Stratospheric HBr mixing ratio obtained from far infrared emission spectra

Emission features of HBr isotopes have been identified in high‐resolution far‐infrared emission spectra obtained with a balloon‐borne Fourier transform spectrometer in the spring of 1979 at 32°N latitude. When six single‐scan spectra at a zenith angle of 93.2° were averaged, two features of HBr isotopes at 50.054 and 50.069 cm −1 were obtained with a signal‐to‐noise ratio of 2.5. The volume mixing ratio retrieved from the average spectrum is 2.0 × 10 −11 , which is assumed to be constant above 28 km, with an uncertainty of 35 percent. This stratospheric amount of HBr is about the same as the current level of tropospheric organic bromine compounds, 25 pptv. Thus, HBr could be the major stratospheric bromine species.