Abstract
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-Å 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.
Highlights
Atmospheric aerosols have multiple effects on climate, air quality, human health and atmospheric visibility (e.g. Charlson, 1969; Horvath, 1993; Laden et al, 2006; Lohmann and Feichter, 2005; Pope and Dockery, 2006; Stevens and Feingold, 2009)
Two types of instruments for measuring ultrafine particle size distributions were used to obtain the results presented in this article: The Differential Mobility Particle Sizer, and the Scanning Mobility Particle Sizer (SMPS)
For the results provided in this paper, only EUSAAR level II data marked as a “Valid measurement” were used
Summary
Atmospheric aerosols have multiple effects on climate, air quality, human health and atmospheric visibility (e.g. Charlson, 1969; Horvath, 1993; Laden et al, 2006; Lohmann and Feichter, 2005; Pope and Dockery, 2006; Stevens and Feingold, 2009). Arithmetic mean of x Geometric mean of x p-th percentile of x (linear) standard deviation of x 10-logarithmic standard deviation of x Autocorrelation (1-h) of x same as x same as x same as x same as x particle formation in the marine environment (O’Dowd et al, 2002), BIOFOR for biogenic aerosol production (Kulmala et al, 2001), or ACE-2 for aerosol-cloud interactions (Raes et al, 2000). This kind of information is sensitive to the representativeness of the data on temporal and often on spatial scales. The methodologies of number size distribution measurements and data handling procedures in both GUAN and EUSAAR networks are very similar and the size distribution measurements results are comparable between the two networks
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