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Comparison between SAGE II and ISCCP high-level clouds. 2: Locating clouds topsA comparison is made of the vertical distribution of high-level cloud tops derived from the Stratospheric Aerosol and Gas Experiment II (SAGE II) occultation measurements and from the International Satellite Cloud Climatology Project (ISCCP) for all Julys and Januarys in 1985 to 1990. The results suggest that ISCCP overestimates the pressure of high-level clouds by up to 50-150 mbar, particularly at low latitudes. This is caused by the frequent presence of clouds with diffuse tops (greater than 50% time when cloudy events are observed). The averaged vertical extent of the diffuse top is about 1.5 km. At midlatitudes where the SAGE II and ISCCP cloud top pressure agree best, clouds with distinct tops reach a maximum relative proportion of the total level cloud amount (about 30-40%), and diffuse-topped clouds are reduced to their minimum (30-40%). The ISCCP-defined cloud top pressure should be regarded not as the material physical height of the clouds but as the level which emits the same infrared radiance as observed. SAGE II and ISCCP cloud top pressures agree for clouds with distinct tops. There is also an indication that the cloud top pressures of optically thin clouds not overlying thicker clouds are poorly estimated by ISCCP at middle latitudes. The average vertical extent of these thin clouds is about 2.5 km.
Document ID
19950043413
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Liao, Xiaohan
(NASA Goddard Institute for Space Studies, New York, NY United States)
Rossow, William B.
(NASA Goddard Institute for Space Studies, New York, NY United States)
Rind, David
(NASA Goddard Institute for Space Studies, New York, NY United States)
Date Acquired
August 16, 2013
Publication Date
January 20, 1995
Publication Information
Publication: Journal of Geophysical Research
Volume: 100
Issue: D1
ISSN: 0148-0227
Subject Category
Geophysics
Accession Number
95A75012
Distribution Limits
Public
Copyright
Other

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