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J Geophys Res Atmos. 2016 Oct 27;121(20):12401-12414. doi: 10.1002/2015JD023723.

Comparison of the SAWNUC model with CLOUD measurements of sulphuric acid-water nucleation.

Author information

1
Goethe University FrankfurtInstitute for Atmospheric and Environmental SciencesFrankfurt am MainGermany; CERNGenevaSwitzerland.
2
Goethe University FrankfurtInstitute for Atmospheric and Environmental SciencesFrankfurt am MainGermany; Now at Institute for Atmospheric and Climate ScienceETH ZurichZürichSwitzerland.
3
SIM University of Lisbon, University of Beira Interior Lisbon Portugal.
4
Paul Scherrer Institute Villigen Switzerland.
5
School of Earth and EnvironmentUniversity of LeedsLeedsUK; Finnish Meteorological InstituteAtmospheric Research Centre of Eastern FinlandKuopioFinland.
6
Department of PhysicsUniversity of HelsinkiHelsinkiFinland; Helsinki Institute of PhysicsUniversity of HelsinkiHelsinkiFinland.
7
Department of Physics University of Helsinki Helsinki Finland.
8
Goethe University Frankfurt Institute for Atmospheric and Environmental Sciences Frankfurt am Main Germany.
9
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.
10
Paul Scherrer InstituteVilligenSwitzerland; Department of PhysicsUniversity of HelsinkiHelsinkiFinland.
11
Department of PhysicsUniversity of HelsinkiHelsinkiFinland; Helsinki Institute of PhysicsUniversity of HelsinkiHelsinkiFinland; Now at Department of Applied PhysicsUniversity of Eastern FinlandKuopioFinland.
12
Department of PhysicsUniversity of HelsinkiHelsinkiFinland; Now at Department of Atmospheric SciencesUniversity of WashingtonSeattleWashingtonUSA.
13
Department of PhysicsUniversity of HelsinkiHelsinkiFinland; Faculty of PhysicsUniversity of ViennaViennaAustria; Institute of Ion Physics and Applied PhysicsLeopold-Franzens UniversityInnsbruckAustria.
14
Goethe University FrankfurtInstitute for Atmospheric and Environmental SciencesFrankfurt am MainGermany; Department of PhysicsUniversity of HelsinkiHelsinkiFinland.
15
Faculty of Physics University of Vienna Vienna Austria.

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 1·106 to 1·109 cm-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.

KEYWORDS:

binary nucleation; ion‐induced nucleation

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