Preprints
https://doi.org/10.5194/amt-2021-314
https://doi.org/10.5194/amt-2021-314

  29 Nov 2021

29 Nov 2021

Review status: this preprint is currently under review for the journal AMT.

A tracer release experiment to investigate uncertainties in drone-based emission quantification for methane point sources

Randulph Morales1,4, Jonas Ravelid1, Katarina Vinkovic2, Piotr Korbeń3, Béla Tuzson1, Lukas Emmenegger1, Huilin Chen2, Martina Schmidt3, Sebastian Humbel1, and Dominik Brunner1 Randulph Morales et al.
  • 1Laboratory for Air Pollution/Environmental Technology, Swiss Federal Institute for Materials Science and Technology, Empa, Dübendorf, Switzerland
  • 2Centre for Isotope Research, University of Groningen, Groningen, Netherlands
  • 3Institute of Environmental Physics, University of Heidelberg, Heidelberg, Germany
  • 4Institute for Atmospheric and Climate Science, ETH Zürich, Switzerland

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

Randulph Morales et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Randulph Morales et al.

Randulph Morales et al.

Viewed

Total article views: 473 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
330 136 7 473 47 1 5
  • HTML: 330
  • PDF: 136
  • XML: 7
  • Total: 473
  • Supplement: 47
  • BibTeX: 1
  • EndNote: 5
Views and downloads (calculated since 29 Nov 2021)
Cumulative views and downloads (calculated since 29 Nov 2021)

Viewed (geographical distribution)

Total article views: 446 (including HTML, PDF, and XML) Thereof 446 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 15 Jan 2022
Download
Short summary
Mapping trace gas emission plumes using in-situ measurements from unmanned aerial vehicles (UAV) is an emerging and attractive possibility to quantify emissions from localized sources. We performed an extensive tracer-release experiment to develop an optimal quantification method and to determine the related uncertainties under various environmental and sampling conditions. Our approach was successful in quantifying local methane sources from drone-based measurements.