Preprints
https://doi.org/10.5194/acp-2021-614
https://doi.org/10.5194/acp-2021-614

  10 Sep 2021

10 Sep 2021

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

Technical note: Interpretation of field observations of point-source methane plume using observation-driven large-eddy simulations

Anja Ražnjević1, Chiel van Heerwaarden1, Bart van Stratum1, Arjan Hensen2, Ilona Velzeboer2, Pim van den Bulk2, and Maarten Krol1,3 Anja Ražnjević et al.
  • 1Meteorology and Air Quality Group, Wageningen University, Wageningen, The Netherlands
  • 2Department of Environmental Modelling, Sensing & Analysis, Organisation for Applied Scientific Research, the Netherlands
  • 3Institute for Marine and Atmospheric Research Utrecht, Utrecht University, the Netherlands

Abstract. This study demonstrates the ability of large-eddy simulation (LES) forced by a large-scale model to reproduce plume dispersion in an actual field campaign. Our aim is to bring together field observations taken under non-ideal conditions and LES to show that this combination can help to derive point source strengths from sparse observations. We prepared a one-day case study based on data collected near an oil well during the ROMEO campaign (ROmanian Methane Emissions from Oil and gas) that took place in October 2019. We set up our LES using boundary conditions derived from the meteorological reanalysis ERA5 and released a point source in line with the configuration in the field. The weather conditions produced by the LES show close agreement with field observations, although the observed wind field showed complex features due to the absence of synoptic forcing. In order to align the plume direction with field observations, we created a second simulation experiment with manipulated wind fields. The estimated source strengths using the LES plume agrees well with the emitted artificial tracer gas plume, indicating the suitability of LES to infer source strengths from observations under complex conditions. To further harvest the added value of LES, higher order statistical moments of the simulated plume were analysed. Here, we found good agreement with plumes from previous LES and laboratory experiments in channel flows. We derived a length scale of plume mixing from the boundary layer height, the mean wind speed and convective velocity scale. It was demonstrated that this length scale represents the distance from the source at which the predominant plume behaviour transfers from meandering dispersion to relative dispersion.

Anja Ražnjević et al.

Status: open (until 02 Dec 2021)

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  • RC1: 'Comment on acp-2021-614', Anonymous Referee #1, 02 Nov 2021 reply

Anja Ražnjević et al.

Anja Ražnjević et al.

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Short summary
Mobile measurement techniques (e.g. instruments placed in cars) are often employed to identify and quantify individual sources of greenhouse gases. Due to road restrictions, those observations are often sparse (temporally and spatially). We performed high-resolution simulations of plume dispersion, with realistic weather conditions encountered in the field, to reproduce the measurement process of a methane plume emitted from an oil well and provide additional information about the plume.
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