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

Severe and extensive denitrification, chlorine activation, and photochemica l ozone loss were observed throughout the lower stratosphere in the 1999-20 00 Arctic vortex. A large number of air parcels sampled between late Februa ry and mid-March, 2000, were photochemically intercomparable for chemical O -3 loss rates. In these air parcels, the temporal evolution of the correlat ions Of O-3 with the NOy remaining after denitrification provides strong ev idence for the role of NOy in moderating O-3 destruction. In 71%-denitrifie d air parcels, a chemical O-3 destruction rate of 63 ppbv/day was calculate d, while in 43%-denitrified air parcels the destruction rate was only 43 pp bv/day. These observational results show that representative denitrificatio n models will be required for accurate prediction of future Arctic O-3 chan ges.