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

Abstract

Stratospheric BrO was spectroscopically monitored by its UV absorption in direct 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 conditions where detailed photochemical model calculations [ Chipperfield , 1999] correctly predict other measured chemical (e.g., NO 2 , O 3 ) and dynamical (e.g. N 2 O, F12, et cetera) tracers, the total stratospheric bromine (organic and inorganic) amount (Br y ) is inferred. An excellent agreement between measured and modeled stratospheric BrO is found, assuming JPL‐97 kinetics and Br y =20 ppt in the photochemical model. As the BrO absorption cross section ( σBrO ) is the only external parameter used in the measurement, our finding tightly constrains the amount of total inorganic bromine (Br y in ), 20±2.5 ppt above 25 km in 1996/97, as well as the photochemistry of stratospheric bromine.