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<article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" article-type="research-article" dtd-version="3.0" xml:lang="en">
<front>
<journal-meta>
<journal-id journal-id-type="publisher">ACPD</journal-id>
<journal-title-group>
<journal-title>Atmospheric Chemistry and Physics Discussions</journal-title>
<abbrev-journal-title abbrev-type="publisher">ACPD</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub">1680-7375</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/acpd-11-33465-2011</article-id>
<title-group>
<article-title>The impact of circulation patterns on regional transport pathways and air quality over Beijing and its surroundings</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Zhang</surname>
<given-names>J. P.</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>Zhu</surname>
<given-names>T.</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>Zhang</surname>
<given-names>Q. H.</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>Li</surname>
<given-names>C. C.</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>Shu</surname>
<given-names>H. L.</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>Ying</surname>
<given-names>Y.</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>Dai</surname>
<given-names>Z. P.</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>Liu</surname>
<given-names>X. Y.</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>Liang</surname>
<given-names>A. M.</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>Shen</surname>
<given-names>H. X.</given-names>
</name>
<xref ref-type="aff" rid="aff4">
<sup>4</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing, 100871, China</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>Shenzhen Academy of Environmental Science, Shenzhen, 518001, China</addr-line>
</aff>
<aff id="aff4">
<label>4</label>
<addr-line>Meteorological Center of North China Air Traffic Management Bureau of CAAC, Beijing, 100621, China</addr-line>
</aff>
<pub-date pub-type="epub">
<day>19</day>
<month>12</month>
<year>2011</year>
</pub-date>
<volume>11</volume>
<issue>12</issue>
<fpage>33465</fpage>
<lpage>33509</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-discuss.net/11/33465/2011/acpd-11-33465-2011.html">This article is available from http://www.atmos-chem-phys-discuss.net/11/33465/2011/acpd-11-33465-2011.html</self-uri>
<self-uri xlink:href="http://www.atmos-chem-phys-discuss.net/11/33465/2011/acpd-11-33465-2011.pdf">The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/11/33465/2011/acpd-11-33465-2011.pdf</self-uri>
<abstract>
<p>This study investigated the air pollution characteristics of
      synoptic-scale circulation in the Beijing megacity, and
      provided holistic evaluation of the impacts of circulation
      patterns on air quality during the 2008 Beijing Summer
      Olympics. Nine weather circulation types (CTs) were
      objectively identified over the North China region during
      2000–2009, using obliquely rotated T-mode principal component
      analysis (PCA). The resulting CTs were examined in relation to
      the local meteorology, regional transport pathways, and air
      quality parameters, respectively. The FLEXPART-WRF model was
      used to calculate 48-h backward plume trajectories for each
      CT. Nine CTs were characterized, with distinct local
      meteorology and air mass origins. CT 1 (high to the west with
      a strong pressure gradient) was characterized by
      a northwestern origin, with the smallest local and
      southeasterly air mass sources, and CT 6 (high to the
      northwest) had air mass sources mostly from the north and
      east. In contrast, CTs 5, 8, and 9 (unique, high to the east,
      and low to the northwest, respectively) were characterized by
      southern and southeastern trajectories, which indicated
      a greater influence of high pollutant emission sources. In
      turn, poor air quality in Beijing (high loadings of
      PM&lt;sub&gt;10&lt;/sub&gt;, BC, SO&lt;sub&gt;2&lt;/sub&gt;, NO&lt;sub&gt;2&lt;/sub&gt;, O&lt;sub&gt;3&lt;/sub&gt;, AOD, and low
      visibility) was associated with these CTs. Good air quality in
      Beijing was associated with CTs 1 and 6. The average
      visibilities (with ±1 σ) in Beijing for CTs 1
      and 6 during 2000–2009 were 18.5 ± 8.3 km and
      14.3 ± 8.5 km, respectively. In contrast, poor
      visibility values of 6.0 ± 3.5 km, 6.6 ± 3.7 km,
      and 6.7 ± 3.6 km were found in CTs 5, 8, and 9,
      respectively. The mean concentrations of PM&lt;sub&gt;10&lt;/sub&gt; for
      CTs 1, 6, 5, 8, and 9 during 2005–2009 were
      90.3 ± 76.3 μg m&lt;sup&gt;−3&lt;/sup&gt;,
      111.7 ± 89.6 μg m&lt;sup&gt;−3&lt;/sup&gt;,
      173.4 ± 105.8 μg m&lt;sup&gt;−3&lt;/sup&gt;,
      158.4 ± 90.0 μg m&lt;sup&gt;−3&lt;/sup&gt;, and
      151.2 ± 93.1 μg m&lt;sup&gt;−3&lt;/sup&gt;, respectively.

&lt;br&gt;&lt;br&gt;
      Analysis of the relationship between circulation pattern and
      air quality during the emission control period suggests that
      CTs are the primary drivers of day-to-day variations in
      pollutant concentrations over Beijing and its vicinity. During
      the Olympics period, the frequency of CT 6 was twice that of
      the mean in August from 2000 to 2009. This CT had northerly
      transport pathways and favorable meteorological conditions
      (e.g. frequent precipitation) for clean air during the
      Olympics. Assuming that relationships between CTs and air
      quality parameters in the same season (month) were constant in
      different years, the relative contributions of synoptic
      circulation to decreases in PM&lt;sub&gt;10&lt;/sub&gt;, BC, SO&lt;sub&gt;2&lt;/sub&gt;,
      NO&lt;sub&gt;2&lt;/sub&gt;, CO, AOD, and horizontal light extinction during the
      Olympics were estimated as 19 ± 14%,
      18 ± 13%, 41 ± 36%, 12 ± 7%,
      19 ± 11%, 25 ± 28%, and
      50 ± 46%, respectively.</p>
</abstract>
<counts><page-count count="45"/></counts>
</article-meta>
</front>
<body/>
<back>
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