SPECTROSCOPIC MEASUREMENT OF BROMINE OXIDE AND OZONE IN THE HIGH ARCTIC DURING POLAR SUNRISE EXPERIMENT 1992

Bromine oxide (BrO) is proposed to be an important agent for troposphe ric ozone depletion, as observed in the high Arctic during springtime. In this paper we report measurements of bromine oxide and ozone by Lo ng Path Differential Optical Absorption Spectroscopy (LPDOAS), 8.6-km light path), performed in April 1992 in Alert (82.3 degrees N, 62.2 de grees W). BrO mixing ratios were found between the detection limit of about 4 ppt to 17 ppt. Because of the frequently poor visibility condi tions, especially during ozone depletion events, long-signal integrati on times (sometimes more than 24 hours) were needed, and short-time Br O-peaks might have escaped detection. A pure in situ chemical mechanis m based on BrO-catalyzed ozone destruction cannot account for the obse rved complete depletion of ozone at the observed BrO mixing ratios. On the other hand, it can be argued that the maximum time for chemical o zone depletion (by any mechanism) may not be much longer than 1 day. A simple scenario involving a combination of advection, atmospheric dis persion, and BrO-catalyzed chemical ozone destruction is described, wh ich could explain the observed ozone loss.