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

Abstract. 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. C₃H₈ background mixing ratios did not substantially vary over the study period with a slight decrease of -0.003 [-0.004; -0.002; 95 % confidence interval] ppb per year. However, C₃H₈ seasonal amplitude showed an increase of about 0.16 % per year from 77.5 to 79.5 % in the study period, with most of the increase between 2016 and 2023. Based on back-trajectory sensitivity analysis, CMN and JFJ 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 Jungfraujoch (Switzerland) 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 by a factor of 3 and 2, respectively, likely due to overlooked C₃H₈ emissions sources and/or inaccurate activity data used to compile the bottom-up inventory.