1Max-Planck-Institute for Nuclear Physics, Heidelberg, Germany
2Danish Meteorological Institute, Copenhagen, Denmark
3Institute for Atmospheric Science and Climate, Consiglio Nazionale delle Ricerche, Rome, Italy
4Institute for Interplanetary Space Physics, Consiglio Nazionale delle Ricerche, Rome, Italy
5Laboratoire de Meteorologie Dynamique, Ecole Polytechnique, Palaiseau, France
6University of Wyoming, Laramie, Wyoming, USA
Abstract. Synoptic scale polar stratospheric clouds (PSCs) that formed without the presence of mountain leewaves were observed in early December 2002 from Kiruna/Sweden using balloon-borne instruments. The physical, chemical, and optical properties of the particles were measured. Within the PSC solid particles existed whenever the temperature was below the equilibrium temperature for nitric acid trihydrate and liquid particles appeared when the temperature fell below an even lower threshold about 3 K above the frost point. The correlation of liquid supercooled ternary solution aerosols with local temperatures is a pronounced feature observed during this flight although the molar ratios H2O/HNO3 were about a factor of 2 higher than model predictions. In addition HCl has been measured for the first time in liquid aerosols. The chlorine isotope signature served as a unique tool to identify unambiguously HCl dissolved in STS particles. Within a narrow temperature range of about three degrees above the frost point, measured HCl molar ratios are below 1 weight%. There is only fair agreement with model predictions.