Atmospheric ethylene (C2H4) observations from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS)

The Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) utilizes solar occultation to collect high-resolution measurements of atmospheric trace gases as the Sun rises or sets from the satellite’s orbiting perspective. This limb-viewing geometry provides unique and vertically resolved observations of Earth’s atmosphere. In this study, we present improved retrievals of ethylene (C${}_2$H${}_4$) from ACE-FTS, offering a comprehensive analysis of its global distribution and temporal variability. The retrievals were enhanced by applying speed-dependent Voigt line shapes to minimize systematic residuals from interfering CO${}_2$ lines, enabling more complete use of the available C${}_2$H${}_4$ spectral information in ACE measurements. The resulting dataset reveals notable enhancements in C${}_2$H${}_4$ concentrations over high northern latitudes, particularly between 5.5 and 8.5 km altitude. Distinct seasonal variability is observed, with elevated concentrations during winter and reduced levels in summer. Furthermore, a long-term decreasing trend of −0.224 ppt/year is identified over the 2004–2024 period, indicating a gradual decline in atmospheric C${}_2$H${}_4$ levels.