Atmos. Chem. Phys. Discuss., 9, 26377-26419, 2009
© Author(s) 2009. 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.
Explaining global surface aerosol number concentrations in terms of primary emissions and particle formation
D. V. Spracklen1, K. S. Carslaw1, J. Merikanto1, G. W. Mann1, S. Pickering1, J. A. Ogren2, E. Andrews2, U. Baltensperger3, E. Weingartner3, M. Boy4, M. Kulmala4, L. Laakso4, H. Lihavainen5, N. Kivekäs5, N. Mihalopoulos6, G. Kouvarakis6, S. G. Jennings8, W. Birmili8, A. Wiedensohler8, R. Weller9, P. Laj10, K. Sellegri11, B. Bonn12, and R. Krejci13
1Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds, LS2 9JT, UK
2NOAA/ESRL Global Monitoring Division, 325 Broadway R/GMD1, Boulder, Co 80305, USA
3Paul Scherrer Institut, Laboratory of Atmospheric Chemistry, 5232 Villigen, Switzerland
4Department of Physicsal Sciences, University of Helsinki, Finland
5Climate Change, Finnish Meteorological Institute, Helsinki, Finland
6Department of Chemistry, University of Crete, University campus, P.O. Box 2208, 71003, Voutes, Heraklion, Crete, Greece
8Department of Physics, National University of Ireland, Galway, Ireland
9Alfred Wegener Institute, Am Handelshafen 12, 27570 Bremerhaven, Germany
10Laboratoire de Glaciologie et Géophysique de l'Environnement CNRS/Université Grenoble 1, Grenoble, France
11Laboratoire de Météorologie Physique, Université Clermont-Ferrand/CNRS, Clermont-Ferrand, France
12J.W. Goethe University, Inst. for Atmospheric and Environmental Sciences, Frankfurt/Main, Germany
13Department of Applied Environmental Science (ITM), Stockholm University, 10691 Stockholm, Sweden

Abstract. We use observations of total particle number concentration at 36 worldwide sites and a global aerosol model to quantify the primary and secondary sources of particle number. We show that emissions of primary particles can reasonably reproduce the spatial pattern of observed condensation nuclei (CN) (R2=0.51) but fail to explain the observed seasonal cycle at many sites (R2=0.1). The modeled CN concentration in the free troposphere is biased low (normalised mean bias, NMB=−88%) unless a secondary source of particles is included, for example from binary homogeneous nucleation of sulfuric acid and water (NMB=−25%). Simulated CN concentrations in the continental boundary layer (BL) are also biased low (NMB=−74%) unless the number emission of anthropogenic primary particles is increased or an empirical BL particle formation mechanism based on sulfuric acid is used. We find that the seasonal CN cycle observed at continental BL sites is better simulated by including a BL particle formation mechanism (R2=0.3) than by increasing the number emission from primary anthropogenic sources (R2=0.18). Using sensitivity tests we derive optimum rate coefficients for this nucleation mechanism, which agree with values derived from detailed case studies at individual sites.

Citation: Spracklen, D. V., Carslaw, K. S., Merikanto, J., Mann, G. W., Pickering, S., Ogren, J. A., Andrews, E., Baltensperger, U., Weingartner, E., Boy, M., Kulmala, M., Laakso, L., Lihavainen, H., Kivekäs, N., Mihalopoulos, N., Kouvarakis, G., Jennings, S. G., Birmili, W., Wiedensohler, A., Weller, R., Laj, P., Sellegri, K., Bonn, B., and Krejci, R.: Explaining global surface aerosol number concentrations in terms of primary emissions and particle formation, Atmos. Chem. Phys. Discuss., 9, 26377-26419, doi:10.5194/acpd-9-26377-2009, 2009.
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