Comparison of measured and modeled stratospheric BrO: Implications for thetotal amount of stratospheric bromine

Stratospheric BrO was spectroscopically monitored by its UV absorption in d irect sunlight on 8 balloon flights that were conducted at middle and high latitudes in 1996 through 2000 [e.g., Ferlemann et al., 1998, 2000]. For co nditions where detailed photochemical model calculations [Chipperfield, 199 9] correctly predict other measured chemical (e.g., NO2, O-3) and dynamical (e.g. N2O, F12, et cetera) tracers, the total stratospheric bromine (organ ic and inorganic) amount (Br,) is inferred. An excellent agreement between measured and modeled stratospheric BrO is found, assuming JPL-97 kinetics a nd Br-y=20 ppt in the photochemical model. As the BrO absorption cross sect ion (sigma (BrO)) is the only external parameter used in the measurement, o ur finding tightly constrains the amount of total inorganic bromine (Br-y(i n)), 20+/-2.5 ppt above 25 km in 1996/97, as well as the photochemistry of stratospheric bromine.