Atmospheric Chemistry and Physics Surface ozone at the Caucasian site Kislovodsk High Mountain Station and the Swiss Alpine site Jungfraujoch: data analysis and trends (1990–2006)

Abstract. Long-term ozone measurements of two back-ground mountain sites, namely the Kislovodsk High Moun-tain Station in Caucasus, Russia (KHMS, 43.70 ◦ N, 42.70 ◦ E, 2070 m a.s.l.) and the Jungfraujoch in Switzerland (JFJ, 46.55 ◦ N, 7.98 ◦ E, 3580 m a.s.l.) are compared. Despite of more than 1.5 km altitude difference ozone mixing ratios are comparable at JFJ an KHMS in the beginning of mea-surements (1990–1993) while the annually averaged levels at JFJ are around 15 ppb higher than the ones at KHMS for the most recent years (1997–2006). The seasonal cy-cle of the surface ozone mixing ratios is characterized by a double spring-summer maximum at both sites with a spring one being more pronounced for the air masses with the longest contact with the upper free troposphere and strato-sphere. Ozone mixing ratio increased at JFJ but decrease