Observational evidence for the role of denitrification in Arctic stratospheric ozone loss

Severe and extensive denitrification, chlorine activation, and photochemical ozone loss were observed throughout the lower stratosphere in the 1999–2000 Arctic vortex. A large number of air parcels sampled between late February and mid‐March, 2000, were photochemically intercomparable for chemical O 3 loss rates. In these air parcels, the temporal evolution of the correlations of O 3 with the NO y remaining after denitrification provides strong evidence for the role of NO y in moderating O 3 destruction. In 71%‐denitrified air parcels, a chemical O 3 destruction rate of 63 ppbv/day was calculated, while in 43%‐denitrified air parcels the destruction rate was only 43 ppbv/day. These observational results show that representative denitrification models will be required for accurate prediction of future Arctic O 3 changes.