Simulation of methane point source emissions and their isotopic signatures using the global/regional climate model MECO(n).

Methane is the second most important anthropogenic greenhouse gas. The globally averaged dry mole fraction has increased considerably since pre-industrial times and its growth even accelerated in 2014, with an annual rise of 12.7 ± 6 ppb. Fossil fuel emissions are one of the primary sources. However, the quantification of methane sources and sinks is still under debate and estimates of anthropogenic emissions show large uncertainties on global and regional scales. Comprehensive measurement campaigns, such as CoMet 1.0 (May-June 2018), are therefore important for assessing climate change mitigation options. CoMet aimed to quantify point source emissions in the Upper Silesian Coal Basin (USCB), where roughly 502 kt/yr of methane are emitted due to coal mining. Differences in isotopic methane source signatures δ¹³C and δD can further help to constrain different source contributions (e.g. thermogenic or biogenic). We simulate methane isotopologues from localized coal mine emissions in the USCB using the on-line three times nested global regional chemistry climate model MECO(n). We use a submodel extension, which includes the kinetic fractionation and make different assumptions on the isotopic source signatures in the USCB. Here we show first results of these simulations and a comparison to flask samples taken during CoMet 1.0.