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

Robert A. Elleman&

David S. Covert

Department of Atmospheric SciencesUniversity of Washington

Drivers.com

PM2.5Size Distribution

www.eere.energy.gov

Importance of Size Distribution Modeling

• Health Effects in Ultrafine

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 2001 Pacific 2001

Observational Datasets

From: http://www.pnl.gov/pnw2001/From: http://www.pnl.gov/pnw2001/

Cassier Tunnel

Slocan Park

Sumas Mtn.Langley Ecole

Golden Ears ParkCassier Tunnel

Slocan Park

Sumas Mtn.Langley Ecole

Golden Ears Park

From http://www.msc.ec.gc.ca/projects/pacific2001/study_sites_e.html

Portland

Seattle

Vancouver

Portland

Seattle

Vancouver

CMAQ v4.4 Number Concentrations

Flight track

Pacific Standard Time = UTC - 8

Ternary Number Concentrations

Flight track

Pacific Standard Time = UTC - 8

• 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– Outdated science in model biases fewer, larger particles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

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.

CS

GR

“Condensation Sink”

H2SO4 Growth Rate=

Nucleation Model # Concentrations

Ternary

obs

Binary/None

Ternary

Binary/None

Ternary w/Proc

Ternary w/Proc

0826PM 0827AM 0827PM Langley Sumas Average

Binary -6,469 -3,961 -14,782 -11,696 -14,147 -10,211

None -6,480 -3,962 -14,784 -11,699 -14,157 -10,216

Ternary 47,944 9,272 15,647 8,583 17,772 19,844

Ternary w/Processing

6,360 -3,521 -13,767 -9,136 -1,982 -4,409

Nucleation Model Size Distributions

• Ternary nucleation with processing to 10 nm best simulates the shape of the size distribution and the Aitken mode diameter

• 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– Outdated science in model biases fewer, larger particles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

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

Organics All Others

Name % Mass in Ait % Mass in Ait Aitken Dgv Aitken sg Acc Dgv Acc sgBase 0.1 0 30 nm 1.7 300 nm 2

Best Guess 10 10 60 nm 1.7 280 nm 1.7

Upper Bound 20 20 50 nm 1.7 280 nm 1.7

All Species

Effect of Emission Size Distribution

Number Enhancement

Dg, aits

g,ait Dg, accs

g,acc

Base 45 2.3 80 2.1

Best Guess 35 2.1 110 2.0

Upper Bound 30 1.8 105 1.9

Size Parameters

Emissions CMAQ

Base 1 1

Best Guess 4 2.4

Upper Bound 13 6.4

CMAQ v4.4

Terna

ryTernary w/Processing

Emission Size Distribution

Conclusion

Contact Information:

Robert Elleman rob@atmos.washington.eduUniversity of Washington (206) 543-9144Department of Atmospheric SciencesSeattle, WA, USA