In-cloud variability of LIDAR depolarization of polar and midlatitude cirrus

Year: 2003

Authors: Del Guasta M., Vallar E.

Autors Affiliation: IFAC CNR, Via Panciatichi 64, Florence 50127, Italy; Physics Department, De La Salle Univ., 2401 Taft Avenue, Manila 1004, Philippines

Abstract: LIDAR depolarization is commonly used for discriminating liquid and ice particles. Since depolarization depends in a complicated manner on particle shape and size, in-cloud variability of depolarization has been used as an indicator of the microphysical homogeneity of cirrus. The comparison between midlatitude (Florence, Italy, 43. 60°N) and polar (Dumont d\’Urville, Antarctica, 66. 68°S) cirrus showed a lower mean depolarization and a higher in-cloud uniformity of cloud depolarization for polar clouds in the (-80, -50°C) temperature range. A wider in-cloud variability of depolarization was observed in polar clouds at higher temperatures (-50, -30°C), reflecting the presence of supercooled liquid layers. The large in-cloud variability of depolarization in Florence cirrus could be explained with a microphysics that is dynamically and chemically perturbed as compared with the polar site. Aged jet contrails are, in fact, present in many Florence cirrus records.

Journal/Review: GEOPHYSICAL RESEARCH LETTERS

Volume: 30 (11)      Pages from: 1578  to: 1578

KeyWords: Ice; Optical radar; Polarization, Polar clouds, Geophysics, cirrus; cloud microphysics; lidar; midlatitude environment; polar region; polarization
DOI: 10.1029/2003GL017163