Controlled-release experiment to investigate uncertainties in UAV-based emission quantification for methane point sources

Abstract. Mapping trace gas emission plumes using in situ measurements from unmanned aerial vehicles (UAVs) is an emerging and attractive possibility to quantify emissions localized sources. Here, we present the results of extensive controlled-release experiment Dübendorf, Switzerland, which was conducted develop optimal quantification method determine related uncertainties under various environmental sampling conditions. Atmospheric methane mole fractions were simultaneously measured a miniaturized fast-response quantum cascade laser absorption spectrometer (QCLAS) active AirCore system mounted on commercial UAV. Emission fluxes estimated mass-balance by flying UAV-based through vertical cross-section downwind point source perpendicular main wind direction at multiple altitudes. A refined kriging framework, called cluster-based kriging, developed spatially map individual measurement points into whole plane, while taking account different spatial scales between background enhanced values plume. We found that new framework resulted better compared ordinary kriging. The average bias ?1 %, residual errors 54 %. Direct comparison QCLAS shows are smoothed 20 s had time lag 7 s. also stretch linearly with rate 0.06 for every second measurement. Applying these corrections successively calculating estimate enhancement accuracy 3 % as its uncorrected counterpart. Optimal plume sampling, including distance, depends turbulence conditions, it furthermore limited numerous parameters such maximum flight accuracy. Under favourable could be quantified uncertainty 30 Uncertainties increase when speeds below 2.3 m s?1 directional variability above 33?, distance 75 m. In addition, flux estimates well-established OTM-33A involving stationary measurements. good agreement found, both approaches being close true release methods usually capturing release.