Atmos. Chem. Phys. Discuss., 12, 3655-3694, 2012
© Author(s) 2012. This work is distributed
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Biogenic influence on cloud microphysics over the global ocean
A. Lana1, R. Simó1, S. M. Vallina2, and J. Dachs3
1Institut de Ciències del Mar (ICM), CSIC, Barcelona, Spain
2EAPS, MIT, Cambridge, Massachusetts, USA
3Department of Environmental Chemistry, IDAEA, CSIC, Barcelona, Spain

Abstract. Aerosols have a large potential to influence climate through their effects on the microphysics and optical properties of clouds and, hence, on the Earth's radiation budget. Aerosol-cloud interactions have been intensively studied in polluted air, but the possibility that the marine biosphere plays a role in regulating cloud brightness in the pristine oceanic atmosphere remains largely unexplored. We used 9 yr of global satellite data and ocean climatologies to derive parameterizations of (a) production fluxes of sulfur aerosols formed by the oxidation of the biogenic gas dimethylsulfide emitted from the sea surface; (b) production fluxes of secondary organic aerosols from biogenic organic volatiles; (c) emission fluxes of biogenic primary organic aerosols ejected by wind action on sea surface; and (d) emission fluxes of sea salt also lifted by the wind upon bubble bursting. Series of global weekly estimates of these fluxes were correlated to series of cloud droplet effective radius data derived from satellite (MODIS). Similar analyses were conducted in more detail at 6 locations spread among polluted and clean regions of the oceanic atmosphere. The outcome of the statistical analysis was that negative correlation was common at mid and high latitude for sulfur and organic secondary aerosols, indicating both might be important in seeding cloud droplet activation. Conversely, primary aerosols (organic and sea salt) showed more variable, non-significant or positive correlations, indicating that, despite contributing to large shares of the marine aerosol mass, they are not major drivers of the variability of cloud microphysics. Uncertainties and synergisms are discussed, and recommendations of research needs are given.

Citation: Lana, A., Simó, R., Vallina, S. M., and Dachs, J.: Biogenic influence on cloud microphysics over the global ocean, Atmos. Chem. Phys. Discuss., 12, 3655-3694, doi:10.5194/acpd-12-3655-2012, 2012.
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