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. Drivers.com PM 2.5 Size Distribution www.eere.energy.gov Importance of Size Distribution Modeling Health Effects in Ultrafine

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 PNW 2001Pacific 2001 Observational Datasets

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 Emission Size Distribution –Can cause consistent number underprediction –Outdated science in model biases fewer, larger particles Nucleation mode –Not all nucleated particles survive to be observed and included in Aitken mode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. Process Nano-mode Few 1 nm particles survive to Aitken 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. “Condensation Sink” H 2 SO 4 Growth Rate =

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

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 Emission Size Distribution –Can cause consistent number underprediction –Outdated science in model biases fewer, larger particles Nucleation mode –Not all nucleated particles survive to be observed and included in Aitken mode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. 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 4 km

12. Effect of Emission Size Distribution Number Enhancement Size Parameters

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

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