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<front>
<journal-meta>
<journal-id journal-id-type="publisher">ACP</journal-id>
<journal-title-group>
<journal-title>Atmospheric Chemistry and Physics</journal-title>
<abbrev-journal-title abbrev-type="publisher">ACP</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub">1680-7324</issn>
<publisher><publisher-name>Copernicus GmbH</publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/acp-9-909-2009</article-id>
<title-group>
<article-title>Exploring the relation between aerosol optical depth and PM&lt;sub&gt;2.5&lt;/sub&gt; at Cabauw, the Netherlands</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Schaap</surname>
<given-names>M.</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>Apituley</surname>
<given-names>A.</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Timmermans</surname>
<given-names>R. M. A.</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>Koelemeijer</surname>
<given-names>R. B. A.</given-names>
</name>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>de Leeuw</surname>
<given-names>G.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff4">
<sup>4</sup>
</xref>
<xref ref-type="aff" rid="aff5">
<sup>5</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>TNO, Business unit Environment, Health and Safety, P.O. Box 80015, 3508 TA Utrecht, The Netherlands</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>National Institute for Public Health and the Environment, P.O. Box 1, 3720 AH Bilthoven, The Netherlands</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>Netherlands Environmental Assessment Agency (MNP), P.O. Box 303, 3720 AH Bilthoven, The Netherlands</addr-line>
</aff>
<aff id="aff4">
<label>4</label>
<addr-line>Finnish Meteorological Institute, Climate Change Unit, P.O. Box 503, 00101 Helsinki, Finland</addr-line>
</aff>
<aff id="aff5">
<label>5</label>
<addr-line>University of Helsinki, Department of Physics, P.O. Box 64, 00014 Helsinki, Finland</addr-line>
</aff>
<pub-date pub-type="epub">
<day>05</day>
<month>02</month>
<year>2009</year>
</pub-date>
<volume>9</volume>
<issue>3</issue>
<fpage>909</fpage>
<lpage>925</lpage>
<permissions>
<license xlink:type="simple">
<license-p>This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.</license-p>
</license>
</permissions>
<self-uri xlink:href="http://www.atmos-chem-phys.net/9/909/2009/acp-9-909-2009.html">This article is available from http://www.atmos-chem-phys.net/9/909/2009/acp-9-909-2009.html</self-uri>
<self-uri xlink:href="http://www.atmos-chem-phys.net/9/909/2009/acp-9-909-2009.pdf">The full text article is available as a PDF file from http://www.atmos-chem-phys.net/9/909/2009/acp-9-909-2009.pdf</self-uri>
<abstract>
<p>Estimates of PM&lt;sub&gt;2.5&lt;/sub&gt; distributions based on satellite data depend critically
on an established relation between AOD and ground level PM&lt;sub&gt;2.5&lt;/sub&gt;. In this study
we performed an experiment at Cabauw to establish a relation between AOD and
PM&lt;sub&gt;2.5&lt;/sub&gt; for the Netherlands. A first inspection of the AERONET L1.5 AOD and
PM&lt;sub&gt;2.5&lt;/sub&gt; data showed a low correlation between the two properties. The
AERONET L1.5 showed relatively many observations of high AOD values paired
to low PM&lt;sub&gt;2.5&lt;/sub&gt; values, which hinted cloud contamination. Various methods were
used to detect cloud contamination in the AERONET data to substantiate this
hypothesis. A cloud screening method based on backscatter LIDAR observations
was chosen to detect cloud contaminated observations in the AERONET L1.5
AOD. A later evaluation of AERONET L2.0 showed that the most data that are
excluded in the update from L1.5 to L2.0 were also excluded by our cloud
screening, which provides confidence in both our cloud-screening method as
well as the final screening in the AERONET procedure. The use of LIDAR
measurements in conjunction with the CIMEL AOD data is regarded highly
beneficial. Contra-intuitively, the AOD to PM&lt;sub&gt;2.5&lt;/sub&gt; relationship was shown to
be insensitive to inclusion of the mixed layer height. The robustness of the
relation improves dependent on the time window during the day towards noon.
The final relation found for Cabauw is PM&lt;sub&gt;2.5&lt;/sub&gt;=124.5&amp;times;AOD&amp;minus;0.34 and is
valid for fair weather conditions. The relationship found between bias
corrected MODIS AOD and PM&lt;sub&gt;2.5&lt;/sub&gt; at Cabauw is very similar to the analysis
based on the much larger dataset from ground based data only. We applied the
relationship to a MODIS composite map to assess the PM&lt;sub&gt;2.5&lt;/sub&gt; distribution over
the Netherlands for the first time. The verification of the derived map is
difficult because ground level artefact free PM&lt;sub&gt;2.5&lt;/sub&gt; data are lacking. The
validity and utility of our proposed mapping methodology should be further
investigated.</p>
</abstract>
<counts><page-count count="17"/></counts>
</article-meta>
</front>
<body/>
<back>
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