STRATOSPHERIC BRO PROFILES MEASURED AT DIFFERENT LATITUDES AND SEASONS - INSTRUMENT DESCRIPTION, SPECTRAL-ANALYSIS AND PROFILE RETRIEVAL

Measurements of stratospheric BrO profiles are reported using a novel DOAS instrument (Differential Optical Absorption Spectrometry) operate d on the LPMA/DOAS balloon gondola (LPMA/Laboratoire de Physique Molec ulaire et Applications) during three flights (Leon, Nov. 23, 1998, Kir una, Feb. 14, 1997, and Gap, June 20,1997). BrO was detected by its vi brational bands (4-0 at 354.7 nm; 5-0 at 348.8 nm) of the A((2)pi)<--X ((2)pi) transition in direct sunlight spectra from balloon ascent, des cent and during solar occultation at maximum (float) altitude. We show that our accuracy is about +/-18% (1 sigma) during balloon ascent (so lar zenith angles, SZA < 88 degrees), and about +/-25% for solar occul tation measurements. For altitudes above the balloon float our observa tions indicate average BrO mixing ratios of (14.4+/-2.5)ppt, (15.6+/-2 .8)ppt, and (15.3+/-2.8)ppt above 30.0 km, 30.0 km, and 39.8 km, respe ctively.