A novel, balloon-borne UV/visible spectrometer for direct sun measurements of stratospheric bromine

• Main Authors: Voss, Karolin, Holzbeck, Philip, Pfeilsticker, Klaus, Kleinschek, Ralph, Wetzel, Gerald, Fuentes Andrade, Blanca, Höpfner, Michael, Ungermann, Jörn, Sinnhuber, Björn-Martin, Butz, André
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2024
• Subjects: article; Verlagsveröffentlichung; Canada; Esrange; Kiruna
• Online Access: https://doi.org/10.5194/egusphere-2023-2912; https://noa.gwlb.de/receive/cop_mods_00070856; https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00069185/egusphere-2023-2912.pdf; https://egusphere.copernicus.org/preprints/2024/egusphere-2023-2912/egusphere-2023-2912.pdf

We report on a novel, medium weight (∼ 25 kg) optical spectrometer coupled to an automated sun tracker (∼ 12 kg) for direct sun observations from azimuth controlled balloon platforms. It is designed to measure a suite of UV/vis absorbing gases (O3, NO2, BrO, OClO, HONO and IO) relevant in the context of stratospheric ozone depletion using the DOAS method. Here, we describe the design and major features of the instrument. Further, the instrument’s performance during two stratospheric deployments from Esrange/Kiruna (Sweden) on 21 August 2021 and from Timmins (Ontario, Canada) on 23 August 2022 are discussed along with first results concerning inferred mixing ratios of BrO above balloon float altitude. Using a photochemical correction for the partitioning of stratospheric bromine ([BrO]/[Bry]) obtained by chemical transport simulations, the inferred total stratospheric bromine load [Bry] amounts to (17.5 ± 2.2) ppt (pure statistical error amounts to 1.5 ppt) in (5.5±1.0) yrs old air, resulting in a stratospheric entry early 2017±1 yr, the latter being inferred from simultaneous measurements of N2O by the GLORIA mid-IR instrument.