UPPER LIMIT FOR STRATOSPHERIC HBR USING FAR-INFRARED THERMAL EMISSION-SPECTROSCOPY

We measure an upper limit for stratospheric HBr from three balloon flights. The observations were made with the FIRS-2 far-infrared Fourier transform spectrometer. The 1-sigma upper limits from the 1988, 1989 and 1990 balloon flights are 13 pptv at 35 km, 7 pptv at 32 km, and 3 pptv at 31 km, respectively. Combining all 3 flights, the weighted average 1-sigma upper limit for HBr is 4 pptv at 32 km. This value is significantly smaller than the only other previously published spectroscopic value of 20 +/- 7 pptv (2-sigma), but is consistent with (albeit well in excess of) a theoretical estimate which predicts roughly 0.4 pptv at this altitude.