organic carbon aerosol colette l. heald university of california, berkeley noaa summer institute,...
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![Page 1: Organic Carbon Aerosol Colette L. Heald University of California, Berkeley NOAA Summer Institute, Steamboat Springs, CO July 12, 2006](https://reader035.vdocuments.us/reader035/viewer/2022062314/56649d495503460f94a25699/html5/thumbnails/1.jpg)
Organic Carbon Aerosol
Colette L. Heald
University of California, Berkeley
NOAA Summer Institute, Steamboat Springs, COJuly 12, 2006
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CURRENT UNDERSTANDING: SOURCES OF ORGANIC CARBON AEROSOL
ReactiveOrganicGases
Oxidation by OH, O3, NO3
Direct Emission
Fossil Fuel Biomass Burning
Monoterpenes
Nucleation or Condensation
Aromatics
ANTHROPOGENIC SOURCESBIOGENIC SOURCES
OC
FF: 45-80 TgC/yrBB: 10-30 TgC/yr
Secondary Organic Aerosol (SOA): 8-40 TgC/yr
*Numbers from IPCC [2001]
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Formation and Transport
Emissions:1. Anthropogenic2. Natural/Biogenic
ORGANIC AEROSOLS: AIR QUALITY, CHEMISTRY AND CLIMATE
Air Quality Impacts:1. Visibility
2. Health
Climate Forcing1. Direct: Scatter solar radiation2. Indirect: ↑ cloud albedo
↑ cloud lifetime
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ORGANIC CARBON AEROSOL: AT THE SURFACE
Organic carbon constitutes 10-70% of aerosol mass at surface.Difficult to distinguish primary from secondary contributions.
2004 NARSTO Assessment
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ACE-ASIA: FIRST OC AEROSOL MEASUREMENTS IN THE FREE TROPOSPHERE
Mean ObservationsMean SimulationObservations+
Concentrations of OC in the FT were under-predicted by a factor of 10-100!
(ACE-Asia aircraft campaign conducted off of Japan during April/May 2001)
GEOS-Chem:Global ChemicalTransport model
[Heald et al., 2005]
[Mader et al., 2002] [Huebert et al., 2003] [Maria et al., 2003]
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CONTRAST: OTHER AEROSOLS IN ASIAN OUTFLOW
Model simulates both the magnitude and profile of sulfate and elemental carbon (EC) during ACE-Asia
Mean ObservationsMean Simulation (GEOS-Chem)
Scavenging ScavengingSecondaryproduction
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ANY INDICATION THAT DIRECT EMISSIONS ARE UNDERESTIMATED?
Biomass Burning:• Satellite firecounts show no active fires in Siberia• Agricultural fires in SE Asia do not contribute in the FT.
No apparent underestimate in primary emissions
Pollution:• There is a free tropospheric background of 1-4 μg sm-3 that is not correlated with CO or sulfate.
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SECONDARY ORGANIC AEROSOL
Biogenic VOCs(eg. monoterpenes)
ReactiveOrganic Gases
Oxidation by OH, O3, NO3
SecondaryOrganic Aerosol
Condensation of low vapour pressure ROGs on pre-existing aerosol
Simulated April Biogenic SOA
FT observations ~ 4g/m3
Simulated SOA far too small!
SOA parameterization [Chung and Seinfeld, 2002]
VOCi + OXIDANTj i,jP1i,j + i,jP2i,j
Parameters (’s K’s) from smog chamber studies
Ai,j
GGi,ji,j
Pi,jEquilibrium (Komi,j) also f(POA)
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SEVERAL STUDIES SUGGESTING UNDERESTIMATE OF SOA
[Volkamer et al., 2006]
Global underestimate in SOA?
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OC AEROSOL OVER NORTH AMERICA: ICARTT CAMPAIGN
NOAA WP-3 Flight tracks
Note: biomass burning plumes were removed
OC aerosol concentrations captured by the model, BUT we cannot simulate variability in observations (R=0.21) incomplete understanding of formation.
ObservedSimulated
Water soluble OC Aerosol
OC aerosol concentrations 3x lower than observed off of Asia
[Heald et al., submitted]
2004: worst fire season on record in Alaska
Emissions derived from MODIS hot spots
[Turquety et al., submitted]
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WHAT DON’T WE UNDERSTAND ABOUT SOA FORMATION?
ROG
Oxidation by OH, O3, NO3
Direct Emission
Monoterpenes
Nucleation or Condensation
Aromatics
OC
Isoprene
CloudProcessing
FF: 45-80 TgC/yrBB: 10-30 TgC/yr
SOA: ?? TgC/yr
Fossil Fuel Biomass Burning
ANTHROPOGENIC SOURCESBIOGENIC SOURCES
Heterogeneous ReactionsAdditionalPrecursors
1. Production moreefficient at low NOx2. Multi-step oxidation
New formation pathways
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CARBON CYCLE AND POTENTIAL RADIATIVE IMPLICATIONS
VOC EMISSIONS500-1000 TgC/yr
[IPCC, 2001]
DISSOLVED ORGANIC CARBON
IN RAINWATER430 TgC/yr
[Wiley et al., 2000]
OC AEROSOL1 µg/m3 from 2-7 km globally = 105 TgC/yr
4 μg/m3 (ACE-Asia)AOD @ 50% RH: 0.057
TOA Radiative Forcing = -1.2 W/m2
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CURRENT WORK: HOW WILL SOA FORMATION RESPOND TO A FUTURE CLIMATE?
Biogenic Emissionsof precursors:T/light/moisture
Anthropogenic Emissions:Increasing aromatic emissionsMore surface area for aerosol condensation
Precipitation:Enhanced removal
Oxidant levels:Effected by
hydrological cycle and anthropogenic
pollution levels
Using a coupled land-atmosphere model
(NCAR CCSM)
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ACKNOWLEDGEMENTS
Daniel Jacob, Rokjin Park, Solène Turquety, Rynda Hudman
Barry HuebertLynn Russell John Seinfeld, Hong Liao
Rodney Weber,Amy SullivanRick Peltier
ITCT-2K4 Science Team
Hosts: Inez Fung & Allen Goldstein