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Investigating Organic Aerosol Loading in the Remote Marine Environment

Investigating Organic Aerosol Loading in the Remote Marine Environment. Kateryna Lapina klapina@atmos.colostate.edu.

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Investigating Organic Aerosol Loading in the Remote Marine Environment

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  1. Investigating Organic Aerosol Loading in the Remote Marine Environment KaterynaLapina 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

  2. 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

  3. Marine AOD: MAN vs GEOS-Chem • Maritime Aerosol Network • provides AOD measurements from various ships of opportunity (2004 – current) http://aeronet.gsfc.nasa.gov/new_web/maritime_aerosol_network.html MODIS vs MAN GEOS-Chemvs MAN 2007 AOD < 0.4 GEOS-Chem: v8-03-01 with sea salt from Jaeglé et al. 2011 What is the source of this bias?

  4. 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

  5. Possible Sources of Fine AOD Bias Sulfate? Sea salt? AOD: GC minus MODIS GC Sea salt AOD Anti- correlated • Obs • GEOS-Chem • Sulfate: generally unbiased • Sea salt cannot account for low model bias in AOD

  6. 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?

  7. 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

  8. Aerosol Composition: Model vs Observations GC standard OM GC_Spracklen08 OM OM • Obs • GC standard • GC_Spracklen08 • GC_Langmann08 OM obs Large underestimation when marine OM not included

  9. Conclusions • 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

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