Chemical characteristics of ice residual nuclei in anvil cirrus clouds: evidence for homogeneous and heterogeneous ice formation

Abstract

Abstract.A counterflow virtual impactor was used to collect residual particles larger than about 0.1 µm diameter from anvil cirrus clouds generated over Florida in the southern United States. A wide variety of particle types were found. About one-third of the nuclei were salts, with varying amounts of crustal material, industrial metals, carbonaceous particles, and sulfates. Ambient aerosol particles near the anvils were found to have similar compositions, indicating that anvils act to redistribute particles over large regions of the atmosphere. Sampling occurred at a range of altitudes spanning temperatures from −21 to −56 • C. More insoluble (crustal and metallic) particles typical of heterogeneous ice nuclei were found in ice crystals at warmer temperatures, while more soluble salts and sulfates were present at cold temperatures. At temperatures below about −35 to −40 • C, soluble nuclei outnumbered insoluble nuclei, evidently reflecting the transition from primarily heterogeneous to primarily homogeneous freezing as a source of anvil ice.

Immersion freezing of ice nucleation active protein complexes

“…In contrast, laboratory studies showed that the majority of non-biological substances found in atmospheric ice crystal residues, i.e., natural mineral dust (e.g., Twohy and Poellot, 2005;Pratt et al, 2009;Kamphus et al, 2010), are only ice active at lower temperatures (e.g., Hoose and Möhler, 2012;Murray et al, 2012). One possible explanation for the observed temperature differences might be the presence of biological material (e.g., bacteria) initiating freezing already at temperatures above −10 • C. This biological material may be internally or externally mixed with other substances in atmospheric aerosol particles (Pratt et al, 2009).…”

Cloud processing of mineral dust: direct comparison of cloud residual and clear sky particles during AMMA aircraft campaign in summer 2006

“…The important role of dust particles acting effectively as ice nuclei (IN) has been rather well recognized (Isono et al, 1959;Heintzenberg et al, 1996;DeMott et al, 2003;Sassen et al, 2003;Twohy and Poellot, 2005). Dust particles may induce diverse indirect effects also through their interaction with warm clouds.…”

Characteristics of Black Carbon Aerosol during the Chinese Lunar Year and Weekdays in Xi’an, China

“…The total climate forcing of BC aerosol has been estimated to be +1.1 W·m , which is ranked as the second largest contributor to anthropogenic radiative forcing after CO2 [3]. Coated BC particles also can act as cloud condensation nuclei (CCN), thereby contributing to the indirect forcing of climate [4]. In addition to the effects on the environment, epidemiological research suggests that BC particles have adverse health effects: they have been implicated in respiratory and cardiovascular diseases [5,6].…”