Analysis of atmospheric neutral and charged molecular clusters in boreal forest using pulse-height CPC K. Lehtipalo1, M. Sipilä1,2, I. Riipinen1, T. Nieminen1, and M. Kulmala1 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
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.
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., 9, 4177-4184, doi:10.5194/acp-9-4177-2009, 2009.