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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>10</volume_number>
		<issue_number>3</issue_number>
		<publication_year>2010</publication_year>
	</journal>
	<doi>10.5194/acpd-10-7215-2010</doi>
	<article_url>http://www.atmos-chem-phys-discuss.net/10/7215/2010/</article_url>
	<abstract_html>http://www.atmos-chem-phys-discuss.net/10/7215/2010/acpd-10-7215-2010.html</abstract_html>
	<fulltext_pdf>http://www.atmos-chem-phys-discuss.net/10/7215/2010/acpd-10-7215-2010.pdf</fulltext_pdf>
	<start_page>7215</start_page>
	<end_page>7264</end_page>
	<publication_date>2010-03-18</publication_date>
	<article_title content_type="html">Combining visible and infrared radiometry and lidar data to test ice clouds optical properties</article_title>
	<authors>
		<author numeration="1" affiliations="1,2">
			<name>A. Bozzo</name>
		</author>
		<author numeration="2" affiliations="1">
			<name>T. Maestri</name>
		</author>
		<author numeration="3" affiliations="1">
			<name>R. Rizzi</name>
			<email>rolando.rizzi@unibo.it</email>
		</author>
	</authors>
	<affiliations>
		<affiliation numeration="1" content_type="html">Dipartimento di Fisica, Università di Bologna, Italy</affiliation>
		<affiliation numeration="2" content_type="html">now at: University of Edinburgh, School of GeoSciences, Edinburgh, UK</affiliation>
	</affiliations>
	<abstract content_type="html">Measurements taken during the 2003 Pacific THORPEX Observing System Test
(P-TOST) by the MODIS Airborne Simulator (MAS), the Scanning High-resolution
Interferometer Sounder (S-HIS) and the Cloud Physics Lidar (CPL) are compared
to simulations performed with a line-by-line and multiple scattering modeling
methodology (LBLMS). Formerly used for infrared hyper-spectral data analysis,
LBLMS has been extended to the visible and near infrared with the inclusion
of surface bi-directional reflectance properties. A number of scenes are
evaluated: two clear scenes, one with nadir geometry and one cross-track
encompassing sun glint, and three cloudy scenes, all with nadir geometry.&lt;br&gt;
&lt;br&gt;
CPL data is used to estimate the particulate optical depth at 532 nm for the
clear and cloudy scenes. Cloud optical depth is also retrieved from S-HIS
infrared window radiances, and it agrees with CPL values, to within natural
variability. MAS data are simulated convolving high resolution radiances.&lt;br&gt;
&lt;br&gt;
The paper discusses the results of the comparisons for the clear cases and
for the three cloudy cases. LBLMS clear simulations agree with MAS data to
within 20% in the shortwave (SW) and near infrared (NIR) spectrum and
within 2 K in the infrared (IR) range. It is shown that cloudy sky
simulations using cloud parameters retrieved from IR radiances systematically
underestimate the measured radiance in the SW and NIR by nearly 50%,
although the IR retrieved optical thickness agree with same measured by CPL.
MODIS radiances measured from Terra are also compared to LBLMS simulations in
cloudy conditions using retrieved cloud optical depth and effective radius
from MODIS, to understand the origin for the observed discrepancies. It is
shown that the simulations agree, to within natural variability, with
measurements in selected MODIS SW bands.&lt;br&gt;
&lt;br&gt;
The paper dwells on a possible explanation of these contraddictory results,
involving the phase function of ice particles in the shortwave.</abstract>
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