Stratospheric and upper tropospheric measurements of long-lived tracers and photochemically active species with GLORIA-B

Abstract. The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is a limb-imaging Fourier-Transform Spectrometer (iFTS) providing high-resolution mid-infrared spectra in the 780–1400 cm^-1 wavenumber range. Originally designed for aircraft, GLORIA has been deployed in eight research campaigns to date. To extend its observational range from the middle troposphere to the middle stratosphere, the instrument was adapted for a stratospheric balloon platform. GLORIA-B completed its first flight from Kiruna (Sweden) in August 2021 and a second from Timmins (Canada) in August 2022 as part of the EU Research Infrastructure HEMERA. The main objectives of these flights were technical qualification and the provision of a first imaging hyperspectral limb-emission dataset from 5 to 36 km altitude. This study evaluates the performance of GLORIA-B using vertical volume mixing ratio (VMR) profiles from the August 2021 flight, focusing on trace gases like O₃, CH₄, CFCs, HCFC-22, and SF₆. Comparisons with in-situ measurements (ozonesonde, MegaAirCore, and cryosampler) show agreement within 10 % for O₃, CH₄, SF₆, and CFC-12, and within 10-20 % for CFC-11, HCFC-22, and CFC-113 up to 18 km, with larger deviations above this altitude. Another objective is analyzing diurnal changes in photochemically active species (N₂O₅, NO₂, ClONO₂, BrONO₂). Observed VMR variations align well with simulations from the EMAC (ECHAM5/MESSy Atmospheric Chemistry) chemistry-climate model, though absolute concentrations differ to a certain extent. Using the nighttime BrONO₂-to-Br_y ratio from simulations, the observed lower stratospheric Br_y amount was estimated to 20.4 ± 2.5 pptv. In summary, the successful deployment of GLORIA on a stratospheric balloon platform has demonstrated the capability of the limb-imaging technique to provide high-quality vertical trace gas profiles up to the middle stratosphere, contributing to a better understanding of the distribution and temporal evolution of key atmospheric species.