title: Comparison of the SAWNUC model with CLOUD measurements of sulphuric acid-water nucleation.
abstract: Binary nucleation of sulphuric acid-water particles is expected to be an important process in the free troposphere at low temperatures. SAWNUC (Sulphuric Acid Water Nucleation) is a model of binary nucleation that is based on laboratory measurements of the binding energies of sulphuric acid and water in charged and neutral clusters. Predictions of SAWNUC are compared for the first time comprehensively with experimental binary nucleation data from the CLOUD chamber at European Organization for Nuclear Research. The experimental measurements span a temperature range of 208-292 K, sulphuric acid concentrations from 1·106to 1·109cm-3, and distinguish between ion-induced and neutral nucleation. Good agreement, within a factor of 5, is found between the experimental and modeled formation rates for ion-induced nucleation at 278 K and below and for neutral nucleation at 208 and 223 K. Differences at warm temperatures are attributed to ammonia contamination which was indicated by the presence of ammonia-sulphuric acid clusters, detected by an Atmospheric Pressure Interface Time of Flight (APi-TOF) mass spectrometer. APi-TOF measurements of the sulphuric acid ion cluster distributions ( (H2SO4)i·HSO4- with i = 0, 1, ..., 10) show qualitative agreement with the SAWNUC ion cluster distributions. Remaining differences between the measured and modeled distributions are most likely due to fragmentation in the APi-TOF. The CLOUD results are in good agreement with previously measured cluster binding energies and show the SAWNUC model to be a good representation of ion-induced and neutral binary nucleation of sulphuric acid-water clusters in the middle and upper troposphere.
authors.affiliation: Goethe University FrankfurtInstitute for Atmospheric and Environmental SciencesFrankfurt am MainGermany; CERNGenevaSwitzerland.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Ehrhart
authors.affiliation: Goethe University FrankfurtInstitute for Atmospheric and Environmental Sciences Frankfurt am Main Germany; Now at Institute for Atmospheric and Climate Science ETH Zurich Zürich Switzerland.
authors.forename: Luisa
authors.initials: L
authors.lastname: Ickes
authors.affiliation: Goethe University FrankfurtInstitute for Atmospheric and Environmental SciencesFrankfurt am MainGermany; CERNGenevaSwitzerland.
authors.forename: Joao
authors.initials: J
authors.lastname: Almeida
authors.affiliation: SIM University of Lisbon, University of Beira Interior Lisbon Portugal.
authors.forename: Antonio
authors.initials: A
authors.lastname: Amorim
authors.affiliation: Paul Scherrer Institute Villigen Switzerland.
authors.forename: Peter
authors.initials: P
authors.lastname: Barmet
authors.affiliation: Paul Scherrer Institute Villigen Switzerland.
authors.forename: Federico
authors.initials: F
authors.lastname: Bianchi
authors.affiliation: Paul Scherrer Institute Villigen Switzerland.
authors.forename: Josef
authors.initials: J
authors.lastname: Dommen
authors.affiliation: School of Earth and Environment University of Leeds Leeds UK; Finnish Meteorological Institute Atmospheric Research Centre of Eastern Finland Kuopio Finland.
authors.forename: Eimear M
authors.initials: EM
authors.lastname: Dunne
authors.affiliation: Department of Physics University of Helsinki Helsinki Finland; Helsinki Institute of Physics University of Helsinki Helsinki Finland.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Duplissy
authors.affiliation: Department of Physics University of Helsinki Helsinki Finland.
authors.forename: Alessandro
authors.identifier: 0000-0001-7425-8272
authors.initials: A
authors.lastname: Franchin
authors.affiliation: Department of Physics University of Helsinki Helsinki Finland.
authors.forename: Juha
authors.initials: J
authors.lastname: Kangasluoma
authors.affiliation: Goethe University FrankfurtInstitute for Atmospheric and Environmental SciencesFrankfurt am MainGermany; CERNGenevaSwitzerland.
authors.forename: Jasper
authors.initials: J
authors.lastname: Kirkby
authors.affiliation: Goethe University Frankfurt Institute for Atmospheric and Environmental Sciences Frankfurt am Main Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Kürten
authors.affiliation: Faculty of PhysicsUniversity of ViennaViennaAustria; Now at Cooperative Institute for Research in Environmental SciencesUniversity of Colorado Boulder, Boulder, Colorado, USA and Chemical Sciences Division, NOAA Earth System Research LaboratoryBoulderColoradoUSA.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Kupc
authors.affiliation: Paul Scherrer Institute Villigen Switzerland; Department of Physics University of Helsinki Helsinki Finland.
authors.forename: Katrianne
authors.initials: K
authors.lastname: Lehtipalo
authors.affiliation: Department of Physics University of Helsinki Helsinki Finland; Helsinki Institute of Physics University of Helsinki Helsinki Finland; Now at Department of Applied Physics University of Eastern Finland Kuopio Finland.
authors.forename: Tuomo
authors.identifier: 0000-0002-2713-715X
authors.initials: T
authors.lastname: Nieminen
authors.affiliation: Paul Scherrer Institute Villigen Switzerland.
authors.forename: Francesco
authors.initials: F
authors.lastname: Riccobono
authors.affiliation: Goethe University Frankfurt Institute for Atmospheric and Environmental Sciences Frankfurt am Main Germany.
authors.forename: Linda
authors.initials: L
authors.lastname: Rondo
authors.affiliation: Department of Physics University of Helsinki Helsinki Finland; Now at Department of Atmospheric Sciences University of Washington Seattle Washington USA.
authors.forename: Siegfried
authors.initials: S
authors.lastname: Schobesberger
authors.affiliation: Department of Physics University of Helsinki Helsinki Finland; Faculty of Physics University of Vienna Vienna Austria; Institute of Ion Physics and Applied Physics Leopold-Franzens University Innsbruck Austria.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Steiner
authors.affiliation: SIM University of Lisbon, University of Beira Interior Lisbon Portugal.
authors.forename: António
authors.initials: A
authors.lastname: Tomé
authors.affiliation: Goethe University FrankfurtInstitute for Atmospheric and Environmental Sciences Frankfurt am Main Germany; Department of Physics University of Helsinki Helsinki Finland.
authors.forename: Daniela
authors.initials: D
authors.lastname: Wimmer
authors.affiliation: Paul Scherrer Institute Villigen Switzerland.
authors.forename: Urs
authors.initials: U
authors.lastname: Baltensperger
authors.affiliation: Faculty of Physics University of Vienna Vienna Austria.
authors.forename: Paul E
authors.initials: PE
authors.lastname: Wagner
authors.affiliation: Goethe University Frankfurt Institute for Atmospheric and Environmental Sciences Frankfurt am Main Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Curtius
keywords: binary nucleation; ion‐induced nucleation