Airborne measurements of bro and the sum of hobr and Br₂ over the tropical west pacific from 1 to 15km during the convective transport of active species in the tropics (CONTRAST) experiment

A chemical ionization mass spectrometer was used to measure BrO and HOBr + Br₂ over the Tropical West Pacific Ocean within the altitude range of 1 to 15 km, during the CONvective TRansport of Active Species in the Tropics (CONTRAST) campaign in 2014. Isolated episodes of elevated BrO (up to 6.6 pptv) and/or HOBr + Br₂ (up to 7.3 pptv) were observed in the tropical free troposphere (TFT) and were associated with biomass burning. However, most of the time we did not observe significant BrO or HOBr + Br₂ in the TFT and the tropical tropopause layer (TTL) above our limits of detection (LOD). The 1 min average LOD for BrO ranged from 0.6 to 1.6 pptv and for HOBr + Br₂ ranged from 1.3 to 3.5 pptv. During one flight, BrO observations from the TTL to the extratropical lowermost stratosphere were used to infer a profile of inorganic bromine (Br_y). Based on this profile, we estimated the product gas injection of bromine species into the stratosphere to be 2 pptv. Analysis of Bry partitioning further indicates that BrO levels are likely very low in the TFT environment and that future studies should target the measurement of HBr or atomic Br.