Stratospheric ozone intrusion episodes recorded at Mt. Cimone during the VOTALP project: Case studies

Continuous measurements of ozone concentrations performed at baseline stations on high mountain summits allow stratosphere-troposphere exchange events to be monitored and their variability over small scales to be studied. In this paper we present two characteristic episodes related to lower stratosphere/upper troposphere vertical transport registered at Mt. Cimone during the VOTALP project and we highlight the use of carbon monoxide (CO) and carbon dioxide (CO2) as non-conventional tracers of lower stratospheric air masses. In this way, stratosphere-troposphere exchange events transporting high ozone concentration into the troposphere have been identified by an accurate analysis of the CO and CO2 behaviour. Moreover, three-dimensional ensemble trajectories, satellite maps (water vapour and total ozone), ground-based ozone measurements and ozone-soundings have been analyzed together with conventional tracers as 7Be and relative humidity as well as the normalized fraction f (7Be, 210Pb) in order to fully characterize the examined events.