GROUND-BASED OZONE DATA RELEVANT FOR THE AASE CAMPAIGN IN 1989

The Airborne Arctic Stratospheric Expedition (AASE) carried out measur ements from Jan. 3 to Feb. 15, 1989. Enhanced levels of chlorine compo unds were found in the Arctic stratosphere, and on two single flights ozone decrease of 17% were measured, interpreted as essential features of the Arctic stratosphere, caused by a combined effect of enhanced a mounts of chlorine compounds and presence of polar stratospheric cloud s. Related model calculations also indicate extended ozone depletion m aximizing in late March 1989 and amount to 5-8% in column at 70-degree s-N. Ground-based ozone measurements, however, show that the most char acteristic features during this period are temporal variations and a s trong enhancement of ozone, probably due to an extended stratospheric warming. From these measurements it is hard to see any effect of an ev entual enhanced burden of stratospheric chlorine, which might show up as an extended and long-lasting decrease of stratospheric ozone, but i ts eventual existence is masked by the temporal variations. As ever, t heoretical predictions and model calculations can be really misleading when proper account of relevant data is omitted.