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MODELING ORGANIC AEROSOL: Where are we going wrong?

MODELING ORGANIC AEROSOL: Where are we going wrong?. Colette L. Heald (heald@atmos.colostate.edu). Telluride Workshop on Organic Aerosol August 4, 2008. ORGANIC CARBON AEROSOL SOURCES. S econdary O rganic A erosol. Semi- Volatiles. Nucleation or ReversibleCondensation. P rimary

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MODELING ORGANIC AEROSOL: Where are we going wrong?

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  1. MODELING ORGANIC AEROSOL: Where are we going wrong? Colette L. Heald (heald@atmos.colostate.edu) Telluride Workshop on Organic Aerosol August 4, 2008

  2. ORGANIC CARBON AEROSOL SOURCES Secondary Organic Aerosol Semi- Volatiles Nucleation or ReversibleCondensation Primary Organic Aerosol Oxidation by OH, O3, NO3 Monoterpenes Sesquiterpenes Aromatics Isoprene Direct Emission Fossil Fuel Biomass Burning BIOGENIC SOURCES ANTHROPOGENIC SOURCES

  3. Empirical parameterization: 2-product model fit to smog chamber studies VOC + Oxidant α1P1 + α2P2 k1 k2 Equilibrium Partitioning Depends on T, [OC] GEOS-Chem OC AEROSOL SIMULATION SecondaryOrganicAerosol Monoterpenes/Sesq: Chung and Seinfeld [2002] Isoprene: Henze and Seinfeld [2006] Aromatics: Henze and Seinfeld [2008] SOA treated as hydrophilic, semi-volatile gases are soluble PrimaryOrganicAerosol Fossil Fuel: Cooke / Bond Biofuel: Logan & Yevich Biomass burning: Duncan / GFEDv2 50% hydrophobic, 50% hydrophillic

  4. GEOS-Chem OC AEROSOL SOURCES SOA: ~30 Tg/yr Monot/Sesq: 12 Isoprene: 14 Aromatics: 4 SOA ~ 1/3 of global source Semi- Volatiles Nucleation or ReversibleCondensation Oxidation by OH, O3, NO3 POA: 69 Tg/yr FF: 11 BF: 8 BB: 50 Monoterpenes Sesquiterpenes Aromatics Isoprene Direct Emission Fossil Fuel Biomass Burning [Park et al., 2003; Henze and Seinfeld, 2008]

  5. WHY MODEL ESTIMATES OF SOA CAN DIFFER EVEN WITH THE “SAME” FRAMEWORK • BVOC emission inventories (EFs, drivers, etc) • Aromatic emission inventories • Oxidants (related to NOx, CO, VOC levels) • Pre-existing seed (which aerosols? With which emissions?) • Reversible formation? • Solubility of SOA and precursor semi-volatiles • Meteorology, esp. precipitation, convection  aerosol lifetime Model estimates of SOA can *easily* differ by a factor of 2. Current models, SOA production: 19-55 Tg/yr.

  6. AN EXAMPLE OF MODEL RANGE Tsigaridis and Kanakidou [2003] showed a large range of simulated OC due to various assumptions about SOA scheme.

  7. ORGANIC CARBON AEROSOL: AT THE SURFACE 2004 NARSTO Assessment Global measurements (surface 0.5-32 μgm-3) [Zhang et al., 2007] Organic carbon constitutes 10-70% of aerosol mass at surface. ISSUE: Measurements do not differentiate POA and SOA IMPORTANT: Always remember what measurements we are targeting (PM1 – PM2.5)

  8. COMPARISONS AT SURFACE SITES IMPROVE (1998) MODEL Factor of 2 underestimate by GISS model apparent (note used OM:OC=1.3) but suggested due to emissions and/or grid scale [Chung and Seinfeld, 2002] OBS Good agreement between GEOS-Chem and IMPROVE observations for OC aerosol concentrations in the US (once primary sources corrected) [Park et al., 2003] Problematic: Can always adjust uncertain primary sources to account for discrepancies…

  9. NEAQS 2002: ORGANIC AEROSOL GROWTH IN ANTHROPOGENIC PLUMES NE US: Urban BVOC: ~ 0.5 ppb NOx: ~ 10 ppb Obs OC ~ 6 (0-20) µg/m3 fOC/aer: ~65% “Anthropogenic” air masses show more aerosol growth than can be explained by the oxidation of aromatics. [de Gouw et al., 2005]

  10. Mean Observations Mean Simulation Observations + ACE-ASIA: FIRST OC AEROSOL MEASUREMENTS IN THE FREE TROPOSPHERE (Spring 2001) Off of Japan: Marine/polluted BVOC: low? NOx: high? Obs OC ~ 4 (1-12) µg/m3 fOC/aer: ~50% (surface), ~80% (aloft) [Mader et al., 2002] [Huebert et al., 2003] [Maria et al., 2003] (only terpene SOA) Concentrations of OC in the FT were under-predicted by a factor of 10-100 We conclude this is missing SOA [Heald et al., 2005]

  11. ACE-ASIA: WHY WE THOUGHT IT WOULD BE SOA BIOMASS BURNING? No fires in Siberia Agricultural fires in SE Asia will not affect FT off of Japan Typical primary aerosol profile (surface source only) Obs Model Scavenging Production? ANTHROPOGENIC? Influence FT?? No correlation with a “pollution” tracer No apparent underestimate of primary sources and/or mechanism to loft into FT

  12. TORCH 2003: BOX MODEL SIMULATIONS REQUIRE LARGE INCREASES IN PARTITIONING TO MATCH OBS Southern UK: rural/occasional London plumes (high T) BVOC: medium? NOx: medium? Obs OC ~ 4 (0-10) µg/m3 fOC/aer: ~46% • To get this agreement: • Add 0.7 µg/m3bkgd • Increase partitioning coefficients by factor of 500 [Johnson et al., 2006] These authors previously found that they needed to increases partitioning by a factor of 5-80 with the MCM to match aromatic SOA formation at the EUPHORE chamber [Johnson et al., 2004; 2005].

  13. MCMA 2003: UNDERESTIMATED ASOA Mexico City: highly polluted BVOC: low NOx: high Obs OC ~ 20 (0-40) µg/m3 fOC/aer: ~70% Excess SOA from first-generation AVOC oxidation [Volkamer et al., 2006]

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

  15. ITCT-2K4: MODEST MODEL UNDERESTIMATE NE US: urban/rural mix BVOC: < 1 ppb NOx: medium Obs OC ~ 1.5 (0-10) µg/m3 fOC/aer: ~43% Sulfur Oxides (SOx) Water soluble OC Aerosol (WSOC) Simulated source attribution Observed Simulated (includes isoprene SOA) While model underestimated only by ~25% we cannot simulate variability in observations (R=0.21)  incomplete understanding of formation. [Heald et al., 2006] Note: biomass burning plumes were removed

  16. MILAGRO 2006: EVOLUTION OF URBAN PLUMES NW US: Mexico (aircraft) BVOC: low NOx: high Obs OC ~ 5 (0-30) µg/m3 fOC/aer: ~60% CAM-Chem simulation including aromatic SOA [Heald et al., 2008] for MILAGRO Model Obs SOA/OC Simulating increasing SOA fraction! Jean-Francois Lamarque, in prep. [Kleinman et al., 2008]

  17. IMPEX: ASIAN PLUME TRANSPORT NW US: Asian plume BVOC: low NOx: low Obs OC ~ 0.5 (0-5) µg/m3 fOC/aer: ~20% Asian Pollution Layers First OC overestimate by model! How does this view match with the outflow from Asia (ACE-Asia)? [Dunlea et al., submitted]

  18. AMAZE-08: OC AEROSOL IN “PRISTINE” CONDITIONS Near Manaus, Brazil: clean tropical BVOC: ~5 ppb NOx: 1-2 ppb Obs OC: ~ 1 (0-4) µg/m3 fOC/aer: ~80% Early Feb: observe significantly more organic aerosol than simulated (rain ends this period)  Likely fire influence (either local of African) Model does not significantly underestimate observed concentrations. Observed OC is pretty low! Preliminary AMS obs: Scot Martin, Qi Zhang (Harvard), Jose Jimenez, Delphine Farmer (CU Boulder)

  19. ADDING TO OUR PICTURE… • Must break down at point where • signatures diluted/removed AMAZE-08 ITCT-2K4 IMPEX MILAGRO Model underestimates not tracking photochemical age in all environments. What can we learn about SOA? This does NOT mean that models are getting better!

  20. LIKELY(?) MODEL WEAKNESSES 1. Current Emissions 2. Missing Precursors? Including semi-volatiles 3. Application of SOA yields  not relevant to ambient? Not including important drivers? 4. Partitioning: T-dependence, amount of pre-existing aerosol mass 5. Fate of gas-phase intermediates? 6. OC aging? 7. Additional formation pathways? (aqueous) 8. The effects of mixing state 9. Improperly characterized solubility, thus, loss

  21. SENSITIVITY OF SOA CONCENTRATIONS TO PRE-EXISTING POA AVAILABILITY Is SOA formation limited by availability of POA? YES NO Important effect on spatial distribution and amount of SOA formed [Park et al., 2006]

  22. IMPLICATIONS OF NEW LAB YIELDS FOR α-PINENE+O3 GEOS-Chem Simulation: Surface JJA SOA from α-pinene+O3 Yield: Griffin et al., 1999 Yield: Shilling et al., 2008 Shilling - Griffin Global annual mean burden of SOA from monoterpenes (when this yield applied for all) almost doubles from 0.28 TgC to 0.48 TgC

  23. MISSING SOURCE:PRIMARY BIOLOGICAL AEROSOL PARTICLES (PBAP) ALGAE VIRUSES BACTERIA POLLEN FUNGUS PLANT DEBRIS Jaenicke [2005] suggests may be as large a source as dust/sea salt (1000s Tg/yr) Elbert et al. [2007] suggest emission of fungal spores ~ 50 Tg/yr How much does this source contribute to sub-micron OC?

  24. MISSING MODEL SOURCE: TERRESTRIALPRIMARY BIOLOGICAL AEROSOL PARTICLES (PBAP) ALGAE VIRUSES BACTERIA POLLEN FUNGUS From Andi Andreae (unpublished data) LARGE particles (> 10 µm) PLANT DEBRIS If we size-segregate the Elbert et al. [2007] estimate of emissions of PBAP, only 2 Tg/yr source of PM1 (total was 50 Tg/yr) Also note, no initial suggestion from AMAZE-08 data that there is a large sub-micron PBAP source in the Amazon ([OC] ~ 1 µg/m3) BUT some data suggests up to 40% of sub-micron OC is cellular…

  25. MARINE PBAP Empirical marine PBAP source (GEOS-Chem) Mace Head Obs Chl-a Mod A source of 8 Tg/yr marine PBAP improves agreement with marine OC obs. Marine PBAP has limited influence on continental OC concentrations. [Spracklen et al., 2008] Other parameterizations for fraction of sea-spray that is organic. More from Maria Kanakidou… [O’Dowd et al., 2008]

  26. AQUEOUS SOA FORMATION SOA source: 2.6 TgC/yr 8.0 TgC/yr • Comprising: • Aqueous oxidation •  organic acids • 2. Oligomerization Irreversible (?) Uptake ~10-3 Glyoxal (45 Tg/yr) Methylglyoxal (145 Tg/yr) oxidation VOCs (esp isoprene) [Fu et al., in press JGR] An in situ SOA source with both biogenic and anthropogenic sources

  27. ONCE WE INCLUDE ALL SOURCES, WILL SIMPLIFIED MODELS BE ABLE TO ACCURATELY SIMULATE OC? Secondary Organic Aerosol Cloud Processing Semi- Volatiles Nucleation or ReversibleCondensation Primary Organic Aerosol Oxidation by OH, O3, NO3 Monoterpenes Sesquiterpenes Aromatics Isoprene Direct Emission Fossil Fuel Biomass Burning

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