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Win Trivitayanurak GEOS-CHEM Meeting Harvard University April 4, 2005

High Time-Resolution Size-Resolved Aerosol Predictions: Learning about CCN from Aerosol Field Campaigns. Win Trivitayanurak GEOS-CHEM Meeting Harvard University April 4, 2005. Outline. Objective Model Development Status Sample results Future work Conclusion. Objectives.

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Win Trivitayanurak GEOS-CHEM Meeting Harvard University April 4, 2005

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  1. High Time-Resolution Size-Resolved Aerosol Predictions: Learning about CCN from Aerosol Field Campaigns Win Trivitayanurak GEOS-CHEM Meeting Harvard University April 4, 2005

  2. Outline • Objective • Model Development Status • Sample results • Future work • Conclusion

  3. Objectives • To implement TOMAS aerosol microphysics in GEOS-CHEM. • To evaluate the microphysics model by comparing aerosol model predictions against ACE Asia field campaign. • Look for potential improvement to the microphysics model: • Nucleation model • Primary aerosol emission size-distributions • Vertical distribution

  4. M1 N1 M2 N2 ... ... mo 2mo … Mass TOMAS Microphysics • TOMAS (TwO-Moment Aerosol Sectional microphysics algorithm) [Adams and Seinfeld, 2002] • Conserve BOTH number and mass concentrations by tracking them for each size bin. • 30 Bins – dry mass boundary • Processes include coagulation, condensation/ evaporation, dry deposition, wet deposition and nucleation

  5. Model Development Status • 30 size-bin sulfate aerosol tracers added to STT array • 30 tracers for aerosol number of each size bin: Nk1, Nk2, Nk3, …., Nk30 • 30 tracers for aerosol mass of each size bin: SF1, SF2, SF3, …., SF30 • Important : aerosol mass and number must go together ! • Transport & convection

  6. Model Development Status … • TOMAS microphysics integrated • Condensation + coagulation + nucleation – ON • GEOS-CHEM processes • Transport – OFF • Convection – OFF • Convective precip. – OFF • LS precip. – ON • Aqueous oxidation – ON but not physical yet. • Dry deposition – ON but not size-dependent yet.

  7. [mg/m3] [mg/m3] Sample results – SO4 mass (L = 1) Original GEOS-CHEM bulk SO4 Sum of 30 bins mass of sulfate

  8. [mg/m3] [mg/m3] Sample results – SO4 mass ( L = 10) Original GEOS-CHEM bulk SO4 Sum of 30 bins mass of sulfate

  9. [mg/m3] [no./cm3] Sample results – Number Concentration( L=1 ) Sum of 30 bins mass of sulfate Sum of 30 bins number of sulfate

  10. [mg/m3] [no./cm3] Sample results – Number Concentration( L= 10) Sum of 30 bins mass of sulfate Sum of 30 bins number of sulfate

  11. Sample results – Size distribution A snapshot at 7/31/2001 taken from grid box (61,31,1) ~ Shanghai, East China dN/dlogDp (cm-3) dM/dlogDp (mg cm-3) Dp(mm) Dp(mm) Sulfate number size distribution Sulfate mass size distribution

  12. Model run time on Linux platform • 1 month of GEOS-CHEM full chemistry run with 4x5 resolution and GEOS 3 meteorology

  13. Future work • Turning on transport & convection • Introduce aqueous phase chemistry wrt each size bin • Introduce size-resolved dry deposition • Adding more aerosol types (sea salt, dust, OC, EC) • Comparison to ACE-Asia

  14. Conclusion • Keeping the aerosol mass and number tracers consistent is crucial for TOMAS • Early stage of TOMAS microphysics in GEOS-CHEM shows a promising future for high time-resolution size-resolved aerosol prediction.

  15. QUESTIONS?

  16. Sulfate size distribution Snapshot at 7/1/2001 0.00HRS Sulfate number size distribution Sulfate mass size distribution

  17. Sulfate size distribution Snapshot at 7/1/2001 3.00HRS Sulfate number size distribution Sulfate mass size distribution

  18. Sulfate size distribution Snapshot at 7/17/2001 Sulfate number size distribution Sulfate mass size distribution

  19. AerosolMicrophysics:Nucleation • Binary nucleation model, H2SO4-H2O system [Jaecker-Voirol and Mirabel, 1989] • In each time step (1hr), first let gas-phase H2SO4 condense onto existing aerosol. • At end of time step, if remaining H2SO4 concentration exceeds critical concentration, then nucleation occurs. [Wexler et al., 1994] Ccrit = 0.16exp(0.1T - 3.5RH - 27.7) • Nucleated particles are introduced to the smallest size bin

  20. AerosolMicrophysics:Nucleation • Nucleation events observed at H2SO4 concentrations below those required by binary nucleation model • Suggest other mechanisms are at work • Ternary nucleation (H2SO4-NH3-H2O) • Ion induced nucleation. • Shall test and see in GEOS-CHEM

  21. Ratio of CCN(0.2%) particulate emission scenario over gas-phase emission scenario[Adams and Seinfeld, GRL 2003] 0 .2 .4 .6 .8 .9 1.0 1.2 2 5 AerosolMicrophysics : Primary Aerosol • Importance of primary ultrafine emissions • Particulate emissions are more efficient than gas-phase emissions at increasing CCN indirect effects. • Need accurate size-distributions of primary aerosols.

  22. OC/EC Sulfate Dust Sea-salt Number Size Distribution Mass Size Distribution Probability Probability Dp (mm) Dp (mm) AerosolMicrophysics : Primary Aerosol • Current Primary Aerosol Size-Distributions • EC/OC:main source of ultrafine particles and aerosol number • Sulfate:also ultrafine • Dust:mostly coarse, some fine • Sea-salt: mostly coarse, some fine

  23. AerosolMicrophysics : Vertical Distribution • Vertical distribution of aerosols affects lifetime because lower aerosols are removed by rain more efficiently. • How good is the vertical profile prediction? • Examine how each process influences vertical distributions sources vs. sinks • Gravitational settling = sink for large particles Enough settling? • Vertical mixing; how good?

  24. Field Campaign • TRACE-P • Feb - Apr 2001 • NW Pacific • Asian Chemical outflow and evolution • Aircraft • ACE-Asia • Late Mar - May 2001 • Ground network: 2000-2003 • Yellow Sea, Sea of Japan, Pacific and ground-based in China and Japan • Asian Aerosol, radiative effect, aerosol processes • Aircraft, R/V (ships), ground stations network [Huebert et al., 2003]

  25. MBL Comparison • Parameters? How to evaluate model? • Nucleation: • SO2, H2SO4, surface area, and number concentrations. Temp, RH. • Do observations agree with theory? Observations during flight 7 of ACE-Asia. dA/dlogDp (mm2cm-3) SO2 (ppbv) C-130 Altitude (m) Diameter (mm) Particle (# cm-3) Temp (°C) [McNaughton et al., JGR 2004 in press]

  26. Formed earlier w/ partial neutralization by NH3 Sulfuric acid with near complete neutralization Or ammoniated species Sulfuric acid or organic compound dN/dlogDp (cm-3) 0.01 0.1 1 10 • Dp (um) Comparison • Primary Aerosol: • Size distribution measured on aircraft. Different volatility suggest aerosol types. • Do the input size distributions of primary aerosols produce accurate total number concentration and size distribution? [McNaughton et al., JGR 2004 in press]

  27. Twin Otter Altitude (m) Sulfate mass conc. (ug/m3) C-130 Altitude (m) Diameter (um) Comparison • Vertical distribution: • Number profile, mass profile, size-resolved profile. • Compare model vs. observations  examine what is too high/low, e.g. production or loss. • Potential improvement? Is it in the aerosol model? [BAHREINI ET AL., 2003] [McNaughton et al., 2004 in press]

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