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Atmos. Chem. Phys., 11, 12007-12036, 2011
© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
Primary versus secondary contributions to particle number concentrations in the European boundary layer
C. L. Reddington1, K. S. Carslaw1, D. V. Spracklen1, M. G. Frontoso2, L. Collins1, J. Merikanto1,3, A. Minikin4, T. Hamburger4, H. Coe5, M. Kulmala3, P. Aalto3, H. Flentje6, C. Plass-Dülmer6, W. Birmili7, A. Wiedensohler7, B. Wehner7, T. Tuch7, A. Sonntag7, C. D. O'Dowd8, S. G. Jennings8, R. Dupuy8, U. Baltensperger9, E. Weingartner9, H.-C. Hansson10, P. Tunved10, P. Laj11, K. Sellegri12, J. Boulon12, J.-P. Putaud13, C. Gruening13, E. Swietlicki14, P. Roldin14, J. S. Henzing15, M. Moerman15, N. Mihalopoulos16, G. Kouvarakis16, V. Ždímal17, N. Zíková17, A. Marinoni18, P. Bonasoni18, and R. Duchi18
1Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds, Leeds, UK
2C2SM – ETH Zürich, Zürich, Switzerland
3Division of Atmospheric Sciences, Department of Physics, University of Helsinki, Helsinki, Finland
4Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany
5School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, UK
6Deutscher Wetterdienst, Meteorologisches Observatorium Hohenpeißenberg, Germany
7Leibniz Institute for Tropospheric Research, Leipzig, Germany
8School of Physics & Centre for Climate and Air Pollution Studies, Ryan Institute, National University of Ireland Galway, University Road, Galway, Ireland
9Paul Scherrer Institut, Laboratory of Atmospheric Chemistry, 5232 Villigen, Switzerland
10Institute for Applied Environmental Research, Stockholm University, Stockholm, Sweden
11UJF-Grenoble 1/CNRS, LGGE UMR5183, Grenoble 38041, France
12Laboratoire de Météorologie Physique, CNRS, Université Blaise Pascal, Aubière cedex, France
13European Commission, Joint Research Centre, Institute of Environment and Sustainability, Ispra, Italy
14Division of Nuclear Physics, Lund University, P.O. Box 118, 22100 Lund, Sweden
15Netherlands Organisation for Applied Scientific Research TNO, Utrecht, The Netherlands
16Environmental Chemical Processes Laboratory, Department of Chemistry, University of Crete, Heraklion, Crete, Greece
17Institute of Chemical Process Fundamentals of the AS CR, Prague, Czech Republic
18CNR-Institute for Atmospheric Sciences and Climate, Bologna, Italy

Abstract. It is important to understand the relative contribution of primary and secondary particles to regional and global aerosol so that models can attribute aerosol radiative forcing to different sources. In large-scale models, there is considerable uncertainty associated with treatments of particle formation (nucleation) in the boundary layer (BL) and in the size distribution of emitted primary particles, leading to uncertainties in predicted cloud condensation nuclei (CCN) concentrations. Here we quantify how primary particle emissions and secondary particle formation influence size-resolved particle number concentrations in the BL using a global aerosol microphysics model and aircraft and ground site observations made during the May 2008 campaign of the European Integrated Project on Aerosol Cloud Climate Air Quality Interactions (EUCAARI). We tested four different parameterisations for BL nucleation and two assumptions for the emission size distribution of anthropogenic and wildfire carbonaceous particles. When we emit carbonaceous particles at small sizes (as recommended by the Aerosol Intercomparison project, AEROCOM), the spatial distributions of campaign-mean number concentrations of particles with diameter >50 nm (N50) and >100 nm (N100) were well captured by the model (R2≥0.8) and the normalised mean bias (NMB) was also small (−18% for N50 and −1% for N100). Emission of carbonaceous particles at larger sizes, which we consider to be more realistic for low spatial resolution global models, results in equally good correlation but larger bias (R2≥0.8, NMB = −52% and −29%), which could be partly but not entirely compensated by BL nucleation. Within the uncertainty of the observations and accounting for the uncertainty in the size of emitted primary particles, BL nucleation makes a statistically significant contribution to CCN-sized particles at less than a quarter of the ground sites. Our results show that a major source of uncertainty in CCN-sized particles in polluted European air is the emitted size of primary carbonaceous particles. New information is required not just from direct observations, but also to determine the "effective emission size" and composition of primary particles appropriate for different resolution models.

Citation: Reddington, C. L., Carslaw, K. S., Spracklen, D. V., Frontoso, M. G., Collins, L., Merikanto, J., Minikin, A., Hamburger, T., Coe, H., Kulmala, M., Aalto, P., Flentje, H., Plass-Dülmer, C., Birmili, W., Wiedensohler, A., Wehner, B., Tuch, T., Sonntag, A., O'Dowd, C. D., Jennings, S. G., Dupuy, R., Baltensperger, U., Weingartner, E., Hansson, H.-C., Tunved, P., Laj, P., Sellegri, K., Boulon, J., Putaud, J.-P., Gruening, C., Swietlicki, E., Roldin, P., Henzing, J. S., Moerman, M., Mihalopoulos, N., Kouvarakis, G., Ždímal, V., Zíková, N., Marinoni, A., Bonasoni, P., and Duchi, R.: Primary versus secondary contributions to particle number concentrations in the European boundary layer, Atmos. Chem. Phys., 11, 12007-12036, doi:10.5194/acp-11-12007-2011, 2011.
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