1. Aerosol Simulation Over North America
Aaron Van Donkelaar
April 2005

2. Remote Sensing of Surface Particulate Matter
M –mass loading
ρ – particle mass density
r – effective radius (AERONET)
τ – aerosol optical depth (MODIS/GEOS-CHEM)
Qext – extinction factor (AERONET)
Z – air mass height (GEOS-CHEM)

3. GEOS-CHEM Underestimates AOD
GEOS-CHEM v , July 2002
GEOS-CHEM Underestimates AOD
MODIS, July 2002
AERONET, July 2002
GEOS-CHEM
51 chemical tracers (SOA enabled)
Up to 1 x 1 degree resolution
Optical Depth at 550nm [unitless]

4. GEOS-CHEM Organic Carbon Too Low
IMPROVE
Mass Concentrations [ug/m3]
July 2002
GEOS-CHEM v Mass Concentrations [ug/m3]
July 2002

5. Summer Organic Carbon Bias
April, 2002
May, 2002
June, 2002
July, 2002
August, 2002
September, 2002
GEOS-CHEM – IMPROVE [ug/m3]

6. Low OC Yield from Isoprene
Recent literature has proposed OC yield from isoprene
Guenther has suggested specific pathways
Assume 1% to 3% Yield
Matsunaga, S. N., Wiedinmyer, C., Guenther, A. B., Orlando, J. J., Thomas, K., Greenberg, J. P., Kajii Y. Isoprene oxidation products are a significant atmospheric aerosol component. in prep.
Claeys, M., Wang, W., Ion, A. C., Kourtchev, I., Gelencser, A., Maenhaut, W. Formation of secondary organic aerosols from isoprene and its gas-phase oxidation products through reaction with hydrogen peroxide. Atmospheric Environment, 38 (2004)
Claeys, M., Graham, B., Vas, G., Wang, W., Vermeylen, R., Pashynska, V., Cafmeyer, J., Guyon, P., Andreae, M. O., Artaxo, P., Maenhaut, W. Formation of Secondary Organic Aerosols Through Photooxidation of Isoprene. Science, 308 (2004),
Recent literature has proposed pathways:
YGA = 8.49×10-2[NOx] ×10-3[Isoprene] – 1.70×10-4[O3] ×10-3
YHA = 8.26×10-2[NOx] ×10-3[Isoprene] – 1.30×10-4[O3] ×10-2
YMG = 5.68×10-2[NOx] ×10-2[Isoprene] ×10-4[O3] – 3.54×10-2
High Uncertainties: Assume 1% to 3% Yield
Matsunaga, S. N. et al. Isoprene oxidation products are a significant atmospheric aerosol component. in prep.
Claeys, M. et al. Formation of secondary organic aerosols from isoprene and its gas-phase oxidation products through reaction with hydrogen peroxide. Atmospheric Environment.
Claeys, M. et al. Formation of Secondary Organic Aerosols Through Photooxidation of Isoprene. Science.

7. GEOS-CHEM – IMPROVE [ug/m3]
OC from Isoprene Corrected Bias -remaining bias from biomass burning regions
April, 2002
May, 2002
June, 2002
July, 2002
August, 2002
September, 2002
GEOS-CHEM – IMPROVE [ug/m3]

8. OC Does Not Correct AOD Bias
GEOS-CHEM w Isoprene Yield, July 2002
OC Does Not Correct AOD Bias
MODIS, July 2002
AERONET, July 2002
GEOS-CHEM
51 chemical tracers (SOA enabled)
Up to 1 x 1 degree resolution
Optical Depth at 550nm [unitless]

9. Preliminary Vertical Structure Evaluation - ICARTT
SO4
GEOS-CHEM
PILS
AMS
NH4
NO3 OC

10. Summary Low yield OC production from isoprene corrects seasonal bias
Biomass burning inventories for 2002 are needed
Continue to evaluate model vertical structure using ICARTT data

11. Acknowledgements Randall Martin Alex Guenther Rokjin Park
Solene Turquety
Easan Drury