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<article language="en">
	<journal>
		<journal_title>Atmospheric Chemistry and Physics Discussions</journal_title>
		<journal_url>www.atmos-chem-phys-discuss.net</journal_url>
		<issn>1680-7367</issn>
		<eissn>1680-7375</eissn>
		<volume_number>9</volume_number>
		<issue_number>2</issue_number>
		<publication_year>2009</publication_year>
	</journal>
	<doi>10.5194/acpd-9-9313-2009</doi>
	<article_url>http://www.atmos-chem-phys-discuss.net/9/9313/2009/</article_url>
	<abstract_html>http://www.atmos-chem-phys-discuss.net/9/9313/2009/acpd-9-9313-2009.html</abstract_html>
	<fulltext_pdf>http://www.atmos-chem-phys-discuss.net/9/9313/2009/acpd-9-9313-2009.pdf</fulltext_pdf>
	<start_page>9313</start_page>
	<end_page>9366</end_page>
	<publication_date>2009-04-09</publication_date>
	<article_title content_type="html">Performance of the line-by-line radiative transfer model (LBLRTM) for temperature and species retrievals: IASI case studies from JAIVEx</article_title>
	<authors>
		<author numeration="1" affiliations="1">
			<name>M. W. Shephard</name>
			<email>mshephar@aer.com</email>
		</author>
		<author numeration="2" affiliations="2">
			<name>S. A. Clough</name>
		</author>
		<author numeration="3" affiliations="1">
			<name>V. H. Payne</name>
		</author>
		<author numeration="4" affiliations="3,4">
			<name>W. L. Smith</name>
		</author>
		<author numeration="5" affiliations="5">
			<name>S. Kireev</name>
		</author>
		<author numeration="6" affiliations="1">
			<name>K. E. Cady-Pereira</name>
		</author>
	</authors>
	<affiliations>
		<affiliation numeration="1" content_type="html">Atmospheric and Environmental Research, Inc., Lexington, Massachusetts, USA</affiliation>
		<affiliation numeration="2" content_type="html">Clough Radiation Associates, LLC., Lexington, Massachusetts, USA</affiliation>
		<affiliation numeration="3" content_type="html">Hampton University, Hampton, Virginia,USA</affiliation>
		<affiliation numeration="4" content_type="html">University of Wisconsin, Madison, Wisconsin, USA</affiliation>
		<affiliation numeration="5" content_type="html">Hampton University, Hampton, Virginia, USA</affiliation>
	</affiliations>
	<abstract content_type="html">Presented here are comparisons between the Infrared Atmospheric Sounding
instrument (IASI) and the &quot;Line-By- Line Radiative Transfer Model&quot;
(LBLRTM). Spectral residuals from radiance closure studies during the IASI
JAIVEx validation campaign provide insight into a number of spectroscopy
issues relevant to remote sounding of temperature, water vapor and trace
gases from IASI. In order to perform quality IASI trace gas retrievals the
temperature and water vapor fields must be retrieved as accurately as possible.
In general, the residuals in the CO&lt;sub&gt;2&lt;/sub&gt; &amp;nu;&lt;sub&gt;2&lt;/sub&gt; region
are of the order of the IASI instrument noise. However, outstanding issues
in the CO&lt;sub&gt;2&lt;/sub&gt; spectral regions remain. There is a large residual
~&amp;minus;1.5 K in the 667 cm&lt;sup&gt;&amp;minus;1&lt;/sup&gt; Q-branch, and residuals in the CO&lt;sub&gt;2&lt;/sub&gt; &amp;nu;&lt;sub&gt;2&lt;/sub&gt;
and N&lt;sub&gt;2&lt;/sub&gt;O/CO&lt;sub&gt;2&lt;/sub&gt; &amp;nu;&lt;sub&gt;3&lt;/sub&gt; spectral regions that sample the troposphere are
inconsistent, with the N&lt;sub&gt;2&lt;/sub&gt;O/CO&lt;sub&gt;2&lt;/sub&gt; &amp;nu;&lt;sub&gt;3&lt;/sub&gt; region being too negative (warmer)
by ~0.6 K. Residuals on this lower wavenumber side of the CO&lt;sub&gt;2&lt;/sub&gt;
&amp;nu;&lt;sub&gt;3&lt;/sub&gt; band will be improved by line parameter updates, while future
efforts to reduce the residuals reaching ~&amp;minus;0.5 K on the higher
wavenumber side of the CO&lt;sub&gt;2&lt;/sub&gt; &amp;nu;&lt;sub&gt;3&lt;/sub&gt; band will focus on addressing
limitations in the modeling of the CO&lt;sub&gt;2&lt;/sub&gt; line shape (line coupling and
duration of collision) effects. Brightness temperature residuals from the
radiance closure studies in the &amp;nu;&lt;sub&gt;2&lt;/sub&gt; water vapor band have standard
deviations of ~0.2–0.3 K with some large peak residuals reaching
&amp;plusmn;0.5–1.0 K. These are larger than the instrument noise indicating that
systematic errors still remain. New H&lt;sub&gt;2&lt;/sub&gt;O line intensities and positions
from Coudert have a significant impact on the retrieved water vapor,
particularly in the upper troposphere where the water vapor retrievals are
10% drier when using line intensities from Coudert compared with
HITRAN2004. In addition to O&lt;sub&gt;3&lt;/sub&gt;, CH&lt;sub&gt;4&lt;/sub&gt;, and CO, the high radiometric
calibration of the IASI instrument combined with an accurate forward model
allows for the detection of minor species with weak atmospheric signatures
in the nadir radiances, such as HNO&lt;sub&gt;3&lt;/sub&gt; and OCS.</abstract>
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</article>

