Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 4 4 2004 10.5194/acpd-4-4455-2004 http://www.atmos-chem-phys-discuss.net/4/4455/2004/ http://www.atmos-chem-phys-discuss.net/4/4455/2004/acpd-4-4455-2004.html http://www.atmos-chem-phys-discuss.net/4/4455/2004/acpd-4-4455-2004.pdf 4455 4488 2004-08-11 Microphysics and heterogeneous chemistry in aircraft plumes &ndash; high sensitivity on local meteorology and atmospheric composition S. K. Meilinger smeili@mpch-mainz.mpg.de B. Kärcher Th. Peter Max Planck Institute for Chemistry, Mainz, Germany DLR Oberpfaffenhofen, Institute for Atmospheric Physics, Wessling, Germany Institute for Atmospheric and Climate Sciences, ETH Zürich, Switzerland An aircraft plume model has been developed on the basis of two coupled trajectory box models. Two boxes, one for plume and one for background conditions, are coupled by means of a mixing parameterization based on turbulence theory. The model considers comprehensive gas phase chemistry for the tropopause region including acetone, ethane and their oxidation products. Heterogeneous halogen, N<sub>2</sub>O<sub>5</sub> and HO<sub>x</sub> chemistry on various types of background and aircraft-induced aerosols (liquid and ice) is considered, using state-of-the-art solubility dependent uptake coefficients for liquid phase reactions. The microphysical scheme allows for coagulation, gas-diffusive particle growth and evaporation, so that the particle development from 1s after emission to several days can be simulated. Model results are shown, studying emissions into the upper troposphere as well as into the lowermost stratosphere for contrail and non-contrail conditions. We show the microphysical and chemical evolution of spreading plumes and use the concept of mean plume encounter time, <i>t</i><sub>1</sub> to define effective emission and perturbation indices (<i>EEI</i>s and <i>EPI</i>s) for the North Atlantic Flight Corridor (NAFC) showing <i>EEI</i>(NO<sub>y</sub>) and <i>EPI</i>(O<sub>3</sub>) for various background conditions, such as relative humidity, local time of emission, and seasonal variations. Our results show a high sensitivity of <i>EEI</i> and <i>EPI</i>s on the exact conditions under which emissions take place. The difference of <i>EEI</i>s with and without considering plume processes indicates that these processes cannot be neglected.