1. Aerosol Optical Thickness
4th GEOS-Chem Users’ Meeting
Effect of Oceanic Organic Carbon Emissions on the Growth of Secondary Particles and Global CCN Abundance
Gan Luo and Fangqun Yu
ASRC, SUNY-Albany,
Kaufman et al., Nature, 2002
Bennartz, JGR, 2006
Aerosol Optical Thickness
Cloud Fraction and Liquid Water Path

2. Observed α-pinene and isoprene over Southern Ocean
Introduction
SOA, formed from the oxidation of phytoplankton-produced isoprene, can affect chemical composition of marine CCN
- Meskhidze and Nenes, Science, 2006
Large uncertainty of marine organic carbon emission
Marine organic aerosol: TgC/yr (Spracklen et al., GRL, 2008)
Marine organic aerosol: TgC/yr (Roelofs, ACP, 2008)
Primary OC: 35~50TgC/yr; SOA produced by isoprene: 25~40 TgC/yr
Marine isoprene: in-situ TgC/yr (Broadgate et al, GRL, 1997);
satellite 0.1TgC/yr (Palmer and Shaw, GRL, 2005);
model ~1.9TgC/yr (Arnold et al, ACP, 2009)
Observed α-pinene and isoprene over Southern Ocean
- Yassaa et al., Environ. Chem., 2008

3. C is Chlorophyll from combined MODIS/SeaWiFS
GEOS-Chem
Meteorology: GEOS-5, 4º×5º, 47 Layers
Emission: EDGAR+EPA/LNEI99+BRAVO+EMEP+STREETS+GFED2
Chemistry: photochemistry + online aerosol chemistry
Aerosol microphysics: Advanced Particle Microphysics
Marine emission of α-pinene and isoprene :
The emission scheme is based on chlorophyll concentration and 10 m wind speed
C is Chlorophyll from combined MODIS/SeaWiFS

4. Yassaa et al., Environ. Chem., 2008
Compare with Ship Measurement
Yassaa et al., Environ. Chem., 2008
Shipboard measurements: ~
OOMPH (Organics over the Ocean Modifying Particles in both Hemispheres) summer cruise in the Southern Ocean
GEOS-Chem
simulated daily average
of α-pinene and isoprene along the shipping route during the same period
Model simulation can capture the major variation of the two species

5. Global Distributions at Surface
127TgC/Yr
602TgC/Yr
127+35TgC/Yr
TgC/Yr

6. Impact on Organic Chemistry
Relative change Zonal average

7. Impact on Sulfur Chemistry
Relative change Zonal average

8. Impact on CCN Abundance
Relative change Zonal average

9. Summary
Marine α-pinene and isoprene emissions and the impacts on chemistry and aerosols have been simulated with GEOS-Chem
Marine emission:
α-pinene: 35TgC/yr, isoprene: 2.1TgC/yr
Marine α-pinene emission can increase SOA mass by up to 60% in the lower troposphere of Southern Hemisphere (40ºS-90ºS). It decreases OH concentration in the region by 1~10%. The associated changes in SO2 and H2SO4 concentrations result in an increase of nucleation rate over Antarctica by up to 10%, and total CCN over Antarctica enhanced by 3~5%
The impact of marine isoprene emission is small

10. Thank You! The End Acknowledgments:
Funding support from NASA, NOAA, and NSF