The reduction in C<sub>2</sub>H<sub>6</sub> from 2015 to 2020 over Hefei, eastern China, points to air quality improvement in China

Abstract. Ethane (C2H6) is an important greenhouse gas and plays a significant role in tropospheric chemistry climate change. This study first presents then quantifies the variability, sources, transport of C2H6 over densely populated highly industrialized eastern China using ground-based high-resolution Fourier transform infrared (FTIR) remote sensing along with atmospheric modeling techniques. We obtained retrieval error 6.21 ± 1.2 (1σ)% degrees freedom (DOFS) 1.47 0.2 (1σ) column-averaged dry-air mole fraction (troDMF) Hefei, (32∘ N, 117∘ E; 30 ma.s.l.). The observed troDMF reached minimum monthly mean value 0.36 0.26 ppbv July maximum 1.76 0.35 December, showed negative change rate −2.60 1.34 % yr−1 from 2015 to 2020. dependencies on meteorological emission factors were analyzed generalized additive models (GAMs). Generally, both have positive influences cold season (December–January–February/March–April–May, DJF/MAM) warm (June–July–August/September–October–November, JJA/SON). GEOS-Chem chemical model simulation captured variability was, thus, used for source attribution. sensitivity simulations concluded that anthropogenic emissions (fossil fuel plus biofuel emissions) natural (biomass burning biogenic accounted 48.1 39.7 respectively. mainly results within (74.1 %), where central, eastern, northern dominated contribution (57.6 %). Seasonal inflow outflow observation site largely related midlatitude westerlies Asian monsoon system. Reduction abundance 2020 decrease local transported emissions, which points air quality improvement recent years.