Preprints
https://doi.org/10.5194/acp-2021-907
https://doi.org/10.5194/acp-2021-907

  15 Nov 2021

15 Nov 2021

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

Assessing representativity of NH3 measurements influenced by boundary-layer dynamics and turbulent dispersion of a nearby emission source

Ruben B. Schulte1, Margreet C. van Zanten1,2, and Jordi Vilà-Guerau de Arellano1 Ruben B. Schulte et al.
  • 1Wageninen University & Research, P.O. Box 47, 6700, AA Wageningen, the Netherlands
  • 2National Institute for Public Health and the Environment (RIVM), Antonie van Leeuwenhoeklaan 9, 3721, MA Bilthoven, the Netherlands

Abstract. This study presents a fine scale simulation approach to assess the representativity of ammonia (NH3) measurements in proximity of an emission source. Close proximity to emission sources (< 5 km) can introduce a bias in regionally representative measurements of the NH3 molar fraction and flux. Measurement sites should therefore be located a significant distance from emission sources, but such requirements are poorly defined and can be difficult to meet in densely agricultural regions. This study presents a consistent criterium to assess the regional representativity of NH3 measurements in proximity of an emission source, calculating variables that quantify the NH3 plume dispersion using a series of numerical experiments at a fine resolution (20 m). Our fine scale simulation framework with explicitly resolved turbulence enables us to distinguish between the background NH3 and the emission plume, including realistic representations of NH3 deposition and chemical gas-aerosol transformations. We introduce the concept of blending-distance, based on the calculation of turbulent fluctuations, to systematically analyze the impact of the emission plume on simulated measurements, relative to this background NH3. This sensitivity analysis includes systematic experiments varying meteorological factors, emission/deposition and NH3 dependences. Considering these sensitivities, we find that NH3 measurements should be located at a minimum distance of 0.5–2.5 km and 1–3.5 km from an emission source, for NH3 molar fraction and flux measurements respectively. The simulation framework presented here can easily be adapted to local conditions and paves the way for future ammonia research at high spatio-temporal resolution.

Ruben B. Schulte et al.

Status: open (until 27 Dec 2021)

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

Ruben B. Schulte et al.

Ruben B. Schulte et al.

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Short summary
We present a fine scale simulation framework, utilizing large-eddy simulations, to assess the representativity of NH3 measurements in proximity of emission sources. We find that the minimum required distance between measurements and a emission source differs for concentration and flux measurements, ranging from 0.5–2.5 km and 1–3.5 km respectively. The simulation framework presented here proves a powerful and versatile tool for future NH3 research at high spatio-temporal resolution.
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