The report use ozone measurement data retrieved in the Arctic with balloon borne ozone sondes for the last 20-30 years. Four stations with the best data series have been selected. Using a Monte Carlo method the yearly period is subtracted from the data and the remains, the anomalies, are correlated towards the area of the Polar Front, the temperature rise of the Nortern Hemisphere and the North Atlantic Oscillation (NAO) and towards one another. It was found that the NAO correlates negatively with ozone anomalies for all four stations albeit the correlations are weak. Besides, the polar front area correlates weakly positive with the ozone anomalies for three out of the four stations. These results, together with the observation that the ozone-anomalies have a brief decorrelation time, indicate that most of the variability in the anomalies should be found in local conditions.

Ozone soundings from 9 Nordic stations with rather different data coverage have been homogenized followed by an interpolation to standard tropospheric pressure levels. A Bayesian model was applied which included a low-frequency variability, an annual cycle with harmonics, the possibility for variability in seasonal amplitude and phasing, and noise. Regarding the low-frequency variability it was found that only Scoresbysund, Ny Aalesund and Sodankyla showed statistical significant changes with a maximum near 2007 followed by a decrease. We hypothesize that this decrease could be explained by an observed decrease in nitrogen oxide in Europe.