The methane record at the ICOS background station at Plateau Rosa: identification of source areas in Europe

Methane and carbon dioxide mole fractions are measured continuously at the atmospheric station at Plateau Rosa since 2018, with a Picarro cavity ring down spectrometer G2301. The station, at 3480 meter MSL, represents an ideal location for, on one hand, measurements of background air and, on the other hand, intercepting air with recent boundary layer contact. Since 2021 the site contributes as an atmospheric station to the ICOS network. In this study we present the methodology used to filter background data, and we provide an analysis of the continuous record of CH4 since 2018. We used Hysplit back trajectories and the FLEXPART atmospheric transport model coupled with EDGAR inventories to identify source areas in Europe. We focused our analysis on April 2022, when the CH4 increment above the baseline was consistently high. We demonstrate how the CH4 mole fraction data measured at the station at Plateau Rosa provide information on the global CH4 trend, and that, with our continuous record, we can detect high emissions events over Europe.