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<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-12-4655-2012</article-id>
<title-group>
<article-title>Hydration or dehydration: competing effects of upper tropospheric cloud radiation on the TTL water vapor</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Wu</surname>
<given-names>L.</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>Su</surname>
<given-names>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>Jiang</surname>
<given-names>J. 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>Read</surname>
<given-names>W. G.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>now at: Joint Institute for Regional Earth System Science and Engineering, University of California, Los Angeles, California, USA</addr-line>
</aff>
<pub-date pub-type="epub">
<day>08</day>
<month>02</month>
<year>2012</year>
</pub-date>
<volume>12</volume>
<issue>2</issue>
<fpage>4655</fpage>
<lpage>4678</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>
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<abstract>
<p>A tropical channel version of the Weather Research and Forecasting (WRF)
model is used to investigate the radiative impacts of upper tropospheric
clouds on water vapor in the tropical tropopause layer (TTL). The WRF
simulations of cloud radiative effects and water vapor in the upper
troposphere and lower stratosphere show reasonable agreement with
observations, including approximate reproduction of the water vapor &quot;tape
recorder&quot; signal. By turning on and off the upper tropospheric cloud
radiative effect (UTCRE) above 200 hPa, we find that the UTCRE induces a
warming of 0.76 K and a moistening of 9% in the upper troposphere at 215 hPa.
However, the UTCRE cools and dehydrates the TTL, with a cooling of 0.82 K and a dehydration of 16% at 100 hPa. The enhanced vertical ascent due
to the UTCRE contributes substantially to mass transport and the dehydration
in the TTL. The hydration due to the enhanced vertical transport is
counteracted by the dehydration from adiabatic cooling associated with the
enhanced vertical motion. The UTCRE also substantially changes the
horizontal winds in the TTL, resulting in shifts of the strongest
dehydration away from the lowest temperature anomalies in the TTL. The UTCRE
increases in-situ cloud formation in the TTL. A seasonal variation is shown
in the simulated UTCRE, with stronger impact in the moist phase from June to
November than in the dry phase from December to May.</p>
</abstract>
<counts><page-count count="24"/></counts>
</article-meta>
</front>
<body/>
<back>
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