74
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region, (2) impact of high humidity, (3) role and
significance of cumulus clouds in venting ozone or
precursors out of the boundary layer, (4) nature and
significance of medium-range oxidant and precursor
transport into and out of the region, (5) role of
land/sea breeze circulation in production of locally
high ozone concentrations, and (6) three-dimensional
spatial distribution of ozone on episodic days.
Task 4: Report the results of all preparatory, planning, data
collection, and analysis tasks.
As illustrated in Figure 16, the overall program could be accom-
plished in about five years at an estimated cost that ranges between 9.5
and 12.4 million dollars. In the event that the preparatory field
studies (i.e., ERN and exploratory mobile sampling) are deleted from the
program, then the estimated cost range would decrease to about 7.75 to
9.9 million dollars; the schedule might be compressed by approximate- ly
six months. The working groups did not, however, recommend the deletion
of the preparatory field studies. On the contrary, they were highly
recommended as necessary to the ultimate success of the program.
Finally, the Gulf Coast oxidant study should seek to integrate and
coordinate its activities with those of other major atmospheric studies
planned for the same time-frame and geographic domain. In particular,
the multi-agency national STORM program (STormscale Operational and Re-
search Meteorology) appears to be one such potentially viable mesoscale
study. STORM has been proposed by a steering committee composed of 13
representatives of member institutions of the University Corporation for
Atmospheric Research (UCAR). The National STORM Program would be sup-
ported at an annual cost of 60 to 120 million dollars per year for 10
years, and would involve major field programs in the east, midwest and
west in 1987, 1991 and 1993 (UCAR, 1983). These field programs would be
designed to obtain detailed observations of stormscale events and pheno-
mena, and would utilize such sophisticated measurement methods as:
digitized doppler and dual-polarized radar; advanced, densely spaced
upper-air sounding systems; automated surface observational networks;
instrumented aircraft; and geostationary and polar-orbiting satellite
display and analysis systems.
75
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A second candidate program is a projected 100 million dollar acid
precipitation study (MATEX) of long-range atmospheric transport and
transformation being considered by the Electric Power Research
Institute. A MATEX design and feasibility study is currently underway
and should be completed later this year, although preliminary
indications are that it could overlap the geographical domain and
schedule of the Gulf Coast oxidant study. Integration of the Gulf Coast
oxidant study with programs like STORM and MATEX should be pursued
because of the benefits of technical synergism and cost savings that
would result.
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SECTION 5
CONCLUSIONS AND RECOMMENDATIONS
The two working groups recommended that some preparatory research
and development efforts should be undertaken in addition to the
principal components of the major study itself. The overall conceptual
design is outlined in Figure 1.
In the preparatory-analysis phase, currently available air quality
and meteorological data from the study region would be compiled to
create a comprehensive data base. The data would be analyzed to provide
a better understanding of temporal and spatial variations of oxidant
throughout the region, and to develop an improved understanding of the
importance of (for example) moisture, synoptic-scale wind flow, long
range transport, land-sea breeze circulation, and low-level jet in the
formation of high oxidant concentrations. Additionally, a photochemical
simulation model would be applied to the Houston metropolitan area as a
test of the hypothesis that oxidant concentrations are anomalous or that
the combination of relatively high HC-to-NOx ratio, high ambient
humidity, and intense sunlight result in chemical conditions that are
different from other regions.
As part of the preparatory measurement/study phase, an enhanced
routine monitoring network (ERN) would be established and operated for
three months to provide a comprehensive Eulerian aerometric data base.
The purpose would be to gain an improved understanding of oxidant
formation and transport, and to develop a detailed research plan for the
primary experimental program. This limited sampling program would focus
on developing sampling strategies, and on obtaining limited data for the
mesoscale land/sea breeze, cloud venting, and medium-range transport
77
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experiments that are anticipated to be conducted later during the
primary field study.
A preliminary, detailed research plan and study design would be
developed for the experimental and analysis phases of the principal Oulf
Coast oxidant transport and transformation study. The plan would
specify numbers and types of airborne platforms, instrumentations
specifications, and sampling strategies and protocols. Also specified
would be comprehensive specifications for the surface aerometric
network, including parameters for measurement, analytical methods, site
locations, sampling frequency, data processing and so forth. All
aspects of tracer applications in the raesoscale and medium-range
transport studies would also be delineated, such as tracer-types, and
release, sampling and analysis methods. Scheduling of the intermediate
range transport case-studies would also be addressed, including
definition of criteria for determining when or where experiments are to
be conducted, and for contingency plans in the event meteorological
conditions are not optimum for the fulfillment of the primary study
objectives.
The three-month primary field study of the oxidant transport and
transformation would have two major aspects: (1) operation.of the
enhanced routine monitoring network, and (2) short-term case studies of
mesoscale and medium-range transport and transformation. The short-term
case studies would consist of (1) mesoscales studies of pollutant
transport and oxidant production within the domain of the land/sea
breeze circulation and (2) medium-range (ca 400-500 km) studies of
oxidant transport out of the Gulf emissions source region. Cloud
venting studies would be an integral component of the mesoscale
experiments. The mesoscale studies would constitute the majority of the
10 case studies recommended, and would rely heavily on a full complement
of airborne platforms in addition to the use of gas tracers with
airborne and surface in situ sampling. Each study would cover a 30-hour
period. On the order of three medium-range transport experiments are
contemplated. Analysis of the processed data would address several
basic issues: (1) relation of ozone formation to the precursor mix of
78
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the region, (2) impact of high humidity, (3) role and significance of
cumulus clouds in venting ozone or precursors out of the boundary layer,
(4) nature and significance of medium-range oxidant and presursor
transport into and out of the region, (5) role of land/sea breeze
circulation in production of locally high ozone concentrations, and (6)
thee-dimensional spatial distribution of ozone on episodic days.
The overall program could be accomplished in about five years at an
estimated cost that ranges between 9.5 and 12.4 million dollars. In the
event that the preparatory field studies (i.e. ERN and exploratory
mobile sampling) are deleted from the program, the estimated cost would
range between 7.75 and 9.9 million dollars and the schedule might be
compressed by approximately six months. The working groups did not,
however, recommend the deletion of the preparatory field studies. On
the contrary, they were recommended highly as necessary to the ultimate
success of the program.
Finally, the Gulf Coast oxidant study should seek to integrate and
coordinate its activities with those of other major atmospheric studies
planned for the same time frame and geographic domain. The multi-agency
national STORM program (STormscale Operational and Research Meteorology)
appears to be one such potentially viable mesoscale study. STORM has
been proposed by a steering committee composed of 13 representatives of
member institutions of the University Corporation for Atmospoheric
Research (UCAR), and would be supported at an annual cost of 60 to 120
million dollars per year for 10 years, (UCAR, 1983). A second candidate
program is a projected 100 million dollar acid precipitation study
(MATEX) of long-range atmospheric transport and transformation being
considered by the Electric Power Research Institute. A MATEX design and
feasibility study is currently lunderway, and sould be completed later
this year. Preliminary indications are that it could overlap the
geographical domain and schedule of the Gulf Coast oxidant study.
Integration of the Gulf Coast oxidant study with programs like STORM and
MATEX should be pursued because of the benefits of technical synergism
and cost savings that would result.
79
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REFERENCES
Cantrell, B.K., F.L. Ludwig, and H.B. Singh, 1982: "A Review of the
Fate of NO and Its Role in Rural Ozone Formation," Revised Task
Report, SRI Project 3643, U.S. Environmental Protection Agency, CR
809330010 Research Triangle Park, NC.
Ching, J.K.S., E.E. Uthe, B.M. Morley, and W. Viezee, 1984:
"Observational Study of Transport in the Free Troposphere," Paper
presented at Fourth Joint Conference on Applications of Air
Pollution Meteorology with APCA, October 16-19, Portland, OR.
Clark, T.L., 1980: "Annual Anthropogenic Pollutant Emissions in the
United States and Southern Canada east of the Rocky Mountains, "
Atmos. Env., Vol. 14, pp. 961-970.
Decker, C.E., L.A. Ripperton, J.J.B. Worth, F.M. Vukovich, W.D. Bach,
J.B. Tommerdahl, F. Smith, and D.E. Wagoner, 1976: "Formation and
Transport of Oxidants Along Gulf Coast and in Northern U.S.,"
Contract No. EPA-450/3-76-033, U.S. Environmental Protection
Agency, Research Triangle Park, NC.
Eaton, W.C., C.E. Decker, J.B. Tommerdahl, and F.E. Dimmock, 1979:
"Study of the Nature of Ozone, Oxides of Nitrogen and Nonmethane
Hydrocarbons in Tulsa, Oklahoma," EPA Report No. EPA-450/4-79-008a.
Horie, Y., M. Marians, J. Trijonis, P. Hurt, N. Chang, 1979: "Analysis
of Oxidant for Precursor Emissions/Ambient Precursor Relationship,"
Final Report TSC-PD-A196-5, Technology Service Corp., Santa Monica,
CA.
Lamb, R.G., 1982: "A Regional Scale (1000 km) Model of Photochemical Air
Pollution — Part 1. Theoretical Formulation," Paper, U.S.
Environmental Protection Agency, NC.
Lambeth, B.W., 1978: "Detailed Case Studies of Summer Ozone Events in
Southern Louisiana," Technical Note, Contract No. 68-02-1383, U.S.
Environmental Protection Agency, Research Triangle Park, NC.
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Lonneman, W.A., J.J. Bufalini, and R.L. Seila, 1976: "PAN and Oxidant
Measurements in Ambient Atmospheres," Env. Sci. & Technol., Vol.
10, p. 374.
Martinez, J.R. and H.B. Singh, 1979: "Survey of the Role of NOX in
Nonurban Ozone Formation," SRI International, Menlo Park, CA.,
Final Report, SRI Project 6780-8.
Niemeyer, L.E., 1977: "Long Range Transport of Ozone Across the
Midwestern and Eastern United States," Atmos. Env., Vol 11, No. 11,
pp. 1119-1120.
Ruff, R.E., L.S. Gasiorek, and H. Shigeishi, 1977: "Master Data File
from the Summer 1975 Northeast Oxidant Transport Study," User's
Manual, SRI International Project 3570-29 for EPA Contract
68-01-2940 (Task 029), U.S. Environmental Protection Agency,
Boston, MA.
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.
Spicer, C.W., D.W. Joseph, and G.F. Ward, 1978: "Investigations of
Nitrogen Oxides Within the Plume of an Isolated City,"
Battelle-Columbus Report to CRC (CAPA-9-77) July.
Spicer, C.W., J.R. Koetz, G.W. Keigley, G.M. Sverdrup, and G.F. Ward,
1981: "A Study of Nitrogen Oxides Reaction within Urban Plumes
Transported over the Ocean," Report for EPA Contract 68-02-2957,
Battelle Laboratories, Columbus, Ohio, 167 pp.
Trijonis, J., 1979: "Historical Emission and Ozone Trends in the Houston
Area," Proc. of Specialty Conf. on Ozone/Oxidants: Interactions
with the Total Environment, (edited by the Air Pollution Control
Association), October 14-17, 1979, Houston, Texas.
U.S. EPA, 1977: "Effectiveness of Organic Emission Control Programs as a
Function of Geographic Location," EPA, OAQPS, Research Triangle
Park, NC.
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Spicer, C.W., J.R. Koetz, 6.W. Keigley, G.M. Sverdrup, and G.F. Ward,
1981: "A Study of Nitrogen Oxides Reaction within Urban Plumes
Transported over the Ocean," Report for EPA Contract 68-02-2957,
Battelle Laboratories, Columbus, Ohio, 167 pp.
Trijonis, J., 1979: "Historical Emission and Ozone Trends in the Houston
Area," Proc. of Specialty Conf. on Ozone/Oxidants: Interactions
with the Total Environment, (edited by the Air Pollution Control
Association), October 14-17, 1979, Houston, Texas.
U.S. EPA, 1977: "Effectiveness of Organic Emission Control Programs as a
Function of Geographic Location," EPA, OAQPS, Research Triangle
Park, NC.
University Corporation for Atmospheric Research, 1983: The National
STORM Program, A Call to Action, Boulder, CO, 34 pp.
lithe E.E., 1983: "Applications of Surface Based and Airborne Lidar
Systems to Environmental Monitoring," J. Air Pol. Contrl. Assoc.,
Vol. 33, No. 12.
Vaughan, W.M., M. Chan, B. Cantrell, and F. Pooler, 1982: "A Study of
Persistent Elevated Pollution Episodes in the Northwestern United
States, Bull. Amer. Meteorol. Soc., 63, pp. 258-266.
Wolff, G.T., P.J. Lioy, G.D. Wight, R.E., Meyers, and R.T. Cederwall,
1977: "An Investigation of Long-Range Transport of Ozone Across
the Midwestern and Eastern United States," Atmos. Env., 11, pp.
797-802.
Wolff, G.T. and P.J. Lioy, 1980: "Development of an Ozone River
Associated with Synoptic Scale Episodes in the Eastern United
States," Env. Sci. and Tech., 14, pp. 1257-1260.
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LIST OF PARTICIPANTS
Dr. Al Bowman
Institute for Storm Research
3600 Mt. Vernon
Houston, TX 77006
Dr. Joseph Bufalini (MD-84)
ASRL
Office of Res. & Development
U.S. EPA
Research Triangle Park, NC 27711
Dr. Jason Ching (MD-80)
ASRL
Office of Res. & Development
U.S. EPA
Research Triangle Park, NC 27711
Dr. John Clarke (MD-80)
ASRL
Office of Res. and Development
U.S. EPA
Research Triangle Park, NC 27711
Dr. Timothy Crawford
Tennessee Valley Authority
Air Resources Program
River Oaks Building
Muscle Shoals, AL 35660
Dr. Kenneth Demerjian (MD-80)
ASRL
Office of Research and Devel.
U.S. EPA
Research Triangle Park, NC 27711
Dr. Basil Dimitriades (MD-59)
ASRL
Office of Research & Devel.
U.S. EPA
Research Triangle Park, NC 27711
Mr. Richard Haws
Research Triangle Institute
Research Triangle Park, NC 27709
Dr. S.A. Hsu
Coastal Studies Institute
Louisiana State University
Baton Rouge, LA 70803
Dr. Donald Lenschow
NCAR
P.O. Box 3000
Boulder, CO 80307
Dr. Waiter A. Lyons
R-SCAN Corporation
511 Eleventh Avenue South
Minneapolis, MN 55415
Dr. James L. McElroy
AMI EMSL-LV
EPA
P.O. Box 15027
Dr. Edwin L. Meyer (MD-14)
Office of Air Qual. Ping.
and Standards
U.S. EPA
Research Triangle Park, NC 27711
Dr. William Pennell
Battelle-PNL
Atmospheric Science Department
P.O. Box 999
Richland, WA 99352
Dr. Fran Pooler
ASRL
U.S. EPA
Research Triangle Park, NC 2711
83
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Dr. Jack Durham (MD-84)
ASRL
Office of Research & Devel.
U.S. EPA
Research Triangle Park, NC 27711
Dr. Marcia Dodge (NMD-84)
ASRL
Office of Research & Devel.
U.S. EPA
Research Triangle Park, NC 27711
Dr. Scott Shipley
NASA Langley Research Center
MS-401A
Hampton, VA 23665
Mr. Eugene Start
NOAA/ARL/Idaho Research Office
Idaho National Engineering Lab.
Idaho Falls, Idaho 83401
Dr. Fred M. Vukovich
Research Triangle Institute
Research Triangle Park, NC 27711
Dr. Stephen Wise
Coordinating Research Council
c/o Mobil Research and Development
Research Department
Paulsboro, NJ 08066
Mr. James Price
Texas Air Control Board
Control Strategy Division
6330 Highway 290 East
Austin, TX 78723
Mr. Kenneth Schere
ASRL
Office of Res. & Devel.
U.S. EPA
Research Triangle Park, NC 27711
Dr. Jack Schreffler
ASRL
U.S. EPA
Research Triangle Park, NC 27711
Dr. Gary K. Tannahill
Exxon Company, USA
800 Bell Avenue
P.O. Box 2180
Houston, TX 77001
Dr. Harry Walker
Monsanto
P.O. Box 711
Alvin, TX 77511
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TECHNICAL REPORT DATA
(Please read Initmctions on tHe rtvme before completing/
1. REPORT NO.
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
CONCEPUTAL DESIGN FOR A GULF COAST OXIDANT TRANSPORT
AND TRANSFORMATION EXPERIMENT
Workshop Proceedings and Recommendations
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Walter F. Dabberdt, William Viezee and
Hanwant B. Singh
B. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
SRI International
333 Ravenswood Ave.
Menlo Park, CA 94025
CDHA1A/02 — 20G4 fFY-85^
11. CONTRACT/GRANT NOT
68-02-3752
12. SPONSORING AGENCY NAME AND ADDRESS
Atmospheric Sciences Research Laboratory—RTP, NC
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA/600/09
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Thirty atmospheric scientists from government, industry, academia, ana
the private research sector participated In a workshop in November 1983, in Durham,
NC to develop'a conceptual design for a study of ozone transport and transformation
in the western Gulf coast area. The purpose of the study would be to better under-
stand the unique meteorology and chemistry of the region, and to effectively adapt
the EPA Regional Oxidant Model to that geographic area. Working groups focused on
the problems of meteorology and atmospheric chemistry and measurement needs and
methods. A conceptual design was developed for a five-year program that would in-
clude preparatory studies,the 3-month primary experimental program, and data ana-
lysis. The preparatory studies would consist of the collection and analysis of all
existing data, simulation modeling, smog chamber studies, Instrument development, and
preliminary, limited field measurements. The primary experiment would consist of an
enhanced monitoring network operated continuously, and frequent, Intensive short-term
experiments; the geographical domain of the study would be about 300 km east-west and
800 km north-south. The routine monitoring would include boundary!ayer profiles of
aerometric parameters by light aircraft and enhanced radiosonde coverage. The inten-
sive studies would rely heavily on sophisticated aircraft platforms such as doppler
radar, UV and IR lidar, backscatter lidar, and 1n-s1tu gas concentration'and flux
measurments; gaseous and fluorescent particulate tracers would also be used.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTlFIERS/OPEN ENDED TERMS [c! COSATI Field/Group
18. DISTRIBUTION STATEMENT
19. SECURITY CLASS /Till! Report)
21. NO. OF PAGES
RELEASE TO PUBLIC
UNCLASSIFIED
20. SECURI
22. PRICE
EPA fftm 2220-1 (R«». 4-77) PRCVIOU* COITION is OBSOLETE
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