Detection of HBr and upper limit for HOBr: Bromine partitioning in the stratosphere



We determine mixing ratio profiles for HBr and upper limits for HOBr in the stratosphere with precisions up to 1.7 and 4.8 parts per trillion, respectively, using the combined data from 7 flights of our far-infrared spectrometer. The measurements suggest that in the range 22–34 km the average mixing ratio of HBr is 2.0±0.8, and that the average mixing ratio of HOBr is less than 2.8 ppt. Our measurements of HBr are in reasonable agreement with a photochemical model which includes 0 or 2% production of HBr through the reaction of BrO with HO2, but in strong disagreement with a model including 5 or 10% HBr production.