ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-11-8893-2011 Number size distributions and seasonality of submicron particles in Europe 2008–2009 Asmi A. 1 Wiedensohler A. 2 Laj P. 3 Fjaeraa A.-M. 4 Sellegri K. 5 Birmili W. 2 Weingartner E. 6 Baltensperger U. 6 Zdimal V. 7 Zikova N. 7 Putaud J.-P. 8 Marinoni A. 9 Tunved P. 10 Hansson H.-C. 10 Fiebig M. 4 Kivekäs N. 11 Lihavainen H. 11 Asmi E. 11 Ulevicius V. 12 Aalto P. P. 1 Swietlicki E. 13 Kristensson A. 13 Mihalopoulos N. 14 Kalivitis N. 14 Kalapov I. 15 Kiss G. 16 de Leeuw G. 11 17 Henzing B. 17 Harrison R. M. 18 Beddows D. 18 O'Dowd C. 19 Jennings S. G. 19 Flentje H. 20 Weinhold K. 2 Meinhardt F. 21 Ries L. 21 Kulmala M. 1 Department of Physics, University of Helsinki, P.O. Box 64, Helsinki, Finland Leibniz Institute for Tropospheric Research, Permoserstraße 15, 04318 Leipzig, Germany Laboratoire de Glaciologie et Géophysique de l'Environnement Université Joseph Fourier – Grenoble 1/CNRS, 38400 St. Martin d'Hères, France Norwegian Institute for Air Research Instituttveien 18, 2027 Kjeller, Norway Laboratoire de Météorologie Physique, UMR 6016, CNRS/University of Clermont-Ferrand, Clermont-Ferrand, France Laboratory of Atmospheric Chemistry, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland Laboratory of Aerosol Chemistry and Physics, Institute of Chemical Process Fundamentals of the AS CR, v.v.i., Rozvojova 135, 16502 Praha 6, Czech Republic European commission, Joint Research Centre, Institute for Environment and Sustainability, 21027 Ispra (VA), Italy CNR-ISAC, Institute of Atmospheric Sciences and Climate, 40129, Bologna, Italy Department of Applied Environmental Science (ITM), Stockholm University (Svante Arrhenius väg 8), 10691 Stockholm, Sweden Research and Development, Finnish Meteorological Institute, Helsinki, Finland Center for Physical Sciences and Technology Savanoriu 231, 02300 Vilnius, Lithuania Department of Physics, Lund University, P.O. Box 118, 221 00 Lund, Sweden Environmental Chemical Processes Laboratory, Department of Chemistry, University of Crete, Greece Institute of Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, Blvd. Tzarigradsko chaussee, 72, 1784 Sofia, Bulgaria Air Chemistry Group of the Hungarian Academy of Sciences, University of Pannonia, P.O. Box 158, 8201 Veszprém, Hungary TNO, Utrecht, The Netherlands National Centre for Atmospheric Science, School of Geography, Earth and Environmental Sciences, University of Birmingham, B15 2TT, UK National University of Ireland Galway, University Road, Galway, Ireland German Meteorological Service, Hohenpeißenberg Observatory, Albin-Schwaiger Weg 10, 82383 Hohenpeißenberg, Germany German Federal Environment Agency (UBA), Messnetzzentrale, Langen, Germany 16 03 2011 11 3 8893 8976 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/11/8893/2011/acpd-11-8893-2011.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/11/8893/2011/acpd-11-8893-2011.pdf

Two years of harmonized aerosol number size distribution data from 24 European field monitoring sites have been analysed. The results give a comprehensive overview of the European near surface aerosol particle number concentrations and number size distributions between 30 and 500 nm of dry particle diameter. Spatial and temporal distribution of aerosols in the particle sizes most important for climate applications are presented. We also analyse the annual, weekly and diurnal cycles of the aerosol number concentrations, provide log-normal fitting parameters for median number size distributions, and give guidance notes for data users. Emphasis is placed on the usability of results within the aerosol modelling community. <br><br> We also show that the aerosol number concentrations of Aitken and accumulation mode particles (with 100 nm dry diameter as a cut-off between modes) are related, although there is significant variation in the ratios of the modal number concentrations. Different aerosol and station types are distinguished from this data and this methodology has potential for further categorization of stations aerosol number size distribution types. <br><br> The European submicron aerosol was divided into characteristic types: Central European aerosol, characterized by single mode median size distributions, unimodal number concentration histograms and low variability in CCN-sized aerosol number concentrations; Nordic aerosol with low number concentrations, although showing pronounced seasonal variation of especially Aitken mode particles; Mountain sites (altitude over 1000 m a.s.l.) with a strong seasonal cycle in aerosol number concentrations, high variability, and very low median number concentrations. Southern and Western European regions had fewer stations, which decreases the regional representativeness of these results. Aerosol number concentrations over the Britain and Ireland had very high variance and there are indications of mixed air masses from several source regions; the Mediterranean aerosol exhibit high seasonality, and a strong accumulation mode in the summer. The highest concentrations were observed at the JRC station in Northern Italy with high accumulation mode number concentrations in the winter. The aerosol number concentrations at the Arctic station Zeppelin in Ny-Ã…lesund in Svalbard have also a strong seasonal cycle, with higher concentrations of accumulation mode particles in winter, and dominating summer Aitken mode indicating more recently formed particles. Observed particles did not show any statistically significant regional work-week or weekday related variation in number concentrations studied. <br><br> Analysis products are made for open-access to the research community, available in a freely accessible internet site. The results give to the modelling community a reliable, easy-to-use and freely available comparison dataset of aerosol size distributions.

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