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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 11, issue 3 | Copyright
Atmos. Meas. Tech., 11, 1565-1582, 2018
https://doi.org/10.5194/amt-11-1565-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 22 Mar 2018

Research article | 22 Mar 2018

Bootstrap inversion technique for atmospheric trace gas source detection and quantification using long open-path laser measurements

Caroline B. Alden1,2, Subhomoy Ghosh3, Sean Coburn1, Colm Sweeney2,4, Anna Karion3, Robert Wright1, Ian Coddington3, Gregory B. Rieker1, and Kuldeep Prasad3 Caroline B. Alden et al.
  • 1Precision Laser Diagnostics Laboratory, University of Colorado at Boulder, Boulder, CO 80309, USA
  • 2Cooperative Institute for Research in Environmental Sciences, Boulder, CO 80309, USA
  • 3National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, USA
  • 4National Oceanic & Atmospheric Administration (NOAA), Boulder, CO 80305, USA

Abstract. Advances in natural gas extraction technology have led to increased activity in the production and transport sectors in the United States and, as a consequence, an increased need for reliable monitoring of methane leaks to the atmosphere. We present a statistical methodology in combination with an observing system for the detection and attribution of fugitive emissions of methane from distributed potential source location landscapes such as natural gas production sites. We measure long (>500m), integrated open-path concentrations of atmospheric methane using a dual frequency comb spectrometer and combine measurements with an atmospheric transport model to infer leak locations and strengths using a novel statistical method, the non-zero minimum bootstrap (NZMB). The new statistical method allows us to determine whether the empirical distribution of possible source strengths for a given location excludes zero. Using this information, we identify leaking source locations (i.e., natural gas wells) through rejection of the null hypothesis that the source is not leaking. The method is tested with a series of synthetic data inversions with varying measurement density and varying levels of model–data mismatch. It is also tested with field observations of (1) a non-leaking source location and (2) a source location where a controlled emission of 3.1 × 10−5kgs−1 of methane gas is released over a period of several hours. This series of synthetic data tests and outdoor field observations using a controlled methane release demonstrates the viability of the approach for the detection and sizing of very small leaks of methane across large distances (4+km2 in synthetic tests). The field tests demonstrate the ability to attribute small atmospheric enhancements of 17ppb to the emitting source location against a background of combined atmospheric (e.g., background methane variability) and measurement uncertainty of 5ppb (1σ), when measurements are averaged over 2min. The results of the synthetic and field data testing show that the new observing system and statistical approach greatly decreases the incidence of false alarms (that is, wrongly identifying a well site to be leaking) compared with the same tests that do not use the NZMB approach and therefore offers increased leak detection and sizing capabilities.

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The location and sizing leaks of methane from natural gas operations poses a real challenge for greenhouse gas emission mitigation efforts and for accurate quantification of emissions inventories. We demonstrate, with synthetic and field tests, a new statistical method for the location and sizing of small trace gas point sources dispersed over large areas, based on measurements of ambient atmospheric conditions made with long-range, open-path laser-based atmospheric observations.
The location and sizing leaks of methane from natural gas operations poses a real challenge for...
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