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Effects of Ice-Crystal Structure on Halo Formation: Cirrus Cloud Experimental and Ray-Tracing Modeling StudiesDuring the 1986 Project FIRE (First International Satellite Cloud Climatology Project Regional Experiment) field campaign, four 22 deg halo-producing cirrus clouds were studied jointly from a ground-based polarization lidar and an instrumented aircraft. The lidar data show the vertical cloud structure and the relative position of the aircraft, which collected a total of 84 slides by impaction, preserving the ice crystals for later microscopic examination. Although many particles were too fragile to survive impaction intact, a large fraction of the identifiable crystals were columns and radial bullet rosettes, with both displaying internal cavitations and radial plate-column combinations. Particles that were solid or displayed only a slight amount of internal structure were relatively rare, which shows that the usual model postulated by halo theorists, i.e., the randomly oriented, solid hexagonal crystal, is inappropriate for typical cirrus clouds. With the aid of new ray-tracing simulations for hexagonal hollow-ended column and bullet-rosette models, we evaluate the effects of more realistic ice-crystal structures on halo formation and lidar depolarization and consider why the common halo is not more common in cirrus clouds.
Document ID
19970008398
Acquisition Source
Langley Research Center
Document Type
Reprint (Version printed in journal)
Authors
Sassen, Kenneth
(Utah Univ. Salt Lake City, UT United States)
Knight, Nancy C.
(National Center for Atmospheric Research Boulder, CO United States)
Takano, Yoshihide
(Utah Univ. Salt Lake City, UT United States)
Heymsfield, Andrew J.
(National Center for Atmospheric Research Boulder, CO United States)
Date Acquired
August 17, 2013
Publication Date
July 20, 1994
Publication Information
Publication: Applied Optics
Publisher: Optical Society of America
Volume: 33
Issue: 21
ISSN: 0003-6935
ISBN: 214590-12
Subject Category
Optics
Report/Patent Number
NASA-CR-202633
NAS 1.26:202633
Accession Number
97N70650
Funding Number(s)
CONTRACT_GRANT: NSF ATM-90-24217
CONTRACT_GRANT: NSF ATM-85-13975
CONTRACT_GRANT: NASA Order L-98110B
CONTRACT_GRANT: NSF ATM-89-14348
CONTRACT_GRANT: NAG1-868
Distribution Limits
Public
Copyright
Public Use Permitted.
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