Abstract

Upper tropospheric cirrus clouds consist of hexagonal ice crystals, which geometrical ray-tracing-theory predicts should regularly produce a variety of optical phenomena such as vivid 22° and 46° halos. Yet, cirrus inconsistently generate such optical displays, while a class of more exotic displays are reported, albeit rarely. I review current knowledge of the cirrus cloud microphysical factors that control ice crystal shape, and hence halo/arc formation, but also appeal to halo enthusiasts to help investigate the causes of unusually complex, brilliant, or rare optical displays. Currently, a wealth of meteorological information can be tapped from the Internet to help advance our knowledge of the basic meteorological factors leading to these rare events.

© 2005 Optical Society of America

Midlatitude cirrus cloud climatology from the Facility for Atmospheric Remote Sensing. IV. Optical displays

Kenneth Sassen, Jiang Zhu, and Sally Benson
Appl. Opt. 42(3) 332-341 (2003)

Cirrus cloud iridescence: a rare case study

Kenneth Sassen
Appl. Opt. 42(3) 486-491 (2003)

Corona-producing cirrus cloud properties derived from polarization lidar and photographic analyses

Kenneth Sassen
Appl. Opt. 30(24) 3421-3428 (1991)

Effects of ice-crystal structure on halo formation: cirrus cloud experimental and ray-tracing modeling studies

Kenneth Sassen, Nancy C. Knight, Yoshihide Takano, and Andrew J. Heymsfield
Appl. Opt. 33(21) 4590-4601 (1994)

Corona-producing ice clouds: a case study of a cold mid-latitude cirrus layer

Kenneth Sassen, Gerald G. Mace, John Hallett, and Michael R. Poellot
Appl. Opt. 37(9) 1477-1485 (1998)