Long-term analysis of atmospheric propane over Southern Europe based on observations conducted at the WMO-GAW station of Monte Cimone

This study presents the analysis of a 13-year time series of continuous measurements of propane (C3H8) from the WMO-GAW station of Monte Cimone (CMN, Italy) between 2011 and 2023. Background trend and pollution events are evaluated to establish how this remote site is influenced by regional and/or global emissions. Over the study period, C3H8 background mixing ratios exhibited a significant decrease of -3.8 [-5; -2.3; 95 % confidence interval] ppt yr−1. C3H8 seasonal amplitude showed a significant decrease of -6.2 [-7.4; -5.1] ppt yr−1 in the study period, driven by a reduction in winter emissions. Based on back-trajectory sensitivity analysis, CMN and Jungfraujoch (JFJ, Switzerland) were found to be predominantly influenced by air masses originating from the central European continent and the western Mediterranean basin. Using the 2022 observations of CMN and JFJ stations, and the Flexpart-Flexinvert inverse modeling framework, we estimated the distribution of regional emissions and compared it with the EDGAR bottom-up emission inventory. In particular, for Italy and France, prior emissions of C3H8 were underestimated approximately by a factor of 2, likely due to overlooked C3H8 emissions sources and/or inaccurate activity data used to compile the bottom-up inventory.