A43C-0237. Investigating Organic Aerosol L oading in the Remote Marine Environment K. Lapina 1 , ([email protected] ), C. L . Heald 1 , D. V. Spracklen 2 , S. R. Arnold 2 , T. S. Bates 3 , J. D. Allan 4 , H. Coe 4 , G. McFiggans 4 , S. R. Zorn 5,6 , F. Drewnick 5 , A. Smirnov 7
Investigating Organic Aerosol Loading in the Remote Marine Environment
K. Lapina1, ([email protected] ), C. L. Heald1,D. V. Spracklen2, S. R. Arnold2, T. S. Bates3, J. D. Allan4, H. Coe4, G. McFiggans4, S. R. Zorn5,6, F. Drewnick5, A. Smirnov7
1Dept. of Atmospheric Science, Colorado State University, USA, 2University of Leeds, UK, 3Pacific Marine Environmental Laboratory, NOAA,USA , 4The University of Manchester, UK, 5Max Planck Institute for Chemistry, Mainz, Germany, 6now at Harvard University, USA, 7NASA/Goddard Space Flight Center, Greenbelt, MD, USA
Model vs Observations
Aerosol loading in the marine environment is investigated using aerosol composition measure-ments from several research ship campaigns (ICEALOT, MAP, RHAMBLE, VOCALS and OOMPH), observations of total AOD column
from satellite (MODIS) and ship-based instruments (Maritime Aerosol Network, MAN), and a global chemical transport model (GEOS-Chem). The model underestimates AOD over the oceanic
regions by 40±20%, compared to satellite and MAN observations. Comparison with cruise data demonstrates that the GEOS-Chem simulation
of marine sulfate is generally unbiased, however surface organic matter (OM) concentrations are largely underestimated. We find that ship-based measurements are consistent with a marine OM source of 9 TgC yr-1or less, however this additional OM source does not explain the model underestimate of marine AOD.
2ox 2.5o,47 vertical levels
Aerosol extinction @ 550 nm
FF/BF: EDGAR, overwritten by regional emission inventories
OC/BC (Bond 2007)
Dust (Fairlie 2006)
Sea Salt (Jaegle 2010)
Annual average aerosol optical depth (AOD) at 550 nm in 2007 for MODIS, GEOS-Chem, % difference (GEOS-Chem minus MODIS) and sea salt component of GEOS-Chem. Model was sampled at the time and location of MODIS overpass.
Scatter plot of a) modeled AOD and b) MODIS AOD against MAN measurements (SP), sampled to coincide with MODIS overpass. Data points with AOD>0.6 are not included in regression analysis and are in grey.
Speciated ship-based measurements (including sea-salt), as well as measurements of total PM10 and PM1 mass may be required to resolve the discrepancy between modeled and observed AOD.
Marine OM: possible explanation for missing AOD?
MAN sampling locations
Global distribution of annual emissions for 2007 of marine OM by Spracklen et al 2008 (left) (based on [Chl-a]), O’Dowd et al 2008 (center), (based on [Chl-a] and meteorological parameters), and sea salt by Jaegle et al 2010 (right).
a) Boxplots for measured and modeled surface sulfate (left) and OM (right). Measurements are shown in grey. Model simulations with marine OM from Spracklen et al 2008, from O’Dowd et al 2008 and without marine emissions are plotted in red, green and blue, respectively. b) Latitudinal distribution (means ± standard deviations) of measured and modeled OM from ship campaigns.
We thank MODIS and SeaWIFS teams for the aerosol and Chl-a products, and NASA for funding.
AOD is computed from the mass concentration (M), extinction efficiency (Qext) and particle mass density for each particle type and wavelength.
Modeled surface OM concentration averaged over the period of each campaign without (left) and with (right) marine OM source by Spracklen et al 2008 overlaid with OM observations. Color scale is saturated at the maximum values in the legend.