Is there a correlation between tropospheric ozone and climate?

Lidar vertical sounding of ozone, water vapour and aerosol at Garmisch-Partenkirchen in the German Alps and long-term in-situ measurements at local mountain stations up to 3 km a.s.l. have been the basis for investigations of atmospheric transport over several decades. The positive ozone trend in the lower free troposphere is dominated by downward transport from the stratosphere. The thin intrusion layers are extremely dry which suggests very low mixing with tropospheric air, in contrast to the traditional view. The related ozone trend at the Zugspitze summit (2962 m a.s.l.) follows the changes in solar radiation. This indicates a correlation of the vertical exchange with the climate. Parallel to this development the background air quality has improved, as demonstrated by the decrease of CO and NOx since 1990.