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

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Investigating Organic Aerosol Loading in the Remote Marine Environment


[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
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 chem
Marine AOD: MAN vs GEOS-Chem
  • Maritime Aerosol Network
  • provides AOD measurements from various ships of opportunity (2004 – current)



AOD < 0.4


v8-03-01 with sea salt from Jaeglé et al. 2011

What is the source of this bias?

measurements of aerosol composition
Measurements of Aerosol Composition
  • Aerodyne Aerosol Mass Spectrometer (AMS) [Jayne et al., 2000; DeCarloet 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
Possible Sources of Fine AOD Bias


Sea salt?

AOD: GC minus MODIS GC Sea salt AOD



  • Obs
  • GEOS-Chem
  • Sulfate: generally unbiased
  • Sea salt cannot account for low model bias in AOD
marine organic matter om
Marine Organic Matter (OM)

From O’Dowd et al. 2004, Nature

Mass fraction (%)

High biological activity

Mass mass (ug/m-3)

Mace Head

Chlorophyll concentrations [mg m-3]

  • 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]

Could marine OM be the reason for low AOD bias in GEOS-Chem?

modeling of sub micron marine om
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

OM = A x [Chl]

%OM = 49.129 x [Chl] + 10

OM = f([Chl], wind speed, SST)

8.9 TgC

8.2 TgC

Marine OM emissions total 8 – 9TgC

aerosol composition model vs observations
Aerosol Composition: Model vs Observations

GC standard OM GC_Spracklen08 OM


  • Obs
  • GC standard
  • GC_Spracklen08
  • GC_Langmann08

OM obs

Large underestimation when marine OM not included

  • The GEOS-Chem model underestimates observed surface OM when no marine OM source is included.
  • Marine OM source of <9 TgCyr-1is 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