Transcontinental stratospheric and upper tropospheric measurements with the new GLORIA-Lite instrument

Abstract. Accurate observations of the vertical distribution and temporal variability of atmospheric trace gases are essential for understanding atmospheric composition and chemistry and for evaluating atmospheric models. The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is a cooled limb-imaging Fourier-Transform Spectrometer (iFTS) providing mid-infrared spectra with high spectral resolution. The newly developed, compact and uncooled instrument GLORIA-Lite (GLITE) is significantly smaller and lighter than its predecessor GLORIA, thanks to recent advances in infrared sensors, tailored electronics, and innovative manufacturing technology. The first balloon version, GLITE-B, was deployed during a transcontinental stratospheric flight from Kiruna (Sweden) via Greenland to Canada in June 2024. Hyperspectral limb-emission measurements in the 750–1450 cm⁻¹ spectral range were obtained from 22 to 24 June, covering an altitude range of 5 to 40 km. The observations were used to retrieve temperature and a wide range of ozone and other species involved in stratospheric ozone chemistry, tracers of stratospheric air motions, and tropospheric air pollutants. Comparisons of the retrieved mean vertical volume mixing ratio (VMR) profiles with Microwave Limb Sounder (MLS) version 6 observations show good agreement over wide altitude ranges, with differences generally within the combined error limits and typically within ±2 K for temperature and ±10 % for O₃, HNO₃, and H₂O. A negative bias of approximately 20 % was found in the MLS N₂O data below 27 km relative to GLITE-B. Comparisons with the ECHAM5/MESSy Atmospheric Chemistry (EMAC) model indicate that the model successfully reproduces observed stratospheric trace-gas variability, chemistry (ClONO₂, NO₂, PAN), and transport characteristics (chlorofluorocarbons, SF₆) in the sunlit summer polar stratosphere, while discrepancies for HCOOH and CH₃OH highlight uncertainties in their sources and atmospheric processing. The CFC-11/CFC-12 tracer–tracer relationship agrees well with previous observations, and the observed SF₆ profiles are consistent with current understanding of stratospheric transport. The results of this first flight demonstrate that GLITE‑B can provide accurate trace gas profiles with high vertical resolution during long-duration balloon flights. Such measurements capture the temporal evolution of atmospheric composition over several days, providing valuable information on transport and photochemical processes and supporting the evaluation and improvement of atmospheric chemistry models.