Winter to winter variability of chlorine activation and ozone loss as observed by ground-based FTIR measurements at Kiruna since winter 1993/94

In the framework of the NDACC (Network for the Detection of Atmospheric Composition Change) long-term FTIR (Fourier Transform Infrared) measurements have been performed at Kiruna since winter 1993/94. In this paper only observations made in the polar vortex are investigated. Due to Kiruna's preferential location with respect to the polar vortex more than 120 days of observation have been collected since 1993. Total column ozone losses of up to 28% have been measured, namely in the winters of 1995, 1996, 2000, 2003, 2005 and 2007. A comparison of observed ozone loss with data from the SAOZ (Systeme d'Analyse par Observation Zenithale) network shows very good agreement. Fully consistent with this, chlorine activation and removal of HNO(3) from the gas phase have been also observed in these winters. In particular, chlorine activation of up to 65% has been measured in the beginning of 2005. Chlorine activation as well as ozone depletion correlates well with meteorological parameters such as stratospheric temperatures and volume of PSCs (Polar Stratospheric Clouds). In addition to studies using ozonesonde data, a correlation of chlorine activation with the volume of PSCs has been found.