Deriving an atmospheric budget of total organic bromine using airborne in situ measurements from the western Pacific area during SHIVA

摘要

During the recent SHIVA (Stratospheric Ozone: Halogen Impacts in a VaryingAtmosphere) project an extensive data set of all halogen species relevant forthe atmospheric budget of total organic bromine was collected in the westernPacific region using the Falcon aircraft operated by the German Aerospaceagency DLR (Deutsches Zentrum für Luft- und Raumfahrt) covering avertical range from the planetary boundary layer up to the ceiling altitudeof the aircraft of 13 km. In total, more than 700 measurements wereperformed with the newly developed fully automated in situ instrumentGHOST-MS (Gas chromatograph for theObservation of Tracers – coupled with aMass Spectrometer) by the Goethe University of Frankfurt(GUF) and with the onboard whole-air sampler WASP with subsequent ground-based state-of-the-art GC / MS analysis by the University of East Anglia(UEA). Both instruments yield good agreement for all major (CHBr₃ andCH₂Br₂) and minor (CH₂BrCl, CHBrCl₂ and CHBr₂Cl)VSLS (very short-lived substances), at least at the level of their 2σmeasurement uncertainties.In contrast to the suggestion that the western Pacific could be a region ofstrongly increased atmospheric VSLS abundance (Pyle et al., 2011), we foundonly in the upper troposphere a slightly enhanced amount of total organicbromine from VSLS relative to the levels reported in Montzka and Reimann etal. (2011) for other tropical regions.From the SHIVA observations in the upper troposphere, a budget for totalorganic bromine, including four halons (H-1301, H-1211, H-1202, H-2402),CH₃Br and the VSLS, is derived for the level of zero radiative heating(LZRH), the input region for the tropical tropopause layer (TTL) and thusalso for the stratosphere.With the exception of the two minor VSLS CHBrCl₂ and CHBr₂Cl,excellent agreement with the values reported in Montzka and Reimann et al. (2011)is found, while being slightly higher than previous studies from ourgroup based on balloon-borne measurements.