TROPOSPHERIC AEROSOL

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TROPOSPHERIC AEROSOL
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Introduction

• Definitions
• Aerosol designates a suspension of particles,
  either solid or liquid, in a gaseous environment.
  Example aerosol from spray canister
• Atmospheric aerosol particles staying in
  suspension in the atmosphere for at least several
  hours, excluding cloud droplets and ice crystals.

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Spatial and Temporal Scales

• Particle sizes
• from 1 nm condensation nuclei
• to 10mm coarse particles
• Concentration
• 50 /cm3 clean atmosphere
• 106 /cm3 in urban environment
• Lifetime
• Up to 2 weeks for the smallest

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Wide Range of Effects

• Aerosol effects
• Air quality
• Respiratory distress, eyes irritation
• Reduction of visibility
• Acid rain
• Climate
• Direct scattering cooling and absorption
  warming of solar and infrared radiation
• Indirect modify clouds properties
• 1st brighter clouds
• 2nd decrease precipitation efficiency
• Biogeochemistry
• Source of nutrient Fe in ocean
• Atmospheric Chemistry
• Heterogeneous reactions
• Reduction of photolysis rates

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Aerosol Optical Depths (AODs) from MODIS
satellite instrument 8 day means
March 14 - 21
June 26 - July 03
October 8 - 15
January 1 - 7
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(No Transcript)
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ANNUAL MEAN PM2.5 CONCENTRATIONS (2002)derived
from MODIS satellite instrument data
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OZONE AND PARTICULATE MATTER (PM) THE TOP TWO
AIR POLLUTANTS IN THE U.S.
millions of people living in areas exceeding
national ambient air quality standards (NAAQS)
EPA, 2003
millions
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Distributions of Aerosol Emission
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We will focus on SO2(g) and BC emissions SO2(g)
forms SO4 aerosol which scatters and cools BC
aerosol absorbs and heats
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GLOBAL SULFUR BUDGET (flux terms in Tg S yr-1)
SO42- t 3.9d
SO2 t 1.3d
cloud
40
OH
H2SO4(g)
5
15
5
OH
NO3
(CH3)2S
60
dep 5 dry 40 wet
10
dep 25 dry 20 wet
(DMS) t 1.0d
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Phytoplankton
Volcanoes
Combustion Smelters
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A1B Version of Future SO2 Emissions Less
Optimistic, But Still Optimistic Vision
x
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TRENDS IN U.S. EMISSIONS OF SO2
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Is This Optimistic Picture or SO2 Emissions
Good News?
Good for local Air Quality? YES Good for Global
Climate?
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IPCC AR4 SPM (2007)
Warming ?
? Cooling
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Carbonaceous aerosols

• Components
• Graphitic or black carbon
• produced by combustion
• Absorb solar radiation
• Organic material
• directly emitted or produced from reactions
  involving gaseous organic precursors.
• Complex mixture of many classes of compounds .

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CARBONACEOUS AEROSOL SOURCE ESTIMATES
ELEMENTAL CARBON
ORGANIC CARBON
GLOBAL
22 Tg yr-1
130 Tg yr-1
UNITED STATES
0.66 Tg yr-1
2.7 Tg yr-1
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Figure above Global distribution of fire counts
retrieved from MODIS instrument for October 2005.
Fire scars and smoke plumes from biomass Burning
in the Congolese savannah (May 2002).
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• BC and OC increase as CO is predicted to increase
  IPCC.
• BC and OC emissions are already dropping and
  continue to do so. alternative vision
• Nobody really knows.

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The Carbon Cycle and Climate Change

• John Dunne

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Preindustrial Carbon Budget
PgC
Fossil Fuel Reserves gt 6000
Atmos - 600
Oil-270
Gas-260
Coal
Plants - 800
Ocean - 38000
Soil - 6000
Carbon Storage in Atmosphere/Land Plants lt Fossil
Fuel Reserves/Soils lt Ocean The excess base in
the ocean determines its ability to take up CO2
acid.
Carbonate Rocks
Ocean Excess Base - 4000
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1980 Carbon Budget
PgC
Fossil Fuel Reserves gt 6000
160
Atmos - 600
120
Coal
Oil-270
Gas-260
Plants - 800
90
50
Ocean - 38000
Soil - 6000
By 1980, a small fraction of fossil fuel reserves
was used. A majority of it was still in the
atmosphere - equilibration with the ocean is
slow. Up to 1980, land was a source of CO2.
Carbonate Rocks
Ocean Excess Base - 4000
90
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2000 Carbon Budget
PgC
Fossil Fuel Reserves gt 6000
270
Atmos - 600
180
Coal
Oil-270
Gas-260
40
Plants - 800
130
Ocean - 38000
Soil - 6000
Utilization of fossil fuels is accelerating. Land
has become a sink of CO2.
Carbonate Rocks
Ocean Excess Base - 4000
130
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2100 Carbon Budget (A1B scenario)
PgC
Fossil Fuel Reserves gt 6000
1600
900 ?
Atmos - 600
Coal
Oil-270
Gas-260
?
Plants - 800
700 ?
Ocean - 38000
Soil - 6000
Large changes to the carbon budget occur before
exhaustion of fossil fuels.
Carbonate Rocks
Ocean Excess Base - 4000
700 ?
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Model atmosphere CO2 Fluxes
CO2 flux (mol m-2 y-1)
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Atmospheric CO2 Over Time
US Climate Change Science Program Strategic Plan,
2003
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Climate Carbon Models will be tested against
growth rate of observed carbon reservoirs
Ocean land store about 10
Ocean land store about 80
Terrestrial carbon model forced with ECMWF fluxes
Understanding gained from observations and
simulations gives more confidence in future
projections and monitoring strategies
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Global Anthropogenic CO2 Budget (PgC)
Time span 1800-1979 1980-1999 Emissions 156
20 117 5 Atmosphere Increase 116 4 65
1 Ocean Increase 90 19 37 8 Land
Increase -50 28 15 9
Sabine and Feely, 2005

• Take home points
• Emissions over last 20 years equal 43 of total
• Over first 180 years, the ocean absorbed 44 of
  emissions
• Over last 20 years, the ocean absorbed 36 of
  emissions
• Land has switched from being a source to a sink

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Projections based on very simple climate
carbon economic models
Historical A1B
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Carbon Feedbacks
PgC
Fossil Fuel Reserves gt 6000
1600
900 ?
Atmos - 600
Oil-270
Gas-260
Coal
?
Plants - 800
700 ?
Ocean - 38000
Soil - 6000
Warming decreases uptake
Carbonate Rocks
Ocean Excess Base - 4000
700 ?
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Carbon Feedbacks
PgC
Fossil Fuel Reserves gt 6000
1600
900 ?
Atmos - 600
Oil-270
Gas-260
Coal
?
Plants - 800
700 ?
Ocean - 38000
Soil - 6000
Acidification decreases uptake
Carbonate Rocks
Ocean Excess Base - 4000
700 ?
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Carbon Feedbacks
PgC
Fossil Fuel Reserves gt 6000
1600
900 ?
Atmos - 600
Oil-270
Gas-260
Coal
?
Plants - 800
700 ?
Ocean - 38000
Soil - 6000
Ocean circulation and biology affect uptake in
diverse ways
Carbonate Rocks
Ocean Excess Base - 4000
700 ?
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Carbon Feedbacks
PgC
Fossil Fuel Reserves gt 6000
1600
900 ?
Atmos - 600
Oil-270
Gas-260
Coal
?
Plants - 800
700 ?
Land use (agriculture, forestry, regrowth, fire,
fire suppression, ) affects uptake in diverse
ways
Ocean - 38000
Soil - 6000
Carbonate Rocks
Ocean Excess Base - 4000
700 ?
34
Carbon Feedbacks
PgC
Fossil Fuel Reserves gt 6000
1600
900 ?
Atmos - 600
Oil-270
Gas-260
Coal
?
Plants - 800
700 ?
CO2 fertilization increases uptake
Ocean - 38000
Soil - 6000
Carbonate Rocks
Ocean Excess Base - 4000
700 ?
35
Carbon Feedbacks
PgC
Fossil Fuel Reserves gt 6000
1600
900 ?
Atmos - 600
Oil-270
Gas-260
Coal
?
Plants - 800
700 ?
Ocean - 38000
Soil - 6000
Warming increases soil respiration
Carbonate Rocks
Ocean Excess Base - 4000
700 ?
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Carbon Feedbacks
PgC
Fossil Fuel Reserves gt 6000
1600
900 ?
Atmos - 600
Oil-270
Gas-260
Coal
?
Plants - 800
700 ?
Ocean - 38000
Warming, wetting and drying affect plants in
diverse ways
Soil - 6000
Carbonate Rocks
Ocean Excess Base - 4000
700 ?
37
Carbon Feedbacks
PgC
Fossil Fuel Reserves gt 6000
1600
900 ?
Atmos - 600
Oil-270
Gas-260
Coal
?
Plants - 800
700 ?
Ocean - 38000
Soil - 6000
Carbonate Rocks
Ocean Excess Base - 4000
700 ?
Long term, rocks will add base to the system
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Preindustrial Carbon Budget
PgC
Fossil Fuel Reserves gt 6000
Atmos - 600
Oil-270
Gas-260
Coal
Plants - 800
Ocean - 38000
Soil - 6000
Carbon Storage in Atmosphere/Land Plants lt Fossil
Fuel Reserves/Soils lt Ocean The excess base in
the ocean determines its ability to take up CO2
acid.
Carbonate Rocks
Ocean Excess Base - 4000
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Future atmospheric CO2 estimates are highly
uncertain. Reliable predictions require fully
coupled realistic carbon-climate models.