A model study of the potential role of the reaction BrO + OH in the production of stratospheric HBr

Abstract

We have used a constrained one-dimensional photochemical model to investigate the effect of a potential minor channel of the fast reaction between BrO + OH to produce HBr. There is no direct evidence for this reaction but the analogous yield of HCl from ClO + OH is thought to be about 5%. With only a 1-2% yield of HBr the modelled HBr mixing ratio between 20-30 km increases from around 0.5 parts per 1012 by volume (pptv) to 1-2 pptv. This brings the model into agreement with recent balloon-borne observations of stratospheric HBr. Should BrO + OH produce HBr with around 1-2% yield then this reaction will dominate HBr production between 20-35 km. As the main loss of HBr is reaction with OH this will lead to steady state HBr:BrO partitioning which is independent of other species, and temperature. Copyright 1997 by the American Geophysical Union.