EPA/600/A-96/010
AN OVERVIEW OF THE NORTH AMERICAN RESEARCH STRATEGY FOR
TROPOSPHERIC OZONE
Kenneth L. Schcrc'
Atmospheric Sciences Modeling Division
Air Resources Laboratory
National Oceanic and Atmospheric Administration
Research Triangle Park, NC U.S.A.
INTRODUCTION
Tropospheric o/.one (O,), and related products
i>t photochemical smug, have been the subiect of
repealed control attempts lor nearly 30 years in
portions of North America. These truce gases art-
known to be harmful to humans, animals,
vegetation, and materials As growth and
industrialization have migrated from urban areas to
suburban and rural areas, these pollutants have
traveled as well. Previous efforts at smog control
often have not met expectations, in part, because of
the incomplete scientific understanding of the
complex physical, chemical, and biological
processes affecting the accumulation of O, Also
contributing to the problem was an inadequate
monitoring network to verify the effectiveness of
past emissions control measures for the precursors
of 0„ notably nitrogen oxides (NO,) and volatile
organic compounds (VOC). A part of the problem
can be attributed to the fact that tropospheric (),
research has been sponsored by a variety of
government and non-government org an i rations, with
their individual efforts largely uncoordinated.
In a major review of the state of-science, the
U.S. National Academy of Sciences (NAS, 1991)
called for a comprehensive program of tropospheric
O, research that would be coordinated across
organizations from government (federal,
state/provincial, and local), industry, academia, and
other private-sector interests within North America.
Hie NAS cited the stratospheric O, research
program as a successful model on which a program
of tropospheric research might be patterned. The
present effort, described here, is known as the North
American Research Strategy for Tropospheric
O/.one (NARSTO). Over the next few years after
the publication of the NAS report, a series of
discussions and workshops took place among the
principal sponsors, performers, and customers of
North American tropospheric Q, research.
Participants came from government organizations,
industry and private sector groups, including the
electric power, automobile, petroleum, and chemical
industries, the university and contractor research
communities, as well as non-profit environmental
interest groups. A broad consensus toward
coordinated collaborative research has emerged from
these discussions, illustrated by the publication of
the NARSTO Research Strategy and Charter (1994).
The principal goals of the 10-year NARSTO
program are to:
develop and implement, a research strategy
reflecting both scientific and policy concerns
conduct timely, productive, pohcv-relevant
tropospheric O, research with frequent and
appropriate reporting of the research results to
the scientific, policy, and air quality
management communities
•	develop and deliver timely, useful, and
scientifically credible assessment tools and
guidance to the policy and air quality
management communities
provide periodic state-of-science assessments of
the North American O, problems and their
control, and to revise the NAP.STO research
strategy based upon the identified assessment
needs and remaining scientific gaps and
uncertainties
•	provide a clearinghouse of current scientific
and technical information generated as part of
NARSTO (i.e., data, publications, results),
ORGANIZATION
An organization has been created to work
toward the NARSTO research goals. It is designed
to provide sustained coordination, collaboration, and
leveraging of resources in tropospheric O, research
across all participating groups. The organization
and management structure aims to facilitate a high
level of individual organizational ownership in the
NARSTO program, and allows for each
organization to maintain its own sovereignty and
decision-making within NARSTO. Figure I
illustrates the NARSTO structure.
The Executive Steering Committee, composed
of less than 12 representatives from the Executive
1 On assignment to the National Exposure Research Laboratory. U S Environmental Protection Agency, Research
Triangle Park. North Carolina

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executive Maeeeur
exECvnvesTHwie
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figure 1. NARSTO organisational structure
Assembly (all NARSTO sponsoring oiganizations).
is responsible for overall guidance and high-level
decision-making within NARSTO. The Stakeholder
Council consists of all public and private parties
which have interests in the outcomes of NARSTO
research. The Science Advisory Council provides
independent peer review of NARSTO plans and
actions, and consists of a panel of internationally
recognized and qualified scientists. The
Management Coordinator is responsible for the day-
to-day operant is and communications of the
NARSTO program. The Science and Resource
Planning Group assists the Management Coordinator
by defining and coordinating the research needed to
address the science and policy concerns, and
recommending which sponsoring organizations
might take responsibility for funding which
activities. At present approximately 70
organizations in North America have signed the
NARSTO Charter, indicating a willingness to fully
participate in the research program. Table I
illustrates a partial list of these organizations.
Most of the real work of NARSTO, pursuing
scientific research and assessment, occurs within the
technical teams. The Analysis and Assessment
Team produces periodic state-of-science
assessments of fundamental knowledge and applied
methods related to tropospheric Oj, coordinates the
assessment-related activities of the other technical
teams, and provides recommendations for data
management, archival, and dissemination. Activities
of the Observations Team consist of methods and
Table I. Partial List of NARSTO
Organizations
Government
U S Dept. of Commerce (NOAA)
U S Environmental Protection Agency
U.S. National Science Foundation
U.S. Dept. of Energy
Environment Canada
Instituto Nacional de Ecologia-Mexico
California Air Resources Board
New York Dept of Envir Conservation
Non-government
Electric Power Research Institute
American Petroleum Institute
Coordinating Research Council
Instituto Mexicano del Petroleo
General Motors Corporation
Ford Motor Company
E I. DuPont deNemours & Company
analysis research applicable for monitoring
networks, research-grade intensive measurements
and field campaigns, and diagnostic analysis of
observations. The Modeling and Chemistry Tenm
pursues air quality and meteorological model
development, model applications and evaluation
research, laboratory and smog chamber studies, and
chemical mechanism development. The Emissions
Team activities include emissions model
development, process and activity analysis, source
and ambient emissions field studies, and emissions
projection and control technology implications
analysis. A Quality Systems Science Center is
being designed by »n ad hoc Quality Systems and
Data Management Team, to ensure that quality
management systems are implemented within
NARSTO. The team plans and conducts audits on
the critical NARSTO program elements, and
coordinates data management, archival, and
dissemination. Finally, the Liaison Team maintains
communication links with the principal customer
communities for NARSTO research, including those
of health and ecological effects research, emissions
control technology research, and public policy and
air quality management. Table 2 lists the current
Team Leaders and their affiliations.

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Table 2. NARSTO Team Leaders
Management Coordinator
Dr. Jeremy Hales (Envair)
Analysis and Assessment Team
Dr. George Hidy (Univ. of California-Riv)
Mr. Kenneth Schere (U.S. EPA)
Observations Team
Dr. Fred Fehsenfeld (NOAA)
Dr. Phil Galvin (New York State-DEC)
Modeling/Chemistry Team
Dr. Robin Dennis (U.S. EPA)
Dr. S T. Rao (New York State-DEC)
Emissions Team
Dr. Kenneth Knapp (U.S. EPA)
Dr. Doug Lawson (Colorado State Univ.)
Quality Systems and Data Management Team
Mr. Ronald Patterson (U.S. EPA)
Liaison Team
Mr. Blaine DeHaven (Pennsylvania-DER)
RESEARCH DIRECTIONS
NARSTO is committed to research that is
relevant to public policy on air quality management.
In working with the policy community, the
following set of policy concerns/questions have
been posed to the NARSTO research community:
•	For a given area, how do we determine that an
O, problem exists, and how do we determine
its severity?
•	What portion of the problem is essentially
.rreducible (based on such factors as natural
emissions of precursors and stratospheric O,
flux) and what portion of the problcn is
potentially controllable?
•	Do we have evidence that existing control
measures are having an impact?
•	What are optimal approaches for reducing
current and future high O, concentrations?
•	What is the magnitude and impact of trans-
national-boundary transport of O, and its
precursors?
•	How can the relevant science and scientific
uncertainties be meaningfully communicated to
the air quality management and policy
communities?
In response to these policy concerns NARSTO
will organize on-goin?, and future research around
several major themes. The first theme is
determining trends in concentrations of 03 and its
precursors (NO,, VOCs, CO) on local and regional
scales in North America. Analysis of 0, exposures
over time by humans and vegetation requires a
sustained effort in urban and rural O, measurements.
Large areas of North America, especially in non-
urban regions that may be sensitive to O, exposures,
do not have adequate monitoring. Sustained
measurements of precursors are seen less often.
The Photochemical Assessment Monitoring Stations
(PAMS) is one such effott in the U.S. PAMS sites
began operating in 1994. Building a record of
precursor measurements is a necessary step in
confirming the accuracy of emissions inventories
and evaluating the effectiveness of emissions
controls on NO,, VOCs, and CO. Normalizing the
trends of these trace gas concentrations for the
variability in the meteorological signal is a
particular challenge in interpreting trends.
A second theme is obtaining a better
understanding of the physical, chemical, and
meteorological processes responsible for O,
accumulation on local and regional scales in North
America. Res arch along this theme pursues
analysis of data taken during intensive field and
laboratory studies focused on particular processes.
Some recent examples of such studies include the
Southern Oxidants Study (SOS), emphasizing the
role of biogenic precursor emissions in oxidant
photochemistry in the southern U.S., the NARSTO-
NE study, focusing on the inter-urban transport of
smog precursors and products in the northeast U.S.
and southeast Canada, and the Mexico City Air
Qualit; Research Initiative (MARI), studying smog
formation processes in a densely populated high-
altitude urban area with complex flow regimes.
Longer-term research in the fundamental chemistry
of oxidant processes is also encompassed by this
theme. Laboratory and smog chamber studies are
needed to further explore poorly understood
chemical pathways, especially for some of the
complex reactive organic species. Another
important component is methods research leading to
improved measurement capabilities for key chemical
and meteorological parameters, especially using
remote sensing technologies to obtain vertical
profiles in the atmosphere.
The third theme is incorporau.ig our evolving
knowledge of processes into the development,
evaluation, and refinement of models that allow us
to diagnostically explain the relevant phenomena
and to predict future atmospheric states based on
perturbations of major forces, such as precursor
emissions reductions or increases. These models
include both observations based diagnostic models
as well as emissions-based chemical-transport
models. Such models have evolved in recent years
to encompass complete modeling systems, including
sophisticated meteorological models with four-
dimensional data assimilation, emissions models
with increasingly realistic emissions activity patterns
and source term magnitudes, and highly-resolved
(temporally, spatially, and chemically) chemical-
transport models. These models contain a synthesis

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of our scientific understanding of how the various
atmospheric processes work and how they
interrelate to produce O, and other smog products.
In conjunction with the intensive field data
discussed above, NARSTO research will evaluate
and improve the evolving class of multi-scale air
quality models. Solomon (1995) provides a review
of many recent Oj field and modeling studies
conducted in North America.
A fourth theme integrates information from the
earlier themes to evaluate and assess the relative
contribution of VOCs and NO,, and their control, to
O, accumulation on local and regional scales. The
relevant question here is whether oxidant production
is limited more by availability of NO. or of VOCs,
and whether this limitation changes from day to day
for a given area, or from area to area on a gi.en
day. A complicating factor in the analysis is the
role of transport of O, and precursors between
urban areas, and from urban areas to rural areas and
vice versa. Recent evidence (NAS, 1991) illustrates
that much of eastern North America may be NO,-
limited for O, formation, but in and around major
urban centers such as Chicago and New York the
highest O, concentrations arc limited more by
VOCs. It is clear that more data collection and
research must yet occur before the best approaches
and technologies can be determined for reducing O,
concentrations on local and regional bases in North
America.
NARSTO Assessment
While a major thrust of NARSTO is
coordinating the research being conducted along the
lines of the above major themes, a short-term goal
is to produce an updated stale-of-science assessment
by 1998. This time period was chosen since it is
just in advance of several key analysis and decision
points for the policy and air quality management
communities in the U S. Timely production of a
NARSTO assessment should assist these
communities in making decisions for the beginning
of the next century that are based on the most
current sound science.
Key components of the assessment will be:
•	Review papers on the statj-of-science both at
the process level and from an integrated
knowledge perspective
•	New analysis of existing data sets using a
common set of diagnostic techniques
« Survey papers on methods development,
including:
comparative assessments of measurement
techniques for key species
evaluation of diagnostic data analysis
techniques (observations-based models)
cross-model comparative evaluations
model sensitivity analyses with process-
level diagnostics
evaluation of current emission inventories
reconciliation techniques between
emissions inventory and ambient data
Another objective of the assessment will be to
provide recommendations on longer-term research
to fill remaining knowledge gaps
SUMMARY
The NARSTO provides for a 10-year research
program in the chemical, physical, and
meteorological aspects of tropospheric O, science.
The research is Mended to conduct both short-term
and long-term studies producing documented results
that are relevant to the customer communities,
including those of policy, effects, and control
technologies Major elements of the program will
include state-of-science assessments, coordination of
on-going research in North America, and the
promotion of new relevant scientific initiatives.
NARSTO is being built on an organizational
structure that encourages all organizations within
North America that sponsor or participate in
tropospheric O, research to participate in the
program.
DISCLAIMER
This paper has been reviewed in accordance
with the U S. Environmental Protection Agency's
peer and administrative review policies and
approved for presentation and publication. Ment-on
of trade names or commercial products does not
constitute endorsement or recommendation for use.
REFERENCES
NARSTO, 1994. NARSTO Research Strategy and
Charter, US Environmental Protection
Agency, Research Triangle Park, NC, 155 pp.
NAS, 1991. Rethinking the Ozone Problem in
Urban and Regional Atr Pollution, National
Academy Press, Washington, DC, 489 pp.
Solomon, P.A., 1995. Regional photochemical
measurement and modeling studies: A summary
of the Air and Waste Management Association
International Specialty Conference. J. Air A
Waste Manage. Assoc. 45:253-286.

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TECHNICAL REPORT DATA
—
1. REPORT NO.
EPA/600/A-96/010
2 .
3 . RE(
4. TITLE AND SUBTITLE
An Overview of the North American Research Strategy
for Tropospheric Ozone
5.REPORT DATE
6.PERFORMING ORGANIZATION CODE
7. AUTHOR (S)
Kenneth L. Scherc
B.PERFORMING ORGANIZATION REPORT
NO.
9 PERFORMING ORGANIZATION NAME AND ADDRESS
Same as Block 12.
10.PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
National Exposure Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
13.TYPE OF REPORT AND PERIOD
COVERED
Proceedings, FY-96
14 SPONSORING AGENCY CODE
EPA/600/9
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Tropospheric ozone (0,), and related products of photochemical smog, have been the
subject of repeated control attempts for nearly 30 years in portions of North
America. These trace gases are known to be harmful to humans, animals, vegetation,
and materials. As growth and industrialization have migrated from urban areas to
suburban and rural areas, these pollutants have traveled as well. Previous efforts
at smog control often have r.ot met expectations, in part, because of the incomplete
scientific understanding of the complex physical, chemical, and biological
processes affecting the accumulation of 0). Also contributing to the problem was
an inadequate monitoring network to verify the effectiveness of past emissions
control measures for the precursors of 0,, notably nitrogen oxides (NO,) and
volatile organic compounds (VOC). A part of the problem can be attributed to the
fact that tropospheric Oj research has been sponsored by a variety of government
and non-government organizations, with their individual efforts largely
uncoordinated.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b.IDENTIFIERS/ OPEN ENDED
TERMS
c.COSATI



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