EVIDENCE FOR ARCTIC OZONE DEPLETION IN LATE FEBRUARY AND EARLY MARCH 1994

Significant chemical ozone (O-3) loss in the 1993-94 Arctic winter occurred mainly during an unusually late cold spell of similar to 10 days in late Feb/early Mar. Over the 30 d period studied (including the cold spell), observed vortex-averaged O-3 at 465 K (similar to 40 hPa) decreased by similar to 10. New three-dimensional, diabatic trajectory calculations show that this observed decrease represents only about half of the net chemical. loss (similar to 20%) during the 30 day period. The resupply of lower stratospheric O-3 by transport in Feb 1994 was considerably greater than in 1993, when transport masked only about a quarter of the chemical loss in Feb/Mar. The net estimated chemical loss over 30 days in 1994 was comparable to that over the same 30 days in 1993, but mainly occurred at a faster rate during the brief cold spell. These results highlight the impact of Arctic interannual variability on the relative roles of chemistry and dynamics in O-3 evolution during recent Arctic winters.