Near UV atmospheric absorption measurements of column abundances during Airborne Arctic Stratospheric Expedition, January - February 1989: 2. OClO observations

Column abundances of OClO were measured during the Airborne Arctic Stratospheric Expedition from January 6 to February 9,1989 by near UV absorption spectroscopy. OClO was detected during AASE inside the vortex and at the edge of the vortex with column abundances of 3 – 10 × 1012 cm−2 under twilight conditions and up to 1 × 1014 cm−2 during the night. For comparison, in the Antarctic winter nighttime column abundances of OClO ranged from 1 – 2.5 × 1014 cm−2, while those at mid-latitudes were below the detection limit, i.e. by at least a factor of 10 lower (Solomon et al., 1988). The measurements are broadly consistent with observed BrO column abundances and chemical model calculations.