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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>1</issue_number>
		<publication_year>2009</publication_year>
	</journal>
	<doi>10.5194/acpd-9-23-2009</doi>
	<article_url>http://www.atmos-chem-phys-discuss.net/9/23/2009/</article_url>
	<abstract_html>http://www.atmos-chem-phys-discuss.net/9/23/2009/acpd-9-23-2009.html</abstract_html>
	<fulltext_pdf>http://www.atmos-chem-phys-discuss.net/9/23/2009/acpd-9-23-2009.pdf</fulltext_pdf>
	<start_page>23</start_page>
	<end_page>58</end_page>
	<publication_date>2009-01-05</publication_date>
	<article_title content_type="html">A daytime climatological distribution of high opaque ice cloud classes over the Indian summer monsoon region observed from 25-year AVHRR data</article_title>
	<authors>
		<author numeration="1" affiliations="1,3">
			<name>A. Devasthale</name>
			<email>abhay.devasthale@smhi.se</email>
		</author>
		<author numeration="2" affiliations="1,2">
			<name>H. Grassl</name>
		</author>
	</authors>
	<affiliations>
		<affiliation numeration="1" content_type="html">Meteorological Institute, University of Hamburg, Hamburg, Germany</affiliation>
		<affiliation numeration="2" content_type="html">Max Planck Institute for Meteorology, Hamburg, Germany</affiliation>
		<affiliation numeration="3" content_type="html">now at: Swedish Meteorological and Hydrological Institute, Norrkoping, Sweden</affiliation>
	</affiliations>
	<abstract content_type="html">A daytime climatological spatio-temporal distribution of high opaque
      ice cloud (HOIC) classes over the Indian subcontinent
      (0–40&amp;deg; N, 60&amp;deg; E–100&amp;deg; E) is presented using
      25-year data from the Advanced Very High Resolution Radiometers
      (AVHRRs) for the summer monsoon months. The HOICs are important for
      regional radiative balance, precipitation and troposphere-stratosphere
      exchange. In this study, HOICs are sub-divided into three classes
      based on their cloud top brightness temperatures (&lt;I&gt;BT&lt;/I&gt;). Class I
      represents very deep convection (&lt;I&gt;BT&lt;/I&gt;&amp;lt;220 K). Class II
      represents deep convection (220 K&amp;le;BT&amp;lt;233 K)
      and Class III background convection (233 K&amp;le;&lt;I&gt;BT&lt;/I&gt;&amp;lt;253 K). Apart from
      presenting finest spatial resolution (0.1&amp;times;0.1 degrees) and long-term
      climatology of such cloud classes from AVHRRs to date, this study for
      the first time illustrates on 1) how these three cloud classes are
      climatologically distributed during monsoon months, and 2) how their
      distribution changes during active and break monsoon conditions. It is
      also investigated that how many overshooting convective clouds reach
      the tropopause layer during individual monsoon months. It is seen that
      Class I and Class II clouds dominate the Indian subcontinent during
      monsoon. The movement of monsoon over continent is very well reflected
      in these cloud classes. During monsoon breaks strong suppression of
      convective activity is observed over the Arabian Sea and the western
      coast of India. On the other hand, the presence of such convective
      activity is crucial for active monsoon conditions and all-India
      rainfall. It is found that a significant fraction of HOICs (3–5%)
      reach the tropopause layer over the Bay of Bengal during June and over
      the north and northeast India during July and August. Many cases are
      observed when clouds penetrate the tropopause layer and reach the
      lower stratosphere. Such cases mostly occur during June compared to
      the other months.</abstract>
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