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 analysed together with conventional tracers as Be-7 and relative humidity as well as the normalised fraction f(Be-7, Pb-210) in order to fully characterise the examined events. (C) 2000 Elsevier Science Ltd. All rights reserved.