1Environmental Science Dept., Lancaster University, Lancaster, UK
2Institute for Atmospheric Physics, DLR, Oberpfaffenhofen, Germany
3Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
4Institute of Atmospheric Sciences and Climate of the National Research Council (CNR-ISAC), Rome, Italy
Abstract. Mountain wave polar stratospheric clouds (PSCs) were detected on 8 February 2003 above the Scandinavian Mountains by in-situ instruments onboard the M55 Geophysica aircraft. The observations of PSC particle composition, backscatter and chlorine activation are studied with a recently developed dynamical microphysical non-equilibrium box model. Results from the microphysical model, run on quasi-lagrangian trajectories, show that the PSC is composed of supercooled ternary (H2O/HNO3/H2SO4) solutions (STS) particles, which are out of equilibrium with the gas phase. The optical properties of the PSC can well be simulated with the model. Up to 0.15 ppbv Cl2 can be released by the PSC within 2 h in reasonable agreement with the measured ClOx concentrations, but high solar zenith angles prevent a direct comparison. Equilibrium calculations commonly used in large scale chemistry transport models poorly represent the measured PSC particle composition and chlorine activation under mountain wave conditions.