1Department of Physics, University of Helsinki, P.O. Box 64, Helsinki, Finland
2Leibniz Institute for Tropospheric Research, Permoserstraße 15, 04318 Leipzig, Germany
3Laboratoire de Glaciologie et Géophysique de l'Environnement Université Joseph Fourier, Grenoble 1/CNRS, 38400 St. Martin d'Hères, France
4Norwegian Institute for Air Research Instituttveien 18, 2027 Kjeller, Norway
5Laboratoire de Météorologie Physique, UMR 6016, CNRS/University of Clermont-Ferrand, Clermont-Ferrand, France
6Laboratory of Atmospheric Chemistry, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
7Laboratory of Aerosol Chemistry and Physics, Institute of Chemical Process Fundamentals of the AS CR, v.v.i., Rozvojova 135, 16502 Praha 6, Czech Republic
8European commission, Joint Research Centre, Institute for Environment and Sustainability, 21027 Ispra (VA), Italy
9CNR-ISAC, Institute of Atmospheric Sciences and Climate, 40129, Bologna, Italy
10Department of Applied Environmental Science (ITM), Stockholm University, Svante Arrhenius väg 8,10691 Stockholm, Sweden
11Research and Development, Finnish Meteorological Institute, Helsinki, Finland
12Center for Physical Sciences and Technology Savanoriu 231, 02300 Vilnius, Lithuania
13Department of Physics, Lund University, P.O. Box 118, 221 00 Lund, Sweden
14Environmental Chemical Processes Laboratory, Department of Chemistry, University of Crete, Greece
15Institute of Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, Blvd. Tzarigradsko chaussee, 72, 1784 Sofia, Bulgaria
16Air Chemistry Group of the Hungarian Academy of Sciences, University of Pannonia, P.O. Box 158, 8201 Veszprém, Hungary
17Netherlands Organisation for Applied Scientific Research TNO, Princetonlaan 6, 3508 TA Utrecht, The Netherlands
18National Centre for Atmospheric Science, School of Geography, Earth and Environmental Sciences, University of Birmingham, B15 2TT, UK
19National University of Ireland Galway, University Road, Galway, Ireland
20German Meteorological Service, Hohenpeißenberg Observatory, Albin-Schwaiger Weg 10, 82383 Hohenpeißenberg, Germany
21German Federal Environment Agency (UBA), Messnetzzentrale, Langen, Germany
Abstract. 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.
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.
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 coverage 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 greatest concentrations were observed at the Ispra station in Northern Italy with high accumulation mode number concentrations in the winter. The aerosol number concentrations at the Arctic station Zeppelin in Ny-\AA lesund in Svalbard have also a strong seasonal cycle, with greater 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.
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.