title: Clarifying the dominant sources and mechanisms of cirrus cloud formation.
abstract: Formation of cirrus clouds depends on the availability of ice nuclei to begin condensation of atmospheric water vapor. Although it is known that only a small fraction of atmospheric aerosols are efficient ice nuclei, the critical ingredients that make those aerosols so effective have not been established. We have determined in situ the composition of the residual particles within cirrus crystals after the ice was sublimated. Our results demonstrate that mineral dust and metallic particles are the dominant source of residual particles, whereas sulfate and organic particles are underrepresented, and elemental carbon and biological materials are essentially absent. Further, composition analysis combined with relative humidity measurements suggests that heterogeneous freezing was the dominant formation mechanism of these clouds.
authors: Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA. djcziczo@mit.edu
authors: Daniel J
authors: DJ
authors: Cziczo
authors: Karl D
authors: KD
authors: Froyd
authors: Corinna
authors: C
authors: Hoose
authors: Eric J
authors: EJ
authors: Jensen
authors: Minghui
authors: M
authors: Diao
authors: Mark A
authors: MA
authors: Zondlo
authors: Jessica B
authors: JB
authors: Smith
authors: Cynthia H
authors: CH
authors: Twohy
authors: Daniel M
authors: DM
authors: Murphy