Tropospheric Aerosol Program--A Vision

Viewgraphs prepared for the

Environmental Sciences Division

U.S. Department of Energy

January, 1999

Tropospheric Aerosol Program

It is proposed that a major research program be initiated...

Directed to improved understanding and capability to
represent in models the chemical and physical processes
controlling the...

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Mass loading, composition, and microphysical
properties of tropospheric aerosols.

Requirement for Tropospheric Aerosol Research
Program

The National Research Council has repeatedly called
for major research efforts directed to tropospheric
aerosols to...

l Develop advanced mathematical, modeling, and
monitoring tools to represent the relationships
between specific sources of particulate matter and
human exposures.
- Research Priorities for Airborne Particulate Matter (1998)

l Reduce uncertainties in aerosol forcing to within
±15% globally and locally.
- Aerosol Radiative Forcing and Climate Change (1996)

Why a Tropospheric Aerosol Program?

Understanding the processes that control
the loading, geographical distribution, and
chemical and physical properties of

anthropogenic atmospheric aerosols is
central to key environmental issues
affecting the nation's energy economy:

lAir Quality (PM-2.5)

l Regional Haze

lClimate Change

Air Quality Standards

New standards for particulate matter of

Diameter < 2.5 µm(PM-2.5 standards).

Mass loading not to exceed:

15 µg m^-3 (annual mean)

65 µg m^-3 (24-h, 98th percentile)

Locations of Coal-Fired and Heavy Oil-Fired Plants
Relative to Potential Non-Attainment Counties

1997 RESOURCE DATA INTERNATIONAL, INC.

Chemical Speciation of sub-2.5 µm Aerosol

Proposed Regional Haze Standards

Most impaired days:

Improvement in visibility by one deciview per 10 (or 15) years.

Decrease of one deciview corresponds to 10 % decrease in
s_ext

Least impaired days:

No worsening of visibility.

Relation between Extinction Coefficient,
Fine Particle Mass Loading and Deciviews

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Mass Loading (for a = 10 m² g^-1), µg m^-3

Time Series of Light Scattering Coefficient and Fine Particle Mass

Time series of light scattering coefficient is scaled to fine particle mass by daily averages.

- Husar, 1997

Correlation of Light Scattering Coefficient and Fine Particle Mass

Husar, 1997

Aerosol Influence on Climate Change

Tropospheric anthropogenic aerosols influence
climate directly by scattering solar radiation and
indirectly by modifying the microphysical and
light scattering properties of clouds.

Uncertainties in aerosol forcing are greatest
source of uncertainty in climate forcing over
the industrial period.

Climate influence of Tropospheric Aerosol
"Whitehouse Effect"

Uncertainty in Aerosol Forcing Dominates Uncertainty
In Climate Forcing Over The Industrial Period

- Schwartz & Andreae (Science, 1996), after IPCC(1996)

Tropospheric Aerosol Program

Application of TAP Research

The same understanding ofthe...

Aerosol Life Cycle...

Processes controlling aerosol loading, composition, and
microphysical properties and...

Evaluated models of these processes...

Are necessary for informed decision-making on PM-2.5,
Regional Haze, and Climate issues.

Objectives, Scope, and Approach of TAP

TAPwill...

Develop the fundamental scientific understanding required to
construct tools for simulating the life cycle of tropospheric
aerosols--the processes controlling their mass loading,
composition, and microphysical properties, all as a function of
time, location, and altitude.
Represent this understanding in models, and apply and evaluate
these models.
Consist of closely linked field, modeling, laboratory, and
theoretical studies focused on formation, growth, transport, and
deposition.
Work closely with other programs in DOE and in other agencies
directed to related aerosolissues.

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Intensive Field Campaigns in TAP

TAPwill...

Conduct a series of intensive field campaigns at a variety of

representative locations.

Focus on aerosol loading, properties, and evolution within the first

200 km of emissions.

Examine the dependence of aerosol evolution on the atmospheric

chemical and photochemical environment.

Examine the dependence of aerosol evolution on controlling

meteorological variables, including temperature and humidity.

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Principal Tasks in TAP

Status of TAP Planning

Presented to BERAC December, 1997.

Concept draft circulated June, 1998.

Presented to DOE/ESD, January, 1999.

Green light to develop program plan.

Need to build consensus for this program within DOE/ACP
community.

Need to develop Interagency consensus for TAP.

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