1. Organic Carbon Aerosol: An Overview (and Insight from Recent Field Campaigns) Colette L. Heald NOAA Climate and Global Change Postdoctoral Fellow (heald@atmos.berkeley.edu) *New Affiliation as of Jan 2008* Colorado State University GEOS-Chem User’s Meeting April 12, 2007

2. ORGANIC CARBON AEROSOL Semi- Volatiles Oxidation by OH, O 3, NO 3 Direct Emission Fossil Fuel Biomass Burning Terpenes Nucleation or Condensation Aromatics ANTHROPOGENIC SOURCESBIOGENIC SOURCES Isoprene S econdary O rganic A erosol P rimary O rganic A erosol

3. GEOS-CHEM OC AEROSOL SIMULATION P rimary O rganic A erosol [Rokjin Park] FF: Cooke / Bond BF: Logan & Yevich BB: Duncan 50% hydrophobic, 50% hydrophillic S econdary O rganic A erosol [Rokjin Park, Hong Liao, Daven Henze] Terpenes: Chung and Seinfeld [2002] Isoprene: Henze and Seinfeld [2006] (v7.04.05) Aromatics: new smog chamber data (Henze) Heterogeneous Chemistry: glyoxal (May Fu) SOA treated as hydrophilic, semi-volatile gases are soluble Empirical parameterization: 2-product model fit to smog chamber studies VOC + Oxidant  α 1 P 1 + α 2 P 2 Equilibrium Partitioning Depends on T, [OC] k 1 k 2

4. GLOBAL OC BUDGET IN GEOS-CHEM SOURCETgC/yr Fossil Fuel10.6 Biofuel7.6 Biomass Burning~25 Terpene SOA9 Isoprene SOA5.5 Aromatic SOA~4 Glyoxal/methylglyoxal uptakeMay’s talk! [Park et al., 2003; Henze and Seinfeld, 2006]

5. ORGANIC CARBON AEROSOL: AT THE SURFACE Organic carbon constitutes 10-70% of aerosol mass at surface. ISSUE: Measurements do not differentiate POA and SOA 2004 NARSTO Assessment

6. 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! We conclude this is missing SOA (ACE-Asia aircraft campaign conducted off of Japan during April/May 2001) v7.01.02 (only terpene SOA) [Heald et al., 2005] [Mader et al., 2002] [Huebert et al., 2003] [Maria et al., 2003]

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

8. WHAT CONTRIBUTES TO OC AEROSOL OVER NORTH AMERICA? NOAA WP-3 Flight tracks OC concentrations in the FT doubled as a result of Alaskan boreal fires. Observed boreal fire Influence down-wind BB filtered using CH 3 CN 2004: worst fire season on record in Alaska

9. DO WE UNDERSTAND OC AEROSOL OVER NORTH AMERICA? Note: biomass burning plumes were removed OC aerosol concentrations 4x lower than observed off of Asia, model within 25% BUT we cannot simulate variability in observations (R=0.21)  incomplete understanding of formation. [Heald et al., 2006] Sulfur Oxides (SOx) Water soluble OC Aerosol (WSOC) Simulated source attribution Observed Simulated v7.02.04 (includes isoprene SOA)

10. WHAT DON’T WE UNDERSTAND ABOUT SOA FORMATION? SVOC Oxidation by OH, O 3, NO 3 Direct Emission Terpenes 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 PRECURSORS CHEMISTRY 1. NOx, SO2/acidity 2. Multi-step oxidation FORMATION PATHWAYS

11. MODELING OC AEROSOL: FUTURE? Better constraints on role of NOx, seed particles, T, RH, and radiative properties CMAQ (A. Carlton) Example: Donahue volatility basis sets Robinson and Donahue suggest primary aerosol emission is misconception… Implementation of smog-chamber results In-cloud SOA formation New SOA Schemes? Semi-volatile primary emissions?

12. ACKNOWLEDGEMENTS Daniel Jacob, Rokjin Park, Solène Turquety, Rynda Hudman Barry Huebert Lynn Russell John Seinfeld, Hong Liao Rodney Weber, Amy Sullivan Rick Peltier ITCT-2K4 Science Team Hosts: Inez Fung & Allen Goldstein