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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-5-10217-2005</article-id>
<title-group>
<article-title>Implementation issues in chemistry and transport models</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Strahan</surname>
<given-names>S. 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>Polansky</surname>
<given-names>B. C.</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>University of Maryland, Baltimore County Goddard Earth Science and Technology Center, 5523 Research Park Dr., Suite 320, Baltimore, MD, 21 228, USA</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>Science Systems and Applications, Inc., 10210 Greenbelt Rd., Suite 600, Lanham, MD, 20 706, USA</addr-line>
</aff>
<pub-date pub-type="epub">
<day>21</day>
<month>10</month>
<year>2005</year>
</pub-date>
<volume>5</volume>
<issue>5</issue>
<fpage>10217</fpage>
<lpage>10258</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/5/10217/2005/acpd-5-10217-2005.html">This article is available from http://www.atmos-chem-phys-discuss.net/5/10217/2005/acpd-5-10217-2005.html</self-uri>
<self-uri xlink:href="http://www.atmos-chem-phys-discuss.net/5/10217/2005/acpd-5-10217-2005.pdf">The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/5/10217/2005/acpd-5-10217-2005.pdf</self-uri>
<abstract>
<p>Offline chemistry and transport models (CTMs) are
versatile tools for studying composition and climate issues requiring
multi-decadal simulations. They are computationally fast compared to coupled
chemistry climate models, making them well-suited for integrating
sensitivity experiments necessary for understanding model performance and
interpreting results. The archived meteorological fields used by CTMs can be
implemented with lower horizontal or vertical resolution than the original
meteorological fields in order to shorten integration time, but the effects
of these shortcuts on transport processes must be understood if the CTM is
to have credibility. In this paper we present a series of CTM experiments,
each differing from another by a single feature of the implementation.
Transport effects arising from changes in resolution and model lid height
are evaluated using process-oriented diagnostics that intercompare CH&lt;sub&gt;4&lt;/sub&gt;,
O&lt;sub&gt;3&lt;/sub&gt;, and age tracer carried in the simulations. Some of the diagnostics
used are derived from observations and are shown as a reality check for the
model. Processes evaluated include the tropical ascent, tropical-midlatitude
exchange, the poleward circulation in the upper stratosphere, and the
development of the Antarctic vortex. We find that faithful representation of
stratospheric transport in this CTM using Lin and Rood advection is possible
with a full mesosphere, ~1 km resolution in the lower stratosphere,
and relatively low vertical resolution (&amp;gt;4 km spacing) in the middle
stratosphere and above, but lowering the lid from the upper to lower
mesosphere leads to less realistic constituent distributions in the upper
stratosphere. Ultimately, this affects the polar lower stratosphere, but the
effects are greater for the Antarctic than the Arctic. The fidelity of lower
stratospheric transport requires realistic tropical and high latitude mixing
barriers which are produced at 2&amp;deg;&amp;times;2.5&amp;deg;, but not lower resolution.
At 2&amp;deg;&amp;times;2.5&amp;deg; resolution, the CTM produces a vortex capable of
isolating perturbed chemistry (e.g.&amp;nbsp;high Cl&lt;sub&gt;y&lt;/sub&gt; and low NO&lt;sub&gt;y&lt;/sub&gt;) required
for simulating polar ozone loss.</p>
</abstract>
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