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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>
<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-2026-914</article-id>
<title-group>
<article-title>Aerosol processing during long-range transport governs the chemical composition of haze over the northern Indian Ocean</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Stegelius</surname>
<given-names>Karin</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Thompson</surname>
<given-names>Pauline</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Karbiener</surname>
<given-names>Pia</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff10">
<sup>10</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Markuszewski</surname>
<given-names>Piotr</given-names>
<ext-link>https://orcid.org/0000-0003-1160-6318</ext-link>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff2">
<sup>2</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>Prevot</surname>
<given-names>Andre S. H.</given-names>
</name>
<xref ref-type="aff" rid="aff4">
<sup>4</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Tripathi</surname>
<given-names>Sachchida N.</given-names>
<ext-link>https://orcid.org/0000-0002-6402-4680</ext-link>
</name>
<xref ref-type="aff" rid="aff5">
<sup>5</sup>
</xref>
<xref ref-type="aff" rid="aff6">
<sup>6</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Mohr</surname>
<given-names>Claudia</given-names>
<ext-link>https://orcid.org/0000-0002-3291-9295</ext-link>
</name>
<xref ref-type="aff" rid="aff4">
<sup>4</sup>
</xref>
<xref ref-type="aff" rid="aff7">
<sup>7</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Heikkinen</surname>
<given-names>Liine</given-names>
<ext-link>https://orcid.org/0000-0001-7837-967X</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>Budhavant</surname>
<given-names>Krishnakant</given-names>
<ext-link>https://orcid.org/0000-0003-2753-3192</ext-link>
</name>
<xref ref-type="aff" rid="aff8">
<sup>8</sup>
</xref>
<xref ref-type="aff" rid="aff9">
<sup>9</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Haslett</surname>
<given-names>Sophie L.</given-names>
<ext-link>https://orcid.org/0000-0003-2985-4846</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>Department of Environmental Science, Stockholm University, Stockholm, Sweden</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>Physical Oceanography Department, Institute of Oceanology, Polish Academy of Sciences, Sopot, Poland</addr-line>
</aff>
<aff id="aff4">
<label>4</label>
<addr-line>PSI Center for Energy and Environmental Sciences, Paul Scherrer Institute, Villigen PSI, Switzerland</addr-line>
</aff>
<aff id="aff5">
<label>5</label>
<addr-line>Department of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur, India</addr-line>
</aff>
<aff id="aff6">
<label>6</label>
<addr-line>Department of Sustainable Energy Engineering, Indian Institute of Technology Kanpur, Kanpur, India</addr-line>
</aff>
<aff id="aff7">
<label>7</label>
<addr-line>Department of Environmental Systems Science, ETH Zurich, Zürich, Switzerland</addr-line>
</aff>
<aff id="aff8">
<label>8</label>
<addr-line>Maldives Climate Observatory at Hanimaadhoo, Hanimaadhoo, Maldives</addr-line>
</aff>
<aff id="aff9">
<label>9</label>
<addr-line>Divecha Centre for Climate Change, Indian Institute of Science, Bangalore, India</addr-line>
</aff>
<aff id="aff10">
<label>10</label>
<addr-line>now at: Department of Environmental Sciences, University of Basel, Basel, Switzerland</addr-line>
</aff>
<pub-date pub-type="epub">
<day>11</day>
<month>03</month>
<year>2026</year>
</pub-date>
<volume>2026</volume>
<fpage>1</fpage>
<lpage>32</lpage>
<permissions>
<copyright-statement>Copyright: &#x000a9; 2026 Karin Stegelius 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-2026-914/">This article is available from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-914/</self-uri>
<self-uri xlink:href="https://egusphere.copernicus.org/preprints/2026/egusphere-2026-914/egusphere-2026-914.pdf">The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-914/egusphere-2026-914.pdf</self-uri>
<abstract>
<p>Each year during the winter period, a persistent haze forms over the Indian subcontinent and the northern Indian Ocean. This has been shown to influence regional warming, rainfall patterns and air quality. Previous studies have demonstrated that this haze is largely anthropogenic in origin, with its composition dominated by sulfate, organic compounds and black carbon. Nevertheless, to date, information about its composition has largely been limited to bulk chemical composition and low time-resolution data. Here, we aim to characterise aerosol composition over the Indian Ocean on the molecular level, in order to identify the impact of different sources and processing in this region. High-time-resolution measurements were conducted at the Maldives Climate Observatory, Hanimaadhoo (MCOH) using a Time-of-Flight Aerosol Mass Spectrometer (AMS) and Chemical Ionisation Mass Spectrometer with a Filter Inlet for Gases and Aerosols (FIGAERO-CIMS). Results showed a remarkably uniform composition, despite variability in source regions and total concentration, indicating strong regional mixing of air masses. Sulfate accounted for approximately 52 % of non-refractory sub-micron particulate mass. Eighteen sulfur-containing organic compounds were identified, some for the first time in this location. Tracers of some sources, particularly biomass burning, were identified in the organic mass spectrum. However, the majority of organic mass was dominated by highly-processed compounds such as dicarboxylic acids. Our results underscore the impact of long-range transport and heterogeneous sulfate-driven chemistry on aerosol composition over the Indian Ocean, with important implications for understanding radiative forcing, aerosol-cloud interactions, and regional climate feedbacks in South Asia.</p>
</abstract>
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<funding-group>
<award-group id="gs1">
<funding-source>Vetenskapsrådet</funding-source>
<award-id>2021-05225</award-id>
</award-group>
<award-group id="gs2">
<funding-source>Bolincentret för klimatforskning, Stockholms Universitet</funding-source>
<award-id>RT1</award-id>
</award-group>
<award-group id="gs3">
<funding-source>Narodowe Centrum Nauki</funding-source>
<award-id>2023/49/B/ST10/00513</award-id>
</award-group>
</funding-group>
</article-meta>
</front>
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