The atmospheric station at Plateau Rosa: use of methane mole fractions and modelling to detect methane source areas in Europe

The atmospheric monitoring station at Plateau Rosa, situated in the Central European Alps and part of the ICOS (Integrated Carbon Observation System) framework since 2021, is measuring methane mole fractions since 2018 with a cavity ring down spectrometer (Picarro G2301). Concentration measurements at this site, 3480 meter AMSL, are particularly valuable for tracking the atmospheric background and global trend of methane, but are also impacted by various source areas in Europe.

In this study, we analyzed the continuous record of methane mole fractions at the station, and we identified prolonged periods (more than 6 hours) of enhanced methane levels over the background that are associated with pollution events at regional scale. From 2020 until 2024, we detected 15 very pronounced pollution events, when air masses were coming mainly from central Europe and the UK. We used the FLEXPART atmospheric transport model coupled to the high-resolution (1 km x 1 km) output of the numerical weather prediction model COSMO to produce concentration footprints and simulate regional methane contributions. We assessed how well this transport model, coupled with different bottom-up inventories (EDGAR, TNO), can capture the selected pollution events. Finally, we compared the source areas identified with the TROPOMI satellite emission plumes measured in Europe.

We demonstrate how methane mole fraction data measured continuously at the station at Plateau Rosa can be used to attribute pollution events to specific regional source areas that might not be accounted by the inventories and are not detectable by satellite data.