ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-10-437-2010 Atmospheric sub-3 nm particles at high altitudes Mirme S. 1 Mirme A. 1 Minikin A. 2 Petzold A. 2 Hõrrak U. 1 Kerminen V. -M. 3 Kulmala M. 4 Institute of Physics, University of Tartu, Ülikooli 18, 50090, Tartu, Estonia Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany Finnish Meteorological Institute, P.O. Box 503, 00101, Helsinki, Finland Department of Physics, University of Helsinki, P.O. Box 64, 00014, Helsinki, Finland 19 01 2010 10 2 437 451 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/10/437/2010/acp-10-437-2010.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/10/437/2010/acp-10-437-2010.pdf

Formation of new atmospheric aerosol particles is known to occur almost all over the world and the importance of these particles to climate and air quality has been recognized. Recently, it was found that atmospheric aerosol particle formation begins at the diameter of around 1.5–2.0 nm and a pool of sub-3 nm atmospheric particles – consisting of both charged and uncharged ones – was observed at the ground level. Here, we report on the first airborne observations of the pool of sub-3 nm neutral atmospheric particles. Between 2 and 3 nm, their concentration is roughly two orders of magnitude larger than that of the ion clusters, depending slightly on the altitude. Our findings indicate that new particle formation takes place throughout the tropospheric column up to the tropopause. Particles were found to be formed via neutral pathways in the boundary layer, and there was no sign of an increasing role by ion-induced nucleation toward the upper troposphere. Clouds, while acting as a source of sub-10 nm ions, did not perturb the overall budget of atmospheric clusters or particles.

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