ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-9-8079-2009 A new parametrization for ambient particle formation over coniferous forests and its potential implications for the future Bonn B. 1 Boy M. 2 Kulmala M. 2 Groth A. 1 Trawny K. 1 Borchert S. 1 Jacobi S. 3 Institute for Atmospheric and Environmental Sciences, Goethe University, Frankfurt, Germany Atmospheric Sciences Division, Department of Physics, University of Helsinki, Finland Hessian Agency for the Environment and Geology, Air Quality Department, Wiesbaden, Germany 27 10 2009 9 20 8079 8090 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/9/8079/2009/acp-9-8079-2009.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/9/8079/2009/acp-9-8079-2009.pdf

Atmospheric new particle formation is a general phenomenon observed over coniferous forests. So far nucleation is either parameterised as a function of gaseous sulphuric acid concentration only, which is unable to explain the observed seasonality of nucleation events at different measurement sites, or as a function of sulphuric acid and organic molecules. Here we introduce different nucleation parameters based on the interaction of sulphuric acid and terpene oxidation products and elucidate the individual importance. They include basic trace gas and meteorological measurements such as ozone and water vapour concentrations, temperature (for terpene emission) and UV B radiation as a proxy for OH radical formation. We apply these new parameters to field studies conducted at conducted at Finnish and German measurement sites and compare these to nucleation observations on a daily and annual scale. General agreement was found, although the specific compounds responsible for the nucleation process remain speculative. This can be interpreted as follows: During cooler seasons the emission of biogenic terpenes and the OH availability limits the new particle formation while towards warmer seasons the ratio of ozone and water vapour concentration seems to dominate the general behaviour. Therefore, organics seem to support ambient nucleation besides sulphuric acid or an OH-related compound. Using these nucleation parameters to extrapolate the current conditions to prognosed future concentrations of ozone, water vapour and organic concentrations leads to a significant potential increase in the nucleation event number.

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