Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 5 6 2005 10.5194/acpd-5-11517-2005 http://www.atmos-chem-phys-discuss.net/5/11517/2005/ http://www.atmos-chem-phys-discuss.net/5/11517/2005/acpd-5-11517-2005.html http://www.atmos-chem-phys-discuss.net/5/11517/2005/acpd-5-11517-2005.pdf 11517 11555 2005-11-10 Conceptual study on nucleation burst evolution in the convective boundary layer – Part III: Physico-chemical characterization O. Hellmuth olaf@tropos.de Modelling Department, Institute for Tropospheric Research, Permoser Str. 15, 04318 Leipzig, Germany In part I of the present paper a revised columnar high-order model to investigate gas-aerosol interactions in the convective boundary layer (CBL) was proposed. In part II the model capability to predict first-, second-, and third-order moments of meteorological variables in the CBL was demonstrated using available observational data. In the present part, the high-order modelling concept is extented to sulfur and ammonia chemistry as well as to aerosol dynamics. Based on the previous CBL simulation, two conceptual scenarios of the evolution of ultrafine condensation nuclei (UCN) in an anthropogenically influenced CBL are investigated. The scenarios differ in the treatment of new particle formation, whereas homogeneous nucleation according to the classical nucleation theory is considered. The first scenario considers nucleation of a binary system consisting of water vapour and sulfuric acid vapour, the second one on nucleation of a ternary system additionally involving ammonia. Here, the two scenarios are discussed in detail, whereas special attention is payed to the role of turbulence in the formation of the typical UCN burst behaviour, that can often be observed in the Prandtl layer.