Measurement of Ambient, Interstitial, and Residual Aerosol Particles on a Mountaintop Site in Central Sweden using an Aerosol Mass Spectrometer and a CVI Frank Drewnick & Johannes Schneider & Silke S. Hings & Nele Hock & Kevin Noone & Admir Targino & Silke Weimer & Stephan Borrmann Received: 6 September 2005 / Accepted: 6 July 2006 / Published online: 17 October 2006 # Springer Science + Business Media B.V. 2006 Abstract The Aerodyne aerosol mass spectrometer (Q-AMS) was coupled with a counterflow virtual impactor (CVI) for the first time to measure cloud droplet residuals of warm tropospheric clouds on Mt. Åreskutan in central Sweden in July 2003. Operating the CVI in different operational modes generated mass concentration and species-resolved mass distribution data for non-refractory species of the ambient, interstitial, and residual aerosol. The ambient aerosol measurements revealed that the aerosol at the site was mainly influenced by long-range transport and regional photochemical generation of nitrate and organic aerosol components. Four different major air masses were identified for the time interval of the experiment. While two air masses that approached the site from northeastern Europe via Finland showed very similar aerosol composition, the other two air masses from polar regions and the British Islands had a significantly different composition. During cloud events the larger aerosol particles were found to be activated into cloud droplets. On a mass J Atmos Chem (2007) 56:1–20 DOI 10.1007/s10874-006-9036-8 F. Drewnick (*) : J. Schneider : S. S. Hings : N. Hock : S. Borrmann Particle Chemistry Department, Max-Planck Institute for Chemistry, J. J. Becherweg 27, D-55128 Mainz, Germany e-mail: drewnick@mpch-mainz.mpg.de F. Drewnick : S. S. Hings : N. Hock : S. Weimer : S. Borrmann Institute for Atmospheric Physics, University of Mainz, J. J. Becherweg 21, D-55128 Mainz, Germany K. Noone : A. Targino Department of Applied Environmental Science, Stockholm University, SE-10691 Stockholm, Sweden S. Weimer EMPA, CH-8600 Dübendorf, Switzerland S. Weimer Paul Scherrer Institute, CH-5232 Villigen, Switzerland