High-fidelity methane plume modelling over coal mines: Integrating Large Eddy Simulations (LES) with remote sensing imagery

Methane (CH4) emissions from coal mine shafts represent 33% of the global CH4 fossil fuel emissions into the atmosphere, and are subject to stricter regulations drafted in recent years (e.g. EU, China). Different measurement strategies have been deployed to quantify the amounts of CH4 released, primarily onboard aircraft and satellites. For the first time, we simulate the CH4 plume dynamics at high resolution using Large Eddy Simulations (LES) forced by meteorological data, obstacles (such as trees and buildings), 1-m terrain topologies, and exact source characterisation. We validated the plume characteristics against path-integrated measurements from a ground-based spectrometer horizontally scanning the coal mine plume from Pniówek V (Poland). We demonstrate that the exit velocity of the mine shaft’s gas, its concentration and the turbulence conditions are the key drivers to reproduce the CH4 plume behaviour and magnitude. We estimated the uncertainties to be 9% (±2.5 m) for the altitude of maximum values and 17% for the peak CH4 enhancement, resulting mainly from wind speed fluctuations. For coal mine shaft plumes, precise source characterisation is critical to simulation accuracy, whereas high-resolution terrain and building data are less essential. This is a direct result of the high-momentum, CH4-rich discharge from the diffusion tower, which dictates the plume trajectory more than local surface geometry.