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
Received: 10 Jun 2011 – Published in Atmos. Chem. Phys. Discuss.: 15 Jul 2011
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.
Revised: 21 Oct 2011 – Accepted: 31 Oct 2011 – Published: 14 Nov 2011
Mikkonen, S., Romakkaniemi, S., Smith, J. N., Korhonen, H., Petäjä, T., Plass-Duelmer, C., Boy, M., McMurry, P. H., Lehtinen, K. E. J., Joutsensaari, J., Hamed, A., Mauldin III, R. L., Birmili, W., Spindler, G., Arnold, F., Kulmala, M., and Laaksonen, A.: A statistical proxy for sulphuric acid concentration, Atmos. Chem. Phys., 11, 11319-11334, doi:10.5194/acp-11-11319-2011, 2011.