EPA Science Advisory Board workshop

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EPA Science Advisory Board workshop Emerging
Scientific Topics Air Pollution Control
Transboundary Air Pollutants December 11, 2003
Russell Dickerson, Univ. Maryland
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Thunderstorms convert local air pollution
problems into global atmospheric chemistry
problems.
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Tropospheric Ozone Formation

1. NOx is the limiting reagent outside urban areas.
2. Efficiency of ozone production falls as NOx
   concentration increases.
3. Lifetimes, wind speeds, and photolysis rates all
   higher aloft.

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Atmospheric Residence Time Increases with Height
Stratosphere
Aerosol Layers
Troposphere
Clouds
Boundary Layer
NASA Astronaut Limb Photo

• Fine Particle residence time in the boundary
  layer, is 3-5 days.
• Residence time in the free troposphere is weeks
  and the transport is hemispheric
• Photo prepared by R. Husar, Washington Univ.

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AEROCE Finding Transport of pollutants from
North America to the North Atlantic via
linkedcold fronts (Prados, 2000)
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Aircraft observations show how cold fronts lift
and transport air pollutants to the east.
Colored line shows King Air flight track.
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TOMS tropospheric ozone (Thompson Hudson)
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Remote sensing of Ozone Surface
network TOMS
?
?
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Seasonal cycle in mean afternoon surface O3 over
the US

• Based on the Harvard global model and surface
  observations

Fiore et al., JGR 2003.
Regional pollution 10-30 ppbv Hemisph.
pollution 5-15 ppbv Natural ozone 15-25
ppbv Stratospheric ozone 0-10 ppbv
US Trend Peaks are falling but bottom is coming
up.
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The ambient EC concentration decreased 50 in 11
yr.
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INDOEX, 1999
INDOEX Indian Ocean Experiment
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Indian Today, 1996.
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Mean Aerosol Optical Depth over INDOEX region
from Dec 2001 to May 2003 from MODIS (Ramanathan
Ramana, Environ. Managers, Dec. 2003).
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Global Fossil Fuel Black Carbon Emissions(Cooke
et al.,1999 Penner et al., 1993 Dickerson et
al., 2002)
Region BC Emissions Tg yr-1
W. Europe 0.58
Eastern Europe 0.68
Africa 0.17
N. America 0.49
C. S. America 0.26
Former USSR 0.69
China Oceania 1.18
Rest of Asia 2.00
Total fossil fuel 6.17
Biomass Burning 5.97
Major greenhouse substance.
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• South Asia emits large quantities of VOCs and
  POM, but little NOx.
• Little ozone is observed over India or the
  Northern Indian Ocean. VOC/NOx ratio too
  high(?).
• This could change as vehicle fleet shifts from
  2-stroke to 4-stroke engines.

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Nitrogen DepositionPast and Presentmg N/m2/yr
5000
2000
1000
750
500
250
100
50
25
5
1993
1860
Galloway et al., 2003
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A systems approach integrating both animal and
crop productions is necessary to evaluate air
emissions. NRC 2003
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Summary Conclusions

• Nonlinearities in chemistry and longer lifetimes
  of trace gases and aerosols in the free
  troposphere promote long-range transport.
• Much of the growth in emissions in the coming
  decades will come from the developing world.
• Asia is different from North America
• Organic aerosol soot from biofuels 2-stroke
  engines.
• Conversion to high-tech combustion could lead to
  more ozone.
• We need interdisciplinary and international
  colaboration.

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The End.
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Modeled Carbon Monoxide TRACE-P/ACE-Asia
Pickering et al., 2002
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Forecasts Observations of Air Pollution Over
the Mid Atlantic
Shot from UMD Research Aircraft Dickerson,
Doddridge, Piety et al.
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Impactor Sample from INDOEX
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Global distribution of AOD (550 nm) for April
May, 2001 and 2002 from MODIS. (Ramanathan and
Ramana, 2003).
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Cruise Track and Air Flow During INDOEX 1999