1. Investigating the Sources of Organic Carbon Aerosol in the Atmosphere Colette L. Heald NOAA Climate and Global Change Postdoctoral Fellow University of California, Berkeley (heald@atmos.berkeley.edu) Daniel J. Jacob, Rokjin J. Park, Solène Turquety, Rynda C. Hudman, Rodney J. Weber, Rick Peltier, Amy Sullivan, Lynn M. Russell Barry J. Huebert, John H. Seinfeld, Hong Liao Young Scientists’ Global Change Conference, Beijing November 7, 2006

2. AEROSOL IMPACTS ON AIR QUALITY AIR QUALITY / HEALTH VISIBILITY Clear Day April 16, 2001 Visibility reduction at Glen Canyon, Arizona due to transpacific transport of Asian dust Particulates contribute to urban smog: [Environmental Working Group Report, 2005] Beijing

3. AEROSOL IMPACTS ON CLIMATE DIRECT EFFECT INDIRECT EFFECT 1.Scattering Radiation = COOLING 2.Absorbing Radiation = WARMING Reflection Refraction Absorption Increase cloud albedo = COOLING Increase cloud lifetime = COOLING

4. ESTIMATED RADIATIVE FORCING OF CLIMATE Secondary OC currently not included in forcing estimates  is it important? [IPCC, 2001]

5. ORGANIC CARBON AEROSOL Reactive Organic Gases Oxidation by OH, O 3, NO 3 Direct Emission Fossil Fuel Biomass Burning Monoterpenes Nucleation or Condensation Aromatics ANTHROPOGENIC SOURCESBIOGENIC SOURCES OC Fossil Fuel: 10-30 TgC/yr Biomass Burning: 45-80 TgC/yr Secondary Organic Aerosol (SOA): 8-40 TgC/yr *Numbers from IPCC [2001] Isoprene

6. 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

7. ACE-ASIA: FIRST OC AEROSOL MEASUREMENTS IN THE FREE TROPOSPHERE Mean Observations Mean Simulation Observations + 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 Chemical Transport model [Heald et al., 2005] [Mader et al., 2002] [Huebert et al., 2003] [Maria et al., 2003]

8. CONTRAST: OTHER AEROSOLS IN ASIAN OUTFLOW Model simulates both the magnitude and profile of sulfate and elemental carbon (EC) during ACE-Asia Mean Observations Mean Simulation (GEOS-Chem) Scavenging Secondary production

9. 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.

10. SECONDARY ORGANIC AEROSOL Biogenic VOCs (eg. monoterpenes) Reactive Organic Gases Oxidation by OH, O 3, NO 3 Secondary Organic Aerosol Condensation of low vapour pressure ROGs on pre- existing aerosol Simulated April Biogenic SOA FT observations ~ 4  g/m 3 Simulated SOA far too small! SOA parameterization [Chung and Seinfeld, 2002] VOC i + OXIDANT j   i,j P1 i,j +  i,j P2 i,j Parameters (  ’s K’s) from smog chamber studies A i,j G i,j P i,j Equilibrium (Kom i,j )  also f(POA)

11. SEVERAL STUDIES SUGGESTING UNDERESTIMATE OF SOA [Volkamer et al., 2006] Global underestimate in SOA?

12. 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. Observed Simulated 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]

13. WHAT DON’T WE UNDERSTAND ABOUT SOA FORMATION? ROG Oxidation by OH, O 3, NO 3 Direct Emission Monoterpenes Nucleation or Condensation Aromatics OC Isoprene Cloud Processing FF: 45-80 TgC/yr BB: 10-30 TgC/yr SOA: ?? TgC/yr Fossil Fuel Biomass Burning ANTHROPOGENIC SOURCESBIOGENIC SOURCES Heterogeneous Reactions 1. Precursors 2. Chemistry Production more efficient at low NOx Multi-step oxidation 3. New formation pathways

14. CARBON CYCLE AND POTENTIAL RADIATIVE IMPLICATIONS VOC EMISSIONS 500-1000 TgC/yr [IPCC, 2001] DISSOLVED ORGANIC CARBON IN RAINWATER 430 TgC/yr [Wiley et al., 2000] OC AEROSOL 1 µg/m 3 in the FT globally ~ 100 TgC/yr AOD @ 50% RH: 0.014 TOA Radiative Forcing = -0.3 W/m 2