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Atmos. Chem. Phys. Discuss., 8, 20661-20685, 2008
www.atmos-chem-phys-discuss.net/8/20661/2008/ doi:10.5194/acpd-8-20661-2008 © Author(s) 2008. This work is distributed under the Creative Commons Attribution 3.0 License. |
Analysis of atmospheric neutral and charged molecular clusters in boreal forest using pulse-height CPC
1Department of Physical Sciences, University of Helsinki, Finland
*also at: Helsinki Institute of Physics, Helsinki, Finland
Abstract. We measured the size distribution of atmospheric neutral and charged clusters and particles down to mobility diameter around 1.5 nm by applying pulse-height CPC technique at SMEAR II station in Hyytiälä, southern Finland during spring 2007 and May 2008. The concentration of molecular clusters smaller than 3 nm seems to be highly variable in boreal forest environment. The concentration varied typically between 500–50 000 cm−3, the medians being 8060 cm−3 in year 2007 and 3380 cm−3 in 2008. By comparing to concentrations measured with ion spectrometers, we conclude that ion clusters and neutral clusters produced by ion-ion recombination are usually not sufficient to explain all of the observed clusters; the median fraction of recombination products from all neutral clusters was 4.9%. Before and during most new particle formation events the cluster formation rate rose only slightly, or remained close to stable. Nocturnal formation of clusters was also frequently observed.
Citation: Lehtipalo, K., Sipilä, M., Riipinen, I., Nieminen, T., and Kulmala, M.: Analysis of atmospheric neutral and charged molecular clusters in boreal forest using pulse-height CPC, Atmos. Chem. Phys. Discuss., 8, 20661-20685, doi:10.5194/acpd-8-20661-2008, 2008.