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Comparison of the SAWNUC model with CLOUD measurements of sulphuric acid‐water nucleation
Author(s) -
Ehrhart Sebastian,
Ickes Luisa,
Almeida Joao,
Amorim Antonio,
Barmet Peter,
Bianchi Federico,
Dommen Josef,
Dunne Eimear M.,
Duplissy Jonathan,
Franchin Alessandro,
Kangasluoma Juha,
Kirkby Jasper,
Kürten Andreas,
Kupc Agnieszka,
Lehtipalo Katrianne,
Nieminen Tuomo,
Riccobono Francesco,
Rondo Linda,
Schobesberger Siegfried,
Steiner Gerhard,
Tomé António,
Wimmer Daniela,
Baltensperger Urs,
Wagner Paul E.,
Curtius Joachim
Publication year - 2016
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2015jd023723
Subject(s) - nucleation , chemistry , cloud chamber , cluster (spacecraft) , ion , ammonia , analytical chemistry (journal) , chromatography , organic chemistry , physics , computer science , nuclear physics , programming language
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 1·10 6 to 1·10 9 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 ( ( H 2SO 4 ) i · HSO 4 −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.