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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Discussion papers
https://doi.org/10.5194/amt-2019-99
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/amt-2019-99
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 20 May 2019

Research article | 20 May 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Measurement Techniques (AMT).

Tracking down global NH3 point sources with wind-adjusted superresolution

Lieven Clarisse1, Martin Van Damme1, Cathy Clerbaux2,1, and Pierre-François Coheur1 Lieven Clarisse et al.
  • 1Université libre de Bruxelles (ULB), Atmospheric Spectroscopy, Service de Chimie Quantique et Photophysique, Brussels, Belgium
  • 2LATMOS/IPSL, Sorbonne Université, UVSQ, CNRS, Paris, France

Abstract. As a precursor of atmospheric aerosols, ammonia (NH3) is one the primary gaseous air pollutants. Given its short atmospheric lifetime, ambient NH3 concentrations are dominated by local sources. In a recent study, Van Damme et al. (2018) have highlighted the importance of NH3 point sources, especially those associated with feedlots and industrial ammonia production. Their emissions were shown to be largely underestimated in bottom-up emission inventories. The discovery was made possible thanks to the use of oversampling techniques applied on 9 years of global daily IASI NH3 satellite measurements. Oversampling allows to increase the spatial resolution of averaged satellite data, beyond what the satellites natively offer. Here, we apply for the first time the so-called superresolution techniques, which are commonplace in many fields that rely on imaging, to measurements of an atmospheric sounder, whose images consist of just single pixels. We demonstrate the principle on synthetic data and on IASI measurements of a surface parameter. Superresolution is a priori less suitable to be applied on measurements of variable atmospheric constituents, in particular those affected by transport. However, by first applying the so-called wind-rotation technique, which was introduced in the study of other primary pollutants, superresolution becomes highly effective to map NH3 at very high spatial resolution. We show in particular that it allows revealing plume transport in much greater detail than what was previously thought to be possible. Next, using this wind-adjusted superresolution technique, we introduce a new type of NH3 map that allows to track down point sources much more easily than the regular oversampled average. On a subset of known emitters, it allows to locate the source within a median distance of 1.5 km. We subsequently present a new global point source catalog consisting of more than 500 localized and categorized point sources. Compared to our previous catalog, the number of identified sources more than doubled. In addition, we refined the classification of industries into five categories: fertilizer, coking, soda ash, geothermal and explosive industry; and introduced a new urban category for isolated NH3 hotspots over cities. The latter mainly consists of African megacities, as clear isolation of such urban hotspots is almost never possible elsewhere due to the presence of a larger diffuse background. The techniques presented in this paper can most likely be exploited in the study of point sources of other short-lived atmospheric pollutants such as SO2 and NO2.

Lieven Clarisse et al.
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Short summary
An imaging technique called superresolution is applied to IASI satellite measurements of atmospheric ammonia (NH3). Taking into account wind fields, this technique allows to reveal NH3 emission sources much better than was previously possible. We present a new global NH3 point source catalog consisting of more than 500 localized and categorized point sources, related to agriculture and five different types of industry.
An imaging technique called superresolution is applied to IASI satellite measurements of...
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