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Investigating Organic Aerosol Loading in the Remote Marine Environment. Kateryna Lapina klapina@atmos.colostate.edu. - PowerPoint PPT Presentation
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Investigating Organic Aerosol Loading in the Remote Marine Environment
Kateryna Lapina klapina@atmos.colostate.edu
Colette Heald, Dominick Spracklen, Steve Arnold, James Allan, Hugh Coe, Gordon McFiggans, Soeren Zorn, Frank Drewnick, Tim Bates, Lelia Hawkins,
Lynn Russell, Sasha Smirnov, Colin O’Dowd and Andy Hind Acknowledgments: SeaWIFS and MODIS teams
Marine AOD: MODIS vs GEOS-Chem From Jaeglé et al. 2011, ACP
New sea salt source function improves agreement of coarse AOD with MODIS
Remaining low GEOS-Chem bias: due to fine mode
Marine AOD: MAN vs GEOS-ChemMaritime Aerosol Network provides AOD measurements from various ships of opportunity (2004 – current)
2007AOD < 0.4
GEOS-Chem: v8-03-01 with sea salt from Jaeglé et al. 2011
What is the source of this bias?
http://aeronet.gsfc.nasa.gov/new_web/maritime_aerosol_network.html
MODIS vs MAN GEOS-Chem vs MAN
Measurements of Aerosol Composition
Aerodyne Aerosol Mass Spectrometer (AMS) [Jayne et al., 2000; DeCarlo et al., 2006; Canagaratna et al., 2007]:
real-time sulfate, OM, nitrate & ammonium fine mode
Ship-based measurements during 2006 – 2008 Fresh pollution excluded from analysis
Possible Sources of Fine AOD Bias
Sulfate: generally unbiased Sea salt cannot account for low model bias in AOD
- Obs- GEOS-Chem
AOD: GC minus MODIS GC Sea salt AOD
Sea salt?
Sulfate?
Anti-correlated
Marine Organic Matter (OM)
Currently not included in GEOS-Chem Wide range of emissions estimates: 2.3 to 75 TgC yr-1
[Spracklen et al., 2008; Roelofs, 2008; Langmann et al., 2008; Gantt et al., 2009; Ito and Kawamiya,
2010; Myriokefalitakis et al., 2010; Long et al., 2011; Vignati et al., 2010]
From O’Dowd et al. 2004, Nature
Mas
s fra
ction
(%)
Mas
s m
ass (
ug/m
-3)
Could marine OM be the reason for low AOD bias in GEOS-Chem?
High biological activity
Chlorophyll concentrations [mg m-3]
Mace Head
Modeling of Sub-micron Marine OM [Chl] as a proxy for bioproductivity [O'Dowd et al., 2004; Yoon et al., 2007]
Based on Spracklen et al. 2008 Based on Langmann et al. 2008
Marine OM emissions total 8 – 9TgC
OM = A x [Chl] %OM = 49.129 x [Chl] + 10OM = f([Chl], wind speed, SST)
8.2 TgC8.9 TgC
Aerosol Composition: Model vs Observations OM
Large underestimation when marine OM not included
Obs
GC standard
GC_Spracklen08
GC_Langmann08
GC standard OM GC_Spracklen08 OM
OM obs
Conclusions
• The GEOS-Chem model underestimates observed surface OM when no marine OM source is included.
• Marine OM source of <9 TgC yr-1 is sufficient to account for observed marine OM concentrations.
• The schemes developed based on satellite-derived chlorophyll-a concentrations do not adequately describe the variability in observed OM.
• Marine OM makes a very small contribution to total marine AOD (~0.003).
Lapina et al. 2011, ACPD
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