Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 6 3 2006 10.5194/acp-6-689-2006 http://www.atmos-chem-phys.net/6/689/2006/ http://www.atmos-chem-phys.net/6/689/2006/acp-6-689-2006.html http://www.atmos-chem-phys.net/6/689/2006/acp-6-689-2006.pdf 689 696 2006-03-01 Composition analysis of liquid particles in the Arctic stratosphere under synoptic conditions C. Weisser K. Mauersberger J. Schreiner N. Larsen F. Cairo A. Adriani J. Ovarlez T. Deshler Max-Planck-Institute for Nuclear Physics, Heidelberg, Germany Danish Meteorological Institute, Copenhagen, Denmark Institute for Atmospheric Science and Climate, Consiglio Nazionale delle Ricerche, Rome, Italy Institute for Interplanetary Space Physics, Consiglio Nazionale delle Ricerche, Rome, Italy Laboratoire de Meteorologie Dynamique, Ecole Polytechnique, Palaiseau, France University of Wyoming, Laramie, Wyoming, USA Synoptic scale polar stratospheric clouds (PSCs) that formed without the presence of mountain lee waves 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 with solid particles still present. The correlation of liquid supercooled ternary solution aerosols with local temperatures is a pronounced feature observed during this flight; average molar ratios H₂O/HNO₃ were somewhat higher than predicted by models. 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, the measured average amount of HCl in liquid particles is below 1 weight%.