Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 2 6 2002 10.5194/acpd-2-2413-2002 http://www.atmos-chem-phys-discuss.net/2/2413/2002/ http://www.atmos-chem-phys-discuss.net/2/2413/2002/acpd-2-2413-2002.html http://www.atmos-chem-phys-discuss.net/2/2413/2002/acpd-2-2413-2002.pdf 2413 2448 2002-12-16 Particle formation at a continental background site: comparison of modelresults with observations U. Uhrner W. Birmili F. Stratmann M. Wilck I. J. Ackermann H. Berresheim Institute for Tropospheric Research, Permoserstr. 15, 04318 Leipzig, Germany Division of Environmental Health and Risk Management, Birmingham University, B15 2TT, UK Institute for Tropospheric Research, Permoserstr. 15, 04318 Leipzig, Germany Ford Research Centre Aachen, Süsterfeldstr. 200, 52072 Aachen, Germany German Weather Service – Deutscher Wetterdienst, Meteorological Observatory Hohenpeissenberg, Albin-Schwaiger-Weg 10, 83282 Hohenpeissenberg, Germany At Hohenpeissenberg (47°48'N, 11°07'E, 988 m asl), a rural site 200-300 m higher than the surrounding terrain, sulphuric acid concentrations, particle size distributions, and other trace gas concentrations were measured over a two and a half year period. Measured particle number concentrations and inferred particle surface area-concentrations were compared with box-model simulations based on a multimodal lognormal aerosol module that included a binary sulphuric acid water nucleation scheme. The calculated nucleation rates were corrected with a factor to match measured particle number concentrations. These corrections varied over a range of 10-3 - 1017. The correction factors were close to 1 for the measurements made in the winter, which represented stable thermal stratification and low wind conditions. In contrast, the correction factors were the largest for measurements made under strong convective conditions. Our comparison of measured and simulated particle size distributions suggest a distant particle-formation process under convective conditions near the interface of the mixed layer and the entrainment zone, followed by downward transport and particle growth. For stable stratification and low winds, our comparisons suggest that particles formed close to the measurement site.