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Aerosol Size Distribution Performance Based on Changes to Particle Emissions and Nucleation

Aerosol Size Distribution Performance Based on Changes to Particle Emissions and Nucleation. Robert A. Elleman & David S. Covert Department of Atmospheric Sciences University of Washington. Importance of Size Distribution Modeling. Health Effects in Ultrafine. Size Distribution. PM 2.5.

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Aerosol Size Distribution Performance Based on Changes to Particle Emissions and Nucleation

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  1. Aerosol Size Distribution Performance Based on Changes to Particle Emissions and Nucleation Robert A. Elleman & David S. Covert Department of Atmospheric Sciences University of Washington

  2. Importance of Size Distribution Modeling • Health Effects in Ultrafine Size Distribution PM2.5 Drivers.com www.eere.energy.gov

  3. CMAQ Simulation • CMAQ v4.4 (September 2004) • 4 km horizontal resolution • 22 levels -- lowest layer is ~30 meters • 4 day spin-up • 3 day simulation • 00 UTC 08/26 – 00 UTC 08/29, 2001 Observational Datasets PNW 2001 Pacific 2001

  4. CMAQ v4.4 Number Concentrations Flight track Pacific Standard Time = UTC - 8

  5. Ternary Number Concentrations Flight track Pacific Standard Time = UTC - 8

  6. Emission Size Distribution • Can cause consistent number underprediction • Outdated science in model biases fewer, larger particles • Nucleation mode • Not all nucleated particles survive to be observed and included in Aitken mode

  7. “Condensation Sink” = H2SO4 Growth Rate Process Nano-mode Kerminen, V.-M., and M. Kulmala, 2002: Analytical formulae connecting the “real” and the “apparent” nucleation rate and the nuclei number concentration for atmospheric nucleation events. J. Aerosol Sci., 33, 609-622. • Few 1 nm particles survive to Aitken mode

  8. Nucleation Model # Concentrations Ternary Ternary w/Proc obs Binary/None Ternary Ternary w/Proc Binary/None

  9. Nucleation Model Size Distributions • Ternary nucleation with processing to 10 nm best simulates the shape of the size distribution and the Aitken mode diameter

  10. Emission Size Distribution • Can cause consistent number underprediction • Outdated science in model biases fewer, larger particles • Nucleation mode • Not all nucleated particles survive to be observed and included in Aitken mode

  11. 4 km Improve Emissions Size Distributions • Scale to 4 km grid • All processes < 4 km scale must be parameterized • Use “urban background” measurements to constrain model • Mostly from traffic Emissions Sensitivity Matrix

  12. Effect of Emission Size Distribution Number Enhancement Size Parameters

  13. Ternary Ternary w/Processing Emission Size Distribution CMAQ v4.4 Conclusion

  14. Contact Information: Robert Elleman rob@atmos.washington.edu University of Washington (206) 543-9144 Department of Atmospheric Sciences Seattle, WA, USA

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