1Department of Physics, P.O. Box 64, 00014 University of Helsinki, Finland
2Helsinki Institute of Physics, P.O. Box 64, 00014 University of Helsinki, Finland
Received: 22 Sep 2008 – Discussion started: 10 Dec 2008
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. 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.
Published: 23 Jun 2009
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., 9, 4177-4184, doi:10.5194/acp-9-4177-2009, 2009.