Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 6 5 2006 10.5194/acpd-6-8485-2006 http://www.atmos-chem-phys-discuss.net/6/8485/2006/ http://www.atmos-chem-phys-discuss.net/6/8485/2006/acpd-6-8485-2006.html http://www.atmos-chem-phys-discuss.net/6/8485/2006/acpd-6-8485-2006.pdf 8485 8510 2006-09-07 Using discriminant analysis as a nucleation event classification method S. Mikkonen santtu.mikkonen@uku.fi K. E. J. Lehtinen A. Hamed J. Joutsensaari M. C. Facchini A. Laaksonen Department of Physics, University of Kuopio, P.O. Box 1627, 70211 Kuopio, Finland Finnish meteorological institute, Kuopio Unit, P.O. Box 1627, 70210 Kuopio, Finland Department of Environmental Sciences, University of Kuopio, P.O. Box 1627, 70211 Kuopio, Finland Istituto di Scienze dell’Atmosfera e del Clima – CNR, Italy Via Gobetti 101, 40129 Bologna, Italy More than three years of measurements of aerosol size-distribution and different gas and meteorological parameters made in Po Valley, Italy were analysed for this study to examine which of the meteorological and trace gas variables effect on the emergence of nucleation events. As the analysis method, we used discriminant analysis with non-parametric Epanechnikov kernel, included in non-parametric density estimation method. The best classification result in our data was reached with the combination of relative humidity, ozone concentration and a third degree polynomial of radiation. <I>RH</I> appeared to have a preventing effect on the new particle formation whereas the effects of O₃ and radiation were more conductive. The concentration of SO₂ and NO₂ also appeared to have significant effect on the emergence of nucleation events but because of the great amount of missing observations, we had to exclude them from the final analysis.