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The frequency of tropopause-level thick and thin cirrus clouds as observed by CALIPSO and the relationship to relative humidity and outgoing longwave radiation

Thin cirrus clouds play an important radiative role in the earth's atmosphere and
climate system, yet are one of the least understood components of the climate system.
With the use of data from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite
Observations (CALIPSO), thin cirrus and thick cloud distributions in the tropics are
analyzed at 121, 100, and 82 hPa. Observations obtained between December 2006 and
November 2007 show that thin cirrus between 30°N and 30°S occur in close proximity
to regions of intense convection and are positively correlated with low values of
outgoing longwave radiation (OLR).
In conjunction with the CALIPSO data, water vapor data from the Earth
Observing System (EOS) Microwave Limb Sounder (MLS), OLR data provided by the
NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their Web site at
http://www.cdc.noaa.gov/, and linearly interpolated NCEP reanalysis temperature data
were used. These data were used to examine how thick and thin cirrus cloud fractions at
121-hPa and 100-hPa are related to relative humidity with respect to ice (RHI), temperature, and OLR. Our observations show that both RHI and convection play
important roles in the development and maintenance of thick and thin cirrus clouds at the
pressure levels of interest. The highest fractions of clouds are almost always seen within
OLR values representative of convection and at relatively high values of RHI. However,
when peaks in cloud fraction are found above the convective threshold, higher RHI
values are needed than are needed when convection is responsible for the formation and
maintenance of these clouds.

Identiferoai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/85992
Date10 October 2008
CreatorsCardona, Allison Leanne
ContributorsDessler, Andrew
PublisherTexas A&M University
Source SetsTexas A and M University
Languageen_US
Detected LanguageEnglish
TypeBook, Thesis, Electronic Thesis, text
Formatelectronic, born digital

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