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<front>
<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>
<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-2026-5855</article-id>
<title-group>
<article-title>EMEPai 1.0.0: A fast regional data-driven air-quality forecast model for Europe</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Lima</surname>
<given-names>Erlend</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Sutterud</surname>
<given-names>Halvard</given-names>
<ext-link>https://orcid.org/0000-0003-1635-1668</ext-link>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Blake</surname>
<given-names>Lewis</given-names>
<ext-link>https://orcid.org/0000-0002-9978-1702</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>Ulimoen</surname>
<given-names>Magnus</given-names>
<ext-link>https://orcid.org/0000-0002-0423-4600</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>Mousing</surname>
<given-names>Erik Askov</given-names>
<ext-link>https://orcid.org/0000-0003-1663-2507</ext-link>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Norwegian Meteorological Institute, Oslo, Norway</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>Statkraft, Oslo, Norway</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>These authors contributed equally to this work.</addr-line>
</aff>
<pub-date pub-type="epub">
<day>30</day>
<month>10</month>
<year>2026</year>
</pub-date>
<volume>2026</volume>
<fpage>1</fpage>
<lpage>24</lpage>
<permissions>
<copyright-statement>Copyright: &#x000a9; 2026 Erlend Lima et al.</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-2026-5855/">This article is available from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-5855/</self-uri>
<self-uri xlink:href="https://egusphere.copernicus.org/preprints/2026/egusphere-2026-5855/egusphere-2026-5855.pdf">The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-5855/egusphere-2026-5855.pdf</self-uri>
<abstract>
<p>Air-quality forecasting over Europe relies largely on chemical transport models, whose computational cost limits forecast resolution and frequency. This study presents EMEPai, a regional data-driven forecasting system designed to emulate atmospheric composition fields produced by the EMEP/MSC-W modeling and data-assimilation framework. The model uses a graph-based encoder&amp;ndash;processor&amp;ndash;decoder architecture to generate three-hourly forecasts for NO&lt;sub&gt;2&lt;/sub&gt;, O&lt;sub&gt;3&lt;/sub&gt;, PM&lt;sub&gt;10&lt;/sub&gt;, PM&lt;sub&gt;2.5&lt;/sub&gt;, and SO&lt;sub&gt;2&lt;/sub&gt; over Europe at 0.1&amp;deg; resolution, with lead times up to 96 hours.&lt;/p&gt;
&lt;p&gt;Against surface observations, its performance exceeds that of the corresponding EMEP hindcast while approaching the skill of the assimilated reanalysis. Reduced skill is found for SO&lt;sub&gt;2&lt;/sub&gt; and during high-concentration events. In an operational forecast setting, EMEPai performs comparably to or better than the CAMS regional ensemble across the evaluated pollutants and forecast lead times. A 96-hour forecast requires only seconds on a single GPU, with the full forecast workflow approximately 230&amp;ndash;460 times faster than the corresponding EMEP/MSC-W worfklow.</p>
</abstract>
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<funding-group>
<award-group id="gs1">
<funding-source>European High Performance Computing Joint Undertaking</funding-source>
<award-id>EHPC-AIF-2025SC03-032</award-id>
</award-group>
</funding-group>
</article-meta>
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