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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>GÃ¶ttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/acp-9-6319-2009</article-id>
<title-group>
<article-title>Atmospheric nanoparticle observations in the low free troposphere during upward orographic flows at IzaÃ±a Mountain Observatory</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>RodrÃ­guez</surname>
<given-names>S.</given-names>
</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>GonzÃ¡lez</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>Cuevas</surname>
<given-names>E.</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>Ramos</surname>
<given-names>R.</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>Romero</surname>
<given-names>P. 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>Abreu-Afonso</surname>
<given-names>J.</given-names>
</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>Redondas</surname>
<given-names>A.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>IzaÃ±a Atmospheric Research Centre, AEMET, Associated Unit to CSIC &quot;Studies on Atmospheric Pollution&quot;, La Marina 20, Planta 6, E38071, Santa Cruz de Tenerife, Canary Islands, Spain</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>University of Huelva, Associated Unit to CSIC &quot;Air Pollution&quot;, Campus El Carmen, E21071, Huelva, Spain</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>Institute for Environmental Assessment and Water Research IDAEA, CSIC, Jordi Girona 18, E08034, Barcelona, Spain</addr-line>
</aff>
<pub-date pub-type="epub">
<day>02</day>
<month>09</month>
<year>2009</year>
</pub-date>
<volume>9</volume>
<issue>17</issue>
<fpage>6319</fpage>
<lpage>6335</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/9/6319/2009/acp-9-6319-2009.html">This article is available from http://www.atmos-chem-phys.net/9/6319/2009/acp-9-6319-2009.html</self-uri>
<self-uri xlink:href="http://www.atmos-chem-phys.net/9/6319/2009/acp-9-6319-2009.pdf">The full text article is available as a PDF file from http://www.atmos-chem-phys.net/9/6319/2009/acp-9-6319-2009.pdf</self-uri>
<abstract>
<p>This study investigates the processes and conditions favouring the formation
of nanoparticles (diameter&lt;10 nm) which are frequently observed on high
mountains reaching the low free troposphere. This was done through an
analysis of a data set collected at IzaÃ±a Global Atmospheric Watch
Observatory (Canary Islands; 2367 m above sea level). This high
mountain supersite is located well above the stratocumulus layer
characteristic of the subtropical oceanic tropospheres. At night, when the
catabic flow regime is well established, free troposphere aerosols were
measured. The development of orographic buoyant upward flows during daylight
resulted in an increase of water vapour, SO&lt;sub&gt;2&lt;/sub&gt; and NO&lt;sub&gt;y&lt;/sub&gt;
concentrations. These ascending airflows perturbed the free troposphere and
resulted in high concentrations of 3â€“10 nm particles (N&lt;sub&gt;3â€“10&lt;/sub&gt;) due to new
particle formation. An analysis of the 5-min average time series allowed
the identification of two main types of N&lt;sub&gt;3â€“10&lt;/sub&gt; event. In Type I events a
linear relationship between N&lt;sub&gt;3â€“10&lt;/sub&gt; and SO&lt;sub&gt;2&lt;/sub&gt; was observed (&lt;i&gt;r&lt;/i&gt;&lt;sup&gt;2&lt;/sup&gt;
coefficients 0.70â€“0.95 and a mean slope of 11 cm&lt;sup&gt;&amp;minus;3&lt;/sup&gt; ppt&lt;sup&gt;&amp;minus;1&lt;/sup&gt;
for 5-min averaged data; SO&lt;sub&gt;2&lt;/sub&gt; concentrations from tens to hundreds of
ppt). These particles seem to be formed during upward transport (probably
within or after the outflows of clouds typically located below IzaÃ±a).
During Type II events, no correlation between SO&lt;sub&gt;2&lt;/sub&gt; and N&lt;sub&gt;3â€“10&lt;/sub&gt; was
observed and 3â€“10 nm particles were formed in-situ at noon and during the
afternoon due to the condensation of vapours linked to photochemistry. New
particle formation was observed almost every day owing to the favourable
conditions associated with the entry of boundary layer air in the low free
troposphere, even if SO&lt;sub&gt;2&lt;/sub&gt; concentrations are rather low at IzaÃ±a
(tens to hundreds of ppt). The low surface area of pre-existing particles,
low temperature and high radiation intensity clearly favoured the formation
of nanoparticles. The low surface area of pre-existing particles in the
upward flows is furthered by in-cloud particles scavenging in the
stratocumulus layer typically located below IzaÃ±a. The higher
temperature and the presence of coarse Saharan dust particles decrease the
efficiency of the new particle formation mechanisms in summer. Thus, the
&quot;N&lt;sub&gt;3â€“10&lt;/sub&gt; versus SO&lt;sub&gt;2&lt;/sub&gt;&quot; slope (for &lt;i&gt;r&lt;/i&gt;&lt;sup&gt;2&lt;/sup&gt;&gt;0.7 cases) was higher in
autumn and winter (~15 cm&lt;sup&gt;&amp;minus;3&lt;/sup&gt; ppt&lt;sup&gt;&amp;minus;1&lt;/sup&gt; as average) than
in summer (2â€“8 cm&lt;sup&gt;&amp;minus;3&lt;/sup&gt; ppt&lt;sup&gt;&amp;minus;1&lt;/sup&gt;). These field observations
suggest that elevated mounts that reaches the free troposphere may act as
source regions for new particles.</p>
</abstract>
<counts><page-count count="17"/></counts>
</article-meta>
</front>
<body/>
<back>
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