Articles | Volume 11, issue 21
Atmos. Chem. Phys., 11, 11319–11334, 2011

Special issue: European Integrated Project on Aerosol-Cloud-Climate and Air...

Atmos. Chem. Phys., 11, 11319–11334, 2011

Research article 14 Nov 2011

Research article | 14 Nov 2011

A statistical proxy for sulphuric acid concentration

S. Mikkonen1, S. Romakkaniemi2, J. N. Smith1,2,3, H. Korhonen3, T. Petäjä4, C. Plass-Duelmer5, M. Boy4, P. H. McMurry6, K. E. J. Lehtinen1,3, J. Joutsensaari1, A. Hamed1, R. L. Mauldin III2,4, W. Birmili7, G. Spindler7, F. Arnold8, M. Kulmala4, and A. Laaksonen1,9 S. Mikkonen et al.
  • 1Department of Applied Physics, University of Eastern Finland, P.O. Box 1627, 70211 Kuopio, Finland
  • 2Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, CO, USA
  • 3Finnish Meteorological Institute, Kuopio unit, P.O. Box 1627, 70211 Kuopio, Finland
  • 4Department of Physics, University of Helsinki, P.O. Box, 00014 Helsinki, Finland
  • 5Hohenpeissenberg Meteorological Observatory, Hohenpeissenberg, Germany
  • 6Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN, USA
  • 7Leibniz Institute for Tropospheric Research, Permoserstrasse 15, 04318 Leipzig, Germany
  • 8Max-Planck-Institute for Nuclear Physics, Heidelberg, Germany
  • 9Finnish Meteorological Institute, P.O. Box 503, 00101 Helsinki, Finland

Abstract. Gaseous sulphuric acid is a key precursor for new particle formation in the atmosphere. Previous experimental studies have confirmed a strong correlation between the number concentrations of freshly formed particles and the ambient concentrations of sulphuric acid. This study evaluates a body of experimental gas phase sulphuric acid concentrations, as measured by Chemical Ionization Mass Spectrometry (CIMS) during six intensive measurement campaigns and one long-term observational period. The campaign datasets were measured in Hyytiälä, Finland, in 2003 and 2007, in San Pietro Capofiume, Italy, in 2009, in Melpitz, Germany, in 2008, in Atlanta, Georgia, USA, in 2002, and in Niwot Ridge, Colorado, USA, in 2007. The long term data were obtained in Hohenpeissenberg, Germany, during 1998 to 2000. The measured time series were used to construct proximity measures ("proxies") for sulphuric acid concentration by using statistical analysis methods. The objective of this study is to find a proxy for sulfuric acid that is valid in as many different atmospheric environments as possible. Our most accurate and universal formulation of the sulphuric acid concentration proxy uses global solar radiation, SO2 concentration, condensation sink and relative humidity as predictor variables, yielding a correlation measure (R) of 0.87 between observed concentration and the proxy predictions. Interestingly, the role of the condensation sink in the proxy was only minor, since similarly accurate proxies could be constructed with global solar radiation and SO2 concentration alone. This could be attributed to SO2 being an indicator for anthropogenic pollution, including particulate and gaseous emissions which represent sinks for the OH radical that, in turn, is needed for the formation of sulphuric acid.

Final-revised paper