²²²Radon (Rn) can be used to distinguish marine and continental air masses or to validate transport models. The Heidelberg Radon Monitor (HRM) measures ²¹⁴polonium (Po), a progeny of Rn. This study presents Po-based Rn activity concentrations measured with the HRM at eight stations in Germany with guidelines for estimating Rn from Po measurements. Comparison between modeled and measured activity concentrations shows that at high relative humidity Po measurements cannot be interpreted as Rn.

We investigated the application of two automatic methods for detecting spikes due to local emissions in greenhouse gas (GHG) observations at a subset of sites from the ICOS Atmosphere network. We analysed the sensitivity to the spike frequency of using different methods and settings. We documented the impact of the de-spiking on different temporal aggregations (i.e. hourly, monthly and seasonal averages) of CO₂, CH₄ and CO 1 min time series.

We present a novel high-resolution inverse modelling system, "FLEXVAR", and its application for the inverse modelling of European CH₄ emissions in 2018. The new system combines a high spatial resolution of 7 km x 7 km with a variational data assimilation technique, which allows CH₄ emissions to be optimized from individual model grid cells. The high resolution allows the observations to be better reproduced, while the derived emissions show overall good consistency with two existing models.

We present a technical description of a statistical methodology for extracting synoptic- and seasonal-length anomalies from greenhouse gas time series. The definition of what represents an anomalous signal is somewhat subjective, which we touch on throughout the paper. We show, however, that the method performs reasonably well in extracting portions of time series influenced by significant North Atlantic Oscillation weather episodes and continent-wide terrestrial biospheric aberrations.

CO₂ measurements from a small unmanned aircraft system (sUAS) can provide a cost-effective way to complement and validate satellite-based measurements of anthropogenic CO₂ emissions. We introduce an sUAS which is capable of determining atmospheric CO₂ mass fluxes from its own sensor data. We show results of validation flights at the ICOS atmospheric station in Steinkimmen and from demonstration flights downwind a CO₂-emitting natural gas processing facility.