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<journal-meta>
<journal-id journal-id-type="publisher">EGUsphere</journal-id>
<journal-title-group>
<journal-title>EGUsphere</journal-title>
<abbrev-journal-title abbrev-type="publisher">EGUsphere</abbrev-journal-title>
<abbrev-journal-title abbrev-type="nlm-ta">EGUsphere</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub"></issn>
<publisher><publisher-name>Copernicus Publications</publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/egusphere-2025-5900</article-id>
<title-group>
<article-title>A machine-learning reference dataset for SO&lt;sub&gt;2&lt;/sub&gt; plumes observed by TROPOMI: uncertainties and emission estimates</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Finch</surname>
<given-names>Douglas P.</given-names>
<ext-link>https://orcid.org/0000-0003-2400-6848</ext-link>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Palmer</surname>
<given-names>Paul I.</given-names>
<ext-link>https://orcid.org/0000-0002-1487-0969</ext-link>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>School of GeoSciences, University of Edinburgh, Edinburgh, UK</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>National Centre for Earth Observation, University of Edinburgh, Edinburgh, UK</addr-line>
</aff>
<pub-date pub-type="epub">
<day>15</day>
<month>01</month>
<year>2026</year>
</pub-date>
<volume>2026</volume>
<fpage>1</fpage>
<lpage>27</lpage>
<permissions>
<copyright-statement>Copyright: &#x000a9; 2026 Douglas P. Finch</copyright-statement>
<copyright-year>2026</copyright-year>
<license license-type="open-access">
<license-p>This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit <ext-link ext-link-type="uri"  xlink:href="https://creativecommons.org/licenses/by/4.0/">https://creativecommons.org/licenses/by/4.0/</ext-link></license-p>
</license>
</permissions>
<self-uri xlink:href="https://egusphere.copernicus.org/preprints/2026/egusphere-2025-5900/">This article is available from https://egusphere.copernicus.org/preprints/2026/egusphere-2025-5900/</self-uri>
<self-uri xlink:href="https://egusphere.copernicus.org/preprints/2026/egusphere-2025-5900/egusphere-2025-5900.pdf">The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2026/egusphere-2025-5900/egusphere-2025-5900.pdf</self-uri>
<abstract>
<p>Sulphur dioxide (SO&lt;sub&gt;2&lt;/sub&gt;) is a major atmospheric pollutant from fossil fuel combustion, metal smelting, and volcanic degassing, impacting human health, acid deposition, and climate forcing. Existing emission inventories are often temporally lagged and spatially coarse, failing to capture high-intensity, sporadic events. To address this, we present a novel, near real-time approach using a U-Net image segmentation model to automatically isolate SO&lt;sub&gt;2 &lt;/sub&gt;plumes from over 31,000 TROPOMI satellite swaths (Jan 2019&amp;ndash;Dec 2024). The model successfully identified 53,993 individual plumes. The highest annual detection rate in 2019 was attributed to massive stratospheric SO&lt;sub&gt;2&lt;/sub&gt; injections from the Raikoke and Ulawun volcanic eruptions. Clustering analysis confirmed plume origins around expected volcanic and industrial hotspots (e.g., Iztacc&amp;iacute;huatl, Norilsk), with volcanic sources dominating the top ten clusters. We derived rapid, physics-informed emission rate estimates for each plume, finding a median rate of 14,629 kg hr&lt;sup&gt;-1&lt;/sup&gt;. This detection threshold for this approach, which we estimate to be ~524 kg hr&lt;sup&gt;-1&lt;/sup&gt;, is four orders of magnitude larger than typical fluxes in the EDGAR inventory, demonstrating the utility of the plume database for detecting extreme, high-intensity events. However, the algorithm struggles to detect sources in high-background regions like China, where high SO&lt;sub&gt;2&lt;/sub&gt; saturation likely prevents individual plume isolation. This study demonstrates machine learning as a powerful tool for transforming atmospheric monitoring, providing the high-cadence, fine-grained quantification of SO&lt;sub&gt;2&lt;/sub&gt; emissions crucial for validating global inventories and ensuring effective environmental management.</p>
</abstract>
<counts><page-count count="27"/></counts>
<funding-group>
<award-group id="gs1">
<funding-source>European Space Agency</funding-source>
<award-id>4000137832/22/I-AG</award-id>
</award-group>
</funding-group>
</article-meta>
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