Investigating Organic Aerosol Loading in the Remote Marine Environment
Kateryna Lapina [email protected]
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