Stratospheric BrO profiles measured at different latitudes and seasons: Atmospheric observations

Stratospheric BrO profiles were measured at different latitudes and in different seasons in 1996/97 during three flights of the LPMA/DOAS balloon gondola (LPMA/Laboratoire Physique Moléculaire et Application and DOAS/Differential Optical Absorption Spectrometry). Using direct sunlight DOAS spectrometry the following BrO mixing ratios were measured; (1) 9 to 14 ppt in the height range from 20 to 30 km (at solar zenith angles, SZA < 88°) during ascent, (2) about (14±2) ppt for altitudes above the balloon float altitude at 30.6 km, 30.0 km, and 39.8 km, and (3) 5 to 10 ppt in the 20–30 km region during sunset. The lower BrO concentrations during sunset than those observed prior at daytime indicate a conversion of BrO into nighttime reservoir species (BrONO2, HOBr, and BrCl). The overall agreement of our UV spectroscopic BrO profiles with recent measurements using the chemical conversion/resonance fluorescence technique is good. Our BrO profiles are also in reasonable agreement with the present stratospheric Bry burden and chemistry. Conversily collocated ground‐based and satellite column measurements, however, show significantly more total atmospheric BrO (50–100%) than the integrated stratospheric BrO balloon profiles can account for. This indicates a global tropospheric BrO background, estimated at 1–2 ppt.