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

[摘要] A counterflow virtual impactor was used to collect residual particles largerthan about 0.1 μm diameter from anvil cirrus clouds generated overFlorida in the southern United States. A wide variety of particle types werefound. About one-third of the nuclei were salts, with varying amounts ofcrustal material, industrial metals, carbonaceous particles, and sulfates.Ambient aerosol particles near the anvils were found to have similarcompositions, indicating that anvils act to redistribute particles overlarge regions of the atmosphere. Sampling occurred at a range of altitudesspanning temperatures from −21 to −56°C. More insoluble (crustal andmetallic) particles typical of heterogeneous ice nuclei were found in icecrystals at warmer temperatures, while more soluble salts and sulfates werepresent at cold temperatures. At temperatures below about−35 to −40°C, soluble nuclei outnumbered insoluble nuclei, evidentlyreflecting the transition from primarily heterogeneous to primarilyhomogeneous freezing as a source of anvil ice.

[学科分类] 大气科学