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Karl Ceulemans – Jean-François Müller – Steven Compernolle – Jenny Stavrakou

Parameterization of Global Monoterpene SOA formation and Water Uptake, Based on a Near-explicit Mechanism. Karl Ceulemans – Jean-François Müller – Steven Compernolle – Jenny Stavrakou Belgian Institute for Space Aeronomy, Brussels, Belgium. ACM Conference, Davis, 2010.

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Karl Ceulemans – Jean-François Müller – Steven Compernolle – Jenny Stavrakou

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  1. Parameterization of Global MonoterpeneSOA formation and Water Uptake, Based on a Near-explicit Mechanism Karl Ceulemans – Jean-François Müller – Steven Compernolle – Jenny Stavrakou Belgian Institute for Space Aeronomy, Brussels, Belgium ACM Conference, Davis, 2010

  2. Secondary Organic Aerosol modeling Atmospheric aerosols SOA in smog chambers ??? Explicit models too large, many model uncertainties Detailed SOA box models Parameter models Aerosol in Global models

  3. Do smog chambers represent atmospheric SOA well? Photochemical aging? ?? = Atmospheric aerosols SOA in smog chambers +OH Parameter model + online aging scheme Parameters from box model simulations Detailed SOA box models Aerosol in Global models

  4. Outline BOREAM: Near-explicit model for α-pinene SOA 10-product model parameterization including aging Water uptake Global modelling

  5. BOREAM : explicit model for α-pinene SOA Gas phase reaction model with additional generic chemistry and aerosol formation module 10000 reactions, 2500 compounds Using KPP solver Capouet et al. (2008), Ceulemans et al. (2010)

  6. Explicit chemistry • Based on advanced theoretical calculations and SARs • Oxidation by OH, O3 and NO3 • Oxidation products react with OH or photolyse (now also in aerosol phase)

  7. Model performance: Photo-oxidation two low-NOx experiments (Ng et al. 2007) most SOA yields within factor 2

  8. 10-productparameter model • 5 scenarios: • OH (low and high-NOx ) • O3 (low and high-NOx ) • NO3 (high-NOx) • Products fit to full model simulations with aging • Diurnal cycle for VOC, OH, HO2 and O3 ; deposition • SOA equilibrium after 12 days

  9. Two-product model parameterizations Odum (1996) Y : SOA mass yield M0 : absorbing organic mass αi : mass stoichiometric coefficient of product i Ki : Pankow (1994) absorption equilibrium constant

  10. Temperaturedependence of parameters 0°C 30°C Absorption equilibrium constant: Stoichiometric coefficient

  11. 10-product model parameters Reactions

  12. 10-product model curvesat 298K More SOA in low-NOx than in high-NOx (factor 8 difference) α-pinene + OH leads to more SOA than α-pinene + O3

  13. Why more SOA in lowthanhigh-NOx ? Hydroperoxides (condensable) Low-NOx High-NOx nitrates Peroxy acyl nitrates More decompositions More volatile products

  14. VerificationatintermediateNOx Full model parameter model (modified)

  15. Sensitivity to photolysis and oxidants Not accounting for photolysis of SOA during aging Accumulation of condensables very high yields Not very sensitive to chosen OH or HO2

  16. Comparisonwithotherparameterizations T = 298 K • Low-NOx : Yields in this study are higher than for others, • Aging impact • Very low-NO x • But, also high yields in Ng et al. (2007) • High-NOx : similar to Presto et al. (2005)

  17. Water uptake • Parameterizations were obtained for dry conditions • Water uptake • increases molecule number absorbing phase more condensation organic compounds • Non-ideality effects • Activity coefficients correct for non-ideality

  18. Fittedactivity coefficients • against BOREAM , (impact water non-ideality on organic fraction)

  19. Impact of water uptake on SOA • Significant increase of SOA due to water • Good agreement between full and parameter model • Constant activity coefficients cause errors at high RH

  20. Global Modeling • Using global CTM IMAGESv2 (Stavrakou et al. 2009) • Parameter model α-pineneused for SOA from all monoterpenes • Other types of OrganicAerosol: • Isoprene: Henze and Seinfeld (2006) • Sesquiterpenes: Griffin et al.(1999) • Aromatics: Henze et al. (2008) • Small dicarbonyls (cloudprocessing and aqueousaerosol): Stavrakou et al. (2009) • POA: non-volatile (Bond et al. 2004, Van der Werf et al. 2006)

  21. Results • U

  22. Global model results (July 2004) Total OA (μg m-3) Total SOA (μg m-3) Monoterpene SOA (μg m-3) fraction of total OA (%)

  23. Modeled impact of water uptake on surface OA concentratios

  24. Results Comparisons with observations: U.S. • too large seasonal variation of OC in Eastern US • MEGAN emissions might be overestimated by a factor of 2 in Eastern US (Warneke et al., 2010; Stavrakou et al., 2010) • water uptake: mostly associated with isoprene SOA, highly uncertain

  25. Comparisons with observations (cont.)

  26. Summary • 10-product model fit to explicit box model BOREAM including aging • Low-NOx SOA higher than previous parameterizations based on smog chambers (impact aging) • Photolysis of compounds in aerosol phase important • Global modeling with IMAGESv2 • Higher SOA than in most previous studies (100-119 Tg/a) • Monoterpenes : 20 Tg/a • Water uptake significantly increases SOA • Agreement over US: reasonable, but underestimations in winter • Still wide spread in SOA for global models

  27. Thankyou for your attention!

  28. α-pinene + O3 and pinonaldehyde chemistry

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